Preparation And Research Of Conductive Carbon Black/nylon 6 Composite Material

Polyamide(abbreviated as PA),is commonly known as nylon,and its main products are PA46,PA6,PA66,PA11,PA612 and so on.It is a widely used engineering plastic material with important commercial value.Among them,semi-crystalline nylon 6(PA6)has a low melting point and density,a wide process temperature range,good impact resistance and solubility resistance,and low price.It is widely used in automotive,electronic,electrical,and mechanical fields.However,PA6 also has defects such as high water absorption,reduced strength and elastic modulus after water absorption,poor product shape and dimensional stability,low dry and low-temperature impact strength,poor resistance to strong acids and alkalis,and high volume resistivity,which limits its application.Carbon nanofillers,such as carbon black(CB),carbon nanotubes,and graphene,are electrically condutive and can improve the antistatic properties of polymers.CB-filled polymers are widely used in industrial application for the overwhelming cost advantage.The addition of high content of carbon black leads to the degradation of material properties.In this paper,conductive carbon black were used as fillers to improve antistatic performance of PA6 and its composites,and polycarbonate(PC),ethylene-vinyl acetate copolymer(EVA)and maleic anhydride grafted ethylene-vinyl acetate copolymer(EVA-g-MAH)were used to strengthen or toughen PA6 and CB/PA6 composites.The effects of different contents of fillers and additive on the structure and properties of PA6 and CB/PA6 composites were studied.Firstly,CB/PA6 composites were prepared by extrusion and granulation of twin-screw extruder,and the test samples were formed by injection molding machine,The effects of carbon black content on the mechanical properties,electrical properties,thermal properties and crystal structure of PA6 were studied;Then the binary composites of PC/PA6,EVA/PA6 and EVA-g-MAH/PA6 were prepared by melt blending of PC,EVA and EVA-g-MAH;Finaly,on the basis of 7.5%CB/PA6 formula,the ternary composites of 7.5%CB/PC/PA6,7.5%CB/EVA/PA6 and 7.5%CB/EVA-g-MAH/PA6 were prepared by melt blending of PC,EVA and EVA-g-MAH.Morphology and structure of PA6 and its composites were studied by using scanning electron microscope(SEM),X-ray diffraction(XRD),thermogravimetric(TG)and differential scanning calorimetry(DSC).The mechanical and electrical properties of the materials were tested.The results showed that the tensile strength of PA6 increased by 3.8%with the addition of 2.5%CB,and the tensile strength and impact strength of PA6 decreased with the increase of CB.With the increase of CB content,the surface resistivity(R)and volume resistivity(ρv)of CB/PA6 composites decreased slowly to 1.35×1011Ωand 1.76×1012 Ω·cm,and then decreased significantly to 2.60×105Ω and 1.16×106Ω·cm,respectively.CB has heterogeneous nucleation effect on PA6 crystal,which promotes the growth of a crystal form of PA6 and inhibits the formation of y crystal form.A small amount of PC can improve the impact strength of PA6.With the increase of PC content,the tensile strength and elongation at break of PC/PA6 decreased,and the hardness of ball indentation increased.Similarly,the tensile strength,tensile modulus,elongation at break and impact strength of 7.5%CB/PC/PA6 were improved by adding 2.5～5%PC.When the content of PC increased further,the tensile properties and impact strength of 7.5%CB/PC/PA6 composites decreased obviously.Compared with PC/PA6.with the increase of PC content.the R and ρv of 7.5%CB/PC/PA6 blends decreased by 2～3 and 4～5 orders of magnitude,respectively.The addition of PC can improve the thermal stability of pure PA6 and 7.5%CB/PA6.A small amount of PC has heterogeneous nucleation effect on PA6,and excessive PC will reduce the crystallization properties of PA6.When the content of EVA is low,there is a certain compatibility between EVA and PA6.When EVA increases to 30%,the compatibility between EVA and PA6 decreased.Compared with PA6 and 7.5%CB/PA6 toughened by EVA,the phase interface between EVA-g-MAH and PA6 is blurred and the compatibility is better.With the increase of EVA content,the R and ρv of EVA/PA6 blends decreased by two orders of magnitude.Compared with 7.5%CB/PA6.the R and ρv of 7.5%CB/EVA/PA6 blends decreased by 4 and 3 orders of magnitude with the increase of EVA content.With the addition of EVA-g-MAH,the R and ρv of EVA-g-MAH/PA6 blends were two orders of magnitude lower than those of EVA/PA6,which were maintained at 1012 Ω and 1011 Ω·cm,respectively.The addition of 10～20%EVA-g-MAH reduced the R and ρv of 7.5%CB/EVA-g-MAH/PA6 blends by 4 and 5 orders of magnitude to 104 Ω and 106 Ω·cm,respectively.Compared with the addition of EVA,the notched impact strength of EVA-g-MAH/PA6 and 7.5%CB/EVA-g-MA/PA6 composites improved a lot.Compared with EVA/PA6(30/70)blends,the thermal decomposition temperature of EVA-g-MAH/PA6(30/70)increased by 5℃.When the EVA content is 10%and 30%,the EVA/PA6 and 7.5%CB/EVA/PA6 composites has EVA crystallization peak.With a small amount of EVA-g-MAH,the crystallinity of PA6 decreased,and the crystallinity of PA6 increased with increasing the content of EVA-g-MAH.