The main factor affecting PBT hydrolysis is the concentration of terminal carboxyl groups. Because PBT contains ester bonds, these bonds break when placed in water at temperatures above its glass transition temperature. The acidic environment created by hydrolysis accelerates the reaction, leading to a sharp decline in performance.
Improving the surface smoothness of PBT injection molded products requires the addition of plastic additives. Since PBT processing temperatures are relatively high, the temperature resistance requirements for plastic additives are even higher, especially in equipment where the drying oven and injection molding machine are integrated.
Therefore, many PBT injection molding manufacturers choose silicone masterbatches containing silicone additives to improve surface smoothness.
However, careful attention must be paid to the compatibility, molecular weight, and high-temperature resistance of the silicone masterbatch with the PBT material. Otherwise, the following issues may occur:
1. Product surface delamination and easy peeling.
The main components of silicone masterbatches are resin carriers and high-molecular-weight organosilicon. If surface delamination and easy peeling occur, it is highly likely due to poor compatibility between the resin carrier in the silicone masterbatch and PBT.
2. Insufficient Smoothness
The silicone masterbatch has a high resin carrier ratio and a low content of high-molecular-weight silicone. While this type of masterbatch is inexpensive, the surface finish may not meet requirements, or the addition ratio needs to be adjusted to a higher level to achieve the desired effect.
3. PBT Products Become Sticky and Show Exudates After a Period of Time
The silicone masterbatch contains excessive low-molecular-weight lubricant. Initially, the finished product may appear fine, but after a period of time, low-molecular-weight substances migrate to the surface.
There may be many more issues not listed here. Please let me know in the comments or via private message, and we can discuss solutions together.
TPU material itself has high viscosity. A single injection mold may contain hundreds or thousands of fibrous strands. If demolding is not done properly, many strands will stick to the mold, and in severe cases, many strands may break. This requires frequent mold cleaning, which is very time-consuming, affects the yield rate, and increases production costs.
Many factors affect demolding results. After excluding factors such as mold, temperature, injection pressure, and raw materials, TPU injection molded toothbrush bristle manufacturers can add a demolding lubricant during the mixing process. Silicone-based demolding lubricants are recommended.
Silicone plastic lubricants are high-efficiency organosilicon polymer lubricants widely used in injection molding/extrusion processes.
Silicone plastic lubricants possess high-temperature resistance and do not degrade at 350 degrees Celsius. During production, they fully melt with the material, interacting with metal surfaces, screws, molds, etc., improving the plasticizing properties of TPU plastic processing, increasing melt flow rate, and achieving easy demolding.
Furthermore, compared to other plastic lubricants, silicone plastic lubricants have non-migrating and non-exudation properties, effectively improving the surface properties of TPU injection molded products.
Adding 0.5% silicone plastic lubricant to TPU injection molded toothbrush bristles solves the problem of difficult demolding.
