Common problems in the production process of PU imitation wood products are: 1. Epidermal bubbles: The current production conditions definitely exist, but there are only a few problems. 2. Epidermal white line: The problem in the current production conditions is how to reduce the white line and repair the place where the white line appears. 3. Skin hardness: According to different requirements of customers, there is currently no exact standard. The analysis of the above issues is as follows: 1. Epidermal bubbles: Depending on the location and phenomenon, the causes are different. Typical reasons are: (1) Problems with foaming guns: a. Generated during the mixing process: try to reduce the bubbles generated when the foaming material flows out of the gun head, such as poor mixing and air leakage from the gun head. b. Mixing speed (for low pressure machines): the higher the speed, the better, and the smaller the flow, the better. c. Do not spray tailings on the product. d. The material temperature is high, the reaction is fast, and the bubbles will be reduced (mainly in winter). e. The proportion of black material is high, the air bubbles increase, and the pressure of the storage tank remains stable. f. Dirt and dust are mixed in the foaming gun head. (2) The influence of the mold: a. The mold temperature is high, the bubbles will be reduced. b. Mold exhaust effect, reasonable inclination angle. c. The mold structure determines that some products are more, and some products are less. d. Mold surface smoothness and mold surface cleanliness. (3) Process control: a. The effect of brushing and not brushing, more injection and less bubbles. b. Late mold closing will reduce air bubbles. c. The way of injection and the distribution of raw materials inside the mold. (4) Influence of release agent: a. Silicone oil release agent has more bubbles and less waxy bubbles 2. The problem of the white line of the product epidermis: When the raw material is injected into the mold, there will be a time difference, so there will be a time difference when the raw material starts to react, so that white lines will be generated at the overlapped part of the interface before and after the reaction. The main reasons for it are: ⑴Mold problem: a. When the mold temperature is 40-50 ℃, the white line will decrease. b. The inclination angle of the mold is different, and the position of the white line is also different. c. The local temperature of the mold temperature is too high, resulting in different reaction times of the raw materials, resulting in white lines. d. If the product is too large or too thick, the white line will increase. e. The mold is partially water stained and the release agent is not dry, resulting in white lines. ⑵ Foaming gun: a. The high temperature of the material will reduce the white line, and the place where the white line appears when the proportion of black material is high is harder. b. (Low pressure machine) The high speed of the gun head, the mixing effect is good, and the white line will be reduced. c. There will be white lines at the head and tail of the material. (3) Process control: a. The increase in the amount of raw material infusion will reduce the white line. b. After injection, brushing will reduce white lines. 3. Product hardness: a. The density of the raw material is high, the hardness of the product increases, but the amount of infusion increases. b. The proportion of black material is high. Epidermal hardness increases. c. When the mold temperature and material temperature are high, the hardness of the product will decrease. d. The release agent will reduce the skin hardness, and the in-mold paint will increase the skin hardness. Qualified products need to be controlled in terms of equipment, raw materials, processes, molds, etc., so it is recommended to seek cooperation from suppliers of polyurethane equipment in the production process.
Post time: Sep-08-2022