Thermal, mechanical and morphological properties of poly (hydroxybutyrate) and polypropylene blends after processing

Abstract

The ever increasing accumulation of plastic waste in the environment has motivated research on polymers that degrade rapidly after being discarded as possible substitutes for conventional inert plastics. Biodegradable polymers can be an alternative, since they have non-toxic residual products and low environmental permanence. Poly (hydroxybutyrate) is a biodegradable polymer with a strong potential for industrial purposes, but its thermal instability and fragility limit its applications. Thus, an alternative to improve the processability and properties of poly (hydroxybutyrate) is to mix it with another polymer, not necessarily a biodegradable one. In this work, different mixtures of poly(hydroxybutyrate) or PHB and polypropylene or PP were extruded and injected. After processing, the blends were studied and their miscibility, mechanical properties and degradability in different soils were analyzed. The main results indicated that the PHB/PP blends had better mechanical properties than pure PHB, as well as improved immiscibility and higher degradation in alkaline soil. The poly-hydroxybutyrate/polypropylene blends showed a tendency for lower crystallinity and stiffness of the polymer matrix, proportional to the amount of polypropylene in the blends, rendering them less stiff and fragile. The degradation tests showed that both pure PHB and blends with 90% PHB and 10% PP were degraded, with loss of their mechanical properties and weight.