Structure-Property Relationship in Melt-Spun Poly(hydroxybutyrate-co-3-hexanoate) Monofilaments

Poly(hydroxybutyrate-co-3-hexanoate) (PHBH) is a biodegradable thermoplastic polyester with the potential to be used in textile and medical applications. We have aimed at developing an upscalable melt-spinning method to produce fine biodegradable PHBH filaments without the use of an ice water bath or offline drawing techniques. We have evaluated the effect of different polymer grades (mol% 3-hydroxy hexanoate, molecular weight etc.) and production parameters on the tensile properties of melt-spun filaments. PHBH monofilaments (diameter < 130 mu m) have been successfully melt-spun and online drawn from three different polymer grades. We report thermal and rheological properties of the polymer grades as well as morphological, thermal, mechanical, and structural properties of the melt-spun filaments thereof. Tensile strengths up to 291 MPa have been achieved. Differences in tensile performance have been correlated to structural differences with wide-angle X-ray diffraction and small-angle X-ray scattering. The measurements obtained have revealed that a synergetic interaction of a highly oriented non-crystalline mesophase with highly oriented alpha-crystals leads to increased tensile strength. Additionally, the effect of aging on the structure and tensile performance has been investigated.

Automated summary

Poly(hydroxybutyrate-co-3-hexanoate) (PHBH) is a biodegradable thermoplastic polyester that shows potential for textile and medical applications. In this study, we aimed to develop a scalable melt-spinning method to produce fine biodegradable PHBH filaments without the need for an ice water bath or offline drawing techniques. We evaluated the effect of different polymer grades and production parameters on the tensile properties of the melt-spun filaments. The results showed that highly oriented non-crystalline mesophase and highly oriented alpha-crystals significantly increased the tensile strength of the PHBH filaments. Aging also had an impact on the structure and tensile performance of the filaments.