Study On The Flame Retardancy Of Phenolic Resin Modified By Carbon Nanotubes

Phenolic resin(PR)is one of three synthetic polymer materials that has become an indispensable functional material for industrial and public life applications.With the impact of safety and environmental protection,it has become a research target to improve the flame retardancy and environmental protection of polymers from the flame retardancy and the flue gas analysis of the polymers in the field of materials.It is urgent to study the flame retardancy and smoke generation characteristics of polymer materials.In this paper,different molar ratios of formaldehyde and phenol were used to prepare phenolic resin(PR)with barium hydroxide as catalyst.The optimum molar ratio of raw materials to prepare PR was characterized by the yield,free formaldehyde content,amount of cure loss and oxygen index(OI).MWCNTs-OH/PR was prepared by in-situ polymerization,and MWCNTs-OH was pretreated by ultrasonic dispersion,mechanical stirring and chemical pretreatment with hydroxylated carbon nanotubes(MWCNTs-OH)as additives.The effects of MWCNTs-OH addition on thermal stability,flame retardancy,flue gas yield,toxic gas yield and mechanical properties of PR were studied by means of oxygen index instrument,thermogravimetric analyzer,cone calorimeter and scanning electron microscope.The results showed PR had the best flame retardancy,good yield,low free formaldehyde and good degree of crosslinking under fixed preparation and curing conditions while the molar ratio of formaldehyde to phenol was 1.3:1.When 0.2wt%-MWCNTs-OH was added,the oxygen index of the sample increased by 3.6%,the flame retardant effect was more obvious,the addition of proper amount of MWCNTs-OH was conducive to reducing the rate of thermal decomposition of PR and the improvement of residual carbon rate.The carbon residue percentage of 0.2wt% MWCNTs-OH increased by about 6.1%,and the activation energy increased at the reaction stage.A comprehensive analysis of the cone calorimetry experiments showed that PHRR,THR,EHC,PCOP and COY were reduced to a certain extent when the MWCNTs-OH content was 0.2wt%,indicating that it was most beneficial to inhibit the production of CO and improve the thermal stability and flame retardancy of material.The proper amount of MWCNTs-OH could promote the formation of carbon layer during the pyrolysis of PR,which helped to steady the integrity and tightness of the carbon layer during carbonization,so it could strengthen the ability of the sample to block the heat transfer to improve the flame retardancy.