In Situ Preparation Of AC/MMT Nanocomposites Foaming Agent And Particle Refinery For Microcellular Foaming

As a new type of foam with excellent thermal and mechanical properties,microcellular foam plays an important role in the field of packaging electrical enclosures,painting the surface of aircrafts,synthesizing industrial sound insulation materials,etc.The method of supercritical fluid has been widely used for the preparation of microcellular foam.However,it still has difficulties for controlling with bubble morphology and rigorous requirements of the experimental device,which greatly limits the application of microcellular foam.On the other hand,in chemical foaming,the size and dispersion of foaming agent directly determine the cell size,density and performance of the foam products.In order to decrease the particle size of the insoluble foaming agent azodicarbonamide(AC),present works,makes an innovative solution of in-situ synthesis.Highly soluble urea is intercalated into the montmorillonite(MMT)layers,the biurea(LDA)was obtained by in-situ condensation,and AC was obtained by in-situ oxidation.The AC-MMT was applied to the epoxy resin to obtain a foamed polymer.Meanwhile,the direct solution intercalation process was applied to the system of MMT and AC to abtain the nanocomposite foaming agent AC-MMT.The product was further refined by gradient washing with the mixed solution.The nanocomposite AC-MMT with high dispersibility was applied to the thermosetting and thermoplastics to produce microcellular foamed polymers.(1)The purified Ca-MMT reacts with urea solution to obtain urea intercalated MMT(Urea-MMT).In-situ condensation reaction of Urea-MMT and hydrazine hydrate under high pressure resulted in the LDA intercalated montmorillonite(LDA-MMT).Finally,the novel nanaocomposites foaming agent AC-MMT was prepared by in situ oxidation.At the optimised oxidation conditions,with 0.5wt%KI as the catalyst and 50wt%H2O2 as the oxidant for 4 h at 65 ? in 1:1 volume ratio of DMSO to H2O,AC-MMT nanocomposite foaming agent with AC content of 40%was obtained.The prepared AC-MMT was applied to an epoxy resin atmospheric foaming to produce a foam product.(2)The intercalated AC-MMT nanocomposite foaming agent was prepared by an improved method of direct intercalation of AC in Ca-MMT.Using a solvent of alcohol,a mixture of alcohol and DMSO as well as the solutions with different concentrations of AC for gradient washing to improve the dispersity of nanocomposite foaming agent.The results show that the mixed solution gradient wash is favorable for the refine the particles of nanocomposite foaming agent.After the mixture solution washing,the AC particles coated on the surface of the agglomerates can be precipitated gradually,while avoided the AC molecules deintercalating from the MMT layers.Finally,the AC-MMT nanocomposite blowing agent with high dispersion and particle size range of 5?10 ?m was obtained.The intercalated AC-MMT with fine particles was applied to the foaming of thermosetting resin-epoxy resin and the thermoplastic polymer-polypropylene system.The foaming conditions such as the foaming temperature,the amount of the AC-MMT and the curing agent,the extrusion screw speed were optimized.In the polypropylene extruded foaming,foamed plastic with average cell diameter of 50?m was prepared with cell density of 106 cell/cm3,which was much better than that with the pure AC.