Nitrile rubber has excellent oil resistance and is often used together with polyvinyl chloride (PVC) to produce sealing products. The finished products have good oil resistance, wear resistance, heat resistance, and chemical corrosion resistance. Reclaimed nitrile rubber retains the basic properties of nitrile rubber and can replace an appropriate proportion of virgin nitrile rubber when blended with PVC to produce rubber-plastic sealing products, effectively reducing raw material costs.
1. Key points in the formulation design for preparing sealing products using nitrile rubber/reclaimed nitrile rubber/PVC blends
When preparing rubber-plastic sealing products using nitrile rubber and reclaimed nitrile rubber as the main raw materials, as the amount of polyvinyl chloride increases, the hardness, tensile strength, tear strength, oil resistance, wear resistance, and permanent deformation of the vulcanized rubber containing both rubber and plastic increase, while elongation at break and elasticity decrease. To improve the compression set performance of the nitrile rubber/reclaimed nitrile rubber/PVC blend, the amount of sulfur and accelerator can be appropriately increased, while paying attention to the tendency for scorching.
In actual production, rubber sealing products can be made from nitrile rubber/nitrile reclaimed rubber/PVC blended materials by using the accelerator TMTD (2-3 parts) and accelerator CZ (2-3 parts) in combination with sulfur (0.5 parts). The vulcanized rubber suitable for both rubber and plastic has good processing performance and relatively low permanent compression deformation. If necessary, a small amount of peroxide can be added. Using a combination of high-abrasion carbon black and semi-reinforcing carbon black can improve the mechanical strength of rubber-plastic compatible rubber.
2. Key Points of the Blending Process for Preparing Sealing Products Using Nitrile Rubber/Nitrile Reclaimed Rubber/PVC
When nitrile rubber is blended with polyvinyl chloride, the plasticizing temperature and blending temperature must be strictly controlled. Nitrile rubber is typically mechanically blended with suspension polyvinyl chloride: the PVC resin is mixed and plasticized with plasticizers and stabilizers on a rolling mill at temperatures above 160°C, then granulated. After that, it is blended with nitrile rubber and anti-aging agents at 90°C to produce a masterbatch rubber, which is finally mixed with the remaining additives at conventional temperatures.
3. Common applications of nitrile rubber/nitrile recycled rubber/PVC blends include the preparation of sealing products.
Nitrile rubber/nitrile recycled rubber/PVC blend materials have characteristics such as oil resistance, wear resistance, aging resistance, high strength, and good processing performance. They can be used to produce various sealing products, mainly including the following three types:
① Heat-aging resistant sealing products, such as framework oil seals, which require rubber-plastic composite materials to have good heat and oil aging resistance as well as physical and mechanical properties; ② Oil-resistant and wear-resistant sealing products, such as various reciprocating motion seals (e.g., E5LYY521), which require rubber-plastic composite materials to have excellent wear resistance; ③ Oil-resistant and low-deformation sealing products, such as O-rings and rectangular seals, which require rubber-plastic composite materials to have low deformation.
When preparing rubber-plastic sealing products by blending nitrile rubber, recycled nitrile rubber, and polyvinyl chloride, sealing product manufacturers also need to select the appropriate recycled nitrile rubber based on actual needs and reasonably determine the proportion of recycled rubber to be added. We will discuss related issues with you later.
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