Characteristic changes in PHBH isothermal crystallization monofilaments by the effect of heat treatment and dip-coating in various solvents

PHBH monofilament was fabricated by the melt-spinning process followed one-step-drawing after isothermal crystallization (IC) near T-g for 24, 48, and 72 h. A feasible way to improve the functionality of monofilament is the incorporation of natural compounds as an antibacterial reagents such as propolis. Moreover, various solvents were used to evaluate the penetration of propolis into PHBH IC monofilaments. The effect of heat treatment by various solvents such as acetone, ethanol, hexane, propanol as well as water, and air in physical change of PHBH IC fibers have been studied. The change in shrinkage and diameter of fibers found to be highly dependent on the temperature of each solvents. The dip-coating as a method to incorporate propolis reagent in ethanol and acetone solution was also evaluated. Acetone-propolis (AP) solution showed excellent penetration into PHBH IC monofilaments. Furthermore, by dip-coating for 5, 10, 15 circle times in AP solution at 50 degrees C affected the physical properties, mechanical properties, and inner structure of PHBH IC monofilaments. The length of IC 24 and 72 h fibers after dip-coating for 15 circle times shrank 25 and 26% from the initial length, respectively. Thus, the diameter of IC fibers expanded and the weight of IC fibers increased as a consequence of the propolis reagent settle in voids of IC monofilaments. IC 24 and 72 h monofilaments after dip-coating showed a reduction in tensile strength and an increase in elongation at break. The crystallinity (WAXD) of IC 24 and 72 h monofilaments was decreased and led to an increase in the thickness of the lamellar crystal (SAXS) by applying dip-coating for 15 circle times. The antibacterial test demonstrated that PHBH IC fibers containing propolis resulted in inhibitors against the growth of Staphylococcus aureus. Additionally, the characteristic changes in PHBH IC fibers can apply for reference as further research regarding drug delivery or the dyeing process by various solvents.