Tpe encapsulated pom raw materials of dechuang chemical industry are highly viscous and difficult to fall off.
Time：2021-10-12Hits：1666
The analysis of the adhesion of hard plastics such as PC, PP, ABS and PA encapsulated by TPE has always been a concern of everyone. Xiaobian has done some homework and collected some information through the network and various aspects.
After TPE encapsulation and secondary injection molding, the soft touch, grip, aesthetics and other functional characteristics of the product are improved by introducing thermoplastic elastomer TPE soft material. The encapsulation (secondary injection molding) of TPE makes TPE and coated substrates (hard plastics) PP, ABS, PC, PA, etc.
According to the principle of chemical similarity and compatibility, it is crucial that TPE and hard plastics have similar polarities, so that TPE and hard plastics can fuse at molecular chain level. Therefore, the type of hard plastic determines the formula of TPE, while the overmolding process (such as the overmolding temperature) directly affects the adhesion between TPE and (PC, PP, ABS, PA) hard plastics. The adhesion analysis of TPE encapsulated PC, PP, ABS, PA, PBT, PET, POM and other hard plastics is as follows:
The formula of TPE:
Different hard plastics, such as PP, PC, ABS and PA, need different TPE formulations and models.
On the coating of different hard plastics:
1. ABS and PC are encapsulated.
ABS and PC are weak to medium polarity plastics, which have certain polarity difference with TPE. By adding modifier (TPU) into the formula, the polarity of TPE can be improved, thus improving the adhesion between TPE and ABS and PC. In addition, it is recommended that the secondary injection temperature be 180~230℃. It can be adjusted according to the actual processing conditions.
2. PP encapsulation.
PP is a plastic with very weak polarity, which is very close to TPE polarity of SEBS substrate. Therefore, the most conventional TPE formula can be directly used for encapsulating PP, without adding polarity modifier. Although TPE for encapsulating PP is the most general type, the secondary injection temperature is also very important, so it is necessary to use enough injection temperature to ensure the fluidity of TPE and coat it on the surface of PP quickly. This injection temperature should be able to ensure the rapid formation of a fusion layer on the surface of PP plastic, which is beneficial to the adhesion between TPE and PP, without causing thermal deformation of PP plastic parts during injection molding. Jinhua Guofeng Rubber & Plastic Co., Ltd. suggested that the encapsulation temperature of secondary injection molding should be 170~220℃. Note: PP is encapsulated, and SBS is not recommended as the modified base material of TPE.
3. Encapsulation of PBT and PET.
PBT and PET semi-crystalline plastics are similar to ABS and PC in polarity. The melting point of PBT is 220℃, and the melting point of PET is as high as 260℃, which requires higher melt temperature of TPE. Therefore, TPE encapsulating PBT and PET requires a higher secondary injection temperature than encapsulating ABS and PC. Bonding is more difficult.
4. Encapsulation of PA6 and PA66.
PA6 and PA66 are semi-crystalline and highly polar plastics, which require high temperature and energy to form a welding layer on the hard plastic surface. The melting point of PA6 is 240℃, and that of PA66 is 260℃. To form firm adhesion, TPE needs higher melt temperature. Generally, TPE encapsulates PA6 at 230~250℃ and TPE encapsulates PA66 at 240~270℃. In addition, PA6 and PA66 are easy to absorb water, which are unfavorable factors for coating adhesion.
5. POM encapsulation.
Encapsulation of POM. Although the melting point of POM is not high, it is only 180℃. However, due to its high crystallinity, it needs high energy to form a welding layer on the coating surface. Meanwhile, due to the self-lubricating property of POM, it is not conducive to the rapid coating of TPE material on the surface of POM hard plastic parts. The TPE encapsulated POM materials developed by Dongguan Dechuang Chemical Co., Ltd. have been successfully applied in the market. The TPE encapsulated POM materials are used in auto parts, snow chains and transportation belts. If you are developing TPE encapsulated POM products, you can contact Dechuang Chemical at any time if you need to know about TPE materials.
In a word, the adhesion analysis of hard plastics such as PC, PP, ABS, PA, PBT, PET and POM encapsulated by TPE depends on the TPE formula and the appropriate encapsulation process. In addition, for high melting point plastics such as PA6, PA66, PBT, etc., the hard plastic parts are preheated before secondary injection molding, which is beneficial to the adhesion between TPE and hard plastics. In the secondary injection molding, high injection temperature (limited by degradation of TPE) and high firing rate are adopted, so that TPE has as much energy and time as possible to realize cladding welding with hard plastic parts such as PA6, PA66 and PBT, thus forming good adhesion.
德创化工 (edit：dechuang)
