Sponge rubber sealing gasket is a kind of vulcanized rubber sealing fittings with sponge-like porous structure, with different hole types such as open pores, closed pores, mixed pores and micropores, light texture, good elasticity, not easy to transfer heat, and can play the role of shockproof, buffering, thermal insulation, sound insulation and so on in the process of use, and are widely used in machinery and equipment. The sponge rubber gasket produced with EPDM rubber as the main raw material has good high and low temperature resistance, weather resistance and ozone resistance, and the appropriate amount of EPDM reclaimed rubber can effectively reduce the cost of raw materials.
1. EPDM rubber and EPDM reclaimed rubber are used together to produce sponge rubber sealing gasket vulcanization formula
(1) EPDM rubber/EPDM reclaimed rubber production of open-cell sponge rubber sealing gasket: 70 parts of EPDM rubber, 30 parts of EPDM reclaimed rubber, 5 parts of zinc oxide, 2 parts of stearic acid, 45 parts of carbon black N762, 35 parts of talc, 65 parts of naphthenic oil, 5 parts of low molecular weight polyethylene, 3 parts of polyethylene, 10 parts of black oil paste, 20 parts of sodium bicarbonate, 2.5 parts of accelerator TMTD, 1 part of sulfur; Total 293.5 copies.
(2) EPDM rubber/EPDM reclaimed rubber production of closed-cell sponge rubber sealing gasket: EPDM rubber 80 parts, EPDM reclaimed rubber 20 parts, zinc oxide 5 parts, stearic acid 1 part, carbon black N550 35 parts, carbon black N990 100 parts, paraffin oil 40 parts, low molecular weight polyethylene 15 parts, foaming agent AC 7.5 parts, urea 2 parts, accelerator M 1 part, sulfur 2 parts; Total 308.5 copies.
2. The difference among open-cell sponge rubber and closed-cell sponge rubber
(1) Open-cell sponge rubber: the internal pores are interconnected to form an open porous structure; It has good air permeability and water absorption, and is able to absorb and retain moisture; It has good resilience and compression set resistance, and can return to its original shape after compression, which is suitable for occasions that require air circulation or water absorption.
(2) Closed-cell sponge rubber: the internal holes are independent of each other and are not connected; Good waterproof, not easy to be penetrated by water, suitable for waterproof sealing; Good air tightness, can effectively prevent gas leakage, suitable for use in the need for sealing; Low thermal conductivity makes it suitable for thermal insulation.
3. Key points of formula design of EPDM reclaimed rubber production sponge rubber sealing gasket
(1) Vulcanization system design: The commonly used vulcanization systems for the production of sponge rubber gaskets by EPDM reclaimed rubber include sulfur vulcanization system and peroxide vulcanization system.
EPDM reclaimed rubber can be combined with accelerator M, accelerator TMTD, etc., when sulfur vulcanization, reclaimed rubber vulcanized rubber has good flexibility and fatigue resistance, and is suitable for sealing gaskets with high toughness requirements. When peroxide vulcanization is used, EPDM reclaimed rubber vulcanized rubber has good heat resistance and compression set resistance, and is suitable for sponge rubber sealing gaskets with high requirements for heat resistance and compression set.
(2) Foaming system design: The commonly used foaming agent in the production of EPDM reclaimed rubber can be divided into inorganic foaming agent (sodium bicarbonate, etc.) and organic foaming agent (foaming agent H, AC, etc.), and the commonly used foaming additives are urea E4LYY620, organic acid, etc. The gases decomposed by the thermal decomposition of inorganic foaming agents are ammonia, carbon dioxide and water vapor, which have high permeability in rubber and are generally used to manufacture open-cell rubber with large holes. The gases released by organic foaming agents are mainly ammonia and nitrogen, which have low solubility and low permeability in rubber compounds, and are suitable for the production of closed-cell sponge rubber.
(3) Design of reinforcing filling system: EPDM rubber has poor rubber strength, and carbon black is mostly used as a reinforcing agent when producing sponge rubber sealing gaskets with EPDM reclaimed rubber, and medium particle thermal cracking carbon black, semi-reinforcing furnace black and fast-pressing furnace black are commonly used; Fillers are often made of hard clay and talc.
(4) Design of softening and plasticizing system: Paraffin oil with good compatibility with EPDM rubber and reclaimed rubber is generally used.
When EPDM sponge rubber gasket is used to reduce costs, it is also necessary to select appropriate anti-aging systems and other operating additives to further improve the processing technology performance of rubber and improve the aging resistance of finished products. In actual production, the production process parameters of sponge rubber sealing gaskets containing EPDM reclaimed rubber can be appropriately adjusted, such as mixing time, mixing temperature, sulfur sum time, vulcanization temperature, etc., to further optimize the comprehensive performance of sponge sealing gaskets, and discuss related issues with you later.
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