Preparation Of Shape Memory Polyurethane Materials And Their Tribological Properties

Shape-memory polymers（SMP）are a class of polymers whose initial shape can be restored by external environmental conditions（light,heat,magnetism,solvents,etc.）after the initial shape of the product has been changed and fixed under certain conditions.Because of its deformation,variable modulus and energy storage characteristics,it has broad application prospects in the field of drive and smart materials.Polyurethane is widely used as a dynamic sealing material because of its high tensile strength,excellent elasticity and wear resistance.However,frictional heat buildup can cause seal failure and low sealing pressure,which seriously affects the scope of polyurethane applications.The design and preparation of high strength shape memory polyurethane materials,using their deformation and corresponding energy conversion,is expected to solve the problem of frictional failure caused by frictional heat.This thesis therefore designs two types of shape-memory polyurethane materials.By constructing polyurethane molecular structures,the self-lubricating properties of polyurethane materials are optimised to regulate their tribological properties in combination with their shape memory properties on the one hand;on the other hand,the tribological properties of the materials are regulated in terms of their mechanical properties by adjusting the transition temperature and mechanical properties of the shape-memory polyurethane.By constructing the relationship between molecular structure and mechanical properties as well as shape memory properties,we reveal the modulation of the mechanical properties,shape memory properties and tribological properties of polyurethane by polymer chain segment structure,cross-linking degree and soft and hard segment content,and provide new ideas for the development of shape memory polyurethane materials and their applications.The main research of this thesis is as follows:（1）By introducing a rigid mesocrystal unit（BP₆）into the polyurethane material,the microstructure of the shape-memory polyurethane material is regulated,thus achieving the regulation of mechanical,thermomechanical and shape-memory properties.In addition,the self-lubricating properties of the mesocrystal unit and the shape memory properties are used to improve the tribological properties of polyurethane materials.（2）Modulation of the transition temperature and mechanical properties of shape memory polyurethanes by constructing epoxy-polyurethane interpenetrating polymer network structures（IPNs）.The mechanism of IPN crosslinking density on the shape memory properties and tribological properties of shape memory polyurethane is investigated,and a new type of shape memory polymer lubricant material is developed.