Association between plasticized starch and polyesters: Processing and performances of injected biodegradable systems

Different formulations of wheat thermoplastic starch (TPS) have been proces sed with various plasticizer/starch ratios and moisture contents. The biode gradable polyesters tested are polycaprolactone (PCL), polyester amide (PEA ), polybutylene succinate adipate (PBSA) and polybutylene adipate co tereph talate (PBAT). TPS and polyesters are melt blended in different proportions by extrusion and then injected to obtain dumbbell specimens. Various prope rties are evaluated such as the mechanical properties (tensile and impact t ests), and the hydrophilic character with contact angle measurements. Addit ionally, uniaxial shrinkage is evaluated. Results show that the addition of polyester to TPS increases the dimensional post-injection stability. Blend modulus values are close to the results of the classical rule of mixture. Elongation at break, resilience values and SEM observations seem to give so me indications about the compatibility between both polymeric systems. PBAT and PEA present better results than PCL and PBSA. Contact angle measuremen t show that we have a drastic increase of the hydrophobic character from 10 % of polyester in the blend. The different combinations of TPS and polyeste rs give a wide range of mechanical behavior for compostable materials, to b e developed in specific applications.