If the plastic industry effectively controls the moisture content, the impact of excessive moisture
If the plastic industry effectively controls the moisture content, the impact of excessive moisture content
Effect of moisture on granulation:
Moisture content. If the moisture content of talc exceeds the standard, it will affect production and processing costs and storage issues, and directly affect the appearance and stability of talc. When applied to insulating paint, it will affect the solid content and insulating properties of the insulating paint, as well as the gel time of the insulating paint. Talcum powder has a large amount of water in the molecule, so it is not easy to remove the water. It takes a long time to analyze the water during drying. Therefore, during the production and processing process, the moisture content of talc needs to be strictly controlled.
The effect of moisture on plastic products:
In the injection molding process, if plastic particles with too high moisture content are used for production, not only will it affect product processing and product quality issues, but it will also increase the scrap rate of the product and ultimately affect the quality of the finished product, such as surface cracking and reflection , And reduced mechanical properties such as impact resistance and tensile strength. Therefore, the control of moisture content is crucial for the production of high-quality plastic products.
The moisture content affects plastic products and may have the following product defects:
1. Product dents and bubbles-caused by hygroscopic materials not being dried well, and residual monomers and other compounds in the materials. To determine the cause of the pores, just observe whether the bubbles of the plastic product appear instantaneously when the mold is opened or appear after cooling. If it occurs instantly when the mold is opened, it is mostly a material problem, and if it occurs after cooling, it is a problem of the mold or injection conditions.
Material problems: ① dry materials, control moisture content ② add lubricant ③ reduce volatiles in materials.
2. Product seam (sew stitching)-product seam is usually caused by low temperature and low pressure at the seam
Material problems: ① material pollution; ② the material fluidity is too poor, add lubricant to improve the fluidity: ④ dry the material to control the moisture content.
3. The product is brittle-due to material degradation or other reasons during the injection molding process.
Material problems: ① material pollution; ② drying materials to control the moisture content; ③ volatiles in the materials; ④ too much material return or too many times of material return; ⑤ material strength is low.
4. Discoloration of materials-due to charring or degradation and other reasons.
Material problems: ① material pollution; ② drying materials to control moisture content; ③ too much volatile matter in the material; ④ material degradation; ⑤ colorant decomposition; ⑥ additive decomposition.
5. Product silver wire and markings
Material problems: ① material pollution; ② dry materials to control moisture content; ③ uneven material particles.
6. Streaks and turbidity appear at the gate of the product-due to "melt fracture" caused by expanding the injection model
Material problems: ① Dry materials to control moisture content; ② Remove pollutants from materials.
7. Changes in product size --- due to abnormal equipment control, irrational injection conditions, poor product design, and changes in material properties
Material problems: ① the performance of each batch of material changes; ② the size of the material is irregular; ③ dry the material to control the moisture content.
8. Product sticking mold-mainly due to poor molding, insufficient ejection, insufficient injection material, and incorrect mold design. If the product is stuck in the mold, the injection process cannot be normal
Material problems: ① Remove material pollution; ② Add lubricant to materials; ③ Dry materials to control moisture content.
9, plastic paste runner-due to the poor contact between the nozzle and the arc of the nozzle, the gate material did not demold together with the product and abnormal filler. Generally, the diameter of the main flow channel is large enough so that the gate material is not completely cured when the part is demoulded.
Material problems: ① clean up material pollution; ② dry materials and control moisture content
10. Nozzle drooling-mainly due to overheating of the material, the viscosity becomes smaller.
Material problems: ① check whether the material is polluted; ② dry the material to control the moisture content
Control of plastic moisture:
Whether in the granulation or injection molding process, raw materials must be tested for moisture during procurement, storage, and transportation to avoid losses caused by excessive moisture. The most commonly used granulation is air-cooled milled surface and water ring milled surface. Plastic particles also need to be tested for moisture before packaging, and they can be bagged only after the moisture reaches the factory requirements; in the injection molding process, before drying And dried plastic particles can not only ensure that the moisture content of the plastic meets the injection molding requirements, but also maximize the control of the drying time, save energy and improve efficiency; some injection molding semi-finished products also need to control their moisture content to meet the next process requirements .