Biodegradable polyester thin films and coatings in the line of fire: the time of polyhydroxyalkanoate (PHA)?

Abstract

From sustainability standpoint, bio-based resins are of crucial importance nowadays rather than fossil-based resins, but the former suffers from low flame retardancy. Bio-based thin films and coatings are in their early stage of development; hence, a long way must be paved to make them resistant against flame/fire. Polylactic acid (PLA)-based biocompatible (timesand some biodegradable) coatings have been in the core of attention, but even among available works one can rarely find a comprehensive report on flame retardancy of PLA thin films and coatings. Attention should also be paid to the fact that first-generation biodegradable polyesters, PLAs, are not fully biodegradable. Moreover, synthesis of PLAs is hooked on crop consumption. On the other hand, polyhydroxyalkanoates (PHAs) with more or less similar structure, but different physical properties due to their lower glass transition temperature compared with PLAs, are known as the second-generation of bio-polyester. Overall, we highlight here that PHAs might be a better candidate for thin film manufacturing thanks to their synthesis by microorganism as well as significant variability of their microstructure that provides a wide range of properties, and notably their full biodegradability compared with PLAs. Though mass production of PHAs is not cost-effective these days and their market just entered into the growth phase, we suggest study on flame retardancy of PHA-based resins, thin films, and coatings for near future. This short communication deals with the current status and future ahead of PHA-based flame retardant thin films and coatings.