Toughening Modification Of Phenolic Foam Plastics And Research On The Structure And Performance

Phenolic foam plastics is a kind of thermal-insulation material with excellent properties:low thermal conductivity, fine flame retardant, fewer smog and innocuous, high temperatureresistance, good resistance to chemical corrosion and so on. However disadvantages in thestructure of phenolic resin with oxidizing phenolic hydroxyl group and methylene group leadto low strength, big brittleness, easy pulverization, no resistance to bending, which limit theapplication of phenolic foam plastics. In order to solve the above problems, it needstoughening modification. Meanwhile we study on the cellular structure and performance ofphenolic foam plastics.Firstly ranges of process parameters were determined by single factor experimentmethod such as viscosity of unmodified phenolic resin, foaming temperature, stirring speed,surface active agent, curing agent, foaming agent. Then orthogonal test was designed tooptimize process parameters of phenolic foam.The results show that the optimal processparameters of orthogonal test are curing agent for15%, foaming agent for22%, surface activeagent for1.5%, temperature for50℃. The properties of phenolic foam plastics prepared usingthe optimal process are as follows: apparent density for61kg/m3,thermal conductivity for0.02997W/(m·K), compressive strength for300KPa, water absorption for3.7%, slag rate for7.9%, oxygen index for45, cell diameter for258μm, film thickness for1.8μm.Secondly physical toughening phenolic foam plastics was prepared by adding PEG. Theresults show that with the increase of the concentration of PEG, apparent density of modifiedphenolic foam firstly increases and then decreases, compressive strength firstly increases andthen decreases, slag rate firstly decreases and then increases, thermal conductivity firstlyincreases and then decreases and increases again, water absorption firstly decreases and thenincreases, oxygen index decreases by degrees. When the concentration of PEG is10%, theproperties of phenolic foam are best. The properties are as follows: apparent density for66kg/m3, thermal conductivity for0.02728W/(m·K), compressive strength for319KPa, waterabsorption for2.8%, slag rate for3.6%, oxygen index for39, cell diameter for244μm, filmthickness for2.0μm. After modified by PEG, the slag rate is from7.8%to3.6%, a drop of54%,which indicate that the toughness of phenolic foam is greatly improved. Meanwhile the results show most of the performance are optimized that the apparent density and compressionstrength increases, the cell diameter, thermal conductivity and water absorption decreases. Butthe oxygen index also decreases, which indicate that the combustion performance degrades.Finally we used the SEM to observe morphology and Nano Measurer size distributioncalculation software was used to analyze SEM image for determine the cell diameter and filmthickness. Then study on the cellular structure and performance of phenolic foam plastics. It isindicated that with the increase of apparent density, cell diameter decreases gradually, thermalconductivity and compressive strength increase gradually. When apparent density is constant,thermal conductivity shows an increasing trend with increasing cell diameter. When allother conditions (chemical structure, apparent density, film thickness, water absorption, ect.)remain unchanged, compressive strength decreases with the increase of cell diameter. Whenall other conditions (chemical structure, apparent density, film thickness, cell diameter, ect.)remain unchanged, compressive strength decreases with the increase of the waterabsorption.When the apparent density of phenolic foam with high closed pore rate is constant,compressive strength shows a decreasing trend with increasing film thickness.