Production of Oriented Fibers out of Poly(Hydroxybutyrate/Hydroxyvalerate) Copolymers and Testing of Mechanical Stability under Static and Cyclic Loads

We investigated the process of production of oriented fibers by melt spinning of biodegradable hydroxybutyrate and hydroxyvalerate (PHBV) copolymers. It was revealed that temperature has a large effect on the stability of extrusion and quality of fibers, and the optimal paramter values were found. We showed that the diameter of fibers and orientation degree depend on the spinning rate which can vary in a wide range (from 2-3 to 40 m/min), not affecting the quality of fibers. We studied the extensibility and deformability of fibers at different temperatures and found the conditions allowing to produce fibers with the diameter of 0.17-0.20 mm with high mechanical characteristics (strength 306 MPa, elasticity modulus 3 GPa, elongation at break 24%), that were stable during the 3 month period of observation. We obtained and analyzed extension curves on which three areas were fixed: linear elasticity, visible deformation, totally nonreversible deformation, which is typical for the elongation curves of polymer elastomers. It was stated that the produced fibers have high mechanical stability at static and cyclic loading conditions (up to 100 MPa); in the area of linear elasticity the deformation of fibers is practically totally reversible after 1000 cycles of loading.