Research On The Relationship Between Properties And Structure Of High Performance Castable Polyurethane Elastomer For Dynamic Loading Application

As it is well known that there are some unbalanced contradictions among three driving performance of tire---low roll resistance, high wet skidding resistance and abrasion resisting property. Especially, the irreconcilable conflict between rolling resistance and wet traction is the key problem in tire industry.Because of their excellent tensile strength, tear strength, load bearing ability, abrasion resistance, solvent resistance, and other physical characteristics, CPUEs have been successfully employed in a growing variety of applications and became one of the six polymeric materials. This kind of material can be delivered by metering pump and casted into mould, then formed via cross-linking reaction. Compared with rubber material, polyurethane elastomer possessed wide range of variable hardness (Shore A 10 ~ Shore D 85),anticorrosion,tear resistance,excellent low temperature performance and oil resistance. Because of fluidity of prepolymer, the processing of polyurethane elastomer is simple, low energy consumption and highly autonomous. With the development of national economy, many CPUE materials with outstanding properties have replaced many special rubber products, especially some articles within tough requirements, such as rubber pads for tank track, road wheel, tire, rubber roller, damping materials and medical cardiovascular materials.In order to make it possible for CPUE used as tire tread, the castable polyurethane elastomers based on poly(ε-caprolactone)-toluene diisocyanate systems were carefully investigated as the model polymer materials. In order to establish the relationship between the formulas and the properties, the influence factors of thermal properties and dynamic mechanical properties were introduced and analysis. Based on the experimental research, the correlationships among the molecular architecture, supermolecular structure and the properties of castable polyurethane elastomers were constructed. The main research contents are listed below: the research on the mechanical properties, inner molecular structure, supermolecular micro domain structure, thermal properties and dynamic properties of two basic systems with two kinds of chain extenders, which were prepared with different molecular weights soft segments and various hard segment contents. And aimed at the requirement of the castable polyurethane elastomer used in the elevated temperature, high loading and harsh alternating stress application, we investigated the relationship of material properties and three main compositions of this polymer, what has been well known as the soft glycol, diisocyanate and chain extender. In addition, the improvement of nano size filler on the properties of castable polyurethane elastomer and its mechanism was studied and discussed systematically. A new concept, intergral polyurethane elastomer, was created based on the relationship between the molecular architecture & inner structure of polyurethane elastomers and thermal properties & dynamic mechanical properties of materials, also this concept stemmed from the thought of the design of polymer materials. Therefore, the study of molecular architecture and structure design of intergral polyurethane elastomer was carried out to obtain an overall balance of excellent roll resistance, wet skidding performance, wear resistance and heat build up (hysteresis). At the same time, the thermal properties of intergral polyurethane elastomer should be improved significantly. The experimental research and the theory innovation should be the theoretical basis for the molecular architecture and structure design of high performance castable polyurethane elastomer for dynamic loading application.Specific as follows:1 In order to establish the relationship between the formulas and the properties, the influence factors of thermal properties and dynamic mechanical properties, such as variety and molecular weight of glycols, content and type of isocyanates and chain-extenders, were introduced and analysis.2 Based on the study of reacting rheology and microstructure of HTPB/IPDI polyurethanes, a viewpoint was proposed like that: thermodynamics incompatibility of soft segments/hard segments of castable polyurethane elastomers, reaction rheology and mobility of soft/hard chain segment are the main factors for micro structure of the segmented polyurethane. And which one is the major should be judged from the experimental results.3 Nano size filler can be used to modify the properties of castable polyurethane elastomer and the improvement of the properties. The modification related to the surface nature of nano size filler and the type of soft polyol. The two nano size SiO2 with different properties had different dispersion and stability in different kinds of CPUE. The hydrophilic AEROSIL 200 could be dispersed in the PCL based system and the final product performed excellent. This filler was not fit for the PTMG based system, there were agglomerating phenomenon, and even some nano-agglomerates with more than 1μm diameter. The hydrophobic AEROSIL R972 could be dispersed homogeneously in both the PCL based system and the PTMG based system. Moreover, both the two types of nano size filler reinforced the PCL based system. The tensile strength and tear strength at 100℃of PCL based CPUE with 5% AEROSIL 200 were 1.84 and 1.13 times than those of the pure PCL CPUE, respectively. And the tensile strength and tear strength at 100℃of PCL based CPUE with 5% AEROSIL R972 were 1.78 and 2.13 times than those of the pure PCL CPUE, respectively.4 The molecular structure difference between traditional vulcanized rubber and CPUE liquid rubber was investigated systematically, and the inner factors resulted in the different mechanical properties & dynamic properties between traditional rubber and CPUE were analyzed. Based on these work, a new concept, integral polyurethane elastomer, was put forward. The multi-component system CPU was prepared based on theoretical and experimental analysis. The mechanical properties of tri-component/tetra-component systems meet the requirement of the designed index. The optimized properties were achieved by acquiring the integrated balance of every index of properties.5 Through the preliminary exploration in integrated CPUE, the breakthrough of polyurethane materials was obtained. That is:(1) Initial modulus of CPUE can be reduced greatly, and the value was comparable to the traditional vulcanized rubber;(2) Glass transition temperature of CPUE can be reduced to the level of the traditional vulcanized rubber;(3) The tanδin 50-100 degrees Celsius temperature range of integral CPUE is lower than that of the traditional vulcanized rubber, that mean the integral CPUE possessed lower heat build up and lower rolling resistance.