How to improve the TPE & PA bonding is not strong?

- Jul 05, 2019-

How to improve the TPE & PA bonding is not strong?


  TPE encapsulated nylon PA, which is very strong to bond, is difficult in the industry. To improve the problem of poor adhesion, we need to start from the following aspects.




  It is necessary to improve the polarity of the TPE compounding system (currently using a grafting agent) to make the polarity close to that of the PA, thereby facilitating adhesion. It is said that the TPU of some production models has good adhesion to PA, but the hardness is limited, and the TPU hardness is usually above 70A. If a lower hardness TPE is required, it is still necessary to improve the polarity of the SEBS system.


2. Suitable overmolding temperature


 The overmolding temperature of the TPE needs to be sufficiently high, and it is preferable to form a certain weld on the surface of the nylon member, and the adhesion is greatly improved. If the molding temperature is low, the adhesion will be unfavorable.


3. Should pay attention to the design of the mold flow channel and the glue inlet


 For products with large coating area and many coating positions, open as many glue inlets as possible to reduce the running time of the melt in the mold. The longer the running time and the running path, the greater the melt temperature of the compound, which is detrimental to the fusion bond. The key to encapsulation is: (hot) fast coating adhesion.


4. Preheating baking of nylon parts


 For ordinary over-molding with ordinary rubber-coated molds instead of two-color machine composite molding, it is recommended to pre-heat or bake nylon parts first, baking time is about 1~2 hours, baking temperature is 120~130°C. The adhesion of TPE to nylon provides more energy for coating adhesion.


5. Nylon parts are made into grooves, fine holes, coated surfaces for grinding, etc.


 Will help the bonding strength of TPE and nylon parts. But this is achieved by physical and mechanical forces, not chemically bonded.

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