Injection molded articles such as TPR/TPE have a dull, matt or uneven color. Many people who have been troubled with TPE, polishing molds from time to time, increasing back pressure; reassembling recipes, adjusting the system! Here are some reasons for everyone to analyze. Only for Injection Molded Products
(1) If the injection speed is too fast, too long a material residence time will cause the surface gloss of the product to decrease (mainly caused by rhyolite or solution rupture).
Problem Solution: The injection speed should be reduced and the residence time should be reduced.
(2) The material has poor thermal stability and is decomposed by heat (this should be better understood but rarely occurs)
Problem Solution: Use a material with good thermal stability, good gloss, or add heat stabilizers to the material.
(3) The temperature of the cylinder is low, and the nozzle temperature is too low to cause the surface gloss of the product to decrease (similar to the fourth point).
Problem Solution: The nozzle temperature should be increased to increase the melt temperature.
(4) The mold temperature is too low and the cooling rate is too fast. When the melt is still filling the mold, a hard shell is formed on the wall of the cavity, and the shell is subjected to various forces to make it white and blemishes. Surface gloss of products
Problem Solution: The surface temperature of the mold should be increased, the cooling rate should be reduced, or local heating should be used at the gate of the mold.
(5) Excessive release dosage can also cause such defects on the surface of the product (excessive release agent and poor material compatibility)
Problem Solution: Should try not to use or use a small amount of release agent, apply evenly.
(6) The surface roughness of the mold is poor, which makes the surface of the product dull (the polishing mold, no consultation, try not to add glass fiber material)
Problem Solution: Carbon tool steel should be selected to carefully polish the mold surface and improve the mold surface finish.
(7) When the back pressure is too low during plasticization, the material will not be plasticized uniformly, and the mixture of the material and the colorant will cause uneven surface color (high-end problem, high-end solution).
Problem Solution: The back pressure should be increased appropriately.
(8) The size of runners and gates is too small, and poor exhaust will also cause the surface of products to have poor gloss (caused scorch).
Solution to the problem: The size of the runners and gates should be increased, and an exhaust slot should be added.
(9) Impurities mixed in the material, without drying can also cause the surface gloss of the product to drop (water marks appear)
Problem Solution: It should be thought to remove impurities, fully dry the material, and if necessary, add a hopper dryer.