Study On The Preparation And Structure Of Middle-high Strength Blending Fiber Of Ultra High Molecular Weight Polyethylene

Ultra high molecular weight polyethylene (UHMWPE) fiber, one of the three high performance fibers in the world, has been widely applied in many fields for its low density, high strength and high modulus. But it is too expensive to be applied in fields of civilian middle-high-strength fiber. So we try to prepare low-cost UHMWPE blending fiber by adding LMWPE into UHMWPE gel spinning.Effects of several processing parameters on the properties of UHMWPE/HDPE(U/H) blending fiber were investigated. A series of U/H blending gels with different U/H weight ratios were prepared at first. Rheological test showed that the viscosity was least when the U/H weight ratio was 5:5, meaning that it was easiest to process in this condition. Effects of U/H weight ratio, UHMWPE concentration and spinneret diameter on the breaking strength of blending fiber were investigated. The optimal processing technic was obtained, i.e. the U/H weight ratio 5:5, the UHMWPE concentration 30g/L and the spinneret diameter 0.5mm. The UH55 blending fiber, with breaking strength 1.4GPa, was a typical middle-high strength fiber.Three kinds of blending fibers, i.e. UHMWPE/HDPE, UHMWPE/LDPE and UHMWPE/LLDPE, were prepared using the optimal processing technic, and the mechanical properties and microstructure of them were investigated. Test results showed that mechanical properties of three kinds of blending fibers were almost equal, i.e. breaking strength about 20cN/dtex and modulus about 380cN/dtex. Diameters of three kinds of blending fibers were all about 20μm, similar with commercial UHMWPE fiber. In other words, three kinds of LMWPE were all suitable to prepare middle-high strength blending fiber with UHMWPE. DSC test results of three kinds of dry blending gels showed that three kinds of LMWPE were all compatible with UHMWPE well.At low draw ratios, morphology of UH, UL and ULL blending fibers were quite different. UH and ULL blending fibers got perfect shish-kebab crystal and higher orientation degrees of crystals while UL blending fiber got incomplete shish-kebab crystal and lower degree of orientation of crystals. It was due to that LDPE got much more branch chains than HDPE and LLDPE. So that it was more diffcult for LDPE to crystallization and orientation. And also phase separation level of LDPE and UHMWPE was higher than the other two. But at high draw ratios, all the three kinds of blending fibers got perfect shish-kebab crystal and high orientation degrees of crystals, and this was the structure basis of almost the same mechanical properties of the three kinds of blending fibers.