Modification Of Melamine Formaldehyde Resin And Its Foam Technology

This paper studied the melamine and formaldehyde as raw materials to synthesize melamine formaldehyde resin in alkaline environment, and then through different foaming technology, the melamine-formaldehyde resin can be made for rigid external wall heat insulation fire retardant foams.First of all, the effect of traditional process conditions to the performance of melamine formaldehyde resin and its foams was discussed. The main factors include the mole ratio of formaldehyde and melamine, reaction temperature, the pH, solid content, the quality of raw materials, foam way and so on. Those were found:the best ratio of melamine and formaldehyde isl:2.0, the best reaction temperature was85℃; under this temperature, the best reaction time was9hours; the best pH under the hydroxyl methylation process was8to9, and the condensation process was7; the best solid content was60-75%. Under the condition of the basic reaction has been explored to the best, we Used three types of modifier to modify the melamine formaldehyde resins. The first type is a small molecular monomers, such as acrylamide, urea, etc; The second type is a high molecular compound, such as polyving akohol, polyacrylamide, etc; The third class is mainly choosing crosslinking agent to modify the resins, such as2-Mercaptobenzothiazole,2,2’-Dibenzothiazole disulfide, etc. Experiment results showed that the improvement of crosslinker to resin and foam performance is limited, but the modified agent of low molecular monomer and polymer modifier on foam performance improvement are more significant.Under the condition of the resin synthesis process is determined, the foaming process of resin were studied. We found that the most significant influence on foaming are curing agent, foaming agent, emulsifier, foaming method, curing, etc. The best foaming condition are that:the curing agent is oxalate, the foaming agent is n-pentane, the emulsifier is MX made by ourselves. At the same time, the method of microwave foaming was employed, the curing temperature and time were controlled at100℃and6h respectively. In addition, under the condition of both mechanical properties and cost, the best foam density is40kg/m3.From scanning electron microscopy analysis, we found that the foam presented a honeycomb closed pore structure, and the foam bubble pores distribute uniformly, with 60-100μ.m diameters. According to the test, the oxygen index is37, the bubble water absorption is6%, the thermal conductivity is0.032w/(m·k), the bending and compressive strength can be close to the ministerial standard of the polystyrene exterior wall insulation board.