Natural latex reclaimed rubber is made from waste natural rubber, waste latex, and their products, retaining the basic properties of natural rubber. It has high strength, good elasticity, and low specific gravity, and can fully or partially replace natural rubber sponge shock-absorbing sealing gaskets, reducing raw material costs. When adding latex reclaimed rubber to sponge shock-absorbing sealing pads, it is necessary to choose appropriate latex reclaimed rubber according to actual needs, appropriately adjust rubber formulations and production processes, and reduce production costs while maintaining the practical performance of the shock-absorbing sealing gasket.
1. Precautions for natural reclaimed rubber production sponge shock-absorbing sealing gaskets
(1) Tips for choosing natural latex reclaimed rubber for sponge shock-absorbing sealing pads
When using latex reclaimed rubber for sponge shock-absorbing sealing pads to reduce costs, it is recommended to choose materials in four steps: "color→ performance→ environmental protection → craftsmanship."
White, light, and colored sponge shock-absorbing sealing pads are made of white natural latex reclaimed rubber, which is light-colored, easy to match, and has a stable appearance; Based on performance indicators such as tensile strength and elongation of shock absorbers, latex reclaimed rubber E6LYY330 should be chosen; Pay attention to limits on heavy metals and polycyclic aromatic hydrocarbons in latex reclaimed rubber, especially for shock-absorbing sealing gaskets used in exports, automobiles, or home appliances; Choosting latex reclaimed rubber with a fineness of ≥60 mesh, no impurities, Mooney viscosity of 45–80, and plasticity of ≥0.5 can ensure uniform mixing and stable foaming.
(2) Key process points for producing sponge shock-absorbing sealing gaskets made from natural latex reclaimed rubber
(1) Thin Pass: When using natural latex reclaimed rubber instead of natural rubber to produce sponge shock-absorbing sealing pads, it is recommended to perform moderate thin passes (3-5 times) before feeding to further improve the plasticity of the compound, ensure uniform dispersion of additives, and destroy residual fiber impurities in the reclaimed rubber to prevent fiber penetration of the bubble walls causing bubble collapse.
(2) Mixing: The "low-temperature mixing" principle is used for latex reclaimed rubber, with roller temperature controlled at 50-60°C; Be sure to add sulfur and accelerators afterward to prevent scorching caused by friction from the rollers; Foaming agents (such as average AC and foaming agent H) should be added after the softener and before the vulcanization system to ensure the foaming agent is evenly distributed in the compound.
(3) Vulcanization: When producing natural latex reclaimed rubber for sponge shock-absorbing sealing gaskets, a "high-temperature short-time" vulcanization process is usually used. During molding, sufficient air discharge cycles (usually 1-2) must be ensured to expel air from the cavity and prevent visible scars or delamination in the finished product.
2. Natural reclaimed rubber sponge shock-absorbing sealing pad formula
(1) Practical formula for producing white sponge shock-absorbing sealing pads using a combination of natural rubber/natural reclaimed rubber
Natural rubber 50 parts, white natural latex reclaimed rubber 50 parts, zinc oxide 5 parts, stearic acid 3 parts, anti-aging agent DOD 2 parts, paraffin 2 parts, light calcium carbonate 40 parts, titanium dioxide 10 parts, petroleum jelly 7 parts, triethanolamine 1 part, diisopropylbenzene peroxide 2.5 parts, foaming agent H 4 parts, urea 0.5 parts, water 3 parts; A total of 180 portions.
(2) Practical formula for producing colored sponge shock-absorbing sealing pads using a combination of natural rubber/natural reclaimed rubber
Natural rubber 50 parts, white natural latex reclaimed rubber 50 parts, zinc oxide 4.5 parts, stearic acid 3 parts, anti-aging agent D 3 parts, paraffin 2 parts, light calcium carbonate 70 parts, accelerator CZ 1.6 parts, accelerator TMTD 0.1 parts, sulfur 0.8 parts, foaming agent H 4 parts, colorant 1 part; A total of 190 portions.
(3) Practical formula for producing black sponge shock-absorbing sealing pads using a combination of natural rubber/natural reclaimed rubber
Natural rubber 20 parts, black natural latex reclaimed rubber 80 parts, zinc oxide 2 parts, stearic acid 5.7 parts, anti-aging agent D 2 parts, paraffin 2 parts, spray carbon black 30 parts, petroleum jelly 15 parts, asphalt 5 parts, accelerator DM 0.8 parts, sulfur 2.5 parts, foaming agent H 4 parts, urea 1 part, water 5 parts; A total of 175 items.
When using natural reclaimed rubber to produce sponge foaming shock-absorbing sealing pads, it is essential to achieve a dynamic balance among foaming and vulcanization through formulation adjustments; If the product surface collapses, it is usually due to excessive foaming agent or slow vulcanization. The amount of foaming agent used can be appropriately reduced or the ratio of accelerators CZ and TT to TT. If there are large or uneven pores, check the dispersion of the mixing or rule out poor venting in the mold. In the future, I will continue to share with you the key points in formula design for sponge shock-absorbing sealing pads mixed with latex reclaimed rubber.
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