application of lignin in thermoplastic materials · biodegradability the disintegration of...

Application of Lignin inThermoplastic Materials

Sen Yang1, Tong-Qi Yuan1, Quentin Shi2 andRun-Cang Sun11Beijing Key Laboratory of LignocellulosicChemistry, Beijing Forestry University, Beijing,People’s Republic of China2Jining Mingsheng New Materials Co., Ltd,Shandong Province, People’s Republic of China

Article Outline

GlossaryDefinition of the SubjectGraphicIntroductionClassification of Lignin Based on the Extraction

ProcedureThe Methods to Improve the Compatibilization

Between Lignin and PolymerLignin-based ThermoplasticsFuture DirectionsBibliography

Abbreviations

AKD Alkyl Ketene DimerASA Alkenyl Succinic Acid AnhydrideASTM American Society for Testing and

MaterialsBML Ball-Milled LigninCTMAB Cetyl Trimethyl Ammonium

BromideDDSA Dodecenyl Succinic AnhydrideDMC Dimethyl CarbonateDMF Dimethyl FormamideDMS Dimethyl SulfateEAA Ethylene Acrylic AcidEHL Enzymatic Hydrolysis LigninEVOH Ethylene-Vinyl Alcohol

HDPE High-density PolyethyleneIL Ionic Liquid LigninsKH550 AminopropyltriethoxysilaneKL Kraft LigninLDPE Low-density PolyethyleneLS LignosulphonatesMDI Methylene Diphenyl DiisocyanateMAH Maleic AnhydrideMSL Methanol Soluble LigninOL Organosolv LigninPBAT Poly(Butylene Adipate-co-

Terephthalate)PBA Poly(butylene adipate)PBT Poly(butylene terephthalate)PEO Poly(ethylene oxide)PE PolyethylenePEG Poly(Ethylene Glycol)PE-b-PEG Polyethylene-block-Poly(ethylene

glycol)PET Poly(ethylene terephthalate)PHB Poly-3-hydroxybutyratePLA Poly(lactic acid)PP PolypropylenePTMG Poly(Trimethylene Glutarate)PVA Poly(vinyl alcohol)SF Soy FlourSL Soda LigninSHL Star-like Hydroxypropyl LigninSPC Soyprotein ConcentrateSPI Soyprotein IsolatesTPS Thermoplastic StarchTBBP-A Tetrabromobisphenol ATBDMSCL Tert-butyldimethylsilyl ChlorideTg Glass Transition Temperature

Glossary

Lignin An abundant biopolymer with a high car-bon content and high aromaticity.

Thermoplastic Materials Become pliable ormoldable above a specific temperature andsolidifies upon cooling.

# Springer Science+Business Media, LLC, part of Springer Nature 2018R. A. Meyers (ed.), Encyclopedia of Sustainability Science and Technology,https://doi.org/10.1007/978-1-4939-2493-6_1015-1

1

http://crossmark.crossref.org/dialog/?doi=10.1007/978-1-4939-2493-6_1015-1&domain=pdf

https://doi.org/10.1007/978-1-4939-2493-6_1015-1

Biodegradability The disintegration of mate-rials by bacteria, fungi, or other biologicalmeans.

Definition of the Subject

Lignin is an abundant and inexpensive naturalpolymer with high thermal stability, stiffness, bio-degradability, antioxidant capacity, and ultravioletradiation absorption properties; thus, it can beused in wide range of applications. However,approaches to bring about the value-added utili-zation of lignin have been extensively sought fordecades. Recently, the development of lignin-based thermoplastic has attracted the attention ofresearchers worldwide. With the present develop-ment of lignin-based thermoplastics in mind, thisreview mainly focuses on three aspects of thetechnical issues associated with lignin-based ther-moplastics and their prospective applications,namely, the modification of lignin for fabricatinglignin-based thermoplastics, the theoretical basisfor blends with high lignin contents, and themethods for realizing efficiently biodegradablelignin-based thermoplastics. To conclude, we dis-cuss the potential for further advancement of thepromising lignin-based materials.

Graphic

See Fig. 1.

Introduction

Lignin is the most abundant aromatic substance innature and the largest contributor to soil organicmatter [1]. About 50 million tons of technicallignins are generated annually as the by-productsof lignocellulosic biorefineries as well as pulpingand papermaking processes [2]. Lignin is a set ofcomplex amorphous aromatic polymers. In thevascular plant cell wall, it functions as a fillingand bonding material that cross-links celluloseand hemicellulose, and also reduces the bacterialdegradation of wood. In addition, lignin also plays

a role in the transport ofwater and nutrients throughcell walls and fibers in the plants’ vascular tissue.The basic framework of lignin is mostly formed ofphenylpropanoid (C6–C3) units with different aro-matic nuclei. Depending on the number and loca-tion of phenolic hydroxyl groups and methoxygroups, there are three types of phenylpropanoidunits, namely, p-hydroxyphenyl (H), guaiacyl (G),and syringyl (S) [3–5]. Generally, the lignin ofgrasses and other monocots consists of a mixtureof H, G, and S units; softwood lignin essentiallyconsists of G units (more than 95%)with low levelsof H units; hardwood lignin is mainly composed ofG and S units and a small amount of H units [6–8].

With the increase in petroleum consumption andthe deterioration of the human living environment,the worldwide need for sustainable alternatives topetroleum-based materials has become urgent. Lig-nin, as the second most abundant biopolymer witha high carbon content and rich aromatic structureon earth, is promising to become a matrix forrenewable materials [3]. Apart from its abundantand inexpensive supply, lignin also has manyattractive properties, such as high thermal stability,resistance to oxidation, biodegradability, ultravioletradiation absorption, and antibacterial, antimicro-bial, and antifungal activities [9–11]. Despite itspotential to serve as a raw material for the chemicalindustries, various difficulties have been encoun-tered when blending lignin with other polymers.Hitherto, the utilization of lignin is inefficient com-pared to other lignocellulosic biopolymers [3]. Atpresent, technical lignin canbeutilized as: (1) onsitecheap fuel to provide power for pulping and papermaking plants [12]; (2) the starting raw material toproduce high-value chemicals [13]; and (3) a pre-cursor or direct functional material, especiallylignin-based thermoplastic. Consequently, most oftechnical lignin is utilized to supply heat, and only avery small part is used in the production of value-added products.

Although converting lignin into value-addedchemicals is one way to unleash its potential, theutilization of lignin on a large scale can hardly beachieved through this approach. In addition, lig-nin depolymerization chemistry must not onlyaccomplish the cleavage of lignin linkages mim-icked by model compounds, but also address the

2 Application of Lignin in Thermoplastic Materials

unique challenge of preventing lignin from self-condensation [14]. Alternatively, the direct utili-zation of lignin as a functional material (especiallylignin-based thermoplastics) could represent apromising approach to promote broader applica-tions of lignin.

Lignin, which possesses attractive thermalproperties, can be used in thermosetting materialsas well as thermoplastics. On the one hand, atelevated temperatures, lignin was found toundergo radical self-initiated polymerization

leading to a dramatic increase in its molecularweight and considerable modifications in itsmolecular characteristics with the concomitantformation of irreversible cross-linking. It can bedefined as a thermosetting material [15, 16]. Onthe other hand, due to the intra- and inter-molecular hydrogen bonds and arbitrary arrange-ment in molecular structure, lignin does not have asharp melting point and thus can be defined as anamorphous polymer [17]. However, lignin con-tains a large number of aromatic ring structures,

Technical Lignin(KL, LS, SL, OL ...)

Purification andRefining

Modification( Methylation,Propoxylation,Esterification ,

Acetylation ...)

Petroleum-based Plastics(PP, PE, PS ...)

Biodegradable Plastics(PLA, PBAT, PHA ...)

Biomass Materials(SPI, Starch ...)

Coupling Agent(KH550 ...)

Plasticizer (MAH ...)Chain Extender

Blend or Crosslinking

Lignin-basedThermoplastics

Application of Lignin inThermoplastic Materials,Fig. 1 Schematicillustration of preparationfor the lignin-basedthermoplastics

Application of Lignin in Thermoplastic Materials 3

so lignin-based materials are usually brittle andexhibit poor flow behaviors [18]. Accordingly,improvements of the flow property and thermalstability are required for converting lignin intouseful thermoplastic materials.

Classification of Lignin Based on theExtraction Procedure

At present, technical lignins are utilized in somehigh-value products, such as carbon fibers, acti-vated carbon, binders and resins, some lowmolec-ular weight chemicals [20]. However, they vary inmolecular weight, structure, and chemical reactiv-ity. In fact, their physical and chemical propertiesare highly dependent on the biomass pretreatmentand subsequent lignin extraction procedure.Accordingly, each technical lignin type should tobe discussed separately.

