Solubility parameter is a physical constant energy density that is a measure of the compatibility of liquid materials, including rubber, because the rubber is liquid under processing conditions. The solubility parameters of various commonly used polymer materials (including rubber and billets) are as follows:
Rubber isoprene 7.8~8.0, natural rubber 7.95, EPDM 7.95, cis-butyl 8.1, styrene-butadiene 8.5~8.6 nitrile rubber 8.7~8.9, neoprene 8.85, chlorosulfonated polyethylene 8.9, plastic Polyethylene 7.8, polypropylene 81, high styrene 85, EVA 9.1 to 9.5, PVC 9.57, nylon 13.6.

In the processing of rubber feets, the practical use of solubility parameters includes the following three aspects:

1 Master the degree of compatibility between different polymers to provide a basis for success and use. For example, the closer the solubility parameters of the two polymer materials are, the better the blending effect is. If the difference between the two is more than 0.5, it is generally difficult to blend evenly, and a compatibilizer is required.

For example, the SP of natural rubber is 7.85, and the difference of butadiene rubber is 0.35, which is within the allowable range, so it is suitable for use in combination. The same considerations apply when designing rubber and plastic blends. If the SP of the two components in the blend differs greatly and is not so compatible, then the contradiction can only be narrowed by the use of a compatibilizer. The function of the compatibilizer is to reduce the surface tension of the two phases, so that the surface at the interface is activated and activated to improve the compatibility. Compatibilizers are often a copolymer that acts as a bridge.

2 When designing rubber feets formula, when selecting liquid additives (such as softeners and plasticizers) for a certain type of rubber, it is also necessary to consider whether the SPs of both of them are close to each other to ensure that these components are uniformly dispersed in the rubber.

3 When preparing the glue, the solvent type should also be combined according to the solubility parameter, because the closer the SP of the two (rubber and solvent) is, the faster the dissolution, and the better the uniformity and stability of the glue.