The problems encountered in the vacuum plastic coating process and the solutions

The vacuum plastic coating process, also known as vacuum metallizing or vacuum deposition, can encounter various challenges and problems during its execution. These issues can impact the quality of the coated products and the efficiency of the manufacturing process. Here are some common problems encountered in the vacuum plastic coating process and their potential solutions:
Pinholes or Porosity in Coating:
Problem: Small holes or pores in the coating can lead to reduced barrier properties and aesthetics.
Solution: Improve the cleanliness of the substrate surface, adjust the coating parameters, and ensure proper degassing of the vacuum chamber to minimize contamination and porosity.
Uneven Coating Thickness:
Problem: Variations in coating thickness across the substrate can result in inconsistent appearance and performance.
Solution: Maintain proper control over deposition rates, substrate rotation or movement, and coating source positioning to ensure uniform deposition.
Adhesion Issues:
Problem: Poor adhesion of the coating to the substrate can result in delamination or flaking.
Solution: Pre-treat the substrate surface with techniques like plasma cleaning or corona treatment to improve adhesion. Ensure proper substrate cleaning and preparation.
Contamination and Impurities:
Problem: Contaminants in the vacuum chamber or on the substrate can lead to defects in the coating.
Solution: Maintain a clean environment within the vacuum chamber, regularly clean the chamber and fixtures, and use high-purity source materials.
Stress and Cracking:
Problem: High residual stress in the coating can lead to cracking or peeling.
Solution: Optimize deposition parameters, such as temperature and deposition rate, to reduce stress. Use stress-relief layers if necessary.
Substrate Warping or Deformation:
Problem: Some plastics may deform or warp under the high vacuum and temperature conditions.
Solution: Choose substrates that are suitable for vacuum coating or implement temperature control methods to minimize substrate distortion.
Phenomenon 1: Bubbling in the groove
Reason analysis:
1. The temperature or pressure does not meet the requirements, resulting in false suction;
2. Insufficient adhesive amount, insufficient spraying amount, or adhesive leakage from the board;
3. Insufficient preheating (softening PVC film) or blistering time (forming time);
4. After vacuum molding, remove the pressure before the temperature drops.
5. The heat resistance of the adhesive itself is not sufficient.
Solution:
1. Increase temperature or vacuum;
2. Increase the amount of glue applied and select high-quality boards;
3. Increase preheating or molding time;
4. After vacuum molding, the temperature should be cooled to room temperature or slightly higher before withdrawing the vacuum.
5. Use with curing agent.
Phenomenon 2: Local blistering
Reason analysis:
1. Uneven glue spraying results in a small amount of local glue, leading to a decrease in bonding strength;
2. The problem with PVC film is that it contains plasticizers, which can easily migrate to the surface during aging or heating, affecting the bonding strength;
3. There is a problem with the heating pipe inside the blister machine, causing uneven temperature.
Solution:
1. Try to ensure a uniform amount of adhesive spraying;
2. Use high-quality PVC film;
3. Timely maintenance of equipment.
Phenomenon 3: Unable to hold or shrink the edge
Reason analysis:
1. When vacuuming, the side temperature is too low or the vacuum degree is insufficient;
2. Insufficient temperature resistance of adhesive;
3. After vacuum molding, remove the pressure before the temperature drops.
Solution:
1. Increase temperature or vacuum;
2. Use with curing agent;
3. After vacuum molding, the temperature should be cooled to room temperature or slightly higher before withdrawing the vacuum.