Melt-spun microbial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers with enhanced toughness: Synergistic effect of heterogeneous nucleation, long-chain branching and drawing process.

A series of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composite fibers were prepared via melt reactive processing where tungsten disulphide (WS2 ) and dicumyl peroxide (DCP) was used as heterogeneous nucleating agent and initiator, respectively. Compared with PHBV or PHBV/WS2 fiber, the resultant LCB-PHBV/WS2 fibers showed improving mechanical performance, a higher nucleation temperature and a rapid crystallization rate due to the synergistic effect between heterogeneous nucleation, long chain branched structure and draw-induced crystallization. Taking the results with a cooling rate of 20 °C/min as an example, the peak crystallization temperature of LCB-PHBV/1.0 wt%WS2 increased from 100.47 °C to 107.40 °C and the crystallization enthalpy increased from 87.95 J/g to 93.03 J/g. Moreover, two different crystalline forms, α-crystal and β-crystal, were found in the prepared PHBV fibers, and the β-crystal part increased with the inducement of the stretching ratio which enhanced the fiber strength, given the tensile strength and elongation at break of the LCB-PHBV/WS2 fibers up to 189.8 MPa and 46.5%, respectively.