Impact Modification of Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-<i>co</i>-3-hydroxyhexanoate) with Terratek FX1515 and Terratek GDH-B1FA

Poly-(3-hydroxybutyrate) (PHB) and poly-(3-hydroxybutyrate-<i>co</i>-3-hydroxyhexanoate) (PHB-<i>co</i>-HHx) are promising alternatives to polyolefins due to their similar processing temperatures and mechanical properties. However, these polymers exhibit brittle failure and poor impact performance, limiting their uses for certain applications. In this work, industrially compostable impact modifiers Terratek FX1515 (FX1515) and Terratek GDH-B1FA (GDH-B1FA) were blended with PHB and PHB-<i>co</i>-HHx at 10, 20, and 30% w/w loadings to assess the mechanical performance of these polymers. Blends containing both impact modifiers show remarkable improvement in the tensile and Izod impact properties of both polymers. The impact strength of PHB-<i>co</i>-HHx blends increases from 2.50 ± 0.09 to 13.81 ± 1.91 kJ/m² (30% FX1515) and 59.23 ± 1.27 kJ/m² (30% GDH-B1FA), whereas PHB blends showed moderate improvement from 2.37 ± 0.07 to 4.07 ± 0.18 kJ/m² (30% FX1515) and 4.79 ± 0.46 kJ/m² (30% GDH-B1FA). Further analysis of the impact surfaces using scanning electron microscopy, dynamic mechanical analysis, and interfacial tension revealed that the better performance of GDH-B1FA blends was due to its inherent elastomeric properties, large domain size, and good compatibility at the polymer-polymer interface. Additionally, biodegradation testing of the neat polymers, impact modifiers, and blends (ASTM D5338, industrial composting) shows that the polymers and impact-modified blends are capable of composting fully within 120 days.