Nano technology based bio degradable plastics

By: Prasad Reddy,M.NM-Tech(FST)2015694708

What does Biodegradable Mean

• Biodegradability : complete assimilation of the degraded products as a food source by the soil microorganisms would ensure returning the carbon into the ecosystem safely and effectively

• According to the European Bio plastics organization,Bio plastics : can be defined as plastics based on renewable resources (bio based) or as plastics which are biodegradable and/or compostable.

• Poor mechanical properties• Low thermal stability• Relative humidity dependancy• Permeable to water

Biodegradable nano-compositesCellulose, starch, zein(from corn) when synthesized as nanofibers

obtain superior properties like; Increased heat resistance High thermal stability improved barrier properties Improved permeable properties

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Shortcoming of bio degradable plastics

Two approaches for nanomaterial making

• Top-down:- by breaking up bulk material & nanolithography

Eg. Mechanical alloying • Bottom-up:- allows nanostructures to be built

from individual atoms Eg: Inert gas condensation

Examples: nanoaluminums, nanotitanium, nanosilver, ZnO, MgO, nanoclays, nanofibres, nanotubes

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POLYMER NANOCLAY NANOCOMPOSITE

Nanocomposite Preparation

• For nanocomposite preparation, (OMLS)Organically Modified Layered Silicates (powder form) and PLA (pellets form) were first dry-mixed by shaking them in a bag.

• The mixture was then melt-extruded by using a twin screw extruder operated at 210 (screw speed = 100 rpm, feed rate=120 gm /min) to yield nanocomposite strands.

• The strands were pelletized and dried under vacuum at 60 for 48 h to remove water.

• The dried nanocomposite pellets were then converted into sheets with a thickness of 0.7–2 mm by pressing with 1.5 MPa at 190 for 3 min.

• The molded sheets were then quickly quenched between glass plates and then annealed at 110 for 1.5 h to crystallize isothermally before being subjected to wide-angle X-ray diffraction, transmission electron microscopy, and dynamic mechanical properties measurements.

Incorporation of polymatrix in to nanoparticles

• In situ polymerization : dissolution of the nanoparticles in the monomer solution before polymerization,

• solvent intercalation :use of a solvent to enhance the affinity between the nanoparticles and the matrix

• melt intercalation : addition of the nanoparticles during extrusion

Source: Chivrac et al., 2009; Shen, Simon, & Cheng,2002).

Basically montmorillonites (MMT) has been used.

• Polylactic acid + MMT = increased thermal resistance

• Polyvinylchloride + MMT = improved optical resistance

• Polyethylene + MMT/SiO2 = improved durability

• Polyamide+multi wall carbon nanotubes = significant flame resistance

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Nanocomposites

Others

•Nanofibres: barrier and mechanical properties, it also displayed high transparency properties

•Silica nanoparticles: improve mechanical or barrier properties of composites

•Starch nanocrystals: mechanical properties

•Titanium dioxide nanoparticulate: block UV light and provide a longer shelf-life for food

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Biopolymers Based Packaging Materials

Starch:Starch is a widely available and easy biodegradable natural resource.1) Preparation of starch composition with other plastics with a low amount of starch to enhance the biodegradability of traditional oil-based polymer materials.2) Starch application is the preparation of starch composite with starch content being more than half by mass and3) starch biodegradable polymers preparation uses the extrusion processing of mixtures of granular starch.

Cellulose

• Cellulose is the most widely spread natural polymer and is derived by a delignification from wood pulp or cotton linters. • It is a biodegradable polysaccharide which can be

dissolved in a mixture of sodium hydroxide and carbon disulphide to obtain cellulose xanthate and then recast into an acid solution (sulfuric acid) to make a cellophane film.• Alternatively, cellulose derivatives can be produced by

derivatization of cellulose from the solvated state, via esterification or etherification of, hydroxyl groups.

Synthesis of Cellulose Nanofibers

Structure and Properties of Cellulose Nanofibers.TEM, SEM, field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), wide-angle Xrayscattering (WAXS), and NMR spectroscopy have been used to study the structure of cellulose nanofibers

Source : Susheel Kalia et.al., 2011

PHA

• The polyhydroxyalkanoates (PHA) family are biodegradable thermoplastic polymers, produced by a wide range of microorganisms. • The polymer is produced in the microbial cells

through a fermentation process and then harvested by using solvents such as chloroform, methylene chloride or propylene chloride. • More than 100 PHA composites are known, of

which polyhydroxybutyrate (PHB) is the most common.• The PHAs have potential as a substitute for many

conventional polymers, since they possess similar chemical and physical properties

Clay delamination/dispersion

Surface coatings Nano silver Zinc oxide Titanium

dioxide Magnesium

oxide

Limitations of bio plastics

• higher price level compared to conventional plastics,• Brittleness(due to high glass transition and

melting temperatures)• Thermal instability, low melt strength, difficult

heat sealability, • high water vapor(hydrophilic nature of starch and

cellulose,) and oxygen permeability restrict the use of PLA films for many food packaging applications

To over come these problems

• To achieve this modifications, a good interaction between the polymer matrix (continuous phase) and the nanofiller (discontinuous phase) is desired (Lagaron & Lopez-Rubio, 2011).

• Coatings : cellulose film with PHB resulted in lower WVP values, higher elastic modulus and tensile strength for films containing 10% or more PHB and better strain at break for films containing 15% or more PHB (Cyras et al., 2009).

• A nitrocellulose or PVdC coating on cellophane improved both O2 and H2O barrier properties (Shen et al., 2009).

• In general, Popa and Belc (2007) stated that chitosan may be used as a biobased coating on polymers with poor gas barrier properties.

• coating of PLA with PLA-Si/SiOx, PCL-Si/SiOx (polycaprolactone) or PEO-Si/SiOx (polyethylene oxide) enhanced the barrier (oxygen and water vapor) properties,

Reference • Nanotechnology for bioplastics opportunities, challenges and

strategies, (2011) Trends in Food Science & Technology 22 611-617.• Nanocomposites for food packaging applications 2009, Henriette M.C.

de Azeredo, Food Research International 42 1240–1253.• Biodegradable Polylactide and Its Nanocomposites: Opening a New

Dimension for Plastics and Composites (2003) Suprakas Sinha Ray,*Masami Okamoto, research gate, DOI: 10.1002/marc.200300008

• Recent trends of Biodegradable polymer: Biodegradable films for Food Packaging and application of Nanotechnology in Biodegradable Food Packaging , (2014) Malathi A. N. Current Trends in Technology and Science ISSN : 2279-0535. Volume : 3, Issue : 2

• Cellulose-Based Bio- and Nanocomposites (2011), Susheel Kalia et.al., International Journal of Polymer Science , Article ID 837875, 35 pages, doi:10.1155/2011/837875,Hindawi Publishing Corporation.

Thank you!!

Our technological powers increase, but the side effects and potential hazards also escalate. Alvin Toffler