Guangdong TPE Encapsulation Material Manufacturer Dechuang Chemical
Source：德創(chuàng)化工Time：2020-04-27Hits：2362
How is TPE encapsulated? As we all know, TPE can be encapsulated with PP, ABS, PS, PC, PA, PS, PE and other plastics. All materials comply with the environmental protection inspection reports of EU ROHS, SGS, REACH, PAHS, 12P and so on. Wear resistance and scratch resistance are good, TPE material feels comfortable and smooth, material fluidity is good, and it is easy to process and form.
Model Selection of TPE Encapsulation
The processing method of secondary injection molding is to coat TPE soft rubber material on the surface of hard plastic products to improve their aesthetic appearance and feel comfort, skid resistance, wear resistance, shock absorption, sealing, grip, etc. In the production process, common injection molding machines, hard rubber products molds and TPE rubber coating molds will be used.
The other is a two-color injection molding machine, which adopts two glue injection ports, and two sets of molds for hard plastic and TPE injection are respectively filled into the two mold heads. During injection, the hard plastic is injected first, and then the TPE melt is injected onto the soft plastic mold by rotating the mold heads with another screw rod, so as to rapidly complete encapsulation and improve the coating effect and production efficiency.
Selection of TPE Coating Material
In order to achieve a firm adhesive coating, we need to use two materials with similar polarity to inject the coating. The difference of solubility parameter (SP) is within 0.5, and the two colloids have good compatibility. When encapsulating ABS and PA with strong polarity, TPE needs to be modified in polarity to improve its SP so that the two materials have good compatibility. TPE and hard plastic with similar polarity melt at the coating interface at high temperature to form an ablation layer, and the two materials penetrate each other to form a firm adhesive coating after cooling. SP of TPE is about 7.2, PP is 7.5, PE is 8.0, PS is 8.5~9.0, ABS is 10.5, PA is 13.6.
TPE Encapsulation Molding Process and Precautions
1, hard plastic parts processing
Before the hard plastic parts are put into the encapsulating mold, the surface shall be clean and free of moisture, garbage and oil stains. For nylon parts, if they are left in the air for more than two hours after injection molding, we all recommend preheating and baking the nylon parts (two-color injection molding machine can be ignored). Baking temperature is 100-140, baking time is 2-4 hours. The meaning of baking: remove moisture from nylon parts and raise the surface temperature of nylon parts. Nylon has high melting point and strong polarity. Preheating before encapsulation is beneficial to improving the bonding strength of encapsulation molding.
2. Cooling Time of Encapsulated Injection Molding
After the encapsulation is completed, it should be properly cooled, and then the mold is opened and taken out. If the adhesive is not cooled, the mold is forced to be opened and taken out, which may lead to strong tensile deformation of the soft adhesive encapsulation position. For TPE with slow cooling and setting, properly prolonging the cooling time can improve the bonding performance of encapsulation.
3, TPE material baking problem
TPE packaging generally does not use vacuum aluminum film paper bags. Whether to bake the sample depends on whether the TPE compound absorbs water easily. If TPE has water absorption, it should be baked at 60~80℃ for about 2 hours. If it is not baked, the moisture in the material will affect the bonding effect, or lead to pits or water lines on the coated surface.
4. Injection pressure, temperature and speed of encapsulation
The injection pressure and speed shall be adjusted by the injection master based on experience according to the product structure, mold runner structure and material fluidity. Injection molding temperature, can provide TPE suppliers with reference processing temperature.
