Structural Modification Of Heat Resistance,Aging Resistance And Toughening Of Foamable Phenolic Resin

Phenolic foam was widely used in construction,aviation,energy and other industries.Its advantages such as light weight,heat insulation,good sound insulation,low thermal conductivity and easy molding and processing were not comparable to other foam plastics.In order to improve the overall performance of phenolic foam,it must be targeted to improve the shortcomings of the foam itself.Improving the toughness and heat resistance of phenolic foam has become the main research direction of phenolic foam.The modification of foamable phenolic resin is of great significance to the modification of phenolic foam.This paper used chemical modification method,two kinds of modifiers were used to modify the heat resistance and toughness of phenolic foam,respectively.The molecular structure of the modified phenolic resin was characterized by the use of infrared spectroscopy(FTIR)and nuclear magnetic resonance carbon spectroscopy(NMR).In addition,physical properties such as viscosity,solid content,free formaldehyde,and gel time were also tested on the modified phenolic resin.Aiming at the thermal properties of the modified phenolic foam,thermogravimetric analysis was performed on the modified phenolic foam by means of thermal weight loss analysis(TG)and other instruments.Phenolic foam has also been tested for quality change rate,dimensional change rate,chalking rate,water absorption rate and compressive strength before and after aging under certain temperature conditions.Aiming at the toughness of the modified phenolic foam,the flexural displacement,impact strength and other mechanical properties of the modified phenolic foam were tested by universal testing machines.In addition,the apparent density,water absorption,and degree of chalking of the foam are also tested.The experimental results show that terephthalyl alcohol can react with phenol under different acid-base catalyst conditions to form two modified phenols with different structures,and then react with paraformaldehyde to produce two modified molecular phenolic resins.Terephthalyl alcohol successfully introduced benzene ring with high thermal stability into phenolic resin structure.Terephthalyl alcohol-modified phenolic foam has excellent performance.After 24 hours of heat aging,themass loss rate of modified phenolic foam was only 4.5%,and the pulverization rate only increased by 3.2%,while the mass loss rate of unmodified foam was as high as 8.2%,and the degree of pulverization increased by4.38%.After aging,the water absorption of modified phenolic foam increased by 0.77%,which was one third of the increase degree of unmodified phenolic foam.In addition,,the reduction degree in compressive strength of unmodified phenolic foam is twice that of its modified foam after aging,showing good heat aging resistance;The experimental results showed that the flexible carbon long chain of cardanol is successfully introduced into the phenolic resin structure.The apparent density of cardanol-modified phenolic foam was up to 0.0482g/cm3 when the amount of modifier is 15%,which is 10.29% higher than that of ordinary phenolic foam.The water absorption of the foam has also reached the lowest at this amount.Compared with unmodified phenolic foam,the cardanol-modified phenolic foam has a reduction in powdering degree of 49.1%,an increase in bending deflection of 72.07%,and an increase in impact strength of 38.19%.The introduction of cardanol has a positive effect on improving the toughness of phenolic foam.