| Phenolic resin is wildly used in friction materials,adhesives,coatings,electronic Packaging and so on,because of its good heat resistance.However,phenolic resin needs toughening modification to meet the requirements of use,because of its brittleness and insufficient adhesive properties.At present,the toughening modification methods include chemical modification and blending modification.In this Paper,thermosetting cardanol modified phenolic resin is prepared by three different synthetic processes with cardanol,phenol and formaldehyde as raw materials and ammonia as catalyst,including cardanol-formaldehyde resin(CF),cardanol-phenol-formaldehyde resin(PCF-A)and mixed phenol(cardanol-phenol-bisphenol)-formaldehyde resin(PCF-B).The structures and properties of three resins are characterized by FT-IR,DSC,TGA and shear strength.Then,phenol-formaldehyde resin(PF)is modified by blending with the three resins,respectively.The curing behavior,thermal stability and adhesive strength of the blend resin are investigated.CF resin has the lowest curing reaction activity.The gel temperature,curing temperature and post treatment temperature of CF resin are 174?,220 and 256? ?,respectively,which are much higher than PF resin(136?,163? and 181?).The thermal stability of CF resin at high temperature is poor.The 5% weight loss temperature and the 600 ?carbon residue rate of CF resin is 385 ?and 8% in the nitrogen atmosphere respectively,which are much lower than PF resin(412 ?and 71%).It has poor adhesive properties,which is 2.89 MPa at room temperature and 0.99 MPa at 150?,respectively.It is found that CF/PF blend show excellent high temperature bonding performance.When the content of cardanol is 20%,the shear strength of CF/PF blend is 6.50 MPa at 250 ?and 4.80 MPa at 300?,respectively,123% and 131% of PF resin.When the content of cardanol in CF/PF blend resin is between 20% and 40%,the curing temperature ranges from 190? ~236 ?,and the 5% weight loss temperature of CF/PF blend in nitrogen atmosphere ranges from 397? ~376?.The gel temperature,curing temperature and post treatment temperature of PCF-A resin are 143?,184 ?and 268?,respectively,which are higher than PF resin,but lower than CF resin.The 5% weight loss temperature and the 600 ?carbon residue rate of PCF-A resin is 407 and 42% in the nitrogen atmosphere respectively,which ?are lower than PF resin,but higher than CF resin.PCF-A resin has good bonding properties at room temperature and 150?.The shear strength at room temperature and 150 is 6.91 MPa and 5.79 MPa,respectively,which is 5% and 28% higher than PF ?resin.It is found that PCF-A/PF blend has excellent thermal stability at high temperature and adhesive properties at room temperature and 150 ?.When the content of cardanol is 20%,the shear strength of PCF-A/PF blend is 6.56 MPa at room temperature and 7.5MPa at 150?,respectively,the shear strength at 150 ?is 65% higher than PF resin.When the content of cardanol in PCF-A/PF blend resin is between 20% and 40%,the curing temperature ranges from 207? ~ 209?,and the 5% weight loss temperature of PCF-A/PF blend resin maintains at 407? in nitrogen atmosphere,which is not significantly lower than PF resin.The gel temperature of PCF-B resin is 126?,lower than PF resin,and curing temperature and post treatment temperature are 166 and 243? ?,respectively,which are higer than PF resin,but the curing reaction activity is the highest among those synthetic resins.The 5% weight loss temperature and the 600 carbon residue rate of ?PCF-B resin is 397 ?and 37% in the nitrogen atmosphere respectively,which are lower than PF resin and PCF-A resin,but higher than CF resin.PCF-B resin has excellent adhesive properties at room temperature and 150?.The shear strength is 8.31 MPa at room temperature and 7.74 MPa at 150?,respectively,which is 27% and 71% higher than PF resin.It is found that PCF-B/PF blend has excellent comprehensive adhesive properties,higher thermal stability at high temperature.When the content of cardanol is 20%,the shear strength of PCF-B/PF blend is 7.61 MPa at room temperature and 6.3MPa at 150 which is 16% and 39% higher than PF resin,?and 6.5MPa at 250 and 4.8MPa at 300? ?respectively,which is 116% and 138% of PF resin.When the content of cardanol in PCF-B/PF blend resin is between 20% and 40%,the curing temperature ranges from 185? ~ 190?,and the 5% weight loss temperature of PCF-B/PF blend in nitrogen atmosphere ranges from 401? ~397?,which is slightly lower than PF resin(412?). |
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