Effect Of Nucleating Agent On Microstructure And Properties Of Flexible Polyurethane Foam

Due to its good damping performance,flexible polyurethane foam is a very ideal mat material in the industry and widely used in the automotive industry,noise control,electronic equipment,medical equipment and other fields,becoming a promising development in the synthetic material products.In electronic equipment such as laptops and mobile phones,mechanical damage may occur due to transportation,storage,and use.Therefore,flexible polyurethane foam as mat material is mostly used for buffer protection.However,due to its trend towards miniaturization,it is required that the foam material has exporousent damping performance at a lower foaming rate.So a higher requirement is imposed on the chemical structure and porous structure of the flexible polyurethane foam.In this thesis,a nucleating agent is introduced into a specific polyurethane matrix structure to improve the microstructure of the porouss and the damping property of the foam.The dissertation mainly studies the influence of the structure and surface modification of nucleating agent on the porous structure and damping properties of flexible polyurethane foams,especially on the surface of silica(SiO2)coated with specific groups that adsorbs the foaming gas.The nucleation effect can be better achieved,and a flexible polyurethane foam meeting application requirements is obtained.The specific research content is as follows:1.The effects of nucleating agents on the microstructure and damping properties of polyurethane foams are studied.Firstly,the basic formula of polyurethane foam prepared with DIPA and NaHCO3 as foaming agent is determined,and then adding different particle sizes SiO2 as nucleating agents in the two systems to prepare polyurethane foam.The results show that the microstructure and the damping performance of the foam are improved.When the particle size of the nucleating agent is 2500 mesh,the foam possess a small pore size,a uniform distribution,a high porosity,and a higher damping property;the effective damping temperatures are 73.82? and 63.25?,and damping factors maxima are 0.935 and 0.902,respectively.2.The effect on surface modification of nucleating agent SiO2 is studied.Three different silane coupling agents,y-amino propyltriethoxy silane(KH550),y-(2,3-epoxypropyloxy)propyltrimethoxy silane(KH560)and y-(acryloyloxy)propyltrimethoxy silane(KH570)are used to modify SiO2,and the modified samples are characterized by Fourier transform infraredspectroscopy,X-ray photoelectron spectroscopy,thermogravimetry and carbon dioxide adsorption.Then the modified samples are respectively introduced to prepare polyurethane foams by using NaHCO3 as a foaming agent.The results show that the amino group of KH5 50 has an adsorption effect on the CO2 gas released by the decomposition of NaHCO3.Therefore,the porosity of the foam prepared by using it as a nucleating agent is improved and the pore size of the pores is uniform.Compared with the unmodified,the effective damping temperature ranges increased from 63.2? to 69.31?,the maximum damping factor from 0.902 to 0.967.3.The thermal conductivity and glass transition temperature of the prepared polyurethane foams are compared.The results show that with the introduction of nucleating agents,the porosity and the open porosity of the porouss are both increased and the thermal conductivity of the foam is increased;when DIPA is used as a blowing agent,the glass transition temperature of the foam is increased,and NaHCO3 is used as a blowing agent.,the glass transition temperature decreases.