Processing and Evaluation of Bio-Based Paramylon Ester/Poly(butylene succinate) Blends for Industrial Applications

Poly(butylene succinate) (PBS) was melt-blended with paramylon based mixed ester, paramylon propionate hexanoate (PaPrHe) and characterized for its morphology, thermal and mechanical properties. The PBS/PaPrHe blends were found to be immiscible throughout the loading range of PaPrHe (10-90 wt%), with individual glass transition peaks. Due to the immiscibility, there was phase separation observed in the bulk, evident by sea-island morphology. However, further observation of the micro-structure revealed that, in low PaPrHe loading (10-30 wt%), there was a micron to sub-micron order distribution of PBS particles and partially miscible PBS/PaPrHe phase. On increasing the PaPrHe to 50 wt% and beyond, the sub-micron scale domains fused to form a co-continuous morphology. As a result, the impact strength of PBS increased from 6.6 to 16.4 kJ/m(2) in the 50/50 blend. Under tensile loading, the strength at break and elongation decreased after the introduction of less-flexible PaPrHe particles in the blend. This could be countered by uniaxially stretching the blended films with 10-30 wt% PaPrHe, after which the tensile strength increased by up to 380% (from 33-52 MPa to 165-200 MPa) compared to the unstretched films, attributable to the increased degree of orientation of the molecular chains. In terms of thermal processability, all the blend ratios had high thermal degradation temperature (>350 degrees C), higher than the melt-flow temperature (124-133 degrees C) providing a wide processing window. Overall, PBS/PaPrHe blend is a novel bio-based blend with properties suitable for packaging, mulching, and related applications.