Preparation,Structure And Properties Of Novel Polyurethane Elastomers Based On Macromolecular Assembly Strategy

Wheels are one of the greatest inventions in the history of human civilization,which have greatly improved working efficiency and liberated productivity.Today,tire manufacturing technology has undergone several major technological and theoretical revolutions.However,with the rapid development of the automotive industry and highways,tires have currently become one of the polymer products with the highest yield at the maximum technological level.In the past five years,energy use due to automobile tires,directly or indirectly,accounts for greater than 6%of the world’s total energy consumption,which accordingly generates approximately 5%of all carbon dioxide emissions.It has raised higher and more pressing demands on the performance of tires because of the social development and environmental pollution problems due to the increasingly serious energy consumption,the increasing of safety accidents,and the emission of a large amount of rubber wear particles,debris,etc.Therefore,based on a macromolecular assembly strategy,we designed and fabricated a high-strength,high-toughness fully-organic elastomer(solution-polymerized styrene-butadiene rubber based polyurethane elastomer material).This novel elastomer delicately balances rolling resistance,wear resistance and wet-skid resistance,addressing the so-called "magic triangle" that has plagued the tire industry for more than century.Preparation of high vinyl content hydroxyl-terminated solution-polymerized styrene-butadiene(HTSSBR)copolymers as soft segments of the elastomers by anionic polymerization of styrene and butadiene,ensures that the prepared elastomers have excellent dynamic mechanical properties and good wet-skid resistance.HTSSBR was crosslinked with highly symmetric isocyanates and polyols,ensuring its high temperature resistance,to generate a uniform network by macromolecular self-assembly.This novel polyurethane elastomer affords a new opportunity for the large-scale application of next-generation high-performance automobile tires that will,in part,resolve a serious global energy and environmental crisis.The first part of this paper(Chapter 3 and 4)is to regulate the soft segment micro structures,such as the mass fraction of soft segments and the molecular weight of soft segment,and the hard segment micro structures,such as the ratio of chain extender and crosslinking agent,and isocyanate species,of HTSSBR-PU elastomers.The effects of micro structure change on its macroscopic properties were systematically studied by FT-IR,1H-NMR,GPC,XRD,TEM,DSC,TGA,TMA,DMA and other characterization methods.At the same time,the mechanism of heat resistance was explained by combining with the molecular dynamics simulations.The second part of this paper(Chapter 5)is to further demonstrate the feasibility of designed and fabricated HTSSBR-PU elastomers in large-scale preparation and industrial application.We combined HTSSBR-PU elastomer with two commercial products("Green Tire" material HT166,High Performance Thermoplastic Polyurethane C85A HPM)that had been marketed on a large scale.The tensile strength and tear strength of HTSSBR-PU elastomer reached 23.8 MPa and 46.3 kN·m-1,which has meet the application requirements of tire industry and rubber industry.Remarkably,compared with the nanocomposites tailored for "green tires",the wear resistance,rolling resistance and wet-skid resistance of HTSSBR-PU are improved by 94.6%,69.8%and 13.8%,respectively;in addition,the energy loss is reduced by 79.1%and the temperature rise is reduced by 59.1%,which was tested under harsh conditions.Compared with that of high-performance thermoplastic polyurethane C85A HPM,the softening temperature of HTSSBR-PU elastomer is improved by approximately 25 ℃.In the third part of this paper(Chapter 6),butadiene rubber-polyurethane elastomers are designed and prepared for tires that have more stringent requirements for rolling resistance and wear resistance in special using environments and their properties were modified by y-ray irradiation.FT-IR,XRD,TEM,DSC,TGA,TMA,DMA,low-field nuclear magnetic analysis and other characterization methods were used to study the influence of different hard segment mass fractions and irradiation dose on their aggregation state structures and macroscopic properties.Meanwhile their irradiation mechanism was explained in detail.Irradiation cross-linking can make the cooperativity of HTPB-PU molecular chain better.With the irradiation dose increased from 0 kGy to 500 kGy,the rolling resistance is reduced by 68.9%,and the upper limit of the irradiation dose is determined with the value of 250～300 kGy.In addition,the radiation cross-linking modification has significantly improved the heat resistance of HTPB-PU elastomers.HTPB-PU elastomers provide new ideas for preparing the next generation of ultra-low rolling resistance and fuel-saving tires and have a broad application prospects.