| Silica is a kind of green environment-friendly and promising inorganic nano rubber reinforcing filler,which has excellent properties of high temperature resistance and electrical insulation,and has a very broad application category.However,because of silica surface with a layer of siloxane and silanol groups and with strong polarity and the strong hydrophilic,the existence of a large number of hydroxyl groups make itself easy to reunite to form large aggregates,that is not conducive to wet and disperse in rubber matrix and influence its enhancement effect,which limits its application in composite materials.Therefore,it has been a hot topic in recent years to modify the surface of silica and improve its dispersibility in rubber matrix and its compatibility with rubber matrix.Ionic liquid is a kind molten salt at room temperature or near room temperature,which is entirely composed of ion,with zero vapor pressure,high thermal stability,non-volatile,high ionic conductivity,etc.It provides opportunity for the development of green environment-friendly composite materials.In order to obtain good physical mechanical properties and excellent dynamic mechanical properties of natural rubber composite materials.The research work will be carried out from the following four parts.The first step,employing ionic liquid 1-allyl-3-methylimidazolium chloride（AMI）to modify silica,the microstructure and surface property of silica of modification before and after were characterized.The result shows that,through AMI modification,particle agglomeration phenomenon between silica weak,hydrophobic property enhance obviously,the actual distribution particle size decrease,the specific surface area increase evidently.AMI have little effect on crystal structure of silica,yet amorphous structure.The second step,modified SiO2/NR composites was prepared with different content AMI for 1、2、3、4phr respectively,The result shows that the dispersion of AIM-modified SiO2 improves obviously,practical distribution size decreases in rubber matrix,interface interaction is strengthen between silica and rubber matrix,content of bound rubber increase evidently,overall mechanical property of composite material is improved.When AMI content is 2phr,the dispersion of silica is the best in rubber matrix,distribution size is the minimum,content of bound rubber reaches the maximum value,overall mechanical property of composite material is the best.Compared with non-modified SiO2/NR composites,tensile strength of AMI-SiO2/NR composite increases by 18%,tear strength advances by 41.4%,modulus at 300%elongation improves by 39.2%,modulus at 100%elongation enhances by 25%,respectively.The third step,According to the different mechanism of modification,considering the covalent bond,hydrogen bond and Van der Waals force as the starting point,silica is modified by Si69,AMI and BMI respectively.The results show that the particle size distribution trend move to the direction of decreasing grain diameter through the modification.The modification effect of ionic liquid is obviously better than that of silane coupling agent,and the distribution curve of silica particles modified by Si69 and BMI is basically consistent,and the size of AMI modified silica powder is the smallest.The glass transition temperature of the modified silica/natural rubber composite increase.The modified composite material with AMI is the highest temperature,following by Si69 and BMI.With the increase of strain,the storage modulus of the composites decreases gradually,the loss factor increase,silica/natural rubber composites storage modulus rank is for AMI>BMI>Si69>unmodified silica,and silica/rubber composite material modified by ionic liquid loss factor is higher.With the increase of shear frequency,the elastic modulus of silica/natural rubber composites increases nonlinearly and the loss factor decline.AMI-m-SiO2/NR composites have the largest storage modulus,lowest mechanical consumption and minimum loss factor.The fourth step,The effects of AMI and vulcanization agent content on the vulcanization kinetics performance of SiO2/CB/NR composite were studied.The results show that with the increase of vulcanization time and curing temperature,the mechanical torque of the composites increases,the slope of vulcanization curve augments,the reaction rate constant becomes bigger,and the curing time is shortened.Compared with the unmodified silica/carbon black/natural rubber composites,the slope of the vulcanization curve of the modified composite material increases obviously,the reaction rate constant is larger,and the reaction activation energy decreases.After the simultaneous use of modified silica and carbon black,the particle size of the filler reduce,and the dispersion effect enhance in the natural rubber composite material,and the dynamic mechanical property increase.The fracture appearance of modified silica/carbon black/natural rubber is rougher and has a different degree of concave and convex structure.With the increase of the content of vulcanizing agent,the minimum and maximum torque of the composite material gradually increase,the scorch time and positive vulcanization time is shortened,the rigidity increase and storage modulus rise.Both AMI and vulcanization agent are able to promote the sequential increase of molecular chains of rubber composites. |
