In the process of rubber mixing and processing, when the process is over (that is, after the next auxiliary machine of the close mixer or the opening mixer finishes the piece) the rubber mixing rubber is sent to the material warehouse for stacking and storage for a period of time, which is called "parking", which means "waiting for maturity". Parking is not a simple static process, nor can it simply be understood as the storage stage before rubber mixing rubber is put into use. In terms of production management, parking can ensure the supply of rubber mixing rubber, so that the production line goes on smoothly; But from a technical point of view, it also serves several indispensable functions.

(1) reduce the shrinkage rate of rubber mixing rubber mixing rubber main material is rich in high elastic elastomer. They are in plasticizing, mixing and other processes to withstand mechanical force of stretching, traction; Once these forces are gone, there is a strong elastic recovery (and contraction) that is inherent in elastic materials. However, shrinkage is detrimental to product molding. In parking, shrinkage occurs throughout the whole process. Although the shrinkage process is relatively slow, it is absolutely necessary for the molding operation to provide shape and dimensional stability for the rubber compound after parking.

(2) it is beneficial to the uniform and stable parking of rubber mixing rubber performance should also be regarded as the process of further uniform dispersion of all kinds of coordination agents. Although in mixing all kinds of coordination agent to help the strong mechanical action of the rubber mixer and be dispersed, but due to the limitation of mixing time, as well as the water contained in the coordination agent itself and agglomeration (block) and other objective reasons, often can not reach the required degree of dispersion uniformity. In the process of parking, although the external force no longer exists, but these powder groups can still continue to disperse with the help of the chain segment movement of rubber macromolecules, to complete the dispersion process in mixing. These processes can not be seen by naked eyes, but can be confirmed by high power electron microscope observation before and after parking, and can be illustrated by performance comparison.

(3) to promote the generation of "binding rubber" when mixing reinforcing agent (carbon black, white carbon black, etc.) into the raw rubber, through the reaction of the active group on the surface and the group on the rubber surface, the generation of "binding rubber" to produce reinforcing effect. Although most of this reinforcing behavior is formed in the mixing stage, due to the limitation of the time of the "mixing cycle", the reinforcing behavior is often incomplete, and it is left to be completed in the parking stage, so as to generate more binding rubber and achieve better reinforcing effect.

(4) to relax the "stress" rubber macromolecules in the process of rubber refining due to the effect of external mechanical force and accumulation of structural fatigue, this kind of fatigue is not removed, often damage the product performance, and the parking process provides time conditions for the relaxation of such structural fatigue.

As for the length of parking time, there is no unified caliber, in general, neither too short, nor too long. If the parking time is too short, often can not fully play a role, so that the above functions can not get full play; And too long parking cycle, will bring some side effects, for example, lead to some high dosage of compound frost. The suitable parking time of rubber compound is 1 ~ 3d(24 ~ 72h) under large production conditions.