The influence and control of injection molding material moisture on injection molding

author: Universe plastic

2024-04-29

During the injection molding process, we often encounter various problems in the products we manufacture, the most common of which are bubbles, spray marks, surface silver wires, etc. in the injection molded products.

The most likely source of these serious quality problems in products is that plastic raw materials contain moisture. For this reason, we must effectively monitor the moisture of raw materials.

What impact does the moisture content of injection molding materials have on injection molded products?

Bubbles and silver wires: Water will vaporize at high temperatures, causing product defects such as bubbles, spray marks, and surface silver wires.

Product dents and bubbles: caused by moisture and other compounds remaining in the material due to insufficient drying of hygroscopic materials.

Product weld marks: Product seams are usually caused by evaporation of water at the seams, uneven temperature and low pressure inside the material.

Product brittleness: caused by evaporation of water and oxidative degradation of gas and materials during the injection molding process.

Material discoloration: caused by evaporation of water inside the material, degradation of gas and coloring materials.

How to control the moisture ratio in injection molding materials

Raw material drying: Before injection molding, use drying equipment to dry the raw materials. The control of drying time is crucial to the subsequent product molding process and product quality.

Moisture detection: Use a professional plastic moisture meter to accurately test the moisture content of plastics. The plastic moisture meter can accurately test the moisture content of plastic in about three minutes to ensure the qualification rate of the finished product.

Environmental control: The hygroscopicity of plastic pellets is affected by air humidity in the production workshop, packaging process, transportation process, storage environment and other factors. The production environment and conditions need to be properly controlled to keep the moisture content of the raw materials within a reasonable range.

Process optimization: According to different plastic material types, such as nylon, PET, PBT, etc., appropriate drying time and temperature need to be determined. For example, nylon is an engineering plastic that easily absorbs water, especially unmodified PA6 and PA66, with water absorption rates as high as 1.5%-1.9%. Therefore, nylon packaging is usually multi-layer aluminum foil bag packaging, which can be used directly. If the raw materials are exposed to the air for more than one hour, they must be dried.

Equipment maintenance: Regularly inspect and maintain drying equipment to ensure equipment efficiency and optimize drying procedures to improve production efficiency.

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