Toward heat resistant polylactide blend fibers via incorporation of low poly[(R)‐3‐hydroxybutyrate‐co‐4‐hydroxybutyrate] content

Blending high content of polyhydroxyalkanoates (PHAs ≥ 30 wt.%) with polylactide (PLA) provides an effective strategy to significantly improve heat resistance of PLA fibers. However, it has proven challenging to maintain good spinnability of the PLA/PHAs blends with the high content of PHAs. In this study, a series of poly(L‐lactide) (PLLA)/poly[(R)‐3‐hydroxybutyrate‐co‐4‐hydroxybutyrate] (P34HB) blend fibers with low P34HB content (≤ 8 wt.%) is successfully fabricated with excellent spinnability. The incorporation of P34HB contributes to a substantially improved heat resistance of the PLLA/P34HB blend fibers, as evidenced by a notable reduction in boiling water shrinkage from ca. 80% to 9%. This exceptionally improved heat resistance is closely related to substantial increase in crystallinity of PLLA in the blend fibers. Specifically, the addition of low P34HB content remarkably enhances chain mobility of PLLA chains, as such reduces crystallization half‐times (t1/2) and accelerates crystallization of PLLA. In fact, the amorphous P34HB phase favors crystal growth of PLLA phase rather than heterogeneous nucleation inferred previously. These results provide a facile and effective method to produce PLLA/P34HB blend fibers with enhanced heat resistance and sound spinnability. A series of substantially improved heat resistant PLLA/P34HB blend fibers with low P34HB content (≤ 8 wt.%) is fabricated with excellent spinnability via melt‐spinning and hot‐drawing processes, due to substantial increase in crystallinity of PLLA. Specifically, amorphous P34HB phase promotes crystal growth of PLLA rather than heterogeneous nucleation, resulting in the significantly enhanced crystallinity of PLLA.