Abstract:

In order to obtain poly(vinylidene fluoride) (PVDF) fibers with high tensile strength, orthogonal test and single factor test were designed to explore the best process parameters of melt spinning of PVDF fibers. Thermal analysis (DSC) , infrared spectrum (FTIR), X- ray diffraction (XRD), and tensile test were carried out to analyze the crystalline structure, crystal orientation and mechanical properties of the fibers. The results showed that: the important order of relevant factors on tensile strength was: winding speed > spineret temperature > spineret size > air gap, optimal winding speed was 10.2 m/min, optimal spineret temperature was 240 °C, optimal spineret size was 2.0 mm, optimal air gap was 40 cm; α-phase crystalline and β-phase crystalline was co-exist in as-spun fibers; by cold drawing, α-phase crystalline could be transformed into the β-phase, the crystallinity and orientation tactor were increased with the increase of draw ratio, which was hilpful to the improvement of mechanical properties, and the tensile strength reached 591 MPa when cold drawing ratio was 6.5.

Key words: ploy (vinylidene fluoride) fibers, melt spenning, tensile strength, crystal transformation, crystal orientation