KL is mainly obtained from the black liquorproduced by Kraft cooking, and the annual pro-duction of KL is up to 4.5 million ton[19, 20]. During Kraft cooking, the hydroxideand hydrosulfide anions react with lignin macro-molecules to cleave a-O-4 and b-O-4 linkages andrelease small lignin fragments into the alkalinesolution [21]. The number of phenolic hydroxylgroups increases due to the breakage of b-arylbonds, which in turn increases the chemical reac-tivities of the resulting KL [22]. Although KLaccounts for 85% of total technical lignins in theworld, only 1–2% of them are used in high valueproducts [23]. LS, by-products of sulfite pulping,are water-soluble anionic polyelectrolytes[24]. During the pulping process, the a-O-4 link-ages in the lignin chains are cleaved and the Ca

and/or Cg positions of the side chains of the C9units are sulfonated with HSO3

�and SO32�

groups [25]. LS possess unique colloidal propertydue to the presence of various functional groups,such as phenolic hydroxyl groups, carboxylicgroups, and sulfur-containing groups. Thus, LSare widely applied in engineering materials, suchas cement additives, glues, particleboards, surfac-tants [20]. SL is a byproduct in the process of sodaor soda-anthraquinone pulping which has recentlyreceived increasing attention [3]. Compared with

LS and KL, SL contains more phenolic hydroxylunits and carboxyl groups and has better biocom-patibility and lower biotoxicity. SL is structurallyclose to natural lignin due to the sulfur-freemedium in the cooking liquor [26]. OL obtainedfrom the organosolv pulping process can be suc-cessively fractionated by using organic solventswith increasing dissolution capacity (i.e., ether,ethyl acetate, methanol, acetone, and dioxane/water) [27]. Compared with other technical lig-nins, OL has lower molecular weights, narrowerpolydispersity index, and it is hardly soluble inwater [28]. EHL is mainly generated from thefermentation process in bioethanol production,and most of the EHL is burned as a fuel forinternal energy consumption [29]. Comparedwith other lignin, EHL has higher activity andabsorbability, which makes it feasible to be usedas an adsorbent. IL can be obtained by fractionat-ing lignocellulosic biomass with ionic liquid. ILhas low molecular weight, high purity, and vari-ous functional groups [30]. However, ionic liq-uids have limitations as reaction media. They maypresent challenges for the separation of reactionproducts, and their expense necessitates highlyefficient solvent recycling [14].

The lignin extracted by different methods pos-sesses different compositions and characteristics.The major chemical properties of various techni-cal lignins are listed in Table 1.

Technical lignins contain various impurities,such as carbohydrates, ash, proteins, and othercompounds. All of them will impact the subse-quent modification process of the lignin and causethe formation of undesirable by-products, thusreducing the yield and deteriorating the perfor-mance of the final products. Additionally, techni-cal lignins are a mixture of lignin species withdifferent molecular weights and structural features[22]. Additionally, technical lignins are a mixtureof lignin species with different molecular weightsand structural features [31]. Ultrafiltration andprecipitation are used for the separation of alde-hydes and residual sulfur [23, 32]. Most of theions are removed by pickling, but there is stillabout 1–3% sulfur in the KL. Sulfur compoundscan poison the catalysts used in chemical conver-sion processes and cause a peculiar smell in the


Applicationof

Lignin

inTh

ermop

lasticMaterials,T

able

1Chemicalcompo

sitio

nof

technicallignins

Param

eter

Ash

(%)

Carbo

hydrates

(%)

S(%

)Mw(D

a)PDI(M

w/

Mn)

Tg(�C)

Water

solubility

Characteristic

References

KL

0.5–1.3

1.0–

2.3

1.25

–1.68

1,50

0–5,00

02.01–3

.512

4–17

4Solub

le(atroo

mtemperature)

Highim

purity

content

[1,22,12

9,13

0,13

1,13

2]

SL

0.7–2.3

1.5–

3.0

2.34

–2.86

1,30

0–5,30

01.12–2

.01

130–

155

Solub

lein

alkalin

esolutio

nHighpu

rity,low

toxicity

HL

1.0–3.0

10.0–2

2.4

–1,30

0–10

,000

4.0–11.0

93–1

39Insoluble

Hyg

roscop

ic,h

igh

reactiv

ity

OL

0.21

–1.7

1.16

–3.3

–50

0–5,00

01.5–2.56

91–9

7Insoluble

Higherchem

ical

purity

LS

4.0–9.3

ND

5.85

1,00

0–5,00

04.2–7.0

327–

138

Solub

leColloidalprop

erties

Thistableismod

ified

accordingto

VishtalandKraslaw

ski[20

]


heat treatment [33]. Currently, the desulfurizationof lignin is still a thorny problem, the use of Raneynickel reduction can effectively remove the sulfurcomponents, but it is expensive for industrialapplication [34].

The Methods to Improve theCompatibilization Between Lignin andPolymer

The trend of the utilization of lignin is to take fulladvantage of its chemical properties. Lignin is aclass of complex amorphous polymers with aro-matic chemical structure, and it is biodegradableby various microorganisms [35]. Directly usinglignin as a precursor or raw material for functionalproducts represents a broad theoretical prospect.One of the approaches to improve the ultimateperformance of the lignin-based thermoplastic isto blend lignin with synthetic polymers. Theexcellent properties of one polymer can compen-sate for the weakness of another polymer[36]. However, lignin contains a variety of poten-tial polymerization sites (abundant phenolic andaliphatic hydroxyl groups, and reactive benzyliccarbon), and when the temperature rises above theglass transition temperature (Tg), irreversiblecross-linking reactions occur on these sites,which make the lignin-based materials rigid withpoor malleability [37]. In addition, it is difficult toblend lignin with other polymers due to theirdifferent polarities. Lignin displays polarity as aresult of its strong intra-molecular and inter-molecular hydrogen bonds. Accordingly, the keyto preparing lignin-based thermoplastics is toimprove the miscibility of lignin with other poly-meric materials. At present, there are three majorapproaches to enhance the miscibility: (1) chemi-cally modifying lignin to reduce its polarity,(2) graft copolymerization of lignin with otherpolymers, and (3) addition of compatibilizers toimprove interfacial compatibility.

Also, due to the presence of multifunctionalgroups (e.g., aromatic and aliphatic hydroxyl,methoxyl, and carbonyl groups), lignin is suitablefor alkylation, alkoxylation, esterification, acety-lation, ammoniation, epoxidation, etc. [38–40].

Modification of Lignin

MethylationLignin contains a large amount of phenolichydroxyl groups that can be substituted by alkoxygroups through nucleophilic aromatic substitutionreactions (SNAr). Full methylation of the phenolichydroxyl groups facilitates the elimination of theintra-molecular hydrogen bonding, significantlyimproves the thermal stability, and remarkablydecreases the Tg [13, 41]. Common methylationreagents include: DMS, diazomethane, methyliodide, but apart from DMS, the other two areineffective and nonselective methylation reagentsfor lignin. Under mild alkaline conditions, DMScan selectively mask the phenolic hydroxylgroups on lignin macromolecules. The resultingphenyl methyl ether groups are less reactive, andthey contribute to avoid the formation of phenoxyradicals at high temperatures [41, 42]. However,DMS is known to be biologically toxic, andimproper use of DMS will be hazardous to healthand cause serious environmental pollution [43].

Recently, an environmentally friendly alterna-tive methylation method for lignin was reportedby Argyropoulos et al. [44]. Lignin was progres-sively methylated to different extents with DMCin the presence of sodium hydroxide or cesiumcarbonate as the base. In turn, carbon dioxide andmethanol released as the by-products of the meth-ylation process were recycled for the synthesis ofDMC [44, 45]. The main disadvantage of usingDMC as a methylating reagent is its variablechemical reactivity which depends on the reactiontemperature. Above 120 �C, DMC can act as amethylating reagent through a base-mediatedbimolecular alkyl cleavage nucleophilic substitu-tion mechanism (Scheme 1a). At lower tempera-ture (ca. 90 �C), DMC can serve as acarboxymethylating reagent through a base-mediated bimolecular acyl cleavage nucleophilicsubstitution mechanism (Scheme 1b) [45, 46].

PropoxylationPropoxylation is a common modification methodto prepare engineering thermoplastics and poly-urethane foams [47]. Oxypropylated lignins withimproved solubility and uniformity are prepared


by reacting lignin with propylene oxide at ele-vated temperature in an alkaline environment[48]. Through an anionic ring-opening polymeri-zation mechanism, the phenolic hydroxyl groupsof lignin are extended with poly(propylene gly-col) chains, which determine the molecularweight, Tg, and functionality of the final ligninderivatives [49].

SilylationSilylated lignins are synthesized by the reaction oflignin with tert-butyldimethylsilyl chloride(TBDMSCl), as shown in Scheme 2a [50]. Thereaction proceeds via a reactive N-tert-butyldimethylsilylimidazole intermediate, priorto the nucleophilic attack to the silicon atom bythe alcoholic hydroxyl group [51]. In addition, thesolvent DMF may act as a catalyst for the reactionby forming the least stable intermediate (silylatedDMF) [52]. After silation, the derivatized ligninsare soluble in a wide range of organic solvents,including solvents with low polarity and clearhydrophobic character with a contact angle withwater higher than 100� [50].

