How to Get Paint to Stick to Plastic

Painting plastic surfaces can be a daunting task, often resulting in poor adhesion if not done correctly. Whether you're looking to rejuvenate outdoor furniture, automotive parts, or household items, keeping paint from peeling off plastic starts with proper preparation and the right products. KBS Coatings offers indispensable products to get paint to stick to plastic: KBS Klean, Fusion SEP Self-Etching Primer and Fusion FPP Flexible Plastics Primer.

Understanding the Challenges of Painting Plastic

Plastic surfaces present unique challenges for paint as they are smooth and non-porous. Traditional paints often struggle to adhere effectively, leading to peeling and flaking. To make paint adhere to plastic, specialized plastic primers are used to create a strong bond between the plastic and the paint, leading to better adhesion and a more durable finish.

What is Plastic Primer?

Plastic primers are typically formulated with special bonding agents that help the paint grip the plastic surface and keep paint from peeling off plastic. These primers may also have flexible properties, which is important since plastics can expand and contract with temperature changes and especially for soft plastics which flex.

For soft plastics KBS Coatings offers Fusion FPP Flexible Plastics Primer. For hard plastics Fusion SEP Self-Etching Primer is recommended.

What’s the Best Primer for Soft Plastics?

Getting paint to stick to soft and flexible plastics, such as rubberized plastics, vinyl, or soft PVC requires a flexible plastic primer. Also known as elastomeric primer or adhesion promoter, flexible plastic primer incorporates a flexing agent that allows the primer to strongly bond to soft plastics and provide a strong yet flexible base coat that will move with the plastic. Thereby avoiding delamination, cracking and peeling.

A primer that’s not intended for soft plastic won’t work well or may not work at all. For example, if a self-etching primer, which is designed for materials like metal and hard plastic can’t flex with soft plastic to remain adhered. Potentially leading to the primer and top coat cracking and peeling.

KBS Fusion FPP - Flexible Plastics Primer

KBS Coatings offers KBS Fusion FPP - Flexible Plastics Primer for promoting a tight bond between flexible plastics and most varieties of top coats. Of note, it can also be used on other surfaces like urethanes, wood, fiberglass, carbon fiber.

Fusion FPP is a user-friendly plastic primer spray paint that’s easy to apply after preparing the surface. The gray colored primer has a fast dry time that allows film thickness to be built quickly.

What’s the Best Primer for Hard Plastics?

Hard plastic primers are made for rigid materials that don’t bend or flex. These primers are formulated to form a strong, durable bond with smooth, non-porous surfaces, such as polycarbonate, acrylic, or ABS plastic. They tend to be more rigid once dried, as hard plastics don’t need the same level of flexibility as soft plastics.

Primers designed for soft plastic can typically be used on hard plastics as their formulations make them conducive to bonding strongly with hard and soft plastics. But they may not be the ideal choice. Flexible primers are designed to handle movement and stress, so they may not provide the same hard, durable finish as a dedicated hard plastic primer.

KBS Coatings SEP - Self-Etching Primer

KBS Coatings Fusion SEP Self-Etching Primer is an adhesion promoting primer not only for hard plastics but also for metals such as steel, brass, and aluminum. On metal surfaces its self-etching ability etches an anchor pattern for best adhesion. It also performs excellently as an inter-coat for adhesion between multiple surface coatings.

Fusion SEP is user-friendly, easy to apply and fast drying. After preparing the surface, it can be sprayed or brushed on. The primer is available in aerosol form as well as in pints, quarts, and gallons.

Step-by-Step Guide to Get Paint to Stick to Plastic

Before applying primer thorough surface preparation is essential:

Step 1: Cleaning

• For primer adhesion that will stop paint from peeling on plastic, any dirt, grease, wax, or other contaminants must be completely removed. KBS Klean is designed for this purpose. It is a strong, concentrated cleaner that doesn’t leave residue that can interfere with primer adhesion. KBS Klean is mixed with warm water and applied with a sponge, bristle brush or scouring pad. Which tool is used depends on how stubborn contaminants are adhered to plastic. After contaminants are removed the surface is thoroughly rinsed with water and completely dried with a clean and lint free cloth or compressed air.

• Detailed use and safety instructions for KBS Klean can be found here: https://www.kbs-coatings.com/kbs-klean-directions.

Step 2: Scuff the Surface

• Scuffing or lightly sanding the plastic can help primer adhesion as it provides a slightly rough texture the primer can grab onto. This is typically more of a preparation procedure for primer on hard plastics, as flexible primers used on soft plastics often don't require sanding as they are designed to bond to plastic without the need for roughening the surface. However, for maximum adhesion, soft plastics can be scuffed.
• Plastic can scratch and gouge easily, which can show through to the final finish. So, it’s recommended to use fine sandpaper (400-600 grit) or steel wool, applied with light pressure in a back-and-forth motion. Adequate scuffing is indicated when the surface sheen has slightly dulled.
• After scuffing, plastic dust residue must be completely removed to avoid primer adhesion issues. This can be done with hot water and a sponge, while use of KBS Klean as described above can produce the most thorough results. Finally, the surface is completely dried with a clean and lint free cloth or compressed air.

Step 3: Primer Application

Safety

Always work in a well-ventilated area and wear appropriate respiratory and eye protection when handling primers and paints.

Temperature and Humidity

Ideal application conditions are between 55-82°F with humidity below 85%. Avoid painting in direct sunlight or excessively humid conditions.

Mixing

Before applying primer be sure it is mixed thoroughly. If stirring, use a paint paddle to mix the primer from top to bottom until thoroughly mixed. Take time to mix thoroughly, at least a minute. If aerosol is used shake the can for at least one minute once the mixing ball moves freely. After every one minute of use, shake the can for 10 seconds. The key is to keep primer components thoroughly mixed together.

Fusion SEP Self-Etching Primer Application

• Fusion SEP can be applied by brush, roller or spray gun, or in aerosol form. We prefer spray gun or aerosol methods for the smoothest and quickest application. When spraying, hold the nozzle 10-14” from the prepared surface and apply in steady, even and over-lapping strokes.
• Apply a light and even coat. A single coat is generally all that is required to get paint to stick to plastic, but additional coats can be added. When needed, apply 2 to 3 light and even coats allowing a 3-5-minute dry time between each coat. Keep the coats light to for proper curing and to avoid runs.
• Fusion SEP will be dry-to-the-touch in 15 minutes. Allow a one-hour dry time before sanding, priming or top-coating. Always coat over within 7 days. If after 7 days, scuff with 300 grit sand paper. There is no need to sand if coated over within 24 hours.
• Detailed use and safety instructions for Fusion SEP Self Etching Primer can be found here; https://www.kbs-coatings.com/fusion-sep-directions.

Fusion FPP – Flexible Plastics Primer Application

• Fusion FPP is applied in aerosol form. Hold the nozzle 10-14” from the prepared surface and apply in steady, even and over-lapping strokes.
• Apply a light and even coat. A single coat is generally all that is required but additional coats can be added to fill in small imperfections. When needed, apply 2 to 3 light and even coats allowing a 3-5-minute dry time between each coat. Keep the coats light to for proper curing and to avoid runs.

Top Coating Fusion SEP – Self-Etching Primer

• Detailed use and safety instructions for Fusion FPP Flexible Plastics Primer can be found here: https://www.kbs-coatings.com/fusion-fpp-directions.

Top Coating Plastic Primers

Both Fusion SEP and Fusion FPP can be top coated with a variety of paints and coatings including KBS BlackTop, KBS MAXX, KBS Top Coater, and KBS Top Coater Aerosol.

Of note, some people are painting plastics as many plastics do not hold up well to UV light which causes them to chalk and fade. This can be avoided by applying solid color top coats for protection against UV.

Top Coating Fusion SEP – Self-Etching Primer and Fusion FPP – Flexible Plastics Primer

• Allow 1 hour for Fusion SEP or Fusion FPP to dry before applying or another topcoat or primer.
• Always coat over Fusion SEP or Fusion FPP within 7 days. If you want to apply after 7 days, scuff the Fusion SEP or Fusion FPP with 300 grit sand paper.
• For exceptionally smooth finishes, lightly sand the primed surface with fine-grit sandpaper (600-800 grit) after it has cured.

Conclusion

The best way how to get paint to stick to plastic is using proper preparation techniques and the right products. KBS Klean, Fusion SEP - Self-Etching Primer and Fusion FPP - Flexible Plastics Primer offer reliable solutions to ensure your painted plastic projects are durable, attractive, and resistant to peeling or cracking over time. By following these steps and tips, you can transform plastic surfaces into beautifully painted finishes that withstand the test of time.

Questions?

If you have any questions, please let us know. +Contact KBS Coatings.