The adhesion of fluoroelastomer, silicone rubber, EPDM rubber and metal has always been a technical difficulty in the rubber industry. In recent years, due to the development of science and technology, the above-mentioned rubber and metal bonded products have become more and more widely used, and the demand has increased continuously. According to data from Shanghai San Ai Fu Company and Sichuan Chenguang Chemical Research Institute No. 2 Plant, the sales volume of fluoroelastomers in Qingdao in 2002 was as much as 100 tons, which was 10 times that of five years ago. The demand for EPDM rubber and silicone rubber is also growing rapidly. The demand for adhesives corresponding to it is also growing rapidly. The adhesives available on the market are difficult to meet the demand, and most of them are imported from abroad. ,expensive. To this end, we have developed FR-1 type adhesives for the hot vulcanization of fluoroelastomers, silicone rubbers, EPDM rubber and metals, which solved technical problems and achieved good results.
1 Experimental section
1.1 Materials
FR 1 adhesive, self-made; fluororubber 2602, 2603, 2463, Shanghai San Aifu Organic Fluorine Material Co., Ltd.; fluororubber G752, Japan Daquan Industry Co., Ltd.; silicone rubber 909, Jiangsu Zhenjiang Hongda Chemical Co., Ltd.; oil-resistant silicone rubber 9470 , Zhejiang Ningbo Changtai Rubber Technology & Trade Co., Ltd.; EPDM rubber 4640, 4570, DuPont, USA; 3# vulcanizing agent (N,N double Cinnamon 16 hexamethylene diamine), Shanghai Reagent No. 1; BPP (Benzyl trichloride) Phenyl Chloride Phosphate), Shanghai Xupu Chemical Plant; Bisphenol AF, Shanghai San Aifu Organic Fluorine Materials Co., Ltd.; Curing Agent DCP, Jiangsu Dacang Chemical Plant; Sulfurizer Double Two Five, Jiangsu Qiangsheng Chemical Co., Ltd.; Other Materials For commercial products.
1.2 Equipment
XK160, XK400 open mill, Q3110 shot blasting machine (blasting), skeleton phosphating production line, 50t, 100t flat vulcanizer.
1.3 Test process
The metal skeleton adopts two kinds of treatment methods: First, the Q3110 drum type shot blasting machine is used for sandblasting, and then the solvent is used to clean the degreasing and degreasing with the butanone, and the binder is applied; secondly, the skeleton is degreased and degreasing by the alkaline solution, and is washed with flowing water. After washing, put it into acid and remove rust, remove it and then rinse it with water, put it in Y836 medium-temperature phosphating solution to be phosphatized, and put it in 15%-2% sodium chromate aqueous solution for passivation and drying. Butanone cleaning, adhesive coating. The rubber compound is mixed with the lower sheet and parked for 24 hours. After the pre-molding, the glue body and the skeleton are put into a mold and vulcanized on a flat vulcanizing machine. The fluorine rubber and the silicone rubber need to be vulcanized again.
Evaluation method of adhesive property: After the vulcanized product was parked for 30 minutes, it was peeled with a needle-nose pliers, and the adhesive property was evaluated by the percentage of the amount of the glue. This method is closer to the actual situation than the pull-pull pull-off test. It can not only observe the amount of glue on the radial part (ie the bottom surface of the product), but also can observe the amount of glue on the axial part, and can also observe the pollution of the mould. Degree [1].
2 Results and Discussion
2.1 for the adhesion of metal skeleton and fluororubber
Before self-manufactured FR 1 adhesives, we used a variety of fluororubber-metal heat-vulcanized adhesives such as Chemlow 607,5150, AP 133, French 512, German CP 22, Italian 3290 1 And its phenolic and isocyanate BN, Lek sodium, etc., found in France's 512, Germany's CP 22 adhesive properties, quality and stability, the amount of glue over 70%, the operation process is simple and easy, but expensive ( 512 yuan per 1 litre, CP 22 per litre 650 yuan). To this end, we have referenced silane adhesives for development. After many trials, trials have been made for a variety of adhesives. We have screened them for quality and cost, and finally decided that FR 1 should be used at about 50 yuan per liter. The adhesive has stable quality, simple preparation process and low manufacturing cost. The adhesive is used for the skeleton oil seal, the valve stem oil seal, and the miniature bearing cover seal and has been approved by many seal manufacturers. The binder also has some selectivity for the rubber formulation, but it is not very obvious. For example, can be used for 3 # curing agent formulations: fluororubber 2602 1100, light magnesium oxide 15, calcium hydroxide 5, filler 15, processing aids 2, 3 # vulcanizing agent 3; formula for low compression set: 2602 1100, Active Magnesium Oxide 5, Calcium Hydroxide 5, Filler 20, Processing Assistant 2, Bisphenol AF2 0, BPP0 6; Nippon Densh., Ltd. G752100 (containing vulcanizing agent), Filler 15, Processing Auxiliary 2, Active Magnesium 5, calcium hydroxide 4. The rubber compound was placed on the surface for 24 hours and then subjected to primary vulcanization (165°C×12min) and secondary vulcanization (200°C×24h). The product was 65×90×12 after phosphating, passivation, and solvent cleaning. Skeleton oil seal. After the peel test, the amount of the fluoro rubber formulated with the 3# vulcanizing agent was over 70%, and the adhesive was firm. The other two test formulas were all covered by more than 70%, which was comparable to that of 512 and CP-22. However, the individual product had a phenomenon of secondary lip breakage, indicating that the rubber had poor tearability. The place of production and the amount of light magnesia have an impact on the adhesive properties. In the production, it was found that the weight of light magnesia was relatively stable in 12 to 15 parts, and there was fluctuation in 12 parts or less, and the strength was higher in 15 parts of rubber.
The quality of light magnesium oxide produced by Dunhuang Chemical Plant in Shanghai and Luohe Chemical Plant in Qingdao is stable. In the production process, poor quality light magnesium oxide is sometimes encountered, which seriously affects the bonding quality (mainly foaming and contaminating the die mold and causing quality degradation). Fillers such as spray carbon black N990, red iron oxide, calcium fluoride, barium sulfate, wollastonite powder, silicon dry soil, etc., as long as the material is not shoddy products, generally do not find that will lead to a decline in the quality of adhesion. The amount of processing aids, ie, dispersants and internal mold release agents, should be controlled within 2 parts as much as possible, as excessive usage may be detrimental to adhesion. The fluoro rubber production site has almost no effect on the bonding. The 2601, 2602, 2603 and 2301, 2602, 2603, and 2463 of Shanghai Chenguang Branch No.2 Plant that have not been used for many years, as long as the Mooney viscosity value is between 60 and 130, the formula is appropriate for the production of skeleton oil seals, Stem oil seals and bearing seals have good adhesive properties, and individual varieties have low viscosity values and are prone to air bubbles and easily contaminated molds, resulting in decreased adhesion. Too high a viscosity value results in poor fluidity and poor tearability resulting in a decrease in adhesion.
2.2 For Silicone Rubber and Metal Bonding
The adhesion of silicone rubber to metal is easier than the adhesion of fluorine rubber to metal. There are many adhesives that make it bond firmly. Such as Chemlok 607, Harbin Institute of Chemical Technology VTPS are very good. We also use FR 1 adhesives to make them firmly bonded. Oil-resistant silicone rubber 9470 made of skeleton oil seals, made of 909 ordinary silicon rubber skeleton oil seals and solar water heaters on the supporting silicone rubber aluminum composite parts, all using FR 1 adhesive mass production, the results of a firm bond, the coating rate are More than 70%, and the process is simple and easy. The difference is that the surface treatment of the aluminum plate is different from that of the iron plate, that is, the aluminum plate is degreased and deoiled with alkali solution and then rinsed with tap water, and put into a mixed solution of 40% sulfuric acid and 3%-5% chromic acid for more than 10 minutes. Rinse with running water and dry. Apply FR 1 adhesive. Pre-baked skeleton is hot vulcanized bonded to silicone rubber. Different batches of different types of silicone rubber have not been found to have an effect on adhesion. We use silicone rubber and white carbon blend masterbatch, only add heat stabilizers such as Fe2O3 and sulfurizing agents such as peroxide DCP or double twenty-five, heat stabilizer is generally about 5 parts, DCP or double The 25th is 0 5 or so.
2.3 for EPDM rubber and metal bonding
The adhesion of EPDM to metal is more difficult. In the past, we used EPDM adhesives to make valve rubber cores. We used Chemolloc 236 and 238 to make ordinary sulfur plus accelerators M, DM and TMTM. C rubber material and iron pieces can be firmly bonded. However, the rubber compound has a large compression deformation, and it is difficult to meet the sealing requirements. Later, a peroxide system and a small amount of sulfur are used as the vulcanization system, and the above-mentioned adhesives are difficult to be firmly bonded. After that, we use FR 1 adhesive to make it firmly bonded, and the coating rate is over 70%. The skeleton oil seals made of 4640 or 4570 EPDM rubber of DuPont Co., Ltd. made of the United States have been heat-vulcanized and bonded by FR 1 adhesives and put into batch production. However, this adhesive is not suitable for the poor adhesion of the rubber with sulfur vulcanizing agent. The EPDM third monomer used in formulation design is ENB (ethylidene norbornene) with an iodine value of about 25 and a Mooney viscosity of between 40 and 80, such as Japan's EP33 and Japan Mitsui Co. The 4045, DuPont's 4640 and 4570, due to the higher iodine value, the lower Mooney viscosity is conducive to bonding, curing speed is also faster. In compound formula design, the amount of DCP used is 3-4 parts, sulfur is 0.4-0.5 parts is better, about 15 parts of white carbon black and a small amount of silane coupling agent are added into the formula, such as silicon 69, about 2 parts or A189, A174 dosage of about 0 5 parts, can improve the adhesive properties, and the quality and stability.
2.4 Bonding process
2.4.1 Effect of Adhesive Preparation Method and Parking Time on Adhesion
The FR 1 adhesive is prepared by using a silane coupling agent as a host material. The addition sequence and the mixing time between the additives in the preparation greatly affect the quality of the adhesive. If the feeding order is not proper or the mixing time between the materials is not well controlled, gels will appear during the preparation and will be scrapped or gel in a short period of time (eg, within 2 months) and fail, or the coagulation will not occur. But the adhesive properties are poor. Therefore, when preparing FR 1 adhesives or when purchasing the adhesive, check for gel or turbidity. The prepared adhesive is best used after being parked for a week, and the freshly prepared adhesive is easy to appear white marks on the skeleton. The adhesive should be placed in a warehouse below 25°C. If the temperature is too high, the gel will be prone to deterioration.
2 ..2 Effect of Solvent on Process Performance
FR 1 binder can be formulated with reagent-grade butanone, methanol, and anhydrous ethanol solvents. When used, the diluent must be the same as the solvent and cannot be used indiscriminately. The adhesives with butanone and methanol as solvent have higher volatility and are coated on the metal skeleton for a short time to volatilize to form an adhesive film. The adhesive of anhydrous ethanol as a solvent and diluent volatilizes slowly, and it takes a long time for coating on the skeleton at room temperature to dry out and form an adhesive film. The adhesives with butanone and methanol as solvents have a strong volatility, poor permeability and diffusibility, and special attention must be paid to dip-coating when dipping. Due to the slow evaporation of anhydrous ethanol, the wettability, permeability, and diffusion of the skeleton are better, but special attention should be paid to the relative humidity of the site, which is easy to use in the rainy days and affects the adhesive performance.
2 4 3 Effect of Dilution Concentration, Pre-baking Conditions, and Vulcanization Conditions on Adhesive Properties
FR 1 adhesive can be used directly without diluent, but sometimes the surface is prone to white film marks. Diluted with diluent to a concentration of 50% (1:1), the adhesive property does not decrease and the quality is stable. The ratio is 1:2. When the adhesive performance decreases, the ratio is better at 1:1. The pre-baking conditions have a great influence on the adhesive performance. Butanone and methanol as solvent binder skeletons are stored for 3 to 5 minutes at room temperature and then pre-baked in a thermostatic oven at 115 to 130°C for 15 to 20 minutes. The binder skeleton with anhydrous ethanol as the solvent was stored at room temperature for 5 minutes and then placed in a constant temperature oven at 130-140°C for pre-drying for 15-20 minutes. If the temperature is too high for a long time, the adhesive performance will decline; if the temperature is too low for too long, the bubbles will tend to appear during vulcanization and the adhesion performance will decrease. The vulcanization conditions of the product also have an effect on the adhesive properties. The vulcanization conditions should be determined according to the product structure and product thickness. Fluorine rubber filling molding press vulcanization, such as skeleton oil seal, curing temperature 160 ~ 170 °C, time 7 ~ 12min; injection pressure curing, such as stem seal, curing temperature can reach 170 ~ 180 °C, time 5 ~ 6min. Silicone rubber injection molding vulcanization, thin products within 5mm 180 °C × 5min, thick products around 10mm 180 °C × 8min. EPDM rubber (crude rubber iodine value of about 25), thin products 180 °C × 5min or so, thick products 180 °C × 8min or so. The vulcanization temperature of the product is lower than 145°C, and the adhesive property is poor. Above 180°C, bubbles tend to appear.
3 Conclusion
(1) FR 1 adhesives can be used to make fluoroelastomers, silicone rubber, EPDM rubber and metal bonding products.
(2) The process is as follows: the skeleton is treated with sandblasting or phosphating, cleaned with butanone and other solvents, then coated with adhesives, dried at room temperature, air-dried, pre-dried, filled with rubber, or injected with rubber.
Source: 21st Century Fine Network