Constitutive Relation And Thermal Aging Performance Of Cast Polyurethane Elastomer

As a major branch of polyurethane,cast polyurethane elastomers have a soft and hardtwo-phase structure that has excellent mechanical properties,physical properties and chemical properties,and are widely used in various fields of the national economy.Automotive,defense,aerospace,medical,construction and many other industries.The CPU1# and CPU2#studied in this paper are the main constituent materials of a product.Due to the special use of the product,the mechanical properties of the CPU1# polyurethane elastomer material and CPU2# polyurethane elastomer material and there are strict requirements for heat aging properties.To this end,this article has conducted in-depth research on the constitutive relationship and thermal aging properties of the two materials.The main research contents are as follows:(1)According to the requirements of engineering products on the mechanical properties of the two materials,polyurethane elastomer materials were prepared.By changing the two process parameters of prepolymer NCO group mass fraction and chain extension coefficient,a variety of formulas CPU1# were prepared;by changing the mass ratio of component B: A component,a variety of formulas CPU2# were prepared.By testing the mechanical properties of the two materials,the influence of the process parameters on the mechanical properties of the two materials is analyzed,and the optimal parameters are obtained.The polyurethane elastomer prepared under this parameter meets the mechanical performance requirements.The results show that the NCO-based mass fraction of 3.91% and the chain extension coefficient of 0.85 are the optimal parameters for the preparation of CPU1#;the mass ratio of component B: component A of 1.05 is the optimal parameter for preparation of CPU2#.(2)Through the uniaxial tensile test of CPU1# and CPU2# after heat aging,the stress-strain relationships of the two materials were obtained,and the MR model,Yeoh model and NH model are selected to fit the stress-strain curves of the two materials,based on the model with the highest fitting accuracy,introduces temperature-related terms,and establishes temperature-dependent constitutive models of the two CPU materials respectively,The results show that for the CPU1# material,the fitting accuracy of the MR model is the highest and the correlation coefficient R2 exceeds 0.9953,which can accurately describe its mechanical properties after thermal aging.For the CPU2# material,when the temperature is below 100?and the strain is greater than 0.4,the MR model can accurately describe its mechanical properties after thermal aging.(3)By conducting thermal aging experiments on the two CPU materials,the changes of the tensile strength and elongation at break of the two CPU materials during the thermal aging process were obtained,and the thermal aging properties of the two CPU materials were compared and analyzed,and the relationship between the tensile properties of the two materials and the temperature and time were polynomial fitted.The results show that the tensile strength and elongation at break of the two CPU show a trend of increasing first and then decreasing with increasing temperature;the thermal stability of CPU1# is better than that of CPU2#;The fitting results can better express the relationship between the tensile properties and the temperature and time during the thermal aging of the two materials.