Esterification and AcetylationEsterification is a potential route to reduce the Tg

of lignin and increase its thermoplasticity [49]. Asearly as 1943, the first article about the modifica-tion of lignin with fatty acids was published by

Lewis et al., and it revealed that lignin-ester deriv-atives gain new and very interesting propertieslike changes in solubility and thermal behaviors[53]. Later, Glasser et al. found that Tg decreaseswith the increase of the degree of esterification[54]. Recently, lignin-ester derivatives are usuallyprepared by reacting lignin with acid anhydride(Either acetic, propionic, or butyric acid anhy-dride) using 1-methylimidazole as the catalyst,as shown in Scheme 3 [55, 56]. Acetylation isthe most fundamental esterification method. Acet-ylated lignin is obtained by reacting lignin withacetic anhydride in the presence of pyridine, asshown in Scheme 2b, and it has better thermalstability and lower Tg than the original lignin[57]. In addition, the acetylated lignin alsoexhibits photostabilization during light irradia-tion, which is attributed to the acetylation of phen-oxy and aliphatic hydroxyl groups in lignin[58]. When the lignin is modified by acetylationor other esterification methods, the hydroxylgroups are replaced by ester substituents. Withthe decrease in the number of hydrogen bonds,the free volume continues increasing and contrib-utes to greater chain mobility [59]. Moreover, byfully eliminating the hydrogen bonds from withinthe structure of lignin, the thermal stability of thederivatized lignin sample is dramaticallyenhanced, whereas its Tg and molecular polarityare reduced [41, 60, 61].

Application of Lignin in Thermoplastic Materials,Scheme 1 The reaction mechanism of DMC.Representing DMC as (a) a methylating reagent via abase-mediated bimolecular alkyl cleavage nucleophilic

substitution mechanism (BAL2) mechanism and as (b) acarboxymethylating reagent via a base-mediated bimolec-ular acyl cleavage nucleophilic substitution (BAC2) mech-anism. (From Argyropoulos et al. [44])


The OthersBesides the above modification methods, graftcopolymerization of lignin with polymers isanother common modification method to formstable covalent bonds between lignin and poly-mers. After activation, the hydroxyl functionalgroups in lignin form seeding sites for the subse-quent graft copolymerization using lignin macro-molecules as initiators. The graft copolymer isusually composed of lignin as the backbonechain and one or more types of polymers as the

branches linking to the backbone by covalentbonding [62]. The properties of the graft copoly-mer depend on the graft groups, the graft length,and the graft density [63]. There are three kinds ofgraft copolymerization for lignin: graft-from,graft-onto, and graft through. In graft-from: thegraft polymer grows from the active site of themain chain polymer, as shown in Scheme 4a. Ingraft-onto: the terminal groups of the grafted poly-mers are covalently linked with the active sites onthe lignin backbone, as shown in Scheme 4b. In

Application of Lignin in Thermoplastic Materials, Scheme 2 The reaction of silylation (a) and acetylation (b).(From Buono et al. [50])

Application of Lignin in Thermoplastic Materials,Scheme 3 Reaction mechanism for lignin esterificationusing 1-methylimidazole as a catalyst. R= –CH3 for acetic

anhydride, –CH2CH3 for propionic anhydride, and–CH2CH2CH3 for butyric anhydride. (From Mousaviounet al. [55])


graft-through: the small molecules are regularlypolymerized to form macromonomer, and in theprocess the lignin backbone is “sewn up” throughthe end of the branched polymer [64].

The economic and effective modification oflignin is the premise for their efficient utilization.However, due to their heterogeneous structure,and poor accessibility to aromatic ortho and parareactive sites, lignin usually exhibits restrictedreactivity during chemical modifications [40]. Inorder to improve its reactivity, lignin is oftenpretreated to modify the structure and increasethe amount of specific functional groups. Thereare three main ways to improve the reactivity oflignin. The first one is to reduce the molecularweight of lignin by depolymerization and othermethods and to separate lignin fragments based onspecific molecular weights and structures.Depolymerizing lignin into oligomers or mono-mers increases the amount of specific functionalgroups. After depolymerization of lignin, theaccessibility of the reactive site is improved,while the reactivities of ortho and para sitesremain unchanged [65]. The second method is tointroduce reactive sites into lignin molecules byphenolation [66]. For instance, adding naphtol-2during the separation of lignin enhances the

reactivities of lignin, decreases the molecularweight of lignin fragments, and prevents conden-sation reactions [67]. The third method to improvethe reactivity of lignin adopts enzyme treatment orgene modification [68–70].

The Modification of Polymers and theAddition of AdditivesLignin is miscible with other polymers that areable to provide sufficient intermolecular interac-tions with lignin macromolecules to lower theenthalpy of mixing to sufficiently negative valueto overcome the opposing entropic contributions[71]. Thus, the compatibility between the twophases depends on the occurrence of exothermicreactions [72]. The compatibility of the differentcomponents in the blends can be distinguished bythe glass transition pattern. If the different com-ponents are completely miscible, the polymershows only one Tg that depends on the Tg ofeach component of the blend, the weight fractionof the individual component in the blend, and thethermodynamics of the intermolecular interac-tions between them [3, 73]. Kubo and Kadla pro-duced miscible plastics in the lignin blendscontaining PEO and PET, whereas the PVA wasimmiscible with lignin [72]. The compatibility of

: Lignin core

: Lignin coreLignin

Lignin

Lignin

Lignin Lignin

Lignin

a

a

: active sites : grafted monomer

: grafted monomer: modified end group

Graft onto

Graft from

b

aApplication of Lignin inThermoplastic Materials,Scheme 4 (a) Graft-fromand (b) graft-onto methodsfor the synthesis of lignin-based copolymers (In thefigures, structure of lignin issimplified to a circle. Notethat real lignin is notspherical). (From Liu andChung [64])


the lignin-PEO blends is based on the hydrogenbonding formed between the hydroxyl hydrogenin lignin and the ether oxygen in PEO [74]. In thelignin-PVA blends, strong hydrogen bonds areformed between the hydroxyl groups of theshort-chain PVA and hardwood KL [75].

Chen et al. blended alkylated lignin with PP toprepare composites and added bromododecane toimprove the compatibility between lignin andPP. They found that alkylated lignin plays animportant role in enhancing flame retardancy andtoughening of the composites [76]. Moreover, thecomposite still maintained certain physical prop-erties of PP, even if the amount of alkylated ligninadded reached to 70%. Kharade et al. reported thatwhen 30%w/w lignin is blended with polyolefins,such as LDPE, HDPE, PP, the impact properties ofthe resultant composites were almost unaffected[77]. In addition, the mechanical properties of thecomposites were significantly improved whenusing EAA or titanate coupling agent. In order toimprove the moldability without affecting the bio-degradability of lignin-PP composites, Ignazioet al. added maleic anhydride-grafted PP as aplasticizer into the blending process [78].

Different hydrophobic molecules, includingCTMAB, PEO, PE-b-PEG, DDSA, and AKD,were investigated to design the hydrophobicity oflignin with the objective of improving the adhesionand compatibility in polymer blends composed ofpolar lignin particles and, for example, nonpolar PP[79–81]. Among all of the investigated approaches,Atifi et al. found that AKD was proved to be thesimplest and most effective for significantlyincreasing the contact angle of lignin while pre-serving the original micrometer size of wet-milled,spray-dried lignin particles. After this treatment,the stiffness of the lignin-PP composite was signif-icantly higher, and the young’s modulus increasedby about 15% (Fig. 2) [79]. That was believed toprincipally ionically adsorb to the anionicallycharged lignin, and the melt AKDs moleculesmay have come into contact with either thehydroxyl groups or moisture trapped in the ligninpowder and then reacted under heat generated byspray drying or during coextrusion with PP to formeither the b-ketoester bond with lignin or a hydro-lyzed ketone. It is well known that the mechanical

properties of the composite mainly depend on threefactors: the size of fillers, the filler-matrix interfa-cial adhesion, and filler loading. For instance, thespray-dried lignin demonstrated a more uniformdistribution in the polymer melts than the dryinglignin in the oven, resulting in a significant increasein the strain or flexibility of the lignin-PP polymerblends [82]. The other relationships of these factorsto the mechanical properties of composites havebeen thoroughly reviewed elsewhere [83].

Through blending lignin with other syntheticpolymers, various functions will be entrusted tothe obtained thermoplastics. Hasan et al. reportedthe blending of softwood KL fractions with PEand examined the contributions of the phenolic-OH stabilization to the antioxidant mechanism[84]. They showed that the phenolic hydroxylgroups play an important role in endowing anti-oxidant properties to lignin. Later, the differencein the thermal stability of PE in blends was foundwhen adding fractionated and unfractionated lig-nin. In the blends, low molecular weight methyl-ated lignin plays a role of plasticizer, possibly dueto its low molecular weight and spherical struc-ture. The high molecular weight lignin enhancesthe stability of the blends, which may be thecontributed by its rigidity and high Tg (due to pstacking operating among its aromatic rings)[85]. Blends formed by the mixing of these twocomponents have a propensity to undergo exten-sive thermal cross-linking. Podolyák et al. pre-pared blends using lignin and EVOHcopolymers to study the effect of hydrogen bond-ing interactions on compatibility and structure[86]. They found that strong hydrogen bondsform between the two components, as shown byFTIR spectroscopy analysis, and the crystallitesize and crystallinity decrease with the increaseof the lignin content (Fig. 3). The size of dispersedlignin particles is determined by competitiveinteractions in the blends; thus, stronger EVOH/lignin interactions result in smaller particle size(Fig. 4). Therefore, the preparation of misciblepolymer/lignin blends must be performed usingother approaches, such as plasticization or chem-ical modification, even if the two components arecapable of forming strong hydrogen bonds witheach other.


