Four dry corn starches with different amylose content were blended at 185°C with poly(lactic acid) (PLA) at various starch:PLA ratios using a lab-scale twinscrew extruder. Starch with 30% moisture content also was blended with PLA at a 1:1 ratio. Each extrudate was ground and dried. The powder was mixed with about 7.5% plasticizer, and injection molded (175°C) into test tensile bars. These were characterized for morphology, mechanical properties, and water absorption. Starch performed as a filler in the PLA continuous matrix phase, but the PLA phase became discontinuous as starch content increased beyond 60%.Tensile strength and elongation of the blends decreased as starch content increased, but no significant difference was observed among the four starches at the same ratio of starch: PLA. The rate and extent of water absorption of starch/PLA blends increased with increasing starch. Blends made with high-amylose starches had lower water absorption than the blends with normal and waxy corn starches.

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Blends of soy protein isolate (SPI) with 10, 20, 30, 40, and 50% poly(ethylene-co-ethyl acrylate-co-maleic anhydride) (PEEAMA), with or without addition of 2.0 wt % methylene diphenyl diisocyanate (MDI), were prepared by mixing with an intensive mixer at 150°C for 5 min, and then milling through a 1-mm sieve. Blends were then compression-molded into a tensile bar at 140°C. Thermal and mechanical properties and water absorption of the blends were studied by differential scanning calorimetry (DSC), dynamical mechanic analysis (DMA), a test of modulus and tensile strength (with an Instron tensile tester), a water absorption test, and scanning electron microscopy (SEM). The blends showed two composition-dependent glass transition temperatures. Furthermore, as the SPI content increased, the melting temperature of PEEAMA remained constant but the heat of fusion decreased. These results indicate that SPI and PEEAMA were partially miscible. Morphology observations support these results. Increasing the PEEAMA content resulted in decreases in the modulus and tensile strengths and increases in the elongation and toughness of the blends. Water absorption of the blends also decreased with increased PEEAMA content. Incorporating MDI further decreased the water absorption of the blends. The mechanism of water sorption of SPI was relaxation controlled, and that of the blends was diffusion controlled.

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L-Lactic acid was allowed to react with small amounts of commercial MgO, Nanoactive s , and Nanoactive Magnesium Oxide Plus s particles, each of which differs in surface area, shape, and reactivity. The reactions were carried out by refluxing the nanoparticles in a solvent suspension of methanol or propanol. Upon addition of the lactic acid monomer, at reflux temperature, two reactions competed with each other: (1) acid-base to yield magnesium lactate salt, and (2) oligomerization to yield a nanocomposite prepolymer. The products were characterized for thermal, chemical, and morphological properties. Additionally, titrations were performed to determine how much MgO was consumed by the acid, and how this changed with nanoparticle size and shape. Polymerization appears to initiate on the surface of the magnesium oxide particles, the results of which are physically unique composites of lactic acid and magnesium oxide, and final properties depend on MgO nanoparticle characteristics. One of the most interesting results was the finding that larger, less reactive MgO favored the acid-base neutralization reaction, while smaller, more reactive MgO particles favored the MgO induced oligomerization pathway.