Which aspects need to consider the shrinkage of TPE materials?

2021-08-18 09:25:45 上海益弹新材料有限公司 Viewd 897

When the TPE starts to cool from the molten state, its molecules align with each other, thereby reducing the overall size of the molded workpiece. Although this shrinkage is usually only in the range of a few thousandths of an inch, it can significantly affect the forming and demolding of the workpiece and the appearance of the final workpiece. If the shrinkage is not uniform, the workpiece that should be flat may bend or warp. In addition, in applications that have strict requirements on allowable errors, unexpected shrinkage may affect the matching of parts and overall components. For these reasons, usually the shrinkage rate must be considered in the production process, so which aspects need to consider the shrinkage of TPE materials?

The following aspects require us to consider the shrinkage of TPE materials:

part demoulding:

When the workpiece contains a core or hollow part, as the elastomer TPE shrinks, it will tightly wrap these parts of the mold, making it difficult to demold the workpiece. Mold design, mold surface finish and processing conditions can all reduce this effect.

Molding conditions:

Molding conditions can significantly affect the degree and nature of shrinkage. If it changes from a high-stress state to a low-stress state quickly, the degree of shrinkage will increase. Rapid cooling of the workpiece and high injection speed or pressure can also affect shrinkage.

In terms of design:

Considering the shrinkage, the mold must be processed to be slightly larger than the required size of the workpiece.

The above is the shrinkage rate that we need to consider in the production process of TPE materials. I hope it can help everyone. In addition, like various other properties of elastomers, shrinkage varies with the direction of polymer flow. The location of the gate will determine the direction of melt flow into the mold, and thus the direction of shrinkage.