Annually Renewable Biodegradable Materials

Robertson et al. [229] blended cross-linking polymerized soybean oil (polySOY) and PLLA to increase the toughness of PLLA. Poly(isoprene-/)-L-lactide), PI-PLLA, block copolymers were used as compatibilizers. Blends of polySOY and PLLA of 85 15 ratio and 5 wt% with PI-PLLA showed tensile toughnesses as high as four times greater than that of unmodified PLLA. 

Epoxidizedsoybean oil (ESO) is produced via conversion of the double bonds of soybean oil with peracids or peroxides, resulting in more reactive oxirane or epoxide moieties, promoting chemical reactions [230-232]. ESO is normally used to plasticize and/or stabilize poly(vinyl chloride) (PVC), chlorinated rubber, and PVOH emulsions [231, 232]. The effects of ESO as a PLA plasticizer were reported elsewhere [230, 233, 234]. In summary, ESO lowered Tg, cold crystallization temperature Tm. enthalpy of cold crystallization (AHcc), tensile strength, and tensile 

Lecithin (an amphiphilic phospholipid) was solution blended with PLLA to improve hydrophilicity and cytocom-patibility of PLLA [235]. With 5 wt% lecithin, the solution-cast blend film possessed an optimum hydrophilic surface, providing the highest adhesion and proliferation of mesenchymal stem cells (MSCs) with a very low toxicity toward MSCs [235]. 

Sebastien et al. [255] prepared solution blended films of chitosan (98% DDA)/PLA (M = 49kDa) composed of 10-30% PLA with 16.6% poly(ethylene glycol) (PEG400) as a plasticizer had reduced water solubility (35-30%) and moisture absorption and an unexpected increase in 

Solution blend membranes of OCS/PLLA composed of 20-80% OCS were determined to be compatible based on FTIR and WAXD results [263]. Furthermore, there was no phase separation in the blend membrane containing 50wt% OCS. Addition of OCS decreased Tm and the crystalline band of PLLA, with emergence of a broad exothermic peak at about 80-90°C in the blend membranes determined by DSC. 

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The biodegradable polymer available in the market today in largest amounts is PEA. PEA is a melt-processible thermoplastic polymer based completely on renewable resources. The manufacture of PEA includes one fermentation step followed by several chemical transformations. The typical annually renewable raw material source is com starch, which is broken down to unrefined dextrose. This sugar is then subjected to a fermentative transformation to lactic acid (LA). Direct polycondensation of LA is possible, but usually LA is first chemically converted to lactide, a cyclic dimer of LA, via a PLA prepolymer. Finally, after purification, lactide is subjected to a ring-opening polymerization to yield PLA [13-17]. 

Starch has been considered an attractive raw material for polymer applications for almost 200 years. Kirchoff s discovery in 1811 that treatment of starch with an acid yields a sweet substance was an unexpected result of the search for a low-cost substitute for natural rubber.1 Considerable research in the development of starch-based polymer materials has been stimulated by the facts that starch is produced from wide variety of sources, is an annually renewable resource and is inherently biodegradable. 

Starch offers several potential advantages as a raw material for plastics applications. It is annually renewable, obtained from a variety of plant sources and is a low-cost material. Interest in its use in biodegradable plastics is also driven by the inherent biodegradability of starch and the ubiquity of microorganisms capable of utilizing starch as a carbon source. 

These environmentally-friendly products include biodegradable and biobased materials based on annually renewable agricultural and biomass feedstock [2], which in turn would not contribute to the shortage of petroleum sources [3]. Biocomposites, which... 

Most of the plastics and synthetic polymers that are used worldwide are produced from petrochemicals. Replacing petroleum-based feedstocks with materials derived from renewable resources is an attractive prospect for manufacturers of polymers and plastics, since the production of such polymers does not depend on the limited supply of fossil fuels [16]. Furthermore, synthetic materials are very persistent in the environment long after their intended use, and as a result their total volume in landfills is giving rise to serious waste management problems. In 1992,20% of the volume and 8% of the weight of landfills in the US were plastic materials, while the annual disposal of plastics both in the US and EC has risen to over 10 million tons [17]. Because of the biodegradability of PHAs, they would be mostly composted and as such would be very valuable in reducing the amount of plastic waste. 

Cellulose, the most abundant renewable and biodegradable polymer, is the promising feedstock for the production of chemicals for their appUcatimis in various industries. Annual production of cellulose in nature is estimated to be lO"—10 t in two forms, partially in a pure form, for example seed hairs of the cotton plant, but mostly as hemicelluloses in cell wall of woody plants (Klenun et al. 1998). The versatility of cellulose has been reevaluated as a useful structural and functional material. The environmental benefits of ceUulosics have become even more apparent (Hon 1996a). Cellulose is revered as a constmction material, mainly in the form of intact wood but also in the form of natural textile fibers like cotton or flax, or in the form of paper and board. The value of cellulose is also recognized as a versatile starting material for subsequent chemical transformation in production of artificial ceUulose-based threads and films as well as of a variety of cellulose derivatives for their utilization in several industries such as food, printing, cosmetic, oil well drilling, textile, pharmaceutical, etc. and domestic life. 

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