Study On The Structure And Properties Of CaSO 4 Whisker/nylon 6 Composites

In this paper,CaS04 whisker(CaSO4w),long carbon fiber(LCF),carbon-fiber powder(CF)and nano SiO2(nano-SiO2)reinforced nylon 6 composites(CaSO4w/PA6,LCF/PA6,CF/PA6 and nano-SiO2/PA6)were prepared by twin screw extruder,and the mechanical properties of four kinds of composites were tested.At the same time,the influence of four kinds of fillers on the mechanical properties of PA6 was compared.The inorganic fillers with better cost performance were selected.The structure,crystallization,thermal,morphological properties and processing ability of CaSO4w/PA6 were analyzed by FTIR,XRD,DSC,TG,SEM.In order to improve the toughness of CaSO4w/PA6 composites,maleic anhydride grafted ethylene-octene copolymer(POE-g-MAH),maleic anhydride-grafted ethylene-vinyl acetate copolymer(EVA-g-MAH),nitrile rubber(NBR)as a modifier were blended with 30wt%CaSO4w/PA6,respectively.In addition,the effects of coupling treatment on the mechanical properties of CaSO4w/PA6 composites were investigated.The results demonstrate that when the same amount of CaSO4 whisker,nano SiO2,long carbon fiber or carbon-fiber powder was added into PA6,the adhesion between CaSO4 whisker or carbon-fiber powder and PA6 was stronger than that of other fillers,which could significantly improve the rigidity and toughness of PA6.Among four kinds of composites,CaSO4w/PA6 composites have high cost performance and comprehensive performance.The addition of 10wt%CaSO4w could increase the rigidity and toughness of PA6.When the content of CaSO4w increased to 30wt%,the mechanical properties of the composite are higher.A small amount of CaSO4w accelerated the crystallization rate of PA6,and the crystallization rate of PA6 decreased with the increase of CaSO4w content.The addition of CaSO4w improved the thermal stability of CaSO4w/PA6 composites.Three kinds of toughening agents(POE-g-MAH,EVA-g-MAH and NBR)have good compatibility with PA6 matrix,and the toughness of 30wt%CaSO4w/PA6 was significantly improved.However,the tensile strength,flexual strength,flexual modulus and hardness of the 30wt%CaSO4w/PA6 composites with toughening agent decreased obviously.A small amount of POE-g-MAH in 30wt%CaS04w/PA6 was beneficial to the formation of complete crystallization of PA6 and improve the melting point of PA6.However,the higher POE-g-MAH content could inhibit the crystallization rate of PA6.EVA-g-MAH or NBR decreased the crystallization rate of PA6 in the 30wt%CaSO4w/PA6 composites.The results of TG indicated that POE-g-MAH could improve the thermal stability of the composites.When 10wt%EVA-g-MAH was added to 30wt%CaSO4w/PA6,the thermal stability of the composites was reduced.20wt%EVA-g-MAH made the thermal stability of the composite was improved.The thermal stability of 30wt%CaSO4w/PA6 was reduced by adding NBR.Compared with the untreated CaSO4w,the interfacial adhesion between CaSO4w and PA6 was further enhanced by CaSO4w treated with 3wt%KH570 silane agents,and the tensile strength,flexural strength,flexural modulus,hardness and impact strength of the composites were obviously improved.When the content of coupling agent increased to 6wt%,the rigidity of the composite increased accompanied by the reduction of impact strength.