Lignin-based Thermoplastics

Application of lignin in thermoplastics is one ofthe most important research topics in the domainof biomass materials. It is also an active researchfield that has attracted many researchers all along.In1975, Falkehag et al. established that the suc-cessful development of useful lignin-based plas-tics and related materials must be based on “theunderstanding of lignin as a reasonable scientificbasis for macromolecules” and “sound scientifi-cally based understanding of lignin as a macro-molecule and its potential roles in materialsystems is most desirable as a platform for appliedstudies” [87]. Later, other studies found that thedegree of softening of the rigid structure of lignindetermined the usage of lignin, and the hard seg-ment of lignin can be used to prepare high modu-lus and high strength materials by cross-linking orstrengthening the soft segments (thermoplastics)[71]. Indeed, the development of lignin-basedthermoplastics mainly depends on altering theviscoelasticity of lignin by chemical modification

or blending with other polymers [71]. This chap-ter mainly introduces lignin-based thermoplasticsfrom two aspects: lignin-based thermoplastics andefficiently biodegradable lignin-based thermo-plastic material.

High Lignin Content Lignin-basedThermoplasticsThe development of lignin-based thermoplasticswith high lignin content has become an attractionin the area of lignin utilization. Currently, lignin ismostly used as a performance-modifying additiveor filler for lignin-based thermoplastics. Such apractice has limited the incorporation level oflignin to less than 40%. Once this threshold isexceeded, the materials become brittle and fragile,regardless of whether lignin is covalently or non-covalently incorporated into the polymeric mate-rials. Accordingly, to achieve large-scaleapplication of thermoplastic materials with highlignin content (> 70%), the inherent thinkingmust be fundamentally novel. As stated earlierby Falkehag et al., “in the attempted uses of lignin

Application of Lignin in Thermoplastic Materials, Fig. 2 Effect of lignin treatment on the mechanical properties ofthe lignin-PP composite blends. (From Atifi et al. [79])


to meet polymer or materials needs, one shouldnot just try to ‘replace’ a synthetic component, butto take new innovative approaches where theuniqueness of lignin as a macromolecule shouldbe exploited” [87].

In the 1990s, Sunil et al. found that non-covalent interactions between the individualmolecular components of KL control distinctassociative processes in various solution condi-tions, which are characterized by a remarkabledegree of specificity [86]. The special associationbehavior between these lignin macromoleculeshas a significant effect on the mechanical proper-ties of the lignin-based polymer materials, and itmay arise from nonbonded orbital interactions[88]. Later, Sarkanen et al. blended 85% KLwith 12.6% PVA to prepare lignin-based thermo-plastics, using 1.6% diethyleneglycol dibenzoateand 0.8% indene as plasticizers. They determinedthat the tensile properties of these newly preparedpolymeric materials were basically controlled bypromoting noncovalent interactions between theconstituent molecules. Moreover, their Young’smodulus was directly dependent on the degree ofassociation of lignin [89]. Considering the

physical properties, melt flow index and the highlignin content, these materials can be consideredthe first generation of lignin-based thermoplasticscontaining very high lignin content. However, themechanical properties of this material are still notoptimal, and in some conditions it may be par-tially dissolved in alkaline water, which deters theeconomic interests and limits its industrialization[89, 90]. Kadla et al. produced thermoplasticblends with underivatized KL and PEO andfound that a small amount of PEO (5–10% w/w)incorporation resulted in partial destruction oflignin supramolecular complexes, resulting inimproved physical properties [91]. However,with the increase of the amount of PEO, themechanical properties of the blends decayed,which may be caused by the increasing size ofthe lignin supramolecular complexes.

Sarkanen et al. also found that the tensile prop-erties of the polymeric materials prepared solelywith methylated or acetylated lignin were similarto polystyrene (Fig. 5), and although the materialswere very fragile, they could be plasticizedthrough forming miscible blends with aliphaticpolyesters [92, 93]. When the methylene/

Application of Lignin in Thermoplastic Materials,Fig. 3 The effect of lignin content on crystallite size andcrystallinity with increasing lignin content. (a) Shift in theposition of the absorbance of the hydroxyl groups in theregion of 3,420–3,450 cm�1. Possible effect of hydrogen

bonding interactions. (b) Changes of the size of dispersedlignin particles in EVOH68/lignin blends as a function oflignin content. Effect of thermodynamic and kinetic fac-tors. (From Podolyák et al. [86])


carboxylate group ratio (CH2/COO) is between2.5 and 3.0, the interaction between the ligninand the polyester chain is appropriate, and thelignin is effectively plasticized. Theintermolecular interactions between KL and ali-phatic polyester molecules should be powerfulenough to compete with those between KL com-ponents in the peripheral regions of the supra-macromolecular complexes, but not so strong asto significantly dismantle these huge associatedentities [92]. When the intermolecular interactionbetween the lignin component and polymer mol-ecule is strong, the complex tends to be

dismantled and a counterproductive increase inthe proportion of polymeric plasticizer is requiredto reach the plasticization threshold [94]. In addi-tion, since low molecular weight components inthe peripheral region of the supra-macromolecularKL complexes can selectively promote the inter-relationships between the different components,low molecular weight alkylated KL componentscan help enhance the plasticizing effect of thealiphatic polyesters [94]. For the polyester chainplasticization effect, there is a plasticizationthreshold, which is inscribed in the correspondingTg-composition curve of the lignin-based

Application of Lignin in Thermoplastic Materials, Fig. 4 The structure of polymer-lignin blends at 30 vol% lignincontent. Matrix polymer: (a) LDPE, (b) EVOH52, (c) EVOH 62, (d) EVOH 68, (e) EVOH76. (From Podolyák et al. [86])


thermoplastics [95]. When the plasticizing thresh-old is exceeded, the low molecular weightalkylated KL components have little effect onthe tensile strength, but their presence extendsthe degree of plastic deformation beforefracture [94].

Lignin-based thermoplastic materials are com-posed of thousands of individual componentsassembled from the ultra-high molecular com-plexes [94]. The integrity of lignin-based thermo-plastic materials depends preeminently on theassociated macromolecular complexes ratherthan individual macromolecular chains. Ligninmacromolecular complexes provide mechanicalsupport as the main body, while other polymersprovide circulation as a soft segment. The stabilityof the lignin complex is provided by the innerdomain that embodies co-facially offset configu-rations of interacting aromatic rings, while thehydrodynamic compactness of macromolecularlignin species arises from powerful noncovalentinteractions between lignin substructures. The

individual lignin components form supra-macromolecular complexes through noncovalentinteractions between the internal co-facial aro-matic rings that are preserved in plastics with thehighest attainable lignin contents [96]. The mutualpenetration of the peripheral components of thelignin macromolecular complex exhibits a highincidence of edge-on orientations between aro-matic rings, which makes it possible to establishcontinuity between adjacent complexes[97]. Through the preferential interactions withperipheral domains, miscible blend componentsmodulate strength and ductility in these quiteoriginal lignin-based plastics [98]. The nonligninmiscible blend components preferentially interactwith these peripheral components, which subse-quently affects the viscoelastic behavior of lignin-based polymer materials [93].

Furthermore, the properties of the materialsalso depend on the composition and casting con-ditions of the blend, as shown in Fig. 5. Aftercasting the solution at 150 �C, the tensile

Application of Lignin in Thermoplastic Materials,Fig. 5 The properties of the material also depend on thecomposition and casting conditions of the blend. (a) Castmaterials composed solely of BML (Mw 2,300 Da,Mw/Mn = 3.0) and methylated BML (MBML), and LSand methylated LS (sMLS). (b) Blends of BML with 5 wt

% TBBP-A, MBML with 5 wt% PEG(Mn = 400), and LSand sMLS both with 15 wt% PTMG. BML, LS, and theirmethylated derivatives were prepared as described previ-ously, but here LS is characterized by Mw = 7,100 Da,Mw/Mn = 3.8. (From Sarkanen et al. [93])


properties of the materials composed solely ofball-milled softwood lignin are comparable tothose of polystyrene [93]. When the solution iscast at 150 �C and then annealed at 180 �C, thetensile properties of the blends containing 85%w/w levels of methylated ball-milled softwoodlignin can surpass those of polystyrene [99].

Efficiently Biodegradable Lignin-basedThermoplastic MaterialThe development of efficiently biodegradablelignin-based thermoplastic materials has becomeanother focus of interest in the field. According tothe definition of the American Society for Testingand Materials (ASTM), biodegradable materialscan be efficiently degraded or decomposed bymicroorganisms through biochemical or physicaleffects under natural conditions and eventuallybecome an integral part of the natural carboncycle [100].

Blending lignin with biodegradable polymers(PLA, PBAT, PHB, etc.) or natural biomaterials,such as soy protein isolates (SPI) and starch, is anestablished method for efficiently preparing bio-degradable composite materials.

