Reinforcement Modification Of Melamine Foam And The Mechanical Properties Of Melamine Foam Sandwich Composites

Melamine foam is a kind of open-cell foam which has advantages of high fire resistance, good thermal insulating, excellent sound absorption and low price of raw materials. It has optimistic market expectations and potential application values in the field of sound insulation, thermal insulation, construction, agriculture, transportation, aerospace and so on. Because of the existence of triazinyl in the melamine macromolecules, melamine foam has the problems of high brittleness, low strength and high pulverulent ratio. These problems restrict the industrial applications of melamine foam, especially rigid melamine foam. How to improve the melamine foam mechanics performance becomes a research hotspot. It has great significance to expand and enhance the application scope of melamine foam products. Based on this background, to analysis and research of melamine foam enhancement method, and to probe the application of melamine foam in the high-performance sandwich composites, this project used melamine resin as raw material to prepare melamine foam. By using process optimization, chemical modification and other methods, this project analyzed the influence on the melamine foam properties. Then investigated the methods of making melamine foam sandwich composites and their properties.In the aspect of melamine foam preparation process optimization, this project used orthogonal experimental design to find out the optimal condition of foaming process parameters. The results show that, in the scope of selected parameters, the optimal condition is 6% foaming agent; 12% curing agent; 1% emulsifier; 120℃2h,70℃2h. It was analyzed from SEM photos that foaming process parameters would affect the cellular structures. It will have high mechanical properties which has small cells and thick skeleton structure. It was analyzed from DSC that the curing exothermic process would be more evenly when add the curing agent. And it would begin to cure with heat release at a lower temperature. After add foaming agent, because of the endothermic gasification, higher temperature would be need when the resin is curing. It was analyzed from rheological test that the viscosity would change slowly without adding curing agent or at a low temperature.Because it is hard to match the foaming speed, the foaming process would be failed. DSC and rheological test made a explain of the optimal condition of foaming process.In the aspect of melamine resin modification, firstly, respectively used 1,4-butanediol, 1,3,5-tris(2-hydroxyethyl) isocyanurate, PEG-400 and pva-1788 for the chemical modification. Secondly, used the modified resin for making melamine foam at the optimal foaming condition. Thirdly, by test the compression performance, FT-IR, TG, LOI, pulverulent ratio and free formaldehyde emission, the comprehensive performance would be studied. Then optimized the species of modifier and its additive amount. The results of compression test shows that small molecule is better than the macromolecule. When add 20% 1,3,5-tris(2-hydroxyethyl) isocyanurate, modified melamine foam has the best compression performance. The compressive strength is 2 times than the original sample. After adding the modifier, foam’s pulverulent ratios declined, which makes it more difficult to break down and improve the mechanical properties. Through the SEM photos, it can be seen that when the foam’s apparent density is 0.3g/cm3, it has the cell membrance structure. There are several holes on the cell membrance. When the cell size is smaller, the foam mechanical properties are better. TG and LOI tests showed that the thermal stabilities and the flame retardant properties of the modified melamine foams were decreased. But in the proportion of modifier, the LOI were all above 30, which means the modified melamine foam still has good fire resistance. Due to not add formaldehyde elimination agent, all melamine foams had high content of free formaldehyde, about 1 mg/g.In the aspect of melamine foam sandwich composites preparation, this project used three kind of three-dimensional spacer fabric which height are 10mm,30mm and 37mm. The melamine foam sandwich composites is made of three-dimensional fabric with 20% 1,3,5-tris(2-hydroxyethyl) isocyanurate modified melamine foam. After compression test and bending test, the results shows that three-dimensional spacer fabric has small impact on the compression properties of melamine foam, but has great enhancement of bending properties. On account of the different performance between the warp direction and the weft direction of three-dimensional spacer fabric, the melamine foam sandwich composites also have different bending properties between warp direction and weft direction. The bending property of weft direction is better.