| In recent years, with the requirements of environmental protection improving, the degree of automation and throughout increasing, and the transport distance extending, transport high-temperature materials by conveyor, such as the cinder from the power plants, the sinter feed and slag from the steel plant etc. The conveyor belt normally transports materials at high temperatures for a long time, so it should have high heat resistance and aging resistance. Therefore, in these cases, heat resistant conveyor belt of reinforcing material-impregnated canvas should obay higher demand:how to improve the high temperature (175℃) adhesion properties between dipped canvases is the main research direction of this issue.Strong canvases, the core of the conveyor belt, were gained through dipping process. There were dipped liquids on the fabric surface after dipped, which helps to molecular diffusion and infiltration in the fiber. During the vulcanization, the rubber film can be chemically bonded to the fabric, the mechanical and physical bonding strength can be improved, so the adhesion between dipped canvases is increased.Polyester and nylon dipped canvases EP (warp is polyester industrial filament, weft is nylon 66 industrial filament)were used in this issue, which will gained after two dipping steps. Firstly, the pre-dipping process: the fabric was pre-dipped and dried in the water-based adhesive system; Secondly, the pre-dipped fabric was handling by resorcinol (R) formaldehyde (F)-latex (L) (RFL) dipping liquids, then dried.Firstly, matrix rubber EPDM/NR was masticated with open rubber mixing machine, then various ingredients were added following a certain order, after several refinings, matrix rubber cooperate with ingredients in order to obtain a uniform test mixed rubber. In the mixing course, the temperature of rollers was maintained between 30℃-50℃, the mixing time is about 30 minutes.The EPDM/NR rubber was vulcanizated after mixed rubber to get the optimum vulcanization process:165℃×20min×2.5MPa. The tensile property of vulcanized rubber was 12.6MPa, elongation at break was 603%, tear strength was 9.3 MPa with this process.The heat-resistant conveyor belt sample was prepared by EP dipped canvas and EPDM/NR mixed rubber according to the way of lamination. The sample was placed 1h after vulcanization at room temperature (20℃) and high temperature (175℃), then the adhesive strength and peeling level of the dipped canvas were tested. It could conclude that the adhesive strength and peel grade of the two dipped canvases were better at room temperature.Things had been done to improve the situation that the sample had low adhesive strength and peeling level at high temperature.Firstly, orthogonal design experiments had been done among three factors(paraffin oil, antioxidant RD, sulphur) to improve the rubber formulation. It can concluded that:optimal amount of rubber formulation was 17 phr paraffin oil, antioxidant RD was 4 phr, sulphur was 1 phr, no other additives variable, whose high temperature adhesive strength was 4.5 N/mm, the peeling level was 5. Its adhesive strength increased 50%, the peeling level was turned into the high-grade.Secondly, orthogonal design experiments had been done among RFL immersion liquid formulation resorcinol(R), formaldehyde(F), butadiene-vinylpyridine copylymer latex(VP), isocyanate. It could conclude that:optimal immersion liquid dosage formulations were:resorcinol 19.8g, formaldehyde 30.4g, VP latex 500g, isocyanate 30g, other compounding ramain unchanged. The new sample, whose adhesive strength was 5.6 N/mm and the peeling level was 5 at high temperature. The adhesive strength increased 39%, the peeling level also reached to a high grade. |
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