In the production process of PDCPD parts, the issue of mold surface stickiness (adhesion of uncured material) frequently occurs, which affects demolding and the surface quality of the parts, leading to increased frequency of mold cleaning. It is recommended to analyze and address this problem through the following aspects:
Impact of Absolute Air Humidity：
Higher absolute humidity in the workshop environment means higher moisture content in the air, resulting in more water molecules adsorbed on the mold surface. Water molecules significantly affect the curing of PDCPD, as even trace amounts of water and oxygen can lead to curing failure, especially for thin-walled parts. The precise requirement for PDCPD molding is as follows: during molding, the mold cavity must first be purged with standard-purity nitrogen (≥99.5%) for more than 20 seconds before the material is injected.
Influence of Injection Mixing Pressure, Feed Rate, and Method：
Low mixing pressure of the A and B components can result in uneven mixing, leading to poor curing and mold sticking. Conversely, excessively high mixing pressure can cause the feed rate to be too fast, resulting in turbulence and splashing of the mixed material in the mold cavity. This can mix with water and oxygen molecules in the cavity, affecting curing and causing adhesion. It is necessary to incorporate secondary mixing and thoroughly consider the mold’s feed method and internal flow channels.
Effects of Initial Production Control and Significant Temperature Deviations：
Low or uneven temperatures of the A and B tanks and the mold can easily lead to poor curing and mold adhesion. Especially during initial production, inadequate control of material and mold temperatures often results in surface adhesion. Additionally, improper mold cleaning methods can introduce impurities on the mold surface and reduce mold temperature due to cooling. This may lead to a vicious cycle where adhesion becomes more frequent with each cleaning, creating a loop of adhesion-cleaning-readhesion-recleaning.
Key Recommendations:
During production, the mold cavity should first be purged with standard-purity nitrogen (≥99.5%) to displace and remove small molecules such as water and oxygen that can deactivate the raw material. This can reduce mold sticking issues by over 90%. It will significantly improve production efficiency and product quality, reduce demolding difficulties, and greatly decrease the frequency of mold cleaning. Standard-purity nitrogen is inexpensive, and its cost can be offset by the reduction in mold cleaning frequency.
Note: The protective nitrogen for raw material tanks and barrels must be of high purity: nitrogen purity ≥99.999%. The nitrogen used for mold cavity purging and displacement can be of standard purity: nitrogen purity ≥99.5%.
