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Can I Fiberglass Over Plastic?

Can I Fiberglass Over Plastic?

Fiberglass is a reinforced plastic material. Manufacturers place glass fibers into a resin matrix to create a strong, durable, and somewhat flexible product that works well in numerous situations. The glass strands are the primary component of the item.

This synthetic material is prepared in several forms and convertible into liquids, films, and gels.

Although fiberglass and carbon fiber are sometimes used interchangeably, they are two different options. You’ll need to ensure you have a fiberglass product if you need to complete a repair over an existing plastic surface.

Can I Fiberglass Over Plastic?

It is possible to repair plastic by using fiberglass. Although it can be challenging to stick fiberglass to a smooth surface, a little scuffing on the plastic foundation overcomes that difficulty. In return, a strong bond that lasts a long time develops.

Fiberglass is a strong material that is useful in repairing several different items. Numerous industries use this product, ranging from boats to airplanes.

Most modern vehicles have some fiberglass incorporated into the interior or exterior, if not both.

A finished fiberglass product provides two essential components: fiber reinforcement and resin. It’s not the same as the batting insulation (which is also fiberglass) that goes into homes.

If you placed resin over fiberglass insulation and allowed it to harden, you would have a reinforced surface similar to what is used to create hulls, shells, and barriers.

Since plastic is essentially resin in another form, the two materials bond well with each other. Adhesives require a rough surface, not a smooth one, to create a strong joint.

If you need to apply fiberglass over plastic, the best way to do that is to lightly sand the surface for the adhesive to latch on to the newly rough areas.

How to Fix Broken Plastic on Vehicles

Plastic components are found in more vehicles today than ever before because you receive excellent strength and safety without a lot of extra weight.

When you look at a vehicle’s engine cover, door panels, and dashboard, you’ll find plastic everywhere. Some components could even be part of the frame.

You can find this same approach used with boats, ATVs, and other recreational vehicles.

Although plastic is a high-quality product, it eventually starts fading and cracking. That leaves you with the task of replacing the item, living with the broken components, or finding a way to repair the issue.

When you have a matching fiberglass panel for a broken plastic component, you can put one on top of the other to complete the repair.

Before taking that step, you might want to see if the plastic is repairable first. You could use epoxy, super glue, or another adhesive to create a strong bond for the item in question. If you can seal the problem, a new paint job could hide the initial problem.

Some products can fill in the cracks first, such as Bondo, to ensure you have a seamless surface that’s ready for new primer and paint.

What Are the Benefits of Using Bondo?

Bondo is a polyester putty. It started as an automotive body filler, but the brand has become synonymous with household and marine repairs. 3M currently holds the trademark for the name, but people use it as a term to refer to any kind of repair putty for automotive body repair purposes.

When you need to complete a plastic repair, Bondo provides several essential benefits that are worth considering.

  • It cures quickly, allowing you to finish a repair in hours instead of days.
  • You can shