New insights in PHBHHx

Abstract

Polyhydroxyalkanoates (PHA) are a family of biobased polymers that have received a great deal of attention the last few decades for certain applications, such as packaging, medical devices, and controlled drug-delivery systems. PHAs are polyesters, that can be produced by a variety of bacteria from a wide range of renewable organic substrates. These polyesters are biodegradable as well as biocompatible. Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) can be considered as a candidate for replacement of specific fossil-based polymers, due to its ductile nature and wider processing window, compared to poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), which are the two most investigated PHAs. The mechanical properties of PHBHHx have been compared to low-density polyethylene, with a possible application for packaging. Unfortunately, the crystallization rate of PHBHHx is very slow, even at low 3-hydroxyhexanoate content. Therefore, many efforts are actually devoted to solve this problem (e.g., by addition of a nucleating agent or selected microfillers or nanofillers). The doctoral research of dr. ing. Jens Vandewijngaarden at the University of Hasselt (Belgium) aimed at the characterization and modification of PHA for application as food packaging material. Focus was placed on the polymer PHBHHx with a 3-hydroxyhexanoate content of 10 mol%. The research, which was performed from 2012 to 2016, involved the effective characterization and pinpointing the major positive and negative properties. Several types of modification techniques were investigated in order to enhance the applicability of these materials.