Exploring the performance of bio-based PLA/PHB blends: A comprehensive analysis

Poly(lactic acid) (PLA) is a bio-based linear aliphatic polyester that is broadly used in biomedical applications. A shortcoming of PLA is its brittleness and low toughness. Poly(hydroxybutyrate) (PHB) is a microbial bioprocessed and biodegradable polyester. To enhance toughness of PLA, it was melt-blended with PHB-based thermoplastic elastomer in various proportions by using a twin-screw extruder. Scanning electron microscope images reveal that PLA forms a continuous phase in PLA/PHB blends reinforced with inclusions of PHB. Fourier transform infrared spectroscopy measurements demonstrate strong intermolecular interactions between PLA and PHB chains. Differential scanning calorimeter thermogramms show that PHB reduces the glass transition temperature of PLA and affects its crystalline structure. When the mass fraction of PHB was 20, the glass transition temperature of the blend decreased to 33.9°C. Rheological measurements demonstrate that blending of PLA with PHB changes qualitatively the dependence of its viscosity on shear rate. Quasi-static (uniaxial tension) and dynamic (impact) tests confirm that blending of PLA with PHB results in a noticeable (by a factor of three) increase in its impact toughness and causes transition from the brittle to ductile regime of fracture. When the mass fraction of PHB was 40, the impact toughness reached to 0.40 kJ/m², almost 3 times to neat PLA.