Study On Crystallization Behavior And Mechanical Properties Of Nucleated Polypropylene Random Copolymer

Polypropylene random copolymer(PPR)is the most used material in plastic pipes for cold and hot water,with high cost performance and convenient construction and installation.PPR is a semi-crystalline polymer.The crystal form of commercial PPR resin is mainly ? crystal,and the material has poor low-temperature impact resistance,which limits the use of PPR pipes in winter and northern cold regions.This research aims to improve the overall performance of PPR materials.By adding self-made ? nucleating agent to PPR resin,combined with process control during pipe processing,the crystal morphology of PPR can be controlled to improve its low-temperature impact resistance.The main research contents of this article are as follows:(1)Using 1,3,5-benzenetricarboxylic acid chloride,cyclohexylamine and aniline as the main raw materials,1,3,5-benzenetricarboxylic acid tricyclohexylamide(BTACA),1,3,5-benzenetricarboxylic acid tris(phenylamide)(BTAPA)and3,5-bis(cyclohexanamide)-1-benzoic acid(BCABA)were prepared.The structures of the nucleating agents were characterized by FTIR and DSC.The nucleation effects of three nucleating agents in PPR and the performance of nucleating PPR were studied.The results showed that BTACA and BTAPA are ?-type nucleating agents of PPR.Meanwhile,BCABA effectively induced the formation of ? crystals in PPR.(2)Combined with the addition of ? nucleating agent and temperature gradient method,a novel stepwise crystallization process for PPR pipes was developed to obtain PPR pipes with higher ? crystal contents in actual production.The DSC method was used to simulate the temperature changes in the actual production process of PPR pipes.The specific temperature range for the rapid growth of ? crystals was determined.The molding process was used for the secondary verification of the stepwise crystallization process.Finally,the insulation sleeve technology was used to renovate the existing lines.The stepwise crystallization method was used for the actual production and extrusion of PPR pipes.(3)The ?/? two-component compound nucleating agents were added to the PPR resin,and the effects of the nucleating agents on the crystallization behavior and crystallization kinetics of PPR were studied.The ? nucleating agent used was BTACA,and the ? nucleating agents were BCABA,rare earth compound WBG,and inorganic nucleating agent calcium pimelate Ca Pi.It was found that the nucleating agents increased the crystallization temperature of PPR and accelerated the crystallization rate.The relative content of ? crystals in PPR depends on the cooling rate,crystallization temperature,and the difference in crystallization temperature changes caused by two individual nucleating agents.The non-isothermal crystallization kinetics was studied using Caze method and Mo method.Friedman method calculation shows that the effective activation energy of crystallization process with the increase of relative crystallinity increased.