Preparation And Properties Of Composite Conductive Rubber Powders

The economic is promoted greatly as the rapid development of rubber industry and automobile industry. However, the consumption and wear of auto tires also generate a lot of waste tires. The accumulation of waste tires not only wastes a large amount of rubber resources, but also causes fire, breeds mosquitoes and carries diseases easily, which has great influence and hazard on the human bodies and environment. Therefore, a safe way must be found to utilize a large amount of discarded tires. However, the waste tire rubber powders is hydrophobic polymer materials, when using it to produce composite materials, the first thing is to solve the problem of the dispersion.In this paper, silane coupling agent was chosen to obtain the modified waste tire rubber powders, improving the hydrophilicity and its compatibility performance with conductive polymer of waste tire rubber powders. And then the rubber powders/polyaniline conductive material (hereinafter referred to as the conductive powders) was prepared by in situ polymerization, and its properties were characterized by series of measures. The optimum process conditions of preparation were also determined. Then, the epoxy resin matrix conductive rubber powders coating was made using composite conductive rubber powders as conductive filler, epoxy resin as matrix, polyamide A651 as curing agent and ethyl acetate as diluent by blending method. The influence of electromagnetic shielding performances and mechanical properties of the epoxy resin matrix conductive rubber powder coating was studied in terms of the content and the particle size of composite conductive rubber powders. The experimental results are as follows:In the process of the modification of waste tire rubber powders with silane coupling agent KH-560, the optimal dosage of silane coupling agent was determined according to the calculation result of the grafting rate between waste tire rubber powder and KH-560, which was added 1.5 mL of KH-560 per gram of waste tire rubber powders. The surface of modified rubber powders was grafted lots of hydrophilic groups and the hydrophilicity was greatly enhanced with its average wetting contact angle reduced from 132° to 34°. The conductive powder was successfully prepared by in situ polymerization. According to the orthogonal test analysis, the influences of the mole ratio of ammonium persulfate and aniline, hydrochloric acid concentration, reaction temperature and reaction time to the conductivity of polyaniline composite conductive rubber powder were discussed. And the optimum process conditions of conductive powder was obtained that the ammonium persulfate and aniline molar ratio is 1:1, hydrochloric acid concentration is 1.0 mol/L, the reaction temperature is 10℃ and the reaction time is 10 h. Under the condition of the optimum process, the conductivity of the prepared conductive rubber powders is 4.79 S/cm.Through the research that is the content of conductive rubber powders on the effects of the properties of epoxy resin matrix conductive rubber powder coating, we can see that the conductivity and shielding effectiveness of epoxy resin matrix conductive rubber powder coating increased at first and then decreased with the increase of dosage of conductive rubber powders. When the dosage of conductive rubber powder was 40%, the highest conductivity was appeared of the coating, which the conductivity was 3.59 S/cm. The Seepage network was formed in the conductive coating. The shielding effectiveness was better than the other conditions, and the shielding effectiveness was reached 24.9 dB at 450 MHz in condition of above. when the dosage of conductive rubber powders was range from 0 to 40%, the adhesive force of coating to substrate was basically no change, keeping at grade 1. And its impact strength basically remained unchange too, but the tensile strength decreased. When the dosage of conductive rubber powders increased to 50%, the adhesive force decreased to grade 2, the impact strength also decreased a little and the tensile strength decreased a lot.Through the research that is the particle size of conductive rubber powders on the effects of the properties of epoxy resin matrix conductive rubber powders coating, we can see that the conductivity and shielding effectiveness of epoxy resin matrix conductive rubber powders coating increased at first and then decreased with the decrease of the particle size of conductive rubber powders. When the particle size of conductive rubber powders was 200 mesh, the electrical conductivity of conductive coating was biggest which was 3.52 S/cm, and the shielding effectiveness was also the best which was 25.2 dB at 450 MHz. When the conductive rubber powders particle size was less than 150 mesh, the adhesive force conductive coating was kept at grade 1. But when the particle size was bigger than 150 mesh, the adhesive force of conductive coating decreased, and when continued to increase the particle size, the coating presented caduceus and the adhesive force was kept at grade 3. When the conductive rubber powders particle size was 200 mesh, impact strength of conductive coating was greater than 50 kg-cm. Within the scope of the 60-200 mesh, the tensile strength of conductive coating increased gradually with the decrease of the particle size of conductive rubber powders. When the particle size was 300 mesh, the tensile strength decreased a little. According to the measured results, it can be obtained that the dosage of conductive rubber powder is 40% and the particle size of conductive rubber powders is 200 mesh.