# Impact Modification of Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with Terratek FX1515 and Terratek GDH-B1FA

## TL;DR

This paper explores how adding two compostable impact modifiers improves the mechanical properties of PHB and PHB-co-HHx polymers while maintaining full biodegradability.

## Contribution

The study introduces two compostable impact modifiers that significantly enhance the mechanical performance of PHB and PHB-co-HHx polymers.

## Key findings

- Blending with GDH-B1FA significantly increased the impact strength of PHB-co-HHx to 59.23 kJ/m² at 30% loading.
- Both impact modifiers improved compatibility and mechanical properties at the polymer interface.
- All materials fully biodegraded within 120 days under industrial composting conditions.

## Abstract

Poly­(3-hydroxybutyrate) (PHB) and poly­(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-co-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-co-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-co-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.