Review of Biopolymer Polyhydroxybutyrate (PHB) and Blends: Modification of Thermal and Mechanical Properties via Additive Manufacturing Processing.

The non-degradable polymers used in daily and commercial application are generally inexpensive; however, their excessive use leads to extensive environmental damage. In light of this, the demand for bio-derived, biocompatible, and biodegradable polymers increases since these materials are potential alternatives to petroleum-derived polymers. Polyhydroxybutyrate (PHB), a class of highly crystalline thermoplastics derived from natural sources, offer significant environmental advantages over fossil fuel-based polymers due to their inherent biodegradability. This eco-friendly profile has spurred research into their commercial applications, ranging from food packaging to pharmaceuticals. However, processing challenges, particularly for polyhydroxybutyrate (PHB)-including high costs and the requirement for elevated temperatures-remain major obstacles. Additionally, PHB-based products are often brittle and exhibit inferior mechanical properties compared to conventional petroleum-based polymers such as polypropylene and polyethylene. This review comprehensively examines the state-of-the-art processing techniques for PHB and their composites. Key properties, such as mechanical performance, thermal behavior, and degradation characteristics, are scrutinized. Furthermore, the review explores mitigation strategies, such as blending and plasticization, aimed at overcoming the mechanical brittleness while upholding the principles of sustainability and maintaining a low carbon footprint.