Cracking (cracking), divided into aging cracking and stress cracking two types. Do a brief analysis of the causes and solutions to countermeasures.

　　1、Aging cracking

　　Analysis of the causes: TPE, TPR blend itself aging resistance is not good enough, SBS system of TPR is easy to be aging, in addition to the quality of the operating oil will also have an impact on the aging resistance of TPE, TPR blend (according to industry veterans, the high degree of hydrogenation of the operating oil, the material aging resistance is correspondingly better).

　　Countermeasures: use SEBS base material; use oil with high hydrogenation degree; add antioxidant to the blending system.

　　2、Stress cracking

　　Analysis of the causes: polymer materials in the molten state, will produce stress orientation along the flow direction, the faster the flow rate, the more obvious the molecular orientation effect. Molecular orientation will produce orientation stress when the orientation occurs. Injection molding or extrusion of products if the process is not appropriate, the stress in the product may not be completely eliminated, the product surface stress effect is more obvious, and will lead to cracking or cracks.

　　Solution.

　　Injection molding products to do pressure treatment, eliminate stress before opening the mold to take out the products; annealing treatment: using a spark gun or (hot air) to do a short heat treatment of the products to eliminate residual stress, reduce and eliminate stress cracking (cracking). Some thicker soft TPE,TPR products are more prone to stress cracking. Generally speaking, stress cracking occurs within half an hour to a few days after the product is processed. And aging cracking occurs in a few days to a month.

　　3, SBS base material of TPR aging resistance is poor, prone to aging cracking

　　Countermeasures: It is recommended to change the SEBS base material TPE.

　　4, SBS base material of TPR shoes, in the process of brushing glue, if there is a crack (cracking), it may be due to glue corrosion

　　Countermeasures: Attention should be paid to the glue try not to brush too much, do not condense in one piece.

　　5, some low hardness size thick TPE products, may be due to injection molding process pressure retention is not enough, stress shrinkage, serious cracking phenomenon will occur

　　Solution: The molding pressure should be strengthened to eliminate stress shrinkage.