EPDM recycled rubber retains the basic performance characteristics of EPDM raw rubber, with excellent high and low temperature resistance, ozone resistance, and excellent weather resistance, which can completely or partially replace EPDM to produce waterproof membranes, effectively reducing raw material costs. When using EPDM recycled rubber to produce waterproof membranes, rubber product manufacturers must choose the right recycled rubber, reasonably design the formula of recycled rubber waterproof membranes, and strictly control the mixing/vulcanization process to reduce more costs on the premise of ensuring the performance of rubber waterproof membranes.
1. Pay attention to the selection of recycled glue for EPDM recycled glue waterproof membrane
It is recommended to give preference to EPDM recycled glue with high ethylene propylene content, high fineness, and few impurities, the surface of the recycled glue is smooth, no microscopic particles, easy to wrap the roller, tensile strength, tear elongation to meet the basic needs of waterproof membrane, and it is not easy to bubble; If necessary, an appropriate amount of butyl recycled rubber can be added to further improve the processing process of the rubber and alleviate the problem of aging and hardening of EPDM compounds.
2. Pay attention to the proportion of recycled glue in the formula of EPDM recycled glue waterproof membrane
When the rubber waterproof membrane formula is mixed with EPDM recycled rubber, the proportion of recycled glue needs to be strictly controlled. Generally, low-grade waterproof membranes can be used with EPDM recycled glue, or combined with butyl recycled glue; Medium and high-end waterproof membranes are mixed with 25%-50% EPDM recycled rubber, taking into account both cost and performance.
3. Pay attention to the variety and dosage of the compound in the formula of EPDM recycled rubber waterproof membrane
After the rubber waterproof membrane is mixed with EPDM recycled rubber, the rubber formula must be adjusted appropriately.
(1) The vulcanization speed of EPDM recycled rubber is generally faster than that of the original rubber, and the scorching safety is higher. When the waterproof membrane containing EPDM recycled rubber is sulfur vulcanized, it is recommended to increase the amount of sulfur E5LYY123 and accelerator by 10%-15%; Commonly used accelerators such as TMTD, ZDC, BZ are used as the main accelerator, and with thiazole accelerators M/DM as auxiliary accelerators, the vulcanization curve is flat, and the vulcanized glue has good physical and mechanical properties.
(2) The use of high wear-resistant carbon black and medium-super wear-resistant carbon black reinforcement can significantly improve the mechanical strength and ductility of EPDM recycled rubber waterproof membrane; Calcium carbonate is used in conjunction with soft terracotta to reduce stomata; Appropriately increase the amount of carbon black, and the recycled glue content is lower than that of the original rubber, and the reinforcement demand is greater.
(3) In the EPDM recycled rubber waterproof membrane softening system, it is recommended to use less operating oil, and choose paraffin oil or naphthenic oil with low volatile content and high aniline point to prevent the shrinkage and deformation of the waterproof membrane; If necessary, add a small amount of coumalon resin or tackification resin to improve the adhesion among the membrane and the base layer; Avoid plasticizers and water-soluble resins that are easy to extract.
4. Strictly control the EPDM recycled rubber waterproof membrane mixing/vulcanization process
(1) Key points of EPDM recycled rubber waterproof membrane mixing
When EPDM recycled rubber and EPDM primary rubber are used together to produce waterproof membranes, it is recommended to mix the recycled rubber and the original rubber evenly, and then add small materials, large materials, carbon black, oil, and vulcanizing agents according to convention. Appropriately extend the mixing time to ensure that the recycled rubber and the original rubber are evenly mixed to avoid local performance differences. When using EPDM recycled rubber alone, part of the recycled rubber can be plasticized in advance and mixed with the remaining recycled glue.
(2) Key points of vulcanization of EPDM recycled rubber waterproof membrane
Commonly used vulcanization methods for rubber waterproof membranes include indirect steam vulcanization tanks (commonly used), hot air vulcanization or natural vulcanization (direct use of semi-finished products after calendering or extrusion). EPDM recycled rubber waterproof membrane is controlled at 120-160 °C when vulcanized by indirect steam vulcanization tank, and a small amount of calcium oxide can be added to prevent foaming when hot air vulcanization is selected.
When using EPDM recycled adhesive to reduce the production cost of waterproof membranes, the selection of recycled adhesive is the top priority: EPDM recycled adhesive is the main raw material, which has high glue content, high and low temperature resistance, anti-aging, high insulation, ozone resistance, erosion resistance, tastelessness, good elasticity, smooth and bright surface of the product, etc., which is an ideal raw material for the production of EPDM rubber waterproof membrane. The full use or partial use of environmentally friendly EPDM recycled rubber can greatly reduce the cost of raw materials while ensuring the quality of waterproof membranes.
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