If the paint isn't sticking to the plastic, the problem is usually that the surface is too glossy. Thoroughly sand the plastic to a matte finish for best results. Keep the spray light to avoid drips. An initial tack coat of about one-third to one-half coverage will help later coats stick better.
Wipe off any dust with a clean cloth. Use a Primer: Apply a plastic primer if your paint requires it. This helps the paint stick better to the plastic surface. Allow the primer to dry completely before painting. Apply Paint: Use thin, even coats of paint, allowing each coat to dry before applying the next.
Sand the Surface to Create a Rough Texture for the Paint to Adhere To. Sanding is an essential step for ensuring good paint adhesion. It creates a slightly rough texture on the plaster wall or door, providing the paint with a better surface to grip.
Plastic is one of the more difficult surfaces to paint because of its smooth surface, and plastic responds to temperature more easily by expanding and contracting, so it's more prone to cracking or flaking over time.
Standard exterior gloss paint is a suitable finish for plastic when used in conjunction with an appropriate primer and undercoat. Either acrylic or oil-based gloss can be used, and both are available in a wide range of colours. Typical application methods include brush, roller and spray.
When spray painting plastic that is soft, like vinyl, a flexible paint is required, and acrylic-based paints and urethane modified acrylic paints adhere better without cracking, flaking, or peeling. Overall, oil-based paint isn't a good spray paint for plastic as it doesn't bond well.
New Unprimed Parts. Painting new unprimed plastic first requires a thorough cleaning of the part: soap and water washing, removing mold release agents, chemical cleaning and inspection are all parts of the pre-sanding cleaning. The part must be sanded and cleaned, then anti-static and/or adhesion promoter is applied.
PEELING PAINT AND POOR PAINT ADHESION
To fix it, start by using a paint scraper to remove any flakes, peels, or old, loose paint from the surface. Then with a putty knife, cover the area with spackle and allow it to dry.
Because, most likely, the surface you are spraying is high gloss plastic. Like any other high-gloss surface, paint does not bond well with it. You need to sand the surface, likely to about 300–400 grit so that the paint has a nice surface to hold on to. You can further protect it by clear coating.
Surface contamination such as dirt, oil, and grease. Polish residues on the surface, which impair the adhesion of the paint. Excessive movement of the substrate, such as joints, imposing stress on the paint film which can result in cracking which in turn lets in moisture, ultimately resulting in a flaking paint film.
Painting and Staining
The acidic qualities of the vinegar will clean and degrease the surface and help the paint adhere. Odors: When applying paint of any kind, keep small dishes of vinegar around the room to absorb paint odors. Keep the dishes out for a few days, adding new vinegar each day.
The application of Vaseline, a brand of petroleum jelly, creates a protective barrier which prevents the paint from adhering to unwanted areas and reduces the risk of peeling or chipping along the door's edges.
Spray paint works especially well for plastic, but you can use acrylic or enamel/model paint as well. It would be even better if the paint is meant for plastic. Check the label, and look for words such as: "Plastic" or "Multi-Surface."
If the paint isn't sticking to the plastic, the problem is usually that the surface is too glossy. Thoroughly sand the plastic to a matte finish for best results. Keep the spray light to avoid drips. An initial tack coat of about one-third to one-half coverage will help later coats stick better.
For optimal results, an epoxy should be used. However, cyanoacrylate glue may also work well for this application. The Infinity SuperTAC 500 Plastic Bonding Glue Sticks are one of the best plastic bonding hot melt options.
“The best way to apply spray paint to a plastic surface is to always clean first and then lightly sand the piece if there are loose debris. Then, use Krylon Fusion All-In-One spray paint for the best adhesion!”
The most common cause of paint peeling (or delamination) is due to inadequate surface preparation. In the case of plastics, you also need to consider the surface tension of the plastic and the surface tension of the primer coating (1st layer). The second most common reason for peeling is solvent entrapment.
Spray paint designed specifically for plastic is often the best choice, as it's formulated to adhere to smooth surfaces. These paints have special bonding agents that help them grip plastic surfaces.
Lightly sanding the surface helps to remove any existing gloss, roughen the surface slightly, and create a better bond for the adhesion spray paint. Additionally, applying a primer or sealer to the surface further enhances adhesion by providing a suitable base for the adhesive paint.
How to Prevent Paint from Sticking. Adjust doors and windows to open and close properly. Sand down any existing coatings if they appear to be thick. Use top-quality interior semi-gloss or gloss latex-based paints.
If painting interior plastics, apply a high-adhesion latex stain-blocking primer. For outdoor plastics, spray-prime with specialized primers formulated specifically for adhesion to plastics.
A little bit of surface texture will help your paint adhere. Take a fine-grit sandpaper (180 to 220 grit is the way to go) and lightly sand the entire surface you intend to paint. Keep your movements gentle, since too much heat and friction can degrade the plastic past the point of no return.
Step 7: Protect the paint with acrylic sealer.
A single coat of sealer may do the trick, but I usually spray on two or three coats. Between each, allow 30 minutes of drying time. After the final sealer coat, wait 24 hours before handling the object to make sure the surface is fully dry and set.