Recently, a user encountered TPE/TPR wrapped products, in the second injection molding wrapped TPE, hard plastic parts deformation problem, a brief analysis of the causes and countermeasures: 1, the hard plastic (usually ABS, PP) parts size is thin or the ratio of length to width and thickness is large, and the molding temperature is relatively high.

　　1, hard plastic (usually ABS, PP) pieces of thin size, or the ratio of length and width to thickness is large, and the molding temperature is relatively high.

　　The thickness of hard plastic parts is thin, in the secondary injection molding TPE, TPR, due to the higher cladding temperature (170 ~ 200 ℃), in the cladding process, the heat is easy to ABS, PP and other rubber parts softened, resulting in its deformation.

　　Solution: Reduce the injection molding cladding temperature and use TPE and TPR grades with lower melting point of the blending system. However, sometimes reduce the cladding temperature on the bonding may have a negative impact, if necessary, you can do mechanical polishing of the surface of the hard plastic parts, or increase the concave line groove.

　　2, in the hard plastic parts of the premise of thin size, the thickness of the soft rubber cladding layer is larger, and the products on the soft rubber elasticity and strength requirements are higher.

　　Styrene elastomer TPE,TPR has a large molding shrinkage, and the thicker the cladding, the greater its shrinkage, and the high elasticity and strength of the performance requirements, but also to strengthen the shrinkage of the material. For some special cladding structure, this shrinkage will aggravate (ABS, PP, etc.) the deformation of hard plastic parts.

　　The solution idea: to reduce the shrinkage of some materials as much as possible under the premise of taking into account the material performance, so as to reduce the resulting impact on the deformation of hard plastic parts.

　　In comparison, the first solution idea is more commonly used in actual cases and more effective, the second solution idea should be applied according to the actual case. The two solution ideas sometimes need to be used together.

　　Supplementary.

　　1. If the above methods are not able to improve the existing problems, in the case of cost allows, replace the hard rubber material with good resistance to high temperature deformation, is also a way to try the idea.

　　2. The design of the glue inlet should be designed to reduce the flow length to thickness ratio as much as possible. Because when filling the mold cavity, the longer the flow path of the melt, the larger the shrinkage will be, which will aggravate the deformation of the hard plastic parts.

　　3. Some TPE, TPR products, due to TPE, TPR surface some sticky (especially obvious in the summer), and improper storage, resulting in products stick together, difficult to separate, forced to pull apart, easy to pull deformation. This is strictly speaking another problem category, but the material or products stick together, may indeed lead to product deformation.