Formulation design (1) The use of NBR and PVC in the selection of NBR polar genes acrylonitrile content is different, the polarity is different, have an impact on the compatibility of the blend and product performance. This formula is selected from NBR-40 manufactured by Lanzhou Chemical Factory. Suspension and emulsion methods can be used to manufacture PVC. Suspension PVC is cheap, but the melting temperature is high during processing. High temperature plasticization and mixing are required; emulsion PVC The price is more expensive, but plasticizers can be used to infiltrate and swell in advance, and no high-temperature plasticizing equipment is required for processing. The degree of polymerization of PVC also has a great influence on the properties of the blend. The high degree of polymerization of PVC can improve the performance of the blend, such as strength, tensile strength, and aging resistance. At the same time, the viscosity and the plasticization temperature of the blend are also increased, making the processing difficult. This formula chooses PVC-RH.
(2) The PVC blends with different amounts of PVC and NBR have different performances. Although PVC and NBR can be blended and blended at any ratio, the properties of the thermoplastic plastics are mainly based on the characteristics of the rubber of the nitrile rubber or the rubber properties of the nitrile rubber. The various blends, but the ratio must also be selected according to the actual use of the product requirements. With a small amount of NBR, the dispersion of NBR in PVC is poor. When the amount of NBR is increased to NBR/PVC=20/80 or more, the NBR will be evenly dispersed in PVC, and the compression set of the product will be reduced; the amount of PVC will be reduced. Increased, tensile strength, aging resistance, product appearance quality improved. According to the performance requirements of automotive seals, this formula uses a blend of NBR/PVC=40/60.
(3) Softening and plasticizing system The main function of the softening and plasticizing system is to reduce the intermolecular force of the polymer and increase the mobility of the polymer molecular chain, that is, to reduce the softening temperature of the polymer. According to the actual performance requirements of products, use of phthalic acid (DOP) and dioctyl sebacate (DOS) and use, the ratio of DOP/DOS = 5/1.
(4) The reinforcement system is usually made of super wear-resistant carbon black, high wear-resistance carbon black, fast-press carbon black, etc. as reinforcing agent, supplemented with proper amount of clay, calcium carbonate, talcum powder as filler to improve the processing performance. At the same time reduce production costs.
(5) The Antioxidant system can use substituted phenolic antioxidants. The antioxidant can have a complexing effect with the stabilizer of PVC and prevent the aging of the PVC molecular chain.
(6) PVC stabilizing system PVC is degraded during processing due to thermal and mechanical shearing, and its products are vulnerable to heat, light and oxygen during use. The selection of stabilizer must be based on the processing technology and the requirements of the final product performance. consider. We use lead stabilizers with good stability and weather resistance.
(7) The degree of unsaturation of the NBR in the vulcanization system is small, and the amount of sulfur can be reduced. When using a high-volume low-sulphur system in combination with a thiuram- and sulfenamide-based system or a thiuram-thiazole, the PVC/NBR blend has excellent physical and mechanical properties. This formula uses thiuram and thiazole together with the low-sulfur system, vulcanization promotion dose of 23 is appropriate.
Indoor Small Formulation Test (1) PVC Plastic Moulding and NBR Plastic Moulding First mix PVC with plasticizer and stabilizer, stir it evenly with a blender, plasticize NBR on an open mill to a plasticity of 0.29 or more, and store for 8 hours before use. . The stirred PVC was plasticized on a hot plastic machine, the roll temperature was generally controlled at about 160e, and the roll distance was 0.51 mm. Under the heat and shearing action of the roll, the PVC was formed into a molten state and wrapped around the roll. (2) Rubber and plastic co-roller technology: After adding PVC to the roller, add NBR plastic compound, heat-smelting uniformly, cut off heating power, pass cooling water, add zinc oxide, antioxidant, stearic acid and carbon black in turn, adjust To the appropriate roller distance, the lower piece is cooled, and each piece must be isolated with a little separating agent, and the blend masterbatch is made by stopping for 8 hours. According to NBR mixing process control roller temperature is about 60e, adding vulcanization accelerator, mixing about 10min, adjust the roller distance is the blend. If the mixing time is too long, scorching will occur, and the structure of the extruded product will be incomplete. (3) Physical and mechanical properties The physical and mechanical properties of the indoor small-formulation test blends are shown in the table. The results show that the physical and mechanical properties at room temperature meet GB7526/87 standards. When the total amount of vulcanization accelerator reaches 3 parts, the tear strength decreases, which is lower than the standard requirement of GB7526)87. When the total amount of vulcanization accelerator reaches 2 parts, the elongation at break of [email protected] hot air aging is lower than the standard requirement. The compression set of Formulations 2 and 3 meets the standard requirements. The brittle temperatures of the three formulations met the standard requirements.
Conclusion Compared with the traditional single rubber compound and plastic modified material, the physical and mechanical properties and surface appearance quality of automobile door and window seals made of PVC/NBR rubber and plastic blends are improved; compared with rubber seals, Hot air aging, surface appearance quality is good; Compared with plastic modified seals, the compression set is small, the surface appearance quality is similar, the texture is fine and tough, easy to use the general equipment of rubber manufacturers to produce, better elasticity. Therefore, the use of PVC/NBR blends is an effective way to improve the automotive seal material.
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