The Processing And Performance Of Poly(1-Butene)/Polypropylene In-Reactor Alloy

Because of the good performance of heat creep resistance,fouling resistance,good recyclability and impact resistance and high temperature resistance,isotactic poly(1-butylene)is used as a special material for high-end polyolefin pipe under high temperature and high stress environment.However,the crystallization rate and the crystal transformation of f polybutene-1 made in China is slow.The short time hydraulic failure pressure and the resistance of constant pressure of PB-1 can be improved by adjusting the structure and formulation.In this paper,by adding molecular weight regulator to domestic commercial PB-1 to adjust the molecular weight and molecular weight distribution of PB-1 and increase the long chain structure in order to improve performance of domestic PB-1 pipes.The in situ synthesized PB-1/PP in-reactor alloy(abbreviated to PBA)was used to replace the domestic PB-1 as the pipe material.The processing and properties were studied to obtain the optimal processing conditions and formula.The effects of processing conditions and molecular weight regulator agent on the structure and properties of PB-1 pipe were studied by using a small single-screw pipe extruder.With the increase of extrusion temperature,the axial strength and hardening modulus of the pipe are increased,and the strain hardening phenomenon is advanced in the process of high temperature stretching.There was no obvious change in pressure resistance at room temperature and high temperature.With adding molecular weight regulator agent,the PB-1 pipe performance is greatly improved,which the short time hydraulic failure pressure at room temperature and high temperature increased by 9%and 5%,respectively.The resistance of constant pressure of PB-1 pipes is increased by15.7%.Both the axial tensile strength and yield strength at high temperature increased by 10%.After adding different fractions of molecular weight regulator agent,it was found that the PB-1 pipes had the best pressure resistance when 5-7wt% of agent was added.The results of DSC and SAXS experiments show that the crystallinity,crystallization speed,crystallization temperature,crystallization perfection,and crystal thickness of the modified PB-1 pipes are significantly increased,which improves the crystallization problem of poly(1-butene)processing.SEM image show that the agent roughen the damaged section of the pipes and there was ductile deformation after adding the modifier,which indicated that the presence of the agent increased the interaction between the chains and improved the pressure resistance of the pipe.The morphology,dimensional stability,tensile properties,crystallization properties,heat resistance,creep properties,short time hydraulic failure pressure and pressure resistance of the PBA pipes were investigated by using a small single-screw pipe extruder with different screw speed,temperature and amount of molecular weight regulator agent.The optimum extrusion process conditions and the appropriate molecular weight regulator agent content were obtained through the above experiments.SEM images show that the molecular weight regulator spontaneously aggregates in the PBA matrix,and occurs in-situ fibrillation,which further improves the mechanical properties and short time hydraulic failure pressure of PBA pipes.Compared with the two kinds of commercial PB materials,the short time hydraulic failure pressure and the resistance of constant pressure of the extruded PBA pipe can be equaled to,which achieve the purpose of processing and modification.