Preperation And Study Of HMWPE/LLDPE/HBP Fibers

High strength high molecular weight polyethylene(HSHMPE)fibers have good prospects in the field of industry and other special areas because of its high strength,high modulus,light weight,excellent chemical resistance,corrosion and impact resistance and other outstanding properties.The molecular weight of HSHMPE is so high that macromolecular chains are flexible structure highly intertwined and the melt viscosity is high.Gel-spinning is a mature method to produce UHMWPE fibers,and the solution concentration is about 8wt%,which results in the high manufacturing cost of HSHMPE fibers.In this thesis,the HMWPE/LLDPE/HBP blend fibers were fabricated by blending modification using LLDPE and Hyper-branched Ploy(ester-amide).The rheological behavior of different HMWPE/LLDPE/HBP spinning solution was studied by ARES-RFS Senior Rotary Rheometer.Non-isothermal crystallization kinetics,morphological and mechanical properties of blend fibers was investigated by differential scanning calorimeter(DSC).The DXLL-20000 testing tester,scanning electron microscopy(SEM)is used in this thesis for studying the mechanical and morphological properties of the fibers.The changes of crystallization were analyzed by Wide angle X-ray diffraction(WAXD)and 2D-WAXD.Rheological properties of the blends have showed in this thesis.The HMWPE/LLDPE/HBP blends were the typical non-Newtonian fluid.At a given shear rate,the viscosity of the blends reduced when the amout of HBP increases,increased when the increases of the molecular weight of HMWPE and reduced when the rise of temperature.Viscous flow activation energy of the blends increased when the content of LLDPE and HBP rose and increased when molecular weight of HMWPE increased.The non-Newtonian index of the blend decreased when the temperature and molecular weight of HMWPE increased,and increased when the amout of LLDPE and HBP increased.When the content of LLDPE and HBP increased,the structural viscosity index became small and the spinnability became good.Storage modulus,loss modulus and complex viscosity of the blend reduced when the temperature and the content of HBP increased,and increased when modecular weight of HMWPE rose.Position and level of the internal friction peak was related with temperature.Han curve of the blends did not depend on temperature.This showed that the blends were homogeneous polymer system.When the shear rate and angular frequency were low,the blends comply with the rule of Cox-Merz.The apparent viscosity of the steady test and the complex viscosity of the dynamic test were closer.Non-isothermal crystallization test of the studies have showed in this thesis.The half crystallization time decreased when cooling rate and the content of LLDPE and HBP reduced,and increased when molecular of HMWPE rose.Trend of the crystallization rate was contray to the crystallization.This showed LLDPE and HBP accelerated crystallization of the HMWPE molecule.Crystallization rate of different blends was roughly same under the same cooling rate and higher than UHMWPE.The crystallization rate of the blend improved when the content of HBP increased.The Avrami index of the blends was same and between one and two.The crystallization mechanism wass substantially same and growth pattern of crystal was one-dimensional.Under the fixed content of LLDPE,when the content of HBP rose,tensile strength of the blend first increased and then decreased.When the content of HBP was 3%,the tensile strength was best.Similarly,the melting temperature and crstallinity of the blend first increased and then decreased when the content of HBP rose.Without LLDPE and HBP,friction surface of HMWPE sample had grain.Added LLDPE,the grain disappeared and the friction surface was the coarser microfiber structure.Added LLDPE and HBP,the friction surface of the sample became finer microifbrils structure.The mechanical properties of the blend fibers first increased and then decreased when the content of HBP rose.When the content of HBP was 3%,the mechnical properties were best.The melting point and crystallinity increased with increasing of the draw ratio.The grain size decreased with increasing of the draw ratio.