Why does TPE thermoplastic elastomer shrink?

With the rapid development of TPE materials, the demand for TPE thermoplastic elastomers is also increasing. However, when some businesses learn about TPE thermoplastic elastomers, they find that TPE thermoplastic elastomers shrink. So why does TPE thermoplastic elastomer shrink? Will its shrinkage have any impact on product processing? Below, Zhongsuwang professionals will solve these problems for you. We hope that after reading, businesses who do not understand can gain a better understanding of TPE materials.

1. When the state of TPE begins to change from molten to cooling, its molecules align with each other, causing the overall dimensions of the molded part to shrink. Although this shrinkage is generally in the range of a few thousandths of an inch, it is enough to significantly affect the molding and demolding of the part, as well as the final appearance of the finished product. If the shrinkage is uneven, it can cause an originally flat part to become warped or deformed. Therefore, when producing TPE, tolerance requirements are relatively strict. For these reasons, shrinkage is usually taken into account during the production of TPE.

2. TPE (TPR) materials based on SBS have good water resistance. Generally, the shrinkage rate of TPE/TPR materials is about 1.5~3%. However, TPU based on polar materials such as polyester or polyether is not water-resistant, but it generally swells when exposed to water rather than shrinks, and the usage conditions are also not certain. Because different formulas have different physical properties, the shrinkage rates produced vary. Each TPE manufacturer has a different shrinkage rate.

3. Molding conditions can significantly affect the degree and nature of shrinkage. If the state changes rapidly from high stress to low stress, the degree of shrinkage will increase. Rapid cooling of the part and high injection speed or pressure can also affect shrinkage.

4. When producing TPE, considering shrinkage from the design aspect, the mold must be machined slightly larger than the required dimensions of the part. The actual shrinkage value can only be known when the specific part is molded. Therefore, it is always best to be conservative beforehand. Some TPEs are more anisotropic than others, meaning they may shrink more in one direction than in another. This factor must be taken into account when designing the mold.

Finally, we obtain that the shrinkage rate of TPE materials is 1.5~3%, which is normal. Moreover, because during the production of TPE, manufacturers usually take the shrinkage of TPE materials into account, its shrinkage will not have any impact on product processing. Therefore, you can rest assured when purchasing.