First, the concept of TPE overmolded PC

　　TPE overmolded PC, which is a unique term in the thermoplastic elastomer TPE industry, means that the thermoplastic elastomer TPE is bonded and overmolded to the surface of PC (polycarbonate) plastic parts by injection molding to give the product some functional requirements.TPE thermoplastic elastomer is a SEBS rubber-modified material with rubber elasticity, and it can be conveniently injected or extruded into the molding. The hardness range of the rubber can be adjusted at ShoreA 0~100 degrees. For overmolding PC TPE rubber material common hardness range of 30 ~ 90 degrees, the appearance of the color or translucent particles. The rubber material has excellent abrasion resistance, good adhesion with PC coating, and the products made are comfortable and smooth to the touch.

　　Second, overlay PC on the performance requirements of the TPE material

　　1.Excellent overlay adhesion

　　(1) overmolding mechanism

　　TPE should be able to through the injection molding overlay way, and PC plastic firmly bonded together. The mechanism of overmolding adhesion is that TPE and PC should have close molecular polarity or solubility parameters, which is conducive to the molecular level penetration of the two materials, in the appropriate injection temperature conditions, TPE to obtain enough energy to be able to microscopic level and PC polymer molecules for the molecular level of compatibility (penetration). At the macro level, TPE and PC are firmly bonded together through high temperature fusion, making it difficult to tear apart.

　　2) Suitable TPE blends

　　As mentioned above, TPE must have close molecular polarity with PC. However, in reality, conventional TPE is non-polar and PC is weakly to moderately polar. It is necessary to modify the polarity of the TPE so that it can be close to the polarity of PC. To find a TPE (TPR) material that can be well overmolded to PC, it is not possible to find a random TPE material on the market that can meet the requirements. Rather, it is necessary for professional TPE manufacturers to provide specialized mixing system of TPE rubber.

　　2. Determination of hardness

　　Users to do a rubberized PC products, the hardness of TPE has a more certain requirements, the hardness can be provided by the user to confirm the physical properties of the table or to provide OK samples. Plastic Bo can provide TPE with hardness of 25~90A, which can be firmly glued to PC material.

　　3.Surface scratch resistance

　　Different products have different requirements for the scratch resistance of TPE material. This need to communicate with the user to confirm, if the user can provide physical OK sample, it is the best.

　　4. Other performance requirements

　　Some special product applications, the requirements for TPE is more unique, Plastic Bo listed some of the special requirements of TPE seen in the following situations

　　A. Transparency

　　Some electronic products with visibility requirements need TPE materials with high transparency;

　　B. Toughness and elasticity

　　Some buttons, cover products, for TPE toughness and resilience have high requirements;

　　C. Flame retardant

　　Some electronic components accessories, wires and plug products, for the TPE plastic-coated PC has certain flame retardant requirements.

　　D. Easy processing and molding

　　Some products with large wrapping surface require TPE with good fluidity to facilitate the smooth progress of wrapping;

　　Some plane wrapping, inverted buckle product wrapping cases, TPE is required to provide good support for mold release.

　　Third, the molding method and the main process parameters

　　1. Molding equipment and processing methods

　　TPE and PC overmolding, there are two types of molding equipment.

　　One is to use ordinary injection molding machine. Open two sets of molds (PC parts injection mold and TPE overmold). Injection PC plastic parts first, then take out the PC parts and put them into another set of overmolding molds for secondary injection of TPE soft rubber. If there is only one injection molding machine, the PC parts processing molds are also changed, for another set of overmolding molds, PC plastic parts manually (or by robot) placed into the overmolding molds, TPE injection molding to the surface of the PC parts.

　　Second, special two-color injection molding machine. Two-color injection molding machine has two or more injection barrels and screw plasticizing injection device, and in the same mold, through the rotary die head to quickly achieve two or more injections, without having to take out the plastic parts into another set of molds to overmolding, thus greatly reducing the molding time, improve processing efficiency.

　　2.Molding process parameters

　　Mold temperature is generally set 30 ~ 50 ℃; injection pressure and screw speed is generally not a hard and fast rule, because of the large differences in different equipment, to the actual adjustment of the appropriate parameters shall prevail; injection temperature, which is a small range, generally in the range of 190 ~ 230 ℃, the characteristics of the rubber material and equipment is an important factor.