Development And Properties Of Toughened Polypropylene Pipe Material

Random copolymerization polypropylene(PPR)has been widely used in industry,life and other fields in recent years because of its excellent comprehensive properties.However,because of its high brittleness and toughness at low temperature,it is easy to cause stress-induced cracking,which affects the production,preservation,handling,installation and use of PPR pipes.In addition,compared with foreign PPR materials,the impact strength of domestic PPR materials is lower,especially the low-temperature impact performance of materials has a certain gap with foreign products.Compared with the common ?-crystalline polypropylene,the ?-crystalline polypropylene has the advantages of high impact strength and thermal deformation temperature,which can make up for the shortcomings of the ?-crystalline polypropylene such as poor low low temperature toughness,low impact strength and low thermal deformation temperature.The modification of PPR with ? nucleating agent has attracted wide attention.In this paper,TMB-5 and WBG-2 nucleating agents were selected to study the toughening of PPR.The effects of different types and additions on the mechanical properties,crystallinity and processing properties of PPR were studied.The better nucleating agents and additions were found through the research.The conclusions are as follows:According to the test and analysis of mechanical properties,the effects of ? nucleating agent TMB-5 and WBG-2 on the impact strength of notched simply supported beams at room and low temperature are remarkable.Considering the performance and cost,it is appropriate to control the mass fraction of the additive at 0.05 %.When the addition of ? nucleating agent WBG-2 is 0.05 %,the impact strength of PPR material at 23 ? can be increased by 23 %,the impact strength at-20 ?can be increased by 47.8 %,and the thermal deformation temperature can be increased by 2 ?.When the addition of ? nucleating agent TMB-5 is 0.05 %,the impact strength at 23 ?can be increased by 18.7 %,the impact strength at-20 ?can be increased by 26.1 %,and the thermal deformation temperature of PPR material can be increased by 3 ?.By comparison,? nucleating agent WBG-2 improves the comprehensive properties of materials better.When the PPR material was toughened by adding 0.05 % nucleating agent WBG-2,all the properties of the modified material were higher than those of the ?-crystalline PP-RCT required by the national standard,especially the low temperature impact performance was excellent,which is 2.3 times of PP-RCT.From DSC melting curve,it can be seen that pure PPR only has a melting endothermic peak of ? crystals,which makes the melting peak of ? crystals move towards high temperature.The initial crystallization temperature increases by 4-6 ?,and the crystallization temperature of materials increases by 3-4 ?.The melting peaks of ? crystals appear obviously near 130 ?after adding ? nucleating agent in PPR.Both nucleating agents can significantly increase the production of ? crystals in PPR.With the addition of ? nucleating agent,the relative content of ? crystals in modified PPR can reach more than 60 % with less addition of nucleating agent.After adding PPR to the two nucleating agents,with the increase of the amount of nucleating agents,the trend of ? first increases,then decreases and then increases.This indicates that the addition of smaller nucleating agents can induce the production of ? crystals,but with the continuous increase of ? nucleating agents,the nucleating ability of ? crystals is reduced.When the dosage of ? nucleating agents increases,the ability of ? nucleating agents will continue to play its role.After adding ? nucleating agent,the crystallization mode of the material changed to homogeneous nucleation and heterogeneous nucleation coexistence.Compared with pure PPR Si,Si decreased significantly,which resulted in a decrease in the crystallization rate of the modified samples.The XRD diffraction patterns show that the peak strengths of(300)and(301)crystal planes of the ? phase are significantly enhanced by adding PPR raw materials and ? nucleating agent.The calculation shows that the content of ? crystal in PPR can be significantly increased by adding two nucleating agents.When 0.05 % of the two nucleating agents were added,the relative content of ? crystalline form of PPR raw material increased by 98 % and 109 % compared with that of pure PPR raw material,and the relative content of ? crystalline form also decreased and increased when the amount of nucleating agent continued to increase.From PLM,it can be seen that the crystallinity of PPR increases with the increase of nucleating agent,and the crystal size decreases.The crystalline form changes from ? crystal to ? crystal,and there is no obvious spherulite and the crystal is disordered.When PPR is added to nucleating agent TMB-5,it mainly expands outward with "dendritic" nucleus and epigenetic "snowflake" crystals.When adding nucleating agent WBG-2 to crystallize,it mainly expands outward with "flower core" nucleus and epigenetic "flake" crystals.From the SEM,it can be seen that the impact section of the modified PPR is remarkably rough after adding ? nucleating agent,and there are some phenomena such as twisted uplift,tearing ravine,etc.The fracture mode of the modified PPR material has been changed significantly,and the toughness of the material has been enhanced.The rheological experiments show that the processing properties of PPR materials are improved by adding 0.05 % TMB-5 and WBG-2 nucleating agents,and the rheological properties are in good agreement with those of foreign products.The extrusion experiment of modified material shows that the extrusion process of the modified product is smooth and the inner and outer surface of the product is smooth,which accords with the appearance characteristics of high quality pipeline.The hydrostatic test of the sample was carried out according to the national standard.The damage time of the tube was prolonged after adding nucleating agent,especially WBG-2.Compared with pure PPR,the damage time was increased by 3.1 times,and the toughening effect was remarkable.Through comprehensive comparison,the toughening effect of rare earth ? nucleating agent WBG-2 on PPR modification is better,and 0.05 % of additives is more suitable.After adding nucleating agent,the properties of the modified products have been significantly improved.The comprehensive properties of the products exceed the performance requirements of PP-RCT in national standards,and the impact properties exceed those of foreign products.The cost advantages of the modified products are obvious,and they have strong market competitiveness.