Starch-based bioplastics reinforced with cellulose nanocrystals from garlic

stalksM.B. Agustin1*, B. Ahmmad2*, E.R. P. De Leon1, J.L. Buenaobra1,

J.R. Salazar1, and  F. Hirose2

1Dept. of Chemistry, CAS, Central Luzon State University, Nueva Ecija, Philippines

2Graduate School of Science and Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan 

Petroleum based plastic

Extreme versatility Lighter weight Resistance to chemicals, water and impact. Better safety and hygiene properties for food

packaging. Excellent thermal and electrical insulation

properties. Relatively inexpensive to produce Extreme durability

Drawback

Let’s go GREEN!

Bioplastics

Form of plastic derived from renewable biomass

Polysaccharides• Starch• Cellulose• Chitin

Proteins• Collagen/gelatin• Silks, fibroin• Casein, albumin

Polyesters• Polyhydroxyalkanoat

es

Others• Lignin• Natural rubber• Lipids• Synthetic

John and Thomas, 2008

Starch –based bioplastic

Starch is plasticized by thermomechanical treatment in the presence of water and a plasticizer like glycerol to produce thermoplastic starch (TPS).

Starch offers the advantages of being cheap and naturally abundant. However, it suffers from having poor mechanical properties and being strongly

hydrophilic.

Reinforcing fillers

Common reinforcing fillers are clay, talc, silica, glass fiber, carbon black, natural fibers and cellulose micro/nanofibrils

Natural fibers and cellulose nanofibrils inherent renewability, less abrasive character, biocompatibility, and low

energy consumption for production

Cellulose

a renewable, biodegradable and the most abundant organic biopolymer on the Earth

the primary structural component of the cell wall of higher plants and it can be obtained from various sources like wood, some bacteria, fungi and some algae.

cellulose content in different plants and trees varies significantly. Cotton (90-99%) Wood (40-50%) Jute (60-70%)

Cellulose

Cellulose nanocrystals (CNCs)

Crystalline cellulose stronger and stiffer than amorphous cellulose and the native cellulose itself (Lin et al, 2008)

Gray, D.G., 2011

Isolation of crystalline cellulose Coconut husk (Rosa et al., 2011) Banana plant wastes (Ellanthikal, S. 2010) Mulberry barks (Li, R. et al., 2009) Palm pressed fiber (Wittaya, T, 2009) Orange mesocarp (Ejikeme, P. 2008) Baggase (Bhattacharya et al., 2008) Wheat and cereal straws (Alemdar, A. and Sain, M. 2008) Flax fibers and straw (Bochek, A.M. et al., 2003) Soy bean husk (Nelson, Y. U. 2000), Ground nut shell and rice husks (Okhamafe, A.O. et al., 1991)

Garlic stalks

Objectives

To isolate and characterize CNCs from garlic stalks

To prepare bioplastic films with varying amount of the isolated CNCs as reinforcing filler and starch as the biopolymer matrix

To evaluate the effect of CNCs in the morphological structure, mechanical properties, thermal stability and water resistance of the bioplastic films.

METHODOLOGY

Isolation of CNC

Sample collection and preparation

Bleaching

Cellulose fibers

Delignification

Isolation of CNC

Acid hydrolysis Dialysis

CharacterizationFTIRXRD

SEM/TEM

Sonication

CNC suspension

Preparation and Testing of Films

Solution casting method Glycerol as plasticizer, water as solvent

Treatments: Starch: CNC ratio

T0 – 100:0 T1 – 100: 2.5 T2 – 100:5 T3 – 100: 10 T4 – 100: 15

Preparation and Testing of Films

Tests done: SEM Mechanical properties Thermogravimetric analysis Moisture uptake

RESULTSCharacterization of Cellulose Nanocrystals

FTIR

FTIRPeak Occurrence (cm-1) Peak Assignment Reference

3442 –OH stretching2922 –CH stretching2364 CO2 Sherman Hsu, 19971639 Adsorbed water Rosa et al., 20101426 –CH deformation Jonoobi et al., 20101377 –CH asymmetric deformation Jonoobi et al., 20101331 –OH in plane deformation Rosa et al., 20101227 Sulfates Mandal and Chakrabarty, 20111062 –COC pyranose ring skeletal

vibrationChang et al., 2010

895 Glucose ring stretching Jonoobi et al., 2010830 Half-ester sulfate group Chen, 2011669 –CH deformation Rosa et al., 2010

XRD

10 20 30 40 50 60 70 80

RGSCNCDGS

Inte

nsi

ty

Diffraction angle, 2/deg

Sample CI (%)Raw garlic

stalks35.6%

Delignified garlic stalks 53.1%

CNC 61.1%

SEM and TEM

Approximate particle diameter using Semafore : 32 nm

Cellulose nanocrystals

Raw garlic stalks Cellulose fibers

RESULTSCharacterization of Bioplastic Films

The prepared bioplastic films

T0: 100:0 T1: 100:2.5 T2: 100:5

T3: 100:10 T4: 100:15

Morphology of bioplastic

Mechanical Properties

Treatment Tensile Strength (MPa) Modulus (MPa)

T0 (100:0) 10.0 327.3

T1 (100:2.5) 14.3 416.2

T2 (100:5) 15.6 439.6

T3 (100:10) 10.5 392.5

T4 (100:15) 9.58 349.98

Thermal property

0

20

40

60

80

100

120

100 200 300 400 500 600

T-0 (100:0)T1 (100:2.5)T2 (100:5)T3 (100:10)T4 (100:15)

Wei

ght

lost

/ %

Temperature / C

-0.1

-0.08

-0.06

-0.04

-0.02

0

100 200 300 400 500 600

T0 (100:0)T1 (100:2.5)T2 (100:5)T3 (100:10)T4 (100:15)

Der

ivat

ive

We

ight

lost

Temperature / C

Moisture uptake

Treatment % Moisture uptake

T0 (100:0) 17.0

T1 (100:2.5) 11.1T2 (100:5) 10.7

T3 (100:10) 15.7

T4 (100:15) 16.3

CONCLUSIONS

Conclusions

Spherical cellulose nanocrystals with an average diameter of 35 nm and crystallinity of 62% can be isolated from garlic stalks through delignification and acid hydrolysis.

The starch to CNC ratio of 100:5 can be considered the optimum in this study. Improvement in tensile strength, modulus and moisture resistance of the film was the highest at this ratio.

Higher CNC load offset the reinforcing effect of CNC attributed to possible agglomeration of CNCs in the starch matrix.

Acknowledgment

The authors gratefully acknowledge the financial support from the International Foundation for Science thru the research grant of M.B.Agustin.

Thank you very much for listening.

Maraming Salamat