Interfacial improvements in poly(3-hydroxybutyrate)-flax fibre composites with hydrogen bonding additives

Improvement of the interfacial properties of composites consisting of poly(3-hydroxybutyrate) and flax fibres was provided by addition of 4,4′-thiodiphenol (TDP) at various concentrations up to 10% v/v. The additive TDP is known to form hydrogen bonds with many functional groups. The flax fibres were initially treated with TDP before being used to prepare the composites. The effects of the TDP on the functional groups of the fibres and the matrix were monitored using Fourier transform infrared spectroscopy and it was confirmed that hydrogen bonding occurred in the composites, which consequently brought about advantageous changes in the dynamic flexural properties. The thermal stability determined by thermogravimetry showed a favourable shift of degradation temperatures to higher values and the thermal properties of the matrix determined from differential scanning calorimetry were also affected. With the aid of scanning electron microscopy and polarised optical microscopy, the composites were shown to exhibit improvement in the fibre–matrix bonding and the dynamic mechanical properties of the matrix changed from brittle to ductile as the TDP content increased.