Biopolymers are expensive and have either property or processing limitations. Most durable bio-resins available in the markets are based on PLA. Bio polymers are made from PLA blended with polymers like PC, PP, ABS, HIPS, PET and PMMA. Fillers, fibers and additives are also added to the blends to prevent degradability, increase HDT, reduce brittleness and speed crystallization. Since current supplies of PLA are limited, volumes of new alloys are limited. Commercial supplies of PLA are growing to meet at upcoming needs. NatureWorks, the sole large-scale supplier, has doubled capacity to 300 mln lb. Few new semi-works PLA plants have been announced in Europe, but construction has yet to begin. PLA is also blended with other bio-resins like PHBV (polyhydroxybutyrate valerate) or other PHAs, which have properties similar to low-end ABS and can reduce brittleness. PHBV also improves PLA’s heat resistance, but the mix loses clarity and is reportedly harder to process. Different polymer blends have distinct properties - ABS mixes easily with PLA, making a two-phase blend that is opaque and also reduces brittleness. Blending PLA with polyethylene or copolyesters also reduces brittleness. Mixtures with polyolefins are opaque, but blends with PMMA are clear. Additives also play a role in strengthening bio-resins for durable uses. Talc, as a nucleating agent speeds PLA crystallization and fairly reduces molding time. Calcium sulfate (dehydrated gypsum) improves heat resistance. Very fine-particle (0.05 micron) silica increases toughness while maintaining clarity. Reinforcing PLA with a network of polymer-crosslinked carbon fibers adds thermal conductivity for use in electronic applications. A special high-aspect-ratio precipitated calcium carbonate also reduces PLA’s brittleness. In 2003, Toray Industries commercialized its Eco-Plastic PLA compounds with chemically coupled kenaf fiber for a spare-tire cover, followed by a laptop cover for Fujitsu, using a 50/50 PLA/PC blend and flame-retardant additives. The blend has the processability, heat resistance and flame resistance required for larger IT devices, according to a NatureWorks white paper. But with less than 50% PC, blend properties are little better than plain PLA; and with more than 50% PC, the processing temperature is so high it degrades the PLA. Unitika Ltd. in Japan reinforces PLA with kenaf fiber to improve strength and HDT for use in cell-phone covers. Some of Unitika’s Terramac PLA-based resins combine nano-additives, plant fibers and mineral fillers to achieve 70% faster crystallization and shorter molding times than conventional PLA. Unitika makes patented PLA/PMMA blends in which the PMMA raises the glass-transition temperature (Tg) while retaining clarity, as well as developing PLA alloys with PP and PC. High-temperature grades will be used for dishes and housewares. Polymaterial Technology Co. in Thailand introduced heat-resistant PLA/PHA and PLA/PHBV compounds for durable applications. These have Tg of up to 80°C for injection molded dishes and housewares. Four commercial EcoHybrid grades are alloys of bio- and petro-based plastics: PLA/PHA/PP, PLA/PHA/TPU, PLA/PHA/PETG, and PLA/PHA/ABS. The company has also developed PLA/nylon 6 compounds for durable applications. Also, a hybrid of 30% PLA, 60% PC, and 10% compatibilizer can withstand exposure to more than 120°C, which is suitable for electronics applications. Mitsubishi Plastics in Japan has applied for a patent on a combination of PLA with titanate-treated metal hydroxides, talc, a char-forming flame retardant, and other fillers for toughness and flame retardance. Mitsubishi is reportedly developing a PLA-based compound for household appliances. Samsung Cheil Industries in Korea alloys PLA with PC or ABS for durable applications like cell phones, three models of which were commercialized last year. Cheil’s biomaterials are now being tested by General Motors and Ford. Stream Source Technologies in Shanghai, injection molds heat-resistant PLA consumer products that look and feel like melamine. Instead of alloying PLA with other polymers, nucleating agents are used to increase heat resistance and mechanical properties. PLA copolymers are being developed to combine the standard “right-handed” L-lactide monomer and the rarer “left-handed” D-lactide monomer. The result is stereocomplex PLLA/PDLA copolymers that have higher strength, crystallinity, and heat resistance. HDT is 320°F for a 50/50 copolymer, vs. 140°F for conventional amorphous PLA. Teijin Ltd., Japan will introduce this year high-heat stereocomplex PLA called Biofront for fibers and automotive. It has a melting point of 410°F vs. 338°F for standard PLA. Tate & Lyle in the UK acquired a patented process to copolymerize stereocomplex PLA two years ago, but the project is on hold for now. Starch from corn, tapioca, rice, potatoes can be chemically processed to turn it into a thermoplastic. Cereplast compounds starch with PP into four grades of BioPP for durable applications. BioPP reportedly has interesting properties of printability, soft touch, static dissipation, and heat resistance similar to conventional PP. Scrap BioPP can be reprocessed with virgin BioPP or with PP copolymers. BioPP scrap could also go into polyolefin decking. The company also plans to introduce Bio-PS and Bio-PE, which will combine 50/50 starch and HIPS or HDPE requiring compatibilizing, as starch bonds readily to PP, but not to PS and PE. Also under development is a thermoplastic composite of wood fiber, starch and other organic ingredients to make sheet and profiles for interior woodwork. A blend of polycarbonate (PC) & polylactic acid (PLA) has been developed by Samsung for mobile phones. Samsung has been able to boost PLA content from 30% to 50% producing a lower-molecular weight PC that processes at 240°C. Blends of PLA can improve the viability of PLA by lowering cost and eliminating limitations on properties. (Source Courtsey: Ptonline)