Study On Properties Of Natural Rubber Reinforced By Silica Composites

Nature rubber?NR?,an important biopolymer,has been presented as one of attractive materials owing to the wonderful properties,such as great elasticity and flexibility,antivirus permeation,low cost,and corrosion resistance.However,NR usually needs to be reinforced with various fillers for most of practical applications in diverse areas?e.g.tire,sealing material,sport equipment,surgical gloves,adhesives,etc?,due to its inherent low strength and modulus.For decades,silica?SiO₂?particles have been wildly applied as active fillers in rubber composites to enhance mechanical properties and deliver multi-functional characteristics.SiO₂ particles are extensively assumed as a superior substitute to common carbon black,whereas inhibiting SiO₂ particles from aggregating is extremely challenging because of their high surface energy and large surface area.Based on this,the SiO₂@AF,ZnO@SiO₂ and p-SiO₂@S composites were prepared by combining silica with aramid fiber,nano zinc oxide and sulfur.The three composites were separately added to the rubber matrix to construct physical and chemical crosslinking points with the rubber matrix,aiming to improve the interface between the filler and the rubber matrix.The three parts of the research work:A facile and rivet-like inspired method of decorating aramid fiber?AF?with silica particles?SiO₂?is proposed to produce hierarchical SiO₂@AF materials which have the largely enhanced interfacial interaction with rubber matrix.AF is first grated with Polyacrylic acid?PAA-AF?in the presence of dicyclohexylcarbodiimide?DCC?and 4-dimethylaminopyridine?DMAP?,and SiO₂ is silanized by 3-aminopropyltriethoxysilane?APES-SiO₂?.Then,SiO₂@AF is fabricated by the electrostatic assembly between negative charged PAA-AF and positive charged APES-SiO₂.In the SiO₂@AF/nature rubber?NR?composite system,hierarchical SiO₂@AF materials with high surface roughness can play a role as“rivets”to immobilize large numbers of NR chains on the surfaces.The higher the weight fraction of immobilized NR chains is,the stronger the interfacial adhesion between SiO₂@AF and NR will be,the better the mechanical properties of SiO₂@AF/NR composite will be obtained.In addition,SiO₂@AF has great superiority in improving the cutting resistance of NR composites,in contrast with unmodified AF and SiO₂.SiO₂@AF is able to be applied as the novel reinforcing filler in rubber composites for high performances.In this article,ZnO/SiO₂ hybrids?ZnO@SiO₂?were produced by the deposition of nanometer-size ZnO?nano-ZnO?on SiO₂ surface via a solvothermal method.The morphology and structures of ZnO@SiO₂ were characterized by Fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?,and scanning electron microscopy?SEM?in detail.Notably,ZnO@SiO₂ not only improves the vulcanization of nature rubber?NR?composites but also superiorly enhances the mechanical properties.The greater the immobilized NR chains on ZnO@SiO₂ is,the stronger the interfacial interaction between ZnO@SiO₂ and NR matrix will be.Furthermore,the mechanical properties including the tensile strength,stress at 100%strain,stress at 300%strain,and elongation at break of NR/ZnO@SiO₂ composites are all higher than those of NR/SiO₂ and NR/cyano-modified?NR/SiO₂-CN?composites.This feather is ascribed to the uniform dispersion of nano-ZnO on SiO₂surface,the high vulcanization efficiency of ZnO@SiO₂,and the strong interfacial interaction between ZnO@SiO₂ and NR matrix.Therefore,ZnO@SiO₂ as the reinforcing filler and cure activator has great superiority in fabricating the high-performance rubber composites.In the third part,the molten sulfur was loaded on the surface of p-SiO₂ by hot melting with high-speed stirring to prepare p-SiO₂@S materials with different mass ratios.Fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?and scanning electron microscopy?SEM?characterization showed that sulfur was successfully deposited on the surface of p-SiO₂.Then p-SiO₂@S was added into NR matrix by a refiner to prepare p-SiO₂@S/NR composite.The vulcanization,bound rubber and mechanical properties of p-SiO₂@S/NR composites have been studied.And the results showed that the vulcanization rate of p-SiO₂@S/NR was obviously accelerated,the bound rubber content of composites was 113%higher than that of p-SiO₂+S/NR.This indicates that the interfacial interaction between p-SiO₂@S and NR matrix is significantly enhanced by the sulfur loading.In addition,the tensile strength,100%stress-strain and 300%stress-strain of 8phr p-SiO₂@S/NR increased by 21.3%,30.7%and 71.9% respectively.