Impact On The Interface Of Aramid/Rubber And UV Resistant Properties By Surface Modified Aramid Fibers

The aramid fibers are high-performance fibers that have excellent tensile strength,modulus,out-bound fatigue resistance properties et al.Aramid/resin composites are widely used in high performance textiles,military and defense territories because of their outstanding properties,such as excellent impact resistance,damage tolerance,fracture toughness and machinable properties.However,the aramid fiber-reinforced rubber composites have poor interfacial adhesion because its obvious skin-core structure,surface lattice density,high-crystalline molecular chain structure and highly steric hindrance effect,which greatly lead to aramid fiber application restricted tyre-cord and conveyor belt.Therefore,it is very important to improve the adhesion strength with rubber matrix through surface modification of aramid fibers.In addition,wavelength of 300 ~ 450 nm,corresponding to UV radiation,is most sensitive to aramid fibers,including ultraviolet light and partial visible light of the sun's rays reach earth,due to its special physical and chemical structure.That will deteriorate fiber structure on the excellent mechanical properties.In this paper,the fiber surface modification is aim to improve the surface adhesion strength and resist UV irradiance property,on account of overcome two major critical drawbacks with aramid fibers.In order to improve the excellent physical and chemical properties of aramid fiber,especially ultraviolet aging resistance performance and the interface adhesion of aramid fiber-reinforced composites,the paper combined with the characteristics of aramid fiber,select waterborne polyurethane pre polymer(WPUP)encapsulated ZnO particles(ZnO@WPUP)to surface modification of aramid fibers.That was improved the ultraviolet irradiation resistance and fibers surface adhesion,utilized ZnO eminent ultraviolet absorption and the shielding effect,also introduced a great deal of reactive functional groups,and so on.First of all,the ZnO@WPUP emulsion were prepared in-situ emulsion polymerization method through isophorone diisocyanate(IPDI)with ethylene glycol.In the process,IPDI as the hard segment of polyurethane pre polymers,participated by catalyst and the chain extender.The nano ZnO generated interfacial polymerization reaction in the surface,eventually forming WPUP wall material coating these particles.The results show that the ZnO@WPUP emulsion modifier particles size reach to 56 nm,uniform dispersion,could storage stability.This method is convenient for industrialization application,which is operate simply,easy to control and friendly to environment.Then,aramid surface modification was the first time KOH treatment of the aramid fibers,treated by modified Zn O emulsion on the secondary processing.The particles with different content of WPUP modified ZnO through the regulation ratio of ZnO and IPDI.This study to research the method above-mentioned the impact of mechanical properties and bonding strength with natural rubber by ZnO@WPUP modified aramid fibers.Results showed that the surface of aramid fibers is coated with a layer of uniform density of ZnO@WPUP particles after dealt with the hybrid coating agent.In addition,the roughness of fibers surface and chemical activity increase sharply,surface invasive greatly improved.The interface bonding performance between fibers and rubber matrix and fibers H pull-out force of Zn O@WPUP modified aramid/rubber composites was significantly improved with the increase of the amount of IPDI in the ZnO@WPUP emulsion.Further,research aramid fibers ultraviolet radiation aging performance with different time UV treated,which use of the UV shielding effect of ZnO@WPUP finishing agent.Meanwhile,evaluated the ultraviolet resistance of ZnO@WPUP modified aramid was analyzed through the surface morphology,crystal properties,and single fiber tensile test et al.The results showed that the unmodified aramid fibers were ultraviolet aging damaged seriously,fracture strength drop and breakage strength retention was only 46.8%.The surface of unmodified aramid fibers appeared obvious etching pits and grooves.But,the influence of tensile properties of aramid fibers with ZnO@WPUP surface modification were weakened,fibers itself damaged lesser,ultraviolet aging speed slowly and breakage strength retention can still remained at 76.9% with ultraviolet irradiation one week.Thereby,the method of ZnO@WPUP surface modification aramid fibers could improve the ultraviolet aging resistance performance effectually.