A Study of Neat and Polycarbonate Blended Poly-L-lactic Acid Glass Transition States (Tg), Utilizing Ethylene-Vinyl Acetate as Potential Processing Aid for Efficient Extrusion Flow
Afendoulis, Peter Constantine
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A glass transition state analysis was performed on 100% recycled polycarbonate (PC) and NatureWorks LLC Poly-L-lactic Acid (PLLA) extrusion grade 2200D blends. The inclusion of PC to the blends resulted in an increasing trend in glass transition state (Tg). Blends were studied at 100:0 (Tg=55-60 °C), 90:10 (Tg=60-65 °C), 80:20 (Tg=65-70 °C), and 70:30 (Tg=75-80 °C) PLLA-PC ratios, respectively. Tg was calculated by examining tensile strength with respect to temperature ranging from 30-90°C on an Instron 4465. PLLA-PC blend of 70:30 produced targeted Tg range above 75 °C, and the application of recycled PC over first generation material allowed for a 25% cost reduction of final product. High differentiation in polymer blend melting points (PLLA: 175 °C, PC: 260 °C) lead to a significantly high viscosity of mixture processing at 220 °C, max = 4936 m-g, calculated by a Haake ORD. Experimentation observed torque variation over time between PLLA-PC blends with and without ethylene-vinyl acetate (EVA). Elvaloy® an ethylene-vinyl acetate copolymer was examined as a potential flow modifier between PLLA-PC 70:30 blends. A substantial decrease of initial torque barrier was shown in EVA blends (max= 1996m-g), allowing for the efficient processing conditions for extrusion.