Study On The Surface Modification Of PPTA Fiber

Poly(P-phenyleneterephthalamide)(PPTA) is a linear chain macromolecule material which has high crystallization and orientation.As a reinforcing material,it has broad application prospects in the fields of aviation,automobile,shipbuilding and special product because of its high strength,high modulus,high temperature-resistance,good corrosion-resistance and good impact resistance.However,it is difficult for PPTA fiber to adhere with resin because of a lower polarity of PPTA fiber surface.For exerting the outstanding mechanical performances,the surface modification on PPTA fiber enhances the fiber-matrix interfacial adhesive strength.Firstly,Technora fiber is treated with 2,4-Diisocyanatotoluene(TDI) solution of different concentration to modify the fiber surface.Filament strength tester,FTIR,SEM and contact angle tests are employed to characterize the changes of the fiber strength,surface functional group, surface micro-morphology and infiltration performance of the fiber.The results show that the roughness and content of polar groups in fiber surface are both increased via this method.The tensile strength increased by 4.6%in average and the contact angle between fiber and water decreased by 19.2°after modification.When fiber is combined with resin,shear strength increases by 40.8%and the surface property of Technora fiber is improved efficiently,then the mechanism of modification has been discussed.Secondly,diisocyanate groups are grafted on the surface of Technora fiber via the TDI treated method,which will react with MWNT-COOH.SEM images indicate that there are many small bright spots on fiber surface.The shear strength of treated fiber increases by 55.06%by pull-out test.The results of contact angle show that the average of contact angle between water and fiber is 45.41°decreased by 23.14°compared with un-treated ones,but the infiltration velocity with water is increased.In final study of paper,it introduces that Technora fiber is treated with terephthaloyl chloride (TPC).In this experiment,reaction time,reaction temperature and solution concentration are controlled via the orthogonal design.The tensile strength,surface micro-morphology,surface functional groups,infiltration performance and interface adhesive performance of treated fiber with matrix are compared with those performance of untreated fiber with matrix that is characterised by the strength tester,SEM,Infrared spectroscopy,Infiltration test and single-wire pull-out experiments.It is concluded that the interface adhesive performance of fiber has been improved and the infiltration performance with water is increased in the condition of no mechanical properties lost.According to the various factors,the optimal experimental condition is that the reaction temperature is 25℃,the concentration of TPC is 1%and the reaction time is 1 hour.