PLA is a linear, aliphatic polyester thermoplas-tic that is produced commercially by ring openingpolymerization of lactide (a cyclic dimer of lacticacid which can be derived from renewableresources) [101, 102]. The good melting process-ability, biodegradability, and biocompatibility ofPLA make it one of the most promising polymersto fully replace petroleum-based polymers. How-ever, PLA also has some defects, such as poor gas-barrier properties, low toughness, and flexibility,as well as poor thermal stability [103]. Some stud-ies have claimed that blending PLAwith lignin isa reasonable way to improve the mechanical prop-erties of PLA and reduce the costs.

Gordobil et al. blended a small amount ofacetylated lignin with PLA, and the thermal sta-bility of the obtained materials was remarkablyimproved. However, the addition of lignin was notbeneficial to the crystallization behavior of PLA,and the mechanical properties of the blendsdecreased significantly when the amount of ligninadded was more than 20% [57]. Wang et al. pre-pared environment-friendly/bio-based

composites of PLA and lignin by melting ablend in a twin-screw extruder and investigatedthe thermal, mechanical, and morphological prop-erties of PLA/lignin composites [104]. Theyfound hydrogen bonding interaction betweenPLA and lignin, but the impact strength of thecomposite materials was inadequate, which maybe attributed to the intrinsic brittleness of PLA andrigidity of lignin particles. In order to improve themechanical properties of lignin-PLA composites,Zhu et al. added the coupling agent(3-aminopropyl)triethoxysilane (KH550) and thecompatibilizer maleic anhydride (MAH) toenhance the interfacial connections [105]. Later,Wei et al. developed an aqueous method for thepreparation of the dodecylated lignin by selec-tively grafting dodecane to hydroxyl-OH andcarboxylic-OH of alkaline lignin. Lignin-g-PLAwas synthesized via grafting-onto approaches,and subsequently lignin-g-PLA and PLA wereinterwoven to prepare blends [106]. Comparedwith the initial PLA, the tensile strength of theblends increased 40-fold, and the Young’s modu-lus, UV resistance, and hydrophobicity gainedvarying degrees of improvement.

Like PLA, PBAT copolymerized by PBA andPBT is also one of the most promising biodegrad-able polymers. PBAT has good high temperaturetolerance, excellent processability, and hightoughness, due to the presence of a flexible ali-phatic chain and rigid aromatic bonds in the struc-ture. By blending PLA with PBAT, Nofar et al.prepared good biodegradable materials, whichovercame various drawbacks of PLA, such asthe brittleness and processability limitations[36]. However, PLA and PBAT are incompatible,and this limits the large-scale commercial use oftheir blends. Adding lignin as a filler is an effec-tive and economic way that not only reduces thecost, but also endows other properties to thePLA/PBAT blends. Chen et al. blended MSLwith PBAT and PLA to prepare composite mate-rials. The differential scanning calorimetry studyindicated that MSL played a key role in bridgingPLA and PBAT, and the blends retained the tough-ness at 30% w/w lignin content[107]. Abdelwahab et al. reported a method thatincorporated ADR as a chain extender to improve


the compatibility and storage modulus of thePLA-PBAT biocomposites containing 20% w/wof OL. ADR provided strong intermolecular inter-actions that bridge the OL with the two incompat-ible PLA–PBAT phases [108].

PHB is a biocompatible and biodegradablethermoplastic polymer, and it is accumulated bya wide variety of microorganisms as an intracel-lular storage source of organic carbon and chem-ical energy [109]. The biodegradability of PHBdepends on the molecular weight, processing con-ditions, and crystallinity [101]. Fabio et al. pre-pared biocomposites of PHB and acetylated ligninby casting from a chloroform solution [109]. Theirfindings revealed that, with the addition of lignin,the thermal resistance of the composites wasenhanced, and consequently the thermal degrada-tion temperature was increased, whereas the over-all crystallization rate and spherulite radial growthof the PHB were reduced.

Although blending lignin with biodegradablepolymers is an effective method to efficientlyproduce biodegradable composite materials, thecost factor limits the application of this method.Thus, researchers have turned their attention toblending lignin with natural biomaterials, suchas SPI and starch.

SPI is a class of inexpensive and abundantnatural biomaterials and one of the three com-monly used soybean proteins (SF, SPC, andSPI). Compared with the other two soybean pro-teins, SPI has higher protein content (SF containsabout 53% protein and 32% carbohydrate; SPCcontains about 72% protein; and SPIs contain atleast 90% protein). Thus, SPI has become a majorraw material for biodegradable soy protein[110]. SPI is a hybrid system composed of pro-teins of different structures and functions, and itsmajor component is soybean globulin. Unlike thepolysaccharide blends, unmodified SPI blendsshow desirable performance (good processability,mechanical properties, and biodegradability) withonly a small amount of small molecular weightplasticizers. Additionally, SPI has the potential tobe modified and then blended with lignin to pre-pare a range of excellent biodegradable biomate-rials, due to the presence of abundant activegroups in the side chains [111].

However, the structure of SPI has two defectsthat hinder its application in the preparation ofbiodegradable materials. On the one hand, SPIhas strong intramolecular and intermolecularinteractions (hydrogen bonds, dipolar interac-tions, ionic bonds, hydrophobic interactions, anddisulfide bonds) which make the compositesbased on SPI exhibit rigidity and brittleness[112]. On the other hand, many hydrophilicamino acid residues (–NH2, –COO, –CONH,etc.) are distributed around the main chain of theSPI molecule, and as a result, the final materialsshow water absorption macroscopically. However,the lack of sufficient moisture resistance leads topoor performance under high humidity or waterconditions. Accordingly, SPI should be modifiedin order to produce materials with better perfor-mance. In general, the physical modifications(heating, freezing, radiation, agitation, ultrasonictreatment, etc.) of SPI only change its advancedstructure and intermolecular aggregation withoutinvolving the primary structure of the protein[113–115]. Chemical modifications of SPI involveintroducing various functional groups into the pro-teins, resulting in protein molecular structural,physical, and chemical changes [116–118]. Enzy-matic modifications alter the functions and proper-ties of SPI by partially degrading the proteins, byincreasing the intramolecular or intermolecularcross-linking, or by connecting specific functionalgenes [119, 120].

Blending is a popular approach to achievefunctionalization of bio-based materials. The pro-cessability, mechanical properties, and hydropho-bicity of the materials are remarkably improvedafter blending the modified SPI with other degrad-able polymer materials. Huang et al. reported amethod for the preparation of integrated plasticsbased on SPI and LS. They found that the stronginteractions between LS and SPI can restrict theeffect of water on the swelling and the damage ofthe materials [121]. However, the poor compati-bility of lignin with SPI resulted in a certaindegree of microphase separation in the lignin-SPI blends. Therefore, MDI was used ascompatibilizer for the lignin/SPI blends. Whenthe amount of MDI was low, concentric pointsof stress were formed between the graft


copolymers and the domains of crosslinkingenrichment, thereby increasing the mechanicalproperties [122]. Later, a biodegradable plasticwas developed with better mechanical propertiesby compounding SHL with SPI. The compositemechanism of SHL and SPI is shown in Scheme 5.Lignin was hydroxylated to form SHL and subse-quently connected to the SPI matrix by stretchingactive hydroxyl groups. Moreover, the separationof the stretching branched chains on the SHLmolecules provided space for the SPI moleculesto penetrate the supra-molecular HL domains toform a structure similar to interpenetrating poly-mer networks [123].

Starch as a cheap, easily biodegradable, andenvironmentally friendly natural polymer hasbecome an important raw material and widelyused in many areas. Due to the similar polarity,lignin and starch are well compatible. It is easier toblend lignin with starch to prepare the efficientlybiodegradable lignin-based thermoplastics, com-pared to blending lignin with other natural bio-materials. However, some of the defects in thestarch structure may affect the performance ofthe final material, such as (A) brittleness in theabsence of suitable plasticizers, and starchbecomes soft with low toughness after plasticiz-ing, (B) hydrophilic and poor water resistance,(C) poor performance under high humidity orwet conditions [124]. Accordingly, nativestarches need to be modified and blended with

other polymers to improve the product properties,so as to extend their application range.

Spiridon et al. examined the effects of lignin onthe optical, thermomechanical properties of TPS.The lignin component in the modified starch com-posite enhanced the thermal stability anddecreased the water absorption in a high-humidityatmosphere [125]. With the addition of lignin, thetransparency of the films decreased [126]. Whenusing alkali lignin-formaldehyde and corn starchto prepare cross-linked film by solution pouring,Shi and Li found that the water absorption rate ofstarch/lignin film was 238.3%, which was1.3-fold higher than that of the corn starch film[127]. Perhaps it can be applied to agriculturecovers as a biodegradable, water absorbent mate-rial. Kaewtatip et al. added KL or EL to TPS as afunctional filler to produce TPS/KL or TPS/ELcomposites by compression molding. Theirresults showed that the tensile strength of theTPS-KL and TPS-EL composites was higherthan for the TPS alone by about 17 and 32%,respectively [128].

