The Affect Of Hygrothermal Aging To The Mechanical Properties Of Polyurethane Elastomer In Toughening Electronics Packaging Material

Toughening the ethoxyline resin with polyurethane elastomer is an important method to compensate for the defects of ethoxyline resin, such as fragile texture and weak toughness after the thermofixation. In recent years, the technology of this method gets more and more attention of the scholars. But for the polyurethane elastomer, its biggest disadvantage is the susceptibility to the hygrothermal aging. Through theoretical and experimental analysis, this paper studied the influences of hygrothermal aging to the polyurethane elastomer’s mechanical properties. The main work of the thesis is summarized as the following aspects:(1) Through comparative analysis the mechanical properties of unaged and hygrothermal aged two types of polyurethane elastomer with different content of cyanate, it was found that:whether for polyester-based polyurethane elastomers or polyether-based polyurethane elastomer, appropriately increasing the content of cyanate within a certain range can not only enhance the strength, but also improve the anti-hygrothermal-aging ability of polyurethane elastomers.If the contents of cyanate are the same, the polyester-based polyurethane elastomers has a higher strength than the polyether-based polyurethane elastomer. In the meantime, the former also has a higher sensitivity to hygrothermal aging.(2) The impact of hygrothermal aging to mechanical properties was studied through experiment. And measured the unidirectional tension mechanical properties of unaged and anged at each day materials.It was found that the decrease of mechanical properties is more obvious in the early stage of aging. It is not a simple liner relation between the decrease of mechanical properties and the aging time.(3) Three deformation strain energy functions were selected, each one adapts to the different degrees of deformation, and the expression forms of them were geted under the circumstances of isotropic elasticity and incompressibility. Based on the principle of least squares method, this paper fitted the constitutive parameters of three deformation strain energy functions by using numerical analysis The variations of the constitutive parameters with aging time were found. Thereby, the three deformation strain energy functions with aging time and initial constitutive parameters as their variables can be geted.