Surfacr Modification Of Aramid Fiber And Investigation Of Its Adhesion Property To Rubber

Lacking of reactive groups on aramid fiber surface lead to poor adhesion of aramid fiber to matrix.Generally,the treating process was consist of first-bathing treatment(i.e.pretreatment using epoxy resin)and second-bathing treatment(i.e.retreatment using RFL).The treatment of aramid fiber surface using first-bathing solution,second-bathing solution,third-bathing solution has been implemented and the formulations of the solutions were changed to improve the adhesion of aramid fiber to rubber in this paper.Effect of the adhesion promoters,such as coumarone resin,polysulfide rubber,phenolic resin PN760,and nanofillers,such as silica,carbon nanotube(CNTs),on adhesion of aramid fiber to natural rubber(NR)and chloroprene rubber(CR)has been researched,the adhesion interfaces were also analyzed.The results suggested that adhesion of aramid fiber to natural rubber has been improved after adding adhesion promoters into the first-bathing solution,such as coumarone resin,polysulfide rubber,chlorinated natural rubber/nitrile rubber(CNR/NBR).Moreover,coumarone resin content in first-bathing solution was adjusted in a small scale,the adhesion property between aramid fiber and natural rubber showed no significant changes,but it improved obviously with increasing polysulfide rubber content in a larger scale.After the first-bathing treatment,aramid was immersed into second-bathing solution containing different fumed silica content,the adhesion property enhanced continuously with increasing fumed silica content.Furthermore,the adhesion property would be also improved if aramid fiber surfaces were coated with third-bathing solution containing PN760 after secong-bathing treatment,and it improved continuously with increasing PN760 content.Scanning Electron Microscope(SEM)was used for analyzing the morphology before and after surface treatment.Second-bathing treatment improved tow collecting of fiber bundle,single fibers were adhered together and formed some grooves.Element dispersion of interface between aramid fiber and natural rubber was also analyzed using Energy Dispersive X-ray Spectroscope(EDX),which was coated with third-bathing solution containing PN760 or immersed into second-bathing solution containing fumed silica.It could be observed that more sulfur,znic dispersed onto the interface because of coating with third-bathing solution,however,there was no regulation after aramid fiber was immersed into second-bathing solution with fumed silica.Therefore,bonding mechanism between treated aramid fiber and natural rubber could be summarized as follows: adhesion promoters or nano-fillers enhanced the dispersion of rubber molecular chains,vulcanizing agent,promoter,active agent onto the adhesion interface and co-vulcanized with latex on the surface of aramid fiber,or reinforce the interface to form a certain modulus gradients,finally fiber and matrix were bonded through physical interaction or chemical bonds.When chloroprene rubber(CR)was reinforced with aramid fiber,using chloroprene rubber latex as the latex phase of second-bathing solution instead of butadiene-vinylpyridine copolymer latex leads a significant improvement of adhesion between aramid fiber and chloroprene rubber.Different grades of chloroprene rubber were utilized to prepare third-bathing solution and coated fiber surface behind second-bathing treatment,adhesion property of fiber to matrix improved,CR2321,with lower crystallization rate and Mooney viscosity,enhanced adhesion more efficiently.After third-bathing treatment with CR2321 or different adhesion promoters,adhesion property has been improved,and the third-bathing solution with CR/PN760 made a highest improvement of adhesion.