Future Directions

The demand for renewable substitutes of tradi-tional petroleum-based polymers has been a driv-ing force in the studies of biocomposites. Lignin,as the second most abundant biopolymer with a

hydroxyalkylation

SPI

III

III IV

aggregationaggregation

Supramolecular domainSupramolecular domain

Lignin

a b

cd

Application of Lignin inThermoplastic Materials,Scheme 5 The structuresof lignin (a) and itshydroxypropyl derivative(b); correspondingsupramolecular domains(C for lignin and D for HL)and the interaction with SPI(I: weak interaction; II:strong interaction; III: nointerpenetration; IV:interpenetration). (FromWei et al. [123])


high carbon content and rich aromatic ring struc-ture on earth, has potential to become a matrix forrenewable materials. However, the use of lignin inrenewable materials is limited due to its strongintermolecular interactions and complex reactiv-ities. At present, the primary challenges in achiev-ing the commercialization of lignin-based plasticsare: (1) the blends exhibit poor compatibilitywhen the lignin content is excessive, (2) with theincrease of lignin content, the mechanical proper-ties of the blends decrease sharply, and (3) the costof modifying or blendingwith other copolymers isexpensive.

The latest advancements in the development oflignin thermoplastic materials point to the follow-ing aspects: (1) improving the compatibility ofcomponents in the blend is an important strategyto increase the amount of added lignin, to furtherachieve its high value application, in the prereq-uisite of meeting the performance demand of theresulting products; (2) regarding the manufactureof lignin materials on a large scale, efforts are alsomade to optimize the technical conditions, anddecrease the costs; and (3) for the large-scalemanufacture of fully degradable lignin thermo-plastic materials, the biodegradability of ligninshould be efficiently exploited.

Bibliography

Primary Literature1. Smita R, Upendranath D (2008) Manipulation of

lignin in plants with special reference too-methyltransferase. Plant Sci 174(3):264–277

2. Gosselink RJA, Jong ED, Guran B, AbächerliA (2004) Co-ordination network for lignin –standardisation, production and applications adaptedto market requirements (eurolignin). Ind Crop Prod20(2):121–129

3. Sen S, Patil S, Argyropoulos DS (2016) Thermalproperties of lignin in copolymers, blends, and com-posites: a review. Green Chem 47(1):4862–4887

4. Buranov AU, Mazza G (2008) Lignin in straw ofherbaceous crops. Ind Crop Prod 28(3):237–259

5. Lochab B, Shukla S, Varma I (2014) Naturally occur-ring phenolic sources: monomers and polymers. RSCAdv 4(42):21712–21752

6. Sarkanen KV, Ludwig CH (1971) Lignins: occur-rence, formation, structure and reaction. Wiley-Interscience, New York

7. Sun R, Lawther JM, Banks WB (1997) A tentativechemical structure of wheat straw lignin. Ind CropProd 6(1):1–8

8. Buranov AU, Mazza G (2008) Lignin in straw ofherbaceous crops. Ind Crop Prod 28(3):237–259

9. Naseem A, Tabasum S, Zia KM, Zuber M, Ali M,Noreen A (2016) Lignin-derivatives based polymers,blends and composites: a review. Int J Biol Macromol93(Pt A):296–131

10. Ugartondo V, Mitjans M, Vinardell MP (2008) Com-parative antioxidant and cytotoxic effects of ligninsfrom different sources. Bioresour Technol99(14):6683–6687

11. Patschinski P, Zhang C, Zipse H (2014) The lewisbase-catalyzed silylation of alcohols–a mechanisticanalysis. J Org Chem 79(17):8348–8357

12. Mohan D, Pittman CU Jr, Bricka M, Smith F,Yancey B, Mohammad J (2007) Sorption of arsenic,cadmium, and lead by chars produced from fastpyrolysis of wood and bark during bio-oil produc-tion. J Colloid Interface Sci 310(1):57–73

13. Funakoshi H, Shiraish N, Norimoto M, Aoki T,Hayashi H (1979) Studies on the thermo-plasticization of wood. Holzforschung33(5):159–166

14. Binder JB, Gray MJ, White JF, Zhang ZC, HolladayJE (2009) Reactions of lignin model compounds inionic liquids. Biomass Bioenergy 33(9):1122–1130

15. Jeong H, Park J, Kim S, Lee J, Ahn N, Roh HG(2013) Preparation and characterization of thermo-plastic polyurethanes using partially acetylated Kraftlignin. Fibers Polym 14(7):1082–1093

16. Sadeghifar H, Cui C, Argyropoulos DS(2012) Toward thermoplastic lignin polymers. Part1. selective masking of phenolic hydroxyl groups inKraft lignins via methylation and oxypropylationchemistries. Ind Eng Chem Res51(51):16713–16720

17. Pouteau C, Dole P, Cathala B, Averous L, BoquillonN (2003) Antioxidant properties of lignin in polypro-pylene. Polym Degrad Stab 81(1):9–18

18. Kubo S, Kadla JF (2005) Hydrogen bonding in lig-nin: a fourier transform infrared model compoundstudy. Biomacromolecules 6(5):2815–2221

19. Tejado A, Peña C, Labidi J, Echeverria JM,Mondragon I (2007) Physico-chemical characteriza-tion of lignins from different sources for use inphenol-formaldehyde resin synthesis. BioresourTechnol 98(8):1655–1663

20. Vishtal A, Kraslawski A (2011) Challenges in indus-trial applications of technical lignins. Bioresources6(3):3547–3568

21. Chakar FS, Ragauskas AJ, Abaecherli A, Guran B,Gosselink RJ, Jong DD (2004) Review of current andfuture softwood Kraft lignin process chemistry. IndCrop Prod 20(2):131–141

22. Vishtal A, Kraslawski A (2011) Challenges in indus-trial applications of technical lignins. Bioresources6(3):3547–3568


23. Fang W, Alekhina M, Ershova O, Heikkinen S, SixtaH (2015) Purification and characterization of Kraftlignin. J Mol Biol 367(4):1023–1033

24. Fan J, Zhan HY (2008) Optimization of synthesis ofspherical lignosulphonate resin and its structure char-acterization. Chin J Chem Eng 16(3):407–410

25. Myrvold BO (2008) A new model for the structure oflignosulphonates: part 1. Behaviour in dilute solu-tions. Ind Crop Prod 27(2):214–219

26. Wörmeyer K, Ingram T, Saake B, Brunner G,Smirnova I (2011) Comparison of different pre-treatment methods for lignocellulosic materials. partii: influence of pretreatment on the properties of ryestraw lignin. Bioresour Technol 102(5):4157–4164

27. Li MF, Sun SN, Xu F, Sun RC (2012) Sequentialsolvent fractionation of heterogeneous bambooorganosolv lignin for value-added application. SepPurif Technol 101(16):18–25

28. Lora JH, Glasser WG (2002) Recent industrial appli-cations of lignin: a sustainable alternative to non-renewable materials. J Polym Environ10(1–2):39–48

29. Suhas, Carrott PJ, RibeiroCarrottMM(2007) Lignin-from natural adsorbent to activated carbon: a review.Bioresour Technol 98(12):2301–2312

30. Muhammad N, Man Z, Mohamad Azmi BK(2012) Ionic liquid- a future solvent for the enhanceduses of wood biomass. Eur J Wood Wood Prod70(1–3):125–133

31. Mandavgane SA, Paradkar GD, Varu J, Pamar R,Subramanian D (2007) Desilication of agro basedblack liquor and green liquor using jet loop reactor.Indian J Chem Technol 14(6):606–610

32. Tafti SF, Tabarsi P, Mansouri N, Mirsaeidi M,Motazedi Ghajar MA, Karimi S (2006) Chronic gran-ulomatous disease with unusual clinical manifesta-tion, outcome, and pattern of inheritance in an iranianfamily. J Clin Immunol 26(3):291–296

33. Öhman F (2006) Precipitation and separation of lig-nin from Kraft Black Liquor. PhD thesis, ChalmersUniversity of Technology, Gothenburg

34. Meryemoglu B, Hesenov A, Irmak S, Atanur OM,Erbatur O (2010) Aqueous-phase reforming of bio-mass using various types of supported precious metaland raney-nickel catalysts for hydrogen production.Int J Hydrogen Energy 35(22):12580–12587

35. Calvo-Flores FG, Dobado JA (2010) Lignin asrenewable raw material. ChemSusChem3(11):1227–1235

36. Nofar M, Heuzey MC, Carreau PJ, Kamal MR,Randall J (2016) Coalescence in pla-pbat blendsunder shear flow: effects of blend preparation andpla molecular weight. J Rheol 60(4):637–648

37. Argyropoulos DS (2014) The emerging bio-refineryindustry needs to refine lignin prior to use.J Biotechnol 4(1):125–126

38. Laurichesse S, Avérous L (2014) Chemical modifi-cation of lignins: towards biobased polymers. ProgPolym Sci 39(7):1266–1290

39. Gordobil O, Moriana R, Zhang L, Labidi J,Sevastyanova O (2016) Assesment of technical lig-nins for uses in biofuels and biomaterials: Structure-related properties, proximate analysis and chemicalmodification. Ind Crop Prod 83(45):155–165

40. Cui C, Sadeghifar H, Sen S, Argyropoulos DS(2013) Toward thermoplastic lignin polymers; partII: thermal & polymer characteristics of Kraft lignin& derivatives. Bioresources 8(1):864–886

41. Wiermans L, Schumacher H, Klaaen CM,Dominguezdemaria P (2014) Unprecedentedcatalyst-free lignin dearomatization with hydrogenperoxide and dimethyl carbonate. RSC Adv5(6):4009–4018

42. Sadeghifar H, Cui C, Argyropoulos DS(2012) Toward thermoplastic lignin polymers. part1. selective masking of phenolic hydroxyl groups inKraft lignins via methylation and oxypropylationchemistries. Ind Eng Chem Res51(51):16713–16720

43. Kumar P, Srivastava VC,Mishra IM (2015) Dimethylcarbonate synthesis via, transesterification of propyl-ene carbonate with methanol by ceria-zinc catalysts:role of catalyst support and reaction parameters.Korean J Chem Eng 32(9):1774–1783

44. Argyropoulos DS, Sen S, Patil S (2015) Methylationof softwood Kraft lignin with dimethyl carbonate.Green Chem 17(2):1077–1087

45. Stanley JNG, Selva M, Masters AF, Maschmeyer T,Perosa A (2013) Reactions of p-coumaryl alcoholmodel compounds with dimethyl carbonate. Towardsthe upgrading of lignin building blocks. Green Chem15(11):3195–3204

46. Memoli S, Selva M, Tundo P (2001)Dimethylcarbonate for eco-friendly methylationreactions. Chemosphere 43(1):115–121

47. Hofmann K, Glasser WG (1993) Engineering plas-tics from lignin. 21. Synthesis and properties ofepoxidized lignin-poly(propylene oxide) copoly-mers. J Wood Chem Technol 13(1):73–95

48. Ahvazi B, Wojciechowicz O, Tonthat TM, HawariJ (2011) Preparation of lignopolyols from wheatstraw soda lignin. J Agric Food Chem59(19):10505–10516

49. Hatakeyama H, Tsujimoto Y, Zarubin MJ, KrutovSM, Hatakeyama T (2010) Thermal decompositionand glass transition of industrial hydrolysis lignin.J Therm Anal Calorim 101(1):289–295

50. Buono P, Duval A, Verge P, Averous L, HabibiY (2016) New insights on the chemical modificationof lignin: acetylation versus silylation. ACS SustainChem Eng 4(10):5212–5222

51. Corey EJ, Shirahama H, Yamamoto H, Terashima S,Venkateswarlu A, Schaaf TK (1971) Stereospecifictotal synthesis of prostaglandins e3 and f3.alpha.J Am Chem Soc 93(6):1490–1491

52. Patschinski P, Zhang C, Zipse H (2014) The lewisbase-catalyzed silylation of alcohols – a mechanisticanalysis. J Org Chem 79(17):8348–8357


53. Lewis WK, Gilliland ER, Bauer WC (2002) Charac-teristics of fluidized particles. J Ind Eng Chem41(6):1104–1117

54. Glasser WG, Gratzl JS, Collins JJ, Forss K, MccarthyJL (2002) Lignin. xvii. preparation and characteriza-tion of acetyl lignin sulfonate methyl esters. Macro-molecules 8(5):565–573

55. Mousavioun P, Doherty W (2010) Chemical andthermal properties of fractionated bagase soda lignin.Ind Crop Prod 31(1):52–58

56. Fox SC, Mcdonald AG (2010) Chemical and thermalcharacterization of three industrial lignins and theircorresponding lignin esters. Bioresources 5(2):990–1009

57. Gordobil O, Egüés I, Llano-Ponte R, Labidi J (2014)Physicochemical properties of pla lignin blends.Polym Degrad Stab 108:330–338

58. Pu Y, Ragauskas AJ (2005) Structural analysis ofacetylated hardwood lignins and their photoyell.Can J Chem 83(12):2132–2139

59. Lisperguer J, Perez P, Urizar S (2009) Structure andthermal properties of lignins: characterization byinfrared spectroscopy and differential scanning calo-rimetry. J Chil Chem Soc 54(4):460–463

60. Monteil-Rivera F, Paquet L (2015) Solvent-freecatalyst-free microwave-assisted acylation of lignin.Ind Crop Prod 65:446–453

61. Cachet N, Camy S, Benjelloun-Mlayah B, CondoretJS, Delmas M (2014) Esterification of organosolvlignin under supercritical conditions. Ind Crop Prod58(58):287–297

62. Hadjichristidis N, Iatrou H, Pitsikalis M, MaysJ (2006) Macromolecular architectures by livingand controlled/living polymerizations. Prog PolymSci 31(12):1068–1132

63. Feng C, Li Y, Yang D, Hu J, Zhang X, HuangX (2011) Well-defined graft copolymers: from con-trolled synthesis to multipurpose applications. ChemSoc Rev 40(3):1282–1295

64. Liu H, Chung H (2017) Lignin-based polymers viagraft copolymerization. J Polym Sci A Polym Chem55:3515–3528

65. Wang DB, Li XM, Yang Q, Zeng GM, Liao DX,Zhang J (2008) Biological phosphorus removal insequencing batch reactor with single-stage oxic pro-cess. Bioresour Technol 99(13):5466–5473

66. Matsushita Y, Imai M, Iwatsuki A, FukushimaK (2008) The relationship between surface tensionand the industrial performance of water-soluble poly-mers prepared from acid hydrolysis lignin, a sacchar-ification by-product from woody materials.Bioresour Technol 99(8):3024–3028

67. Areskogh D, Li J, Gellerstedt G, HenrikssonG (2010) Investigation of the molecular weightincrease of commercial lignosulfonates by laccasecatalysis. Biomacromolecules 11(4):904–910

68. Areskogh D, Li J, Gellerstedt G, HenrikssonG (2010) Structural modification of commercial

lignosulphonates through laccase catalysis andozonolysis. Ind Crop Prod 32(3):458–466

69. Senamartins G, Almeidavara E, Duarte JC(2008) Eco-friendly new products from enzymati-cally modified industrial lignins. Ind Crop Prod27(2):189–195

70. Weng JK, Li X, Bonawitz ND, Chapple C (2008)Emerging strategies of lignin engineering and degra-dation for cellulosic biofuel production. Curr OpinBiotechnol 19(2):166–172

71. Rials TG, Glasser WG (1986) Engineering plasticsfrom lignin- xiii. Effect of lignin structure on poly-urethane network formation. Holzforschung40(6):353–360

72. Kadla JF, Kubo S (2004) Lignin-based polymerblends: analysis of intermolecular interactions inlignin–synthetic polymer blends. Compos PartA-Appl Sci 35(3):395–400

73. Lu X, Weiss RA (1992) Specific interactions andionic aggregation in miscible blends of nylon-6 andzinc sulfonated polystyrene ionomer. Macromole-cules 25(23):6185–6189

74. And SK, Kadla JF (2004) Poly(ethylene oxide)/organosolv lignin blends: relationship between ther-mal properties, chemical structure, and blend behav-ior. Macromolecules 37(18):6904–6911

75. And SK, Kadla JF (2003) The formation of strongintermolecular interactions in immiscible blends ofpoly(vinyl alcohol) (PVA) and lignin.Biomacromolecules 4(3):561–567

76. Chen F, Dai H, Dong X, Yang J, Zhong M (2011)Physical properties of lignin-based polypropyleneblends. Polym Compos 32(7):1019–1025

77. Kharade AY, Kale DD (2015) Lignin-filled polyole-fins. J Appl Polym Sci 72(10):1321–1326

78. Blanco I, Bottino FA (2016) Thermal characteriza-tion of a series of novel hepta cyclopentyl bridgedposs/ps nanocomposites. J Therm Anal Calorim125(2):637–643

79. Atifi S, Miao C, Hamad WY (2017) Surface modifi-cation of lignin for applications in polypropyleneblends. J Appl Polym Sci 134(29):45103

80. Shi Z, Fu F, Wang S, He S, Yang R (2013) Modifi-cation of chinese fir with alkyl ketene dimer (AKD):processing and characterization. Bioresources8(1):581–591

81. Yang S, Zhang Y, Yu J, Zhen Z, Huang T, TangQ (2014) Antibacterial and mechanical properties ofhoneycomb ceramic materials incorporated with sil-ver and zinc. Mater Des 59(6):461–465

82. Miao C, Hamad WY (2017) Controlling lignin parti-cle size for polymer blend applications. J Appl PolymSci 134(14):44669

83. Fu SY, FengXQ, Lauke B,Mai YW (2008) Effects ofparticle size, particle/matrix interface adhesion andparticle loading on mechanical properties ofparticulate–polym Composite. Compos PartB 39(6):933–961


84. Sadeghifar H, Argyropoulos DS (2015) Correlationsof the antioxidant properties of softwood Kraft ligninfractions with the thermal stability of its blends withpolyethylene. ACS Sustain Chem Eng 3(2):349–356

85. Cui C, Sun R, Argyropoulos DS (2014) Fractionalprecipitation of softwood Kraft lignin: isolation ofnarrow fractions common to a variety of lignins. ACSSustain Chem Eng 2(4):959–968

86. Podolyák B, Kun D, Renner K, Pukánszky B (2017)Hydrogen bonding interactions in poly(ethylene-co-vinyl alcohol)/lignin blends. Int J Biol Macromol107:1203–1211

87. Falkehag SI (1975) Lignin in materials. Appl PolymSymp 28:247–257

88. Dutta S, Sarkanen S (1990) A new emphasis instrategies for developing lignin-based plastics. MrsProc 197(31):31–39

89. Li Y, Mlynár J, Sarkanen S (1997) The first 85%Kraft lignin-based thermoplastics. J Polym SciPolym Phys 35(12):1899–1910

90. Lewis NG, Davin LB, Sarkanen S (1999) 3.18–thenature and function of lignins. Compr Nat ProdChem 3(18):617–745

91. Kadla JF, Kubo S (2003) Miscibility and hydrogenbonding in blends of poly(ethylene oxide) and Kraftlignin. Macromolecules 36(20):7803–7811

92. Yan L, Sarkanen S (2002) Alkylated Kraft lignin-based thermoplastic blends with aliphatic polyesters.Macromolecules 35(26):9707–9715

93. Sarkanen S, Chen Y, Wang YY (2016) Journey topolymeric materials composed exclusively of simplelignin derivatives. ACS Sustain Chem Eng4(10):5223–5229

94. Bula K, Klapiszewski Ł, Jesionowski T (2015) Anovel functional silica/lignin hybrid material as apotential bio-based polypropylene filler. PolymCompos 36(5):913–922

95. Chiellini E, Solaro R (2004) Biodegradable polymersand plastics. Chem Int 26(6):28–29

96. Chen YR, Sarkanen S (2003) Macromolecular ligninreplication: a mechanistic working hypothesis.Phytochem Rev 2(3):235–255

97. Wang YY, Chen YR, Sarkanen S (2017) Blend con-figuration in functional polymeric materials with ahigh lignin content. Faraday Discuss 202:43–59

98. Li Y, Sarkanen S (2000) Thermoplastics with veryhigh lignin contents. ACS Symp 742:351–366

99. Wang YY, Chen Y, Sarkanen S (2015) Path to plasticscomposed of ligninsulphonates (lignosulfonates).Green Chem 17(11):5069–5078

100. Wang H (2012) Research progress on biodegradablematerial of modified soy protein isolate. New ChemMater 40(1):16–18

101. Garrison TF, Murawski A, Quirino RL (2016) Bio-based polymers with potential for biodegradability.Polymers 8(7):262–284

102. Mu C, Xue L, Zhu J, Jiang M, Zhou Z (2014)Mechanical and thermal properties of toughened

poly(l-lactic) acid and lignin blends. Bioresources9(3):5557–5566

103. Jamshidian M, Tehrany EA, Imran M, Akhtar MJ,Cleymand F, Desobry S (2012) Structural, mechani-cal and barrier properties of active pla–antioxidantfilms. J Food Eng 110(3):380–389

104. Wang S, Li Y, Xiang H, Zhou Z, Chang T, ZhuM (2015) Low cost carbon fibers from bio-renewablelignin/poly(lactic acid) (pla) blends. Compos SciTechnol 119:20–25

105. Zhu J, Xue L, Wei W, Mu C, Jiang M, Zhou Z (2015)Modification of lignin with silane coupling agent toimprove the interface of poly(l-lactic) acid/lignincomposites. Bioresources 10(3):4315–4325

106. Ren W, Pan X, Wang G, Cheng W, Liu Y (2016)Dodecylated lignin-g-PLA for effective tougheningof PLA. Green Chem 18(18):5008–5014

107. Chen R, Abdelwahab MA, Misra M, Mohanty AK(2014) Biobased ternary blends of lignin, poly(lacticacid): and poly(butylene adipate-co-terephthalate):the effect of lignin heterogeneity on blend morphol-ogy and compatibility. J Polym Environ22(4):439–448

108. Abdelwahab MA, Taylor S, Misra M, Mohanty AK(2006) Thermo-mechanical characterization ofbioblends from polylactide and poly(butyleneadipate-co-terephthalate) and lignin. Polym Eng Sci300(3):299–311

109. Bertini F, Canetti M, Cacciamani A, Elegir G,Orlandi M, Zoia L (2012) Effect of ligno-derivativeson thermal properties and degradation behavior ofpoly(3-hydroxybutyrate)-based biocomposites.Polym Degrad Stab 97(10):1979–1987

110. Kim JT, Netravali AN (2010) Mechanical, thermal,and interfacial properties of green composites withramie fiber and soy resins. J Agric Food Chem58(9):5400–5407

111. Staswick PE, Hermodson MA, Nielsen NC(1984) The amino acid sequence of the A2B1a sub-unit of glycinin. J Biol Chem 259(21):13424–13430

112. SemO,Wagner JR (2002) Hydrolysates of native andmodified soy protein isolates: structural characteris-tics, solubility and foaming properties. Food Res Int35(6):511–518

113. Sheard PR, Fellows A, Ledward DA, Mitchell JR(1986) Macromolecular changes associated with theheat treatment of soya isolate. Int J Food Sci Technol21(1):55–60

114. Kato A, Tanimoto S, Muraki Y, Oda Y, Inoue Y,Kobayashi K (1994) Relationships between confor-mational stabilities and surface functional propertiesof mutant hen egg-white lysozymes constructed bygenetic engineering. J Agric Food Chem42(1):227–230

115. Lee M, Lee S, Song KB (2005) Effect of g-irradiationon the physicochemical properties of soy proteinisolate films. Radiat Phys Chem 72(1):35–40


116. Brandenburg AH, Weller CL, Testin RF (2010) Edi-ble films and coatings from soy protein. J Food Sci58(5):1086–1089

117. Zhu D, Damodaran S (2014) Chemical phosphoryla-tion improves the moisture resistance of soy flour-based wood adhesive. J Appl Polym Sci131(13):378–387

118. Park SK, Bae DH, Rhee KC (2000) Soy protein bio-polymers cross-linked with glutaraldehyde. J Am OilChem Soc 77(8):879–884

119. Matsumura Y, Kang IJ, Sakamoto H, Motoki M,Mori T (1993) Filler effects of oil droplets on theviscoelastic properties of emulsion gels. FoodHydrocoll 7(3):227–240

120. Zhang J, Mungara P, Jane J (2001) Mechanical andthermal properties of extruded soy protein sheets.Polymer 42(6):2569–2578

121. Huang J, Zhang L, Chen F (2003) Effects of lignin asa filler on properties of soy protein plastics.I. Lignosulfonate. J Appl Polym Sci88(14):3284–3290

122. Huang J, Zhang L, Wei H, Cao X (2010) Soy proteinisolate/Kraft lignin composites compatibilized withmethylene diphenyl diisocyanate. J Appl Polym Sci93(2):624–629

123. Wei M, Fan L, Huang J, Chen Y (2016) Role of star-like hydroxylpropyl lignin in soy-protein plastics.Macromol Mater Eng 291(5):524–530

124. Kalambur S, Rizvi SSH (2006) An overview ofstarch-based plastic blends from reactive extrusion.J Plast Film Sheeting 22(1):39–58

125. Spiridon I, Teaca CA, Bodirlau R (2011) Preparationand characterization of adipic acid-modified starchmicroparticles/plasticized starch composite filmsreinforced by lignin. J Mater Sci 46(10):3241–3251

126. Bodirlau R, Teaca CA, Spiridon I (2013) Influence ofnatural fillers on the properties of starch-based

biocomposite films. Compos Part B-Eng44(1):575–583

127. Shi R, Li B (2016) Synthesis and characterization ofcross-linked starch/lignin film. Starch-Starke68(11–12):1224–1232

128. Kaewtatip K, Thongmee J (2013) Effect of Kraftlignin and esterified lignin on the properties of ther-moplastic starch. Mater Des 49:701–704

129. Heitner C, Dimmel DR, Schmidt JA (2010) Ligninand lignans: advances in chemistry. Lignin andLignans Adv Chem 397(24):521–555

130. Fernández-Rodríguez J, García A, Coz A, LabidiJ (2015) Spent sulphite liquor fractionation intolignosulphonates and fermentable sugars by ultrafil-tration. Sep Purif Technol 152(4):172–179

131. El Mansouri NE, Salvado J (2006) Structural charac-terization of technical lignins for the production ofadhesives: application to lignosulfonate, Kraft, soda-anthraquinone, organosolv and ethanol process lig-nins. Ind Crop Prod 24(1):8–16

132. Kun D, Pukánszky B (2017) Polymer/lignin blends:interactions, properties, applications. Eur PolymJ 93(1):618–641

Books and Reviews1. Duval A, Lawoko M (2014) A review on lignin-based

polymeric, micro- and nano-structured materials. ReactFunct Polym 85:78–96

2. Hu TQ (2002) Chemical modification, properties, andusage of lignin. Kluwer, New York

3. Liu WJ, Hong J, Yu HQ, Bruijnincx PCA, Rinaldi R,Weckhuysen B (2015) Thermochemical conversion oflignin to functional materials: a review and future direc-tions. Green Chem 17(11):4888–4907

4. Upton BM, Kasko AM (2015) Strategies for the con-version of lignin to high-value polymeric materials:review and perspective. Chem Rev 116(4):2275–2306


application of lignin in thermoplastic materials · biodegradability the disintegration of...

Documents