In various industries, painting on plastic surfaces is widely applied. Coatings not only enhance appearance but also protect the base material. However, a common issue is paint peeling after a short time of use. Plastic surfaces inherently have low adhesion, and without proper technical measures, coatings degrade quickly.
Causes of Paint Peeling on Plastic
Plastic surface not treated properly
One of the most common reasons is the lack of surface preparation. Plastics have low surface energy, which makes paint molecules adhere poorly. If the surface is not cleaned of grease and dust, or not sanded, plasma-treated, or corona-treated, the coating will detach quickly. Technical manuals emphasize that this step is critical to adhesion performance. Proper pretreatment not only improves bonding but also ensures even, smooth film formation.
Not using a dedicated plastic primer
Many manufacturers skip a primer designed for plastics. In fact, primer acts as an intermediate bridge, linking the substrate with the topcoat. Without this layer, adhesion is weak and peeling occurs after only a few uses. For plastics such as PP and PE, primer is essential to achieve long-lasting coating performance.
Using the wrong type of coating
Not every paint system is suitable for plastic substrates. Some plastics, such as PP and PE, are highly inert and cannot be coated with conventional paints. These materials require specialized systems like two-component polyurethane (2K PU) or coatings with strong adhesion promoters. If the wrong product is applied, the coating cracks, lifts at the edges, or peels in large patches despite proper application.
Moisture or contaminants on the surface
Another overlooked factor is residual moisture and contaminants. Traces of grease, fine dust, or even a thin water film can prevent adhesion. When a coating is applied over an unclean surface, peeling becomes almost inevitable. This explains why many manufacturers face failures even when they select the correct paint.
Lack of adhesion promoter
For difficult substrates like PP or PE, primer alone is often not enough. Additional adhesion promoters are required. A common choice is chlorinated polyolefin, which significantly enhances bonding strength. Without it, coatings adhere only temporarily and peel off under mechanical impact or humid conditions. Research shows adhesion promoters are a key factor for long-term stability.
Application errors during coating
Application technique plays a critical role. Frequent mistakes include applying too thick, over-thinning, or skipping proper drying time between coats. In addition, painting in high humidity or at temperatures below standard prevents proper film formation. These mistakes lead to premature peeling even when correct materials are chosen.
SOLUTIONS TO PREVENT PAINT PEELING ON PLASTIC
Standard surface preparation
Before application, plastic surfaces must be carefully prepared. Steps include cleaning with isopropanol or a neutral solution, then light sanding to create mechanical roughness. Finally, dust should be blown off with compressed air to ensure a completely clean base. Proper preparation greatly reduces peeling risk and improves coating performance.
Using a dedicated primer
Primers formulated for plastics, especially chlorinated polyolefin-based, are highly effective in improving adhesion. Tests show that coated products with primer retain color and bond strength far better than those without. It is a small investment with significant long-term benefits.
Choosing the right coating system
To ensure durability, waterborne or solvent-based 2K PU systems are strongly recommended. These coatings not only provide excellent adhesion but also maintain flexibility and impact resistance. Sourcing from reputable suppliers ensures consistent quality and reliable product performance.
Maintaining proper application conditions
Environmental conditions directly influence coating quality. Humidity should remain below 70%, and application should not be carried out below 10°C. Moreover, drying intervals between coats must strictly follow the technical datasheet of the paint manufacturer. This step ensures stable bonding and long-lasting protection.
VICHEM – OFFICIAL DISTRIBUTOR OF HIGH-QUALITY COATING ADDITIVES IN VIETNAM
Vichem is an official distributor of coating additives, fully compliant with legal regulations in Vietnam. We not only provide high-quality products but also deliver international-standard after-sales services. Our services include:
- Technical consulting: Supporting customers in choosing the right products for their applications.
- Color matching tests: Our experts conduct matching tests to ensure design standards are met.
- Application support: Assisting clients in integrating products into production lines for optimal efficiency.
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