Research On Preparation And Temperature Sensitivity Of Rigid Polyurethane Foaming Material

The temperature-sensitive rigid polyurethane foam material is a thermosetting shape-memory polymer material with temperature-sensitive properties,which can change the initial shape under the stimulation of external temperature changes and fix the deformation after the temperature is lowered.While raise the temperature again,the material can be restored to its original shape through a unique thermodynamic recovery process.This property makes temperature-sensitive rigid polyurethane foam materials widely used in petroleum engineering,aerospace,biomedical and other fields.In this paper,modified MDI synthetic rigid polyurethane foaming materials were used.Firstly,the temperature sensitive polyurethane matrix resin was studied,the effects of the type of polyols,the type of chain extenders,the content of hard segment and the isocyanate content of modified MDI on the properties of polyurethane matrix resin were investigated.On the basis of the polyurethane matrix resin,the foaming agent was added to the raw materials to study the influence of different factors on the properties of the rigid polyurethane foaming material.After the foaming materials were obtained,the properties of foaming materials were studied under different synthetic conditions as well as the influence of the cell structure.Finally,the material was tested for aging and temperature resistance.The relevant experimental results are as follows:(1)In the synthesis of temperature-sensitive polyurethane matrix resin,the sample prepared by polycarbonate diol has the highest glass transition temperature and the best mechanical properties,and the deformation and deformation recovery temperature are the highest;Among the polyurethane matrix resins prepared by different chain extenders,when the molecular weight of the chain extender is larger and the flexibility is better,the mechanical properties of the prepared sample are lower,the glass transition temperature is lower,but the temperature sensitivity of the material is improved.The higher the content of hard segment,the higher the mechanical properties and glass transition temperature of the material,and the higher the speed of deformation recovery at high temperature;Adjusting the different isocyanate content in the modified MDI,it is found that the higher the isocyanate content,the higher the mechanical properties,deformation and deformation recovery temperature of the material,but the recovery rate of deformation will decrease.(2)In the synthesis of temperature-sensitive rigid polyurethane foam materials,Polycarbonate diols with different molecular weight ratios,as the proportion of PCDL20 increases,the glass transition temperature and deformation and deformation recovery temperature of the material increase,but the mechanical properties decrease slightly,the cell size of the material increases,and the open porosity decreases.Different types of polycarbonate diols,T4691 foams have the best mechanical properties and the highest glass transition temperature.Changing the chain extender in the raw material,it is found that as the molecular weight of the chain extender increases,the mechanical properties of the material decrease and the cell size becomes larger.The cell size of the material decreases with the increase of the hard segment content,and the mechanical properties and deformationa as well as deformation recovery temperature also increases with the increase of the hard segment content.As the amount of foaming agent increases,the cell size of the material becomes larger and the mechanical properties decrease.Using AK-8818 as a foam stabilizer,the material has the finest cell structure and the highest mechanical properties,and Niax L-6164 has a good effect as a cell opener.(3)As the temperature of the raw material increases,the cell size of the material becomes smaller and the opening ratio decreases.The faster the mixing speed,thehigher the mechanical properties of the material and the smaller the cell size.The mechanical properties of the material increase first and then decrease with the increase of the filling coefficient.The excessive filling coefficient causes the cells of the material to appear and foam.The combination of a suitable chemical blowing agent and a physical blowing agent can improve the mechanical properties of the material,but an excessive proportion of the physical blowing agent leads to a decrease in the performance of the material.(4)Among different types of polyols,polycarbonate diol has the best heat aging resistance,and as the molecular weight of the polyol increases,the temperature resistance decreases,and PCDL10 has the best temperature resistance.The shorter the molecular chain of the chain extender,the higher the initial mechanical properties of the obtained material,but the heat aging resistance and temperature resistance are poor.The temperature resistance and heat aging resistance of the material increase with the increase of the hard segment content.