Melt processing of PHBV for functional fibres: effect of additives on process parameters

The objective of this study is to understand the effects of organic and inorganic additives on melt processing of biodegradable poly(3-hydroxybutyrate-co-valerate) (PHBV) polymer. For this purpose, PHBV compounds including different proportions of titanium dioxide (TiO2) and alpha-cellulose (0.5, 1 and 2%) (w/w) as additive were produced by melt-extrusion. The effect of additives on morphological, thermal and rheological properties was investigated using fluorescence microscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis and rheometry. X-ray diffraction and Raman spectroscopy were used to analyse crystal structure changes. Thermal characterization results suggest that the crystallization temperature and the degree of crystallinity increased with increasing additive content which may improve the processability of fibres and increase the tensile properties. The melting point of compounds shifted to higher temperatures and thermal stability slightly enhanced with the insertion of additives. TiO2 reduced the moisture content which can prevent the hydrolysis during extrusion. The morphological analyses revealed the presence of additives and well dispersion of cellulose. The flow behaviour of compounds improved in the presence of additives. As a conclusion, the improved properties of biodegradable polymer compounds are expected to ease the melt-spinning of PHBV fibres.