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ABSTRACT:The blending of thermoplastic starch (TPS) with other biodegradable polyesters such as polyesteramide could be an interesting way to produce new biodegradable starch-based materials. Different mixes of wheat starch and polyesteramide (BAK) were melt blended by extrusion. After pelletization, granules were injection molded to produce test specimens. A range of blends was studied with glycerol (plasticizer)/starch content ratios varying from 0.14 to 0.54. BAK concentrations were up to 40 wt %, TPS remaining as the major phase in the blend. Various properties were examined with mechanical, thermomechanical (dynamic mechanical thermal analyzer) and thermal (differential scanning calorimetry) analysis. Hydrophobicity was determined with contact angle measurements. Thanks to the knowledge of the properties of each polymeric system, we analyzed the blends' behavior by varying each component concentration. The material aging was also studied. We showed that structural changes occurred during several weeks after injection. We noticed a certain compatibility between both polymeric systems. The addition of BAK to TPS matrix allowed us to overcome the weaknesses of pure thermoplastic starch: low mechanical properties, high moisture sensitivity, and high shrinkage in injection, even at 10 wt % BAK.

In previous works, we had shown that blending plasticised wheat starch (PWS) with biodegradable polyesters improves properties such as the water resistance. The present study was more specifically based on PWS/cellulose fibres composites. In addition, these multiphase systems (blends and composites) have been tested with respect to thermoforming applications. The composites shown an increase in modulus and strength, improved temperature stability and glass transition shifts. After sheet extrusion, each type of materials (blends and composites) was thermoformed. The ageing of the resulting thermoformed trays was tested in storage conditions from 4°C to ambient temperature, composites based‐materials show reduced ageing compared to PWS.