The vaporization temperature of water is 100℃, and typically injection molding temperatures exceed 100℃. Water vaporizes at high temperatures, causing product defects such as bubbles, jet marks, and silver streaks on the surface. Therefore, the moisture content of plastic is an important factor affecting the processing technology, appearance, and characteristics of products, and must be monitored.

The moisture content of plastic affects the following product defects:

Product dimples and bubbles: Caused by inadequate drying of hygroscopic materials and residual monomers and other compounds in the material. To determine the cause of pores, observe whether the bubbles in the plastic products appear instantly when the mold is opened or after cooling. If they appear instantly when the mold is opened, it is mostly a material problem; if they appear after cooling, it belongs to mold or injection molding condition problems.

Product weld lines: Product weld lines are usually caused by low temperature and low pressure at the weld line.

Product embrittlement: Due to degradation of materials during injection molding or other reasons.

Material discoloration: Due to scorching, degradation, and other reasons.

Silver streaks and patterns on products

Four key points for pre-drying of molding basics for plastic moisture content:

Commonly used drying equipment for plastic moisture content:

Key factors of drying equipment: air flow rate, air temperature, air humidity, drying volume.

Checking the drying effect with air-shot material blocks: This method is applicable to most materials, but for some materials, even if the moisture content exceeds the standard, there may not be such obvious manifestations.