| High isotactic polybutene-1 alloy in reactor(polybutene alloy,PBA)is a new type of polyolefin material prepared by using ZN catalyst.As a novel material,PBA is composed of high isotactic polybutene,polypropylene and propylene-butene block copolymers obtained in reactor.On the basis of the excellent thermal creep properties,wear resistance,toughness and processability of high isotactic polybutene(i PB),PBA can shorten the time of crystal transformation through the introduction of butenepropylene block copolymer,improve the Vicat softening temperature and bending properties.In this paper,the high-temperature mechanical properties and crystallinity of commercial i PB and PBA were systematically compared,and the thermal-oxidative aging properties of the two materials and the hot-water aging properties of the asprepared pipes were systematically studied.The mechanical properties and crystallinity of PBA and i PB at different temperatures showed that the strain hardening moduli of PBA were the same at 25°C(normal temperature),100°C(before melting onset temperature)and 115°C(melting onset temperature).Better than i PB,the lamellar thickness of PBA is thinner than that of i PB,which is beneficial to improve its strain hardening modulus.The crystallization temperature of PBA is higher than that of i PB,and the crystallization half-peak width is narrower.The polypropylene and propylene-butene block copolymer contained in PBA can be used as crystallization nucleating agents to promote the crystallization of i PB components in PBA.At the same time,the crystallization rate of i PB was accelerated.Taking 100 °C as the temperature of the thermal oxidative aging treatment of the materials,the thermal oxidative aging treatment of the material was carried out for different time.The comparison of performance and structure between the two materials after thermal oxidative aging was explored.The results showed that the properties of polybutene and polybutene alloy materials were significantly improved in a short period of time.Among them,the properties of PBA remained in a high range of aging time.After 24 h,the performance of PBA is better than that of i PB obviously.With the prolongation of aging time,the material of i PB is obviously aged,and the elongation at break is obviously reduced.Microscopically,in this aging process,the OIT and melt index of i PB change in a certain degree.PBA is relatively stable during aging processing.The reason may be that the material properties are improved due to the annealing treatment of the material during the short-time thermal-oxidative aging process.However,the performance of i PB decreased at the later aging stage of the thermo-oxidative aging process.This is further proved by the delamination of the samples after 144 h heat treatment aging.Using a small single-screw extruder,PBA and i PB pipes with d=20.4±1.3mm and?=1.3±0.2mm were prepared,and the pipes were subjected to 95? hot water aging experiments for 0?50 days.The results show that,compared with the i PB pipe,the room temperature blasting performance of the PBA pipe is better than that of the i PB pipe before and after aging.And the tensile modulus,thermal stability and Vicat softening temperature of the PBA pipe before and after aging are also better than those of the i PB.The morphology observation of the crack of extruded pipe after blasting at room temperature shows that the crack of the PBA pipe is more slender than that of the i PB,which belongs to the ductile fracture.The crack of the pipe does not appear brittle fracture similar to the i PB pipe until the aging time reaches to 50 d.The reason may be that the propylene-butene block copolymer existing in PBA can be connected between the crystals of polypropylene and polybutene,which acts as a more stable tie molecule than the amorphous polybutene in i PB,so that Polybutene has more excellent properties. |
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