Study On The Preparation Of Ultra High Molecular Weight Polyethylene/Low Density Polyethylene Blending Fiber

Ultra high molecular weight polyethylene (UHMWPE) fiber is considered as one of the three high performance fibers in the world. Owning the characteristics of low density, high strength, high moduIus,UHMWPE fiber has been widely used in many areas. But its development in the field of civilian middle-high-strength fiber is limited by high cost, so we decide to prepare the low-cost UHMWPE blending fiber by using UHMWPE/LMWPE blending gel.Decalin and white oil is used respectively as solvent to prepare UHMWPE/LMWPE blending gel materials. Tensile testing shows that the tensile strength, rupture ratio and Young’s modulus of UHMWPE/LDPE blending gel material is the best. Increasing draw ratio can effectively improve the tensile properties of blending gel filaments. When the content of LDPE is50%, after drawing125times the tensile strength of the blending gel is1.2GPa; finally decide to use the UHMWPE/LDPE=5:5blending gel to prepare fiber.The steady and oscillation rheological properties of UHMWPE/LDPE blending gel spinning dope were studied by rotational rheometer. The steady-state test result shows that with the constant concentration of UHMWPE, the apparent viscosity of UHMWPE gel would decrease with the addition of LDPE. Rheology results indicated that the molecular chain in blending gel can achieve unwind-balancing at150℃in the range of gel spinning shear rates; the low structural viscosity Index of UHMWPE/LDPE blending gel in which the solid content was10%ensure that the orientation texture remain stable at150℃, and that is practicable for gel spinning. Oscillation test result shows that the range of linear viscoelastic region narrowed with the increasing of shear frequency and the decreasing of temperature; sol-gel transition of UHMWPE and the blending gel occured at110℃and120℃, respectively. Storage modulus and loss modulus increasing with the increasing of frequency, viscoelastic transition point of the two kinds of gels moved to higher frequency when the temperature increased and was approximately equal under150℃; for two kinds of gels, the phase separation occurs at110℃, when the temperature is higher than130℃, the blending gel is more stable; within the test frequency and temperature range, relaxation time of the two kinds of gels was closed and decreased with the increasing of shear frequency. Finaly,150℃and blending gel with a solid content of10%was select for the following spinning. At150℃, using the industrial white oil as solvent, the UHMWPE/LDPE=5:5blending gel with a solid content of10%as spinning dope, after extrusion, extraction, drying and multi-stage hot drawing, the UHMWPE/LDPE blending fiber with the diameter of30μm, tensile strength of1.25GPa was prepared. POM, SEM, DSC and XRD tests have done to characterize the blending fiber under different treatment conditions, the result shows that extracting with tension and multi-stage hot drawing give better compatibility to the two components in the blending fiber, making the fiber more densification and leading to more perfect crystallization in fiber, so the fiber has higher melting point and better performance.