Effect of the orientation and rheological behaviour of biodegradable polymer nanocomposites

• Nanocomposites based on commercial biodegradable polymer were investigated.
• Effect of the orientation during non-isothermal elongational flow was assessed.
• Different clay nanofillers lead to different rheological behaviour due to their polarity.
• Mechanical properties are significantly dependent on the draw ratio.
• Nanocomposites subjected to significant non-isothermal elongational flow can behave like a polymer blend.

The recent increasing interest towards biodegradable polymers has favoured the investigation on these systems, showing also their limits. On the other hand, the success achieved by nanocomposites has fostered the search for new systems where the polymer matrix is biodegradable. The final properties can depend on a number of factors, including the biodegradable polymer used as well as the nanosized filler, their mutual compatibility, the filler dispersion and the processing conditions. In this work, nanocomposites based on a starch-derived matrix and three different lamellar silicates were prepared, and the effects of the elongational flow on the dispersion, the improvement of intercalation/exfoliation and the possible aligning of the nanosilicate particles along the flow direction was investigated. Rheological, morphological and tensile tests showed that the properties were significantly different upon varying the compatibility between the polymer matrix and the nanofiller, as well as the draw ratio and therefore the orientation degree.

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