Preparation And Properties Of Silicon Carbon Black-Basalt Fiber/Polyamide 6 Composites

Fiber-reinforced polymer composites have the advantages of high strength,light weight,corrosion resistance,self-lubrication,and high fatigue strength.They have become an important choice for automobiles to replace traditional steel materials.Basalt fiber(BF)is a high performance natural green fiber and it is one of the key fibers in China.Its production process has low pollution,low emissions,high chemical stability,and excellent mechanical properties,which has gradually attracted people's attention.Basalt fiber is formed by drawing volcanic basalt ore through platinum-rhodium plate at high temperature.Under the influence of surface tension,basalt fiber has a smooth surface and low activity,which makes it difficult to form a good interface with high-molecular polymers and affects the load in composite materials.The internal stress transmission has limited the development of basalt fiber composites.In this paper,we used polyamide 6(PA6)as the matrix and basalt fiber as the reinforcement to prepare the binary composite material.At the same time,the biomass material silicon carbon black(SiCB)was introduced to improve the surface activity of the fiber and the interfacial bonding ability between the basalt fiber and polyamide 6.Chemical grafting method was adopted and polydopamine(PDA)produced by dopamine self-polymerization was used as a medium,using active groups on the surface of polydopamine to graft silicon carbon black to the surface of basalt fiber.And by adjusting the concentration of silicon carbon black,fiber surface roughness could be changed,which was used to prepare a fiber reinforced body with high activity and clear morphology.The composite material was prepared with PA6 resin and its microscopic characterization was characterized.Compared with unmodified BF/PA6 composites,the thermal stability and crystallinity of SiCB(PDA)-BF/PA6 composites were improved.At high shear rate and shear stresse,the shear thinning behavior was observed.When the concentration of silicon carbon black is 2.0g / L,the SiCB(PDA)-BF/PA6 composite material has the best performance.At this time,the tensile strength,flexural strength and impact strength of the composite materials were increased by 59.3%,23.6% and 89.3 %,respectively.Surface coating method was adopted and waterborne polyurethane(PU)emulsion was used as a medium to modificate the surface of basalt fiber with silicon carbon black by precipitation coating method.By changing the content ratio of silicon carbon black in waterborne polyurethane emulsion,the surface morphology of silicon carbon black on basalt fibers was controlled,and a rough surface fiber reinforcement was prepared.The composite material was prepared with PA6 resin and characterized.Compared with the unmodified BF / PA6 composite,the thermal stability and the crystallinity of SiCB(PU)-BF/PA6 composites increased slightly,and the apparent shear viscosity of SiCB(PU)-BF/PA6 composites increased.Under shear rate and shear stress,the SiCB(PU)-BF/PA6 composite exhibited shear thinning pseudoplastic fluid behavior.When the proportion of silicon carbon black in the aqueous polyurethane emulsion was 1.0%,the mechanical properties of the SiCB(PU)-BF/PA6 composite material were the best.The tensile strength is increased by 45.3%,the bending strength is increased by 12.9%,and the impact strength is increased by 80.8 %.The two basalt fiber modification methods were compared and analyzed.The same points were as follows: chemical grafting method and surface coating method can ensure that the fiber has no damage and improve the surface activity of the fiber,which could improve the interface adhesion between the fiber and the PA6 resin matrix;combining modification Scanning electron microscope images of fibers and cross-sections showed that silicon carbon black could be uniformly dispersed on the fiber surface and increase the surface roughness of the fiber.The bonding effect between the modified basalt fiber and the resin matrix was strengthened,and the mechanical strength of the composite material was improved.At the same time,the molten state are all pseudo-plastic fluids.Differences were as follows: the improvement of mechanical properties of composites by chemical grafting method was higher than that by surface coating method;when the content of silicon carbon black on the surface of the modified fiber was high,the chemical grafting method promoted the conversion of the composite material from ? crystal form to ? crystal Type;both chemical grafting and surface coating method have different effects on the crystallinity of composites.