The petroleum resin is a yellow to brown resinous solid, having a molecular weight of 600-8000, a softening point of 66 to 125 ° C, a relative density of 0.97 to 0.975, a flash point of 260 ° C, an acid value of 0 to 2, and a saponification value of 0 to 29 and a refractive index of 1.58 to 1.60. Petroleum resins have good characteristics such as low acid value, good compatibility, low melting point, water resistance, ethanol resistance and chemical resistance. Petroleum resins are soluble in paraffinic hydrocarbons and chlorinated hydrocarbons, but insoluble in lower alcohols and ketones.
Some of the key properties in the many properties of petroleum resins are as follows:
- Softening point The solid petroleum resin must be uniformly dispersed into the rubber matrix by kneading. Therefore, the softening point must be within the temperature range of the elastomeric viscous flow state. In the production of rubber feets, the temperature of the mixer mixing chamber is generally controlled at 100 to 120 ° C, which matches the softening point of the petroleum resin.
- The acid value reflects the total content of the acidic substance in the resin. It can also measure the change of the hydroxy compound when the resin is parked, which is important for controlling the storage stability of the resin.
- The ash content is used to evaluate the amount of inorganic matter in the resin, and the amount of the remaining catalyst can be understood to understand the degree of removal of the unreacted catalyst in the resin.
- Compatibility reflects the degree of compatibility of the resin with the compound after it is added to the compound. If the compatibility is not good, it will inevitably appear frosting during rubber storage or rubber feets storage, which will affect the appearance and feel of the product, and even affect the service life.
In summary, the petroleum resin used in rubber feet should generally have a low acid value, which means good stability and good compatibility with the rubber main material, meaning that the effective duration after compatibility is relatively long, and the melting point is relatively low. To prevent the surface of its sneeze product from affecting the service life. The melting point should be suitably lower to speed up its flow in the rubber to obtain a better dispersion effect, especially when used as a tackifier and softener, but also to prevent softening points from being too low for certain requirements. Products with certain mechanical properties are not good. In addition, water resistance and chemical resistance should be considered.