In the thermoplastic elastomer industry, TPE typically refers to composite functional materials modified from SEBS. TPE elastomer soft rubber possesses comprehensive properties and is commonly used as a soft rubber material in secondary injection molding, overmolding, two-color injection molding, and co-extrusion of soft and hard materials.  

(I) Main Advantages of TPE in Overmolding Applications 
 1 TPE elastomer soft rubber is used in secondary injection molding and overmolding. Due to its excellent anti-slip properties and comfortable elastic touch, TPE materials enhance the tactile feel of products and improve grip. 
 2 TPE elastomer soft rubber can be adjusted to the appropriate hardness (hardness range Shore 25-90A) and physical properties (such as wear and scratch resistance, adhesion, melt flow index, etc.) based on product requirements. This provides various material application solutions for different products. 
 3 TPE is commonly used in overmolding processes for products such as handles, grips, and electronic components. The material provides a comfortable touch, improves grip, enhances product aesthetics, and increases added value. Most of these products are exported to developed countries and regions such as the United States, Japan, and the European Union. TPE elastomer soft rubber is an environmentally friendly raw material, free from phthalates, halogens, and the 38 SVHC substances regulated by REACH. It complies with environmental testing standards such as ROHS, REACH, NP, EN71, and PAHS, fully meeting the environmental requirements of developed countries and regions like the United States, Japan, and the European Union. 

(II) Main Mechanisms of TPE Overmolding 
TPE overmolding can be categorized into true overmolding and false overmolding. True overmolding utilizes the compatibility between the soft and hard rubber during softening and melting (compatibility mainly depends on the solubility parameter SP of the materials; the closer the SP values, the better the compatibility). A bonding layer forms at the interface between the hard and soft rubber, significantly enhancing the adhesion of TPE soft rubber to hard plastics. False overmolding hardly involves material compatibility; instead, the bonding is achieved through mechanical force, mold and product design, surface treatment, and interlocking mechanisms to join the soft and hard rubber.

(III) TPE Overmolding Processing Technology 
TPE overmolding typically employs a secondary injection molding process. The pre-molded hard plastic part is fixed in the overmolding mold, and TPE soft rubber is injected and bonded onto the hard plastic part at an appropriate temperature. The product is then obtained after cooling. The injection temperature for overmolding varies depending on the hard plastic material being overmolded. The temperature must ensure that both the hard plastic and TPE soft rubber soften to promote compatibility at the interface. To achieve true overmolding, the injection temperature for TPE overmolding PP is typically around 170-190°C; for ABS, around 220-220°C; for PC, slightly higher than for ABS; and for PA nylon, the injection temperature should reach around 240°C. 

(IV) Common Materials for TPE Overmolding 
In TPE overmolding applications, TPE soft rubber serves as the outer soft layer. Common hard materials paired with it are primarily plastics, but also include metals and fabrics. TPE bonding with fabrics is mainly used in luggage and bag products, and like overmolding with metals, it is generally false overmolding. True overmolding is more common in secondary injection molding and two-color injection molding, where the main material for TPE overmolding is plastic. TPE can bond firmly with commonly used general-purpose plastics such as PP, GPPS, HIPS, ABS, and engineering plastics like PC, PC/ABS, PA, and their modified materials.
The adhesion between TPE and POM polyoxymethylene remains a challenge in the elastomer industry. The solubility parameter SP of POM (22.6) is significantly different from that of TPE (7.2-7.6), meaning the two materials are inherently incompatible. Currently, no suitable compatibilizer has been found to achieve good adhesion between them.
Special Note: Dongguan Juye Plastic Technology Co., Ltd. is a manufacturer specializing in the research, development, production, and sales of thermoplastic elastomers such as TPE, TPR, TPV, TPE overmolding ABS, TPE overmolding PP, TPR toy materials, TPE folding buckets, TPE folding basins, high-end TPE folding bathtubs, TPE overmolding PC, and various other plastic products. These products comply with human skin testing standards, do not cause allergic, mutagenic, or rejection reactions to human tissues, and meet environmental directives such as FDA, REACH, and Rohs. The company has passed ISO9001:2015 quality management system certification, ensuring quality. For inquiries and consultations, please contact: 0769-82827851, 13827205072, Ms. Zhang.