Which hard adhesives can TPE adhesive materials be coated with
Time：2019-12-19Hits：2074
The analysis of the adhesiveness of hard plastics such as TPE-coated PC, PP, ABS and PA has always been a matter of concern. The editor has also done some homework and collected some information through the Internet and various aspects.
TPE is encapsulated by secondary injection molding. By introducing thermoplastic elastomer TPE soft material, the soft touch, grip, aesthetics and other functional characteristics of the product are improved. TPE encapsulation (secondary injection molding) molding enables TPE and coated substrates (hard plastic) PP, ABS, PC, PA, etc. to be well coated and bonded.
In order to make TPE and hard plastic adhere well, according to the principle of chemical similarity and compatibility, the key is that TPE and hard plastic should have similar polarity, so that TPE and hard plastic can fuse at molecular chain level. Therefore, the type of hard plastic determines the formula of TPE, and the secondary injection molding process (e.g. the secondary injection molding temperature is, etc.) directly affects the adhesion between TPE and (PC, PP, ABS, PA) hard plastic. The adhesion of TPE coated hard plastic such as PC, PP, ABS, PA, PBT, PET, POM is analyzed as follows:
Formula of TPE Coating Material:
Different hard plastics, such as PP, PC, ABS, PA, etc., require different TPE formulations and models.
Regarding the coating of different hard plastics:
1, ABS, PC encapsulation
ABS and PC are weak to medium polarity plastics with certain polarity difference from TPE. By adding modifier (TPU) into the formula, the polarity of TPE can be improved, thus improving the adhesion of TPE to ABS and PC. In addition, the temperature for secondary injection is recommended to be 180~230℃. The details 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 the polarity of TPE of SEBS substrate. Therefore, the most conventional TPE formula can be directly used for encapsulated PP without adding additional polar modifiers. Although the TPE for encapsulated PP is the most common type, the secondary injection temperature used is also very important. Sufficient injection temperature must be used to ensure the fluidity of TPE and fast coating on the PP surface. This injection temperature should be able to ensure the rapid formation of a fusion layer on the PP plastic surface, which is beneficial to the adhesion of TPE and PP without causing thermal deformation of PP plastic parts during injection. Dongguan Dechuang Chemical Co., Ltd. suggested that the secondary injection molding temperature should be 170~220℃. Note: SBS is not recommended as TPE modified base material for PP encapsulation.
3. PBT, PET Encapsulation
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℃. TPE is required to have higher melt temperature. Therefore, for PBT and PET coated with TPE, the required secondary injection temperature is higher than that of ABS and PC coated with rubber. Bonding is more difficult.
4, PA6, PA66 encapsulation
PA6 and PA66 are semi-crystalline strong polar plastics, which require higher temperature and energy to form a weld layer on the surface of the hard plastic. The melting point of PA6 is 240℃ and the melting point of PA66 is 260℃. In order to form a firm bond, TPE needs a higher melt temperature. Generally, TPE encapsulates PA6 at 230~250℃ for secondary injection molding and 240~270℃ for TPE encapsulating PA66. In addition, PA6 and PA66 are easy to absorb water, which are unfavorable factors for coating adhesion.
5. POM encapsulation
POM encapsulation. Although the melting point of POM is not high, only 180℃. However, due to its high crystallinity, high energy is required to form a weld layer on the coating surface. At the same time, 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. Therefore, in China, I haven't heard of any TPE manufacturer who said that the POM package was secure.
In short, the analysis of the adhesiveness of hard plastics such as TPE-coated PC, PP, ABS, PA, PBT, PET, POM depends on the TPE formula and the appropriate coating process. In addition, for high melting point plastics such as PA6, PA66 and PBT, the hard plastic parts are preheated before secondary injection, which is beneficial to the adhesion of TPE and hard plastic. During the secondary injection, high injection temperature (limited to TPE degradation) and high firing rate are adopted to enable TPE to have as much energy and time as possible to realize cladding welding with hard plastic parts such as PA6, PA66, PBT and the like, thus forming good adhesion.
德创化工 (edit：dechuang)
