There are many factors affecting EPDM automobile seal VOC, mainly the volatile amount of rubber material itself, the type of surface coating, the type of double-sided adhesive tape paste, coated adhesive, curing process, product parking time, environmental temperature and so on.
1. The coating
At present, the surface of the sealing strip is mainly sprayed with two kinds of coating materials to improve wear resistance and reduce surface gloss, one is polyurethane coating, mainly wear resistance; The other is organosilicon coating, which mainly reduces surface gloss and friction coefficient [1]. Solvents are commonly used in coatings. The previous coating generally uses toluene, xylene and other organic matter with lower cost as solvent, but it will cause residue on the surface of the sealing strip after spraying, and volatilize after a long time, resulting in VOC volatilize value of the sealing strip product exceeds the standard. Now the new coating is generally water-based coating, VOC content is relatively low, the overall impact on the sealing strip is basically small.
2. Adhesive or adhesive tape
Automobile sealing strip is generally covered with some double-sided adhesive tape or foam for assembly and sealing. When pasting adhesive tape and foam, it is necessary to use end coating or glue to improve the adhesion with the sealing strip body. But the existing glue and bottom coating solution is generally solvent-based solution, which contains a large number of volatile organic compounds, so it is easy to cause the large VOC volatilization of the seal strip assembly. Generally, the assembly method and structure of the product should be improved to reduce the amount of adhesive tape and sealing foam.
3. Vulcanization process
Because the seal VOC test is carried out at high temperature, so in the sealing strip vulcanization process to increase the temperature of microwave hot air vulcanization furnace can also reduce the VOC residue in the sealing strip products. The usual method is to improve the vulcanization temperature of the product or extend the length of the hot air vulcanization line body, so that the low molecular matter in the seal strip as far as possible, reduce residue, reduce the volatile VOC of the seal strip assembly.
4. Parking time
Due to the parking process, the organic matter in the sealing strip will slowly volatilize, so with the extension of time, the residual VOC in the sealing strip should be less and less. After the study, the sealing strip parked for 15 d compared with the first day, its VOC volatilization can be reduced by more than 70%, this is especially obvious for benzene.
5. Ambient temperature
VOC is mainly benzene and aldehydes. The volatilization temperature of aldehydes is lower than that of benzene. Generally, as the temperature rises, the rate of volatilization of organic matter will accelerate. By comparison, compared with 20℃ storage for a week, 40℃ storage for a week after the seal VOC volatilization can reduce more than 80%, this figure is more than 95% lower than 0℃ storage for a week. Ambient temperature has a great effect on benzene, but a little effect on aldehydes. This is mainly because the boiling point of aldehydes is generally below 0℃, and the temperature has little influence on the evaporation rate.
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