1.the effect of 2k molding is better than 2-step molding?
Simply speaking: The first step of the hard mold is still hot when it is injection and immediately enters the second cavity of the 2K injection molding machine.；The intermediate transfer process also does not absorb moisture, that is, it is easy to be burned by the high temperature TPE melt on the surface to form an ultra-thin layer, and there is no influence of water vapor on the surface being adsorbed;
2.Use a higher barrel (melt) temperature as much as possible within the processing tolerance of the TPE material;
Otherwise, how easy is TPE to heat the surface of the hard plastic material?
3.In the second step of covering wire, the hard mold is used as the cavity of the insert as much as possible.
The hard plastic temperature is high, the TPE high temperature melt is cooled slowly, and there is enough heat and enough time to ablate the hard plastic to form a super-thin layer;
4.In the second step of covering wire, the TPE melt is injected at a high rate of fire as much as possible without generating a TPE flash.
High rate of fire, TPE has a short spreading time on the hard plastic surface, and a longer time ablates the hard plastic surface during the molding cycleThe rate of fire is high, the friction between the TPE and the hard plastic surface causes frictional heat generation, and the TPE melt temperature is also cooled down, and it is used for contacting and ablating the hard plastic surface for a longer time;High rate of fire, most TPE (except TPU, TPU melt viscosity is more sensitive to temperature) The melt viscosity is shear thinning and the surface tension is reduced, which is conducive to spreading on the hard plastic surface.
5.To avoid moisture absorption or smudging on the hard plastic surface, especially in the case of two-step injection molding, it is more likely to occur during the process of stopping and transferring the hard plastic.
Polar hard plastics such as PC, PBT, PET, POM, especially strong polar hard plastics such as PA6, PA66, surface moisture absorption leads to the formation of intermolecular bonds, and the natural encapsulation bonding force is reduced;The surface of the hard plastic part is dirty, such as the uncleanness of the workshop worker’s gloves or the adhesion of the glove cotton fiber to the surface of the polar hard plastic part, which naturally affects the encapsulation of the TPE melt;TPE coated with polar hard plastic is definitely a polar formula, which does not pay attention to moisture, and also affects the bonding effect of the rubber;