Refurbished Dulled Black PP Parts Due to Sun Exposure or Aging Using Canned Spray Paint

Some of the polypropylene (PP) parts used in rear fenders, chain guards, under covers, etc. are unpainted in their original plastic color at the time of molding. These parts, which are mainly black, can turn white and become shabby with UV rays and aging.

Light and strong, but low weather resistance is polypropylene's weak point.

Although not cracked or scratched, this is a typical example of PP parts that have become dull and white with age. Even if you try to find good used parts, there is not much difference in condition because all out-of-print model have the same age. In the past, it was common to apply a silicon spray every now and then to bring out the shine, even if only slightly, and then a chemical called plastic revival agent appeared. Both of them can recover temporarily, but it was necessary to apply repeatedly.

When painting plastic black spray, the base coat is just as important as any other coating. Just because it is easy to apply with a one-component canned spray, if you skimp on the base coat, you will definitely fail. In particular, it is essential to degrease PP surfaces that have been coated with silicone spray. Scrape off the chain rubs from the back of the chain cover with a scraper, and then wash the chain carefully with Mama Lemon and hot water, which is neutral and has high degreasing properties.

Polypropylene (PP) is the material used in parts that are subject to vibration and impact while riding, specifically the front and rear fenders, radiator shrouds, scooter floorboards, and under panels. Among various resins, PP is light in specific gravity, easy to work with, and has excellent strength, so it is commonly used not only in motorcycles and automobile parts, but also in electrical appliances, tableware, and construction materials.

One of the main features of PP is its coloration. The fenders and exterior parts of trail motorcycles are made of PP in a variety of colors. These parts are not painted, but rather remain the same color as they were when they were molded, and the high transparency of PP itself makes it easy for dyes (toners) to work. Another commonly used plastic is ABS, but it is less transparent and must be painted.

It is also very flexible, which makes it the perfect material for trail models that are often tumbled in the bushes or on dirt trails when driving in the woods or off-road.

Although it is a convenient material, PP has a weakness in that it is not weather resistant and turns white when exposed to ultraviolet rays. Many people have experienced that the surface of a polyethylene bucket left outdoors becomes matted and crispy, and the handle cracks when it is lifted after being filled with water. The same thing can happen to the PP parts of a motorcycle. Although the parts are stronger than a polyethylene bucket and will not break easily, the black parts will lose their color and turn white, and the red and yellow parts will fade and become cracked.

This is the nature of the material itself, so while surface protection such as silicone sprays and coatings can slow down the deterioration process, they cannot stop it. The best thing to do is to keep your motorcycle in the garage when you are not driving it, and reduce the number of times you drive it as much as possible, but refraining from driving your motorcycle in order to protect the parts is not the way to go.

In addition, although the black parts provide an accent to tighten up the vehicle body, there is a problem that the texture will change if you rely too much on waxes and coatings in the hope of preventing deterioration. Furthermore, spraying too much silicone spray on the scooter's step board can make it slippery and affect safety.

Flexible polypropylene is not suitable for coating

The difference between before and after degreasing and cleaning is not so big because the silicone is not applied from the beginning. Not only cracks and chips, but also there is no thick coating on the black plastic to fill the gouges and shallow scratches caused by other motorcycles' steps and scratches, so the surface finish is important to fix.

The image shows a different package design from the product currently on sale, but the plastic black, which is easy to use and provides a good finish, has become a standard Daytona product. The ingredients are a one-component acrylic synthetic plastic, which does not have the fuel resistance of urethane paints. It is also not solvent resistant, so it is not possible to wipe off-chain rub on the painted surface with a parts cleaner.

This is the current package as of 2021.

When choosing to repaint a black PP part that has faded to white, the properties must be understood: PP is flexible, as explained earlier, whereas a typical paint film will harden on drying. As a result, the paint film can easily peel from the surface of PP parts.

ABS side covers and fenders will also deform to some extent if you grab them with both hands and twist them, but not as much as PP so the paint film will not come off. If they are bent to a level beyond common sense, only the paint film will peel off and crack, but the same is true of the paint film on gasoline tanks. In contrast, the fenders of trailers are also deformed greatly under normal use. In contrast, the fenders of trailers are also heavily deformed under normal use, but because they are molded, there is no paint film and it will not peel off.

In addition, PP itself has poor adhesion and paintability, so it is impossible to paint it as a solution to fading. If you still want to, you can apply a softener to the base of the topcoat to improve adhesion to the material and maintain the flexibility of the cured paint film. This technique is used when painting PP parts with custom paint.

Painting is inappropriate for some types of components. The reason why scooter step boards continue to be made of unpainted PP even though they are known to deteriorate with prolonged use is that it is obvious that putting your foot on the painted surface will damage the paint. You may not step on the gas tank or side covers, but the step board is a part that everyone steps on, and if it were finished in the same urethane paint as the exterior parts, it would become scratched in no time.

In the days when custom 250cc class big scooters were all the rage, the streets were filled with vehicles that had even PP parts painted on, such as step boards and floor tunnels, but there were many scooters where the paint had peeled off due to poor adhesion, or where shoes rubbed against the paint when getting on and off the scooter.

Special paint with thin film and good adhesion can restore the texture without damaging it.

It's hard to know how much to apply to the plastic black without shine, but it's basic to apply a thin layer as same as other paint. If the paint is applied thickly from the start, it is easy for unevenness to appear, and the wet feeling will not disappear for a long time only in the areas where drying has failed. In addition, if you apply a thick layer when the oil is not sufficiently degreased, crater-like depressions will appear only in the areas where oil remains. Such problems are easy to find with a thin coat.

The painted area will look wet, but the luster will subside in a short time. The main feature of the paint is that it is a coating but does not have a thick film of paint, which reproduces the texture of the PP parts. This spray paint is ideal for easily and casually repairing a rear fender that is completely white around the license plate or a chaincase that is completely black only because the motorcycle shop's sticker was removed.

Despite some weaknesses, there are supplies that can restore the appearance of PP used as motorcycle parts if they are black parts that have deteriorated over time due to the advantages that outweigh them. The Plastic Black from Daytona is a paint that is not coated with something silicone-like, but with a matte black. I have already mentioned that PP is a difficult material to paint, but this product is a special paint that has been designed to match the characteristics of PP to provide the necessary properties for painting.

Some PP parts, which are suitable for good processability and delicate designs, have fine unevenness called "wrinkles" to enhance the surface texture. When general paints are used, the grain is often painted in due to the thickness of the paint film, but plastic black has a thin paint film and does not affect the texture of the grain. The paint on Daytona is described as lusterless, but the painted surface is not at the level of complete lusterless, rather the material texture of PP at the time of molding is well expressed.

The installation method is simple, just use a combination of hot water and kitchen detergent to thoroughly remove dirt and oil from soil and rain, and you're ready to go. You can spray without any pre-treatment such as a surfacer or primer. The luster will be pulled out from the sprayed side, and it dries in 20-30 minutes under the condition of 20℃ temperature and 65% humidity.

Here we have painted the chain guard which was faded like white powder, but the finish is so natural that you don't feel it was painted. It's not like repainting painted parts, it's the same color as the molded parts, so it's a perfect finish. If there are scratches or gouges on the surface due to falls or carelessness, it is important to correct them with the material because it is not possible to cover them with a thick film. Also, even though the coating is thin and has a natural finish, it is still painted, so don't get your hopes up too high because if you rub the step board of your scooter with the sole of your shoe, it will look like you scratching the painted surface.

However, there is no doubt that it is effective for restoring black PP parts that have been whitened by UV rays and aging. If you have been using silicone spray paint regularly, why don't you try painting with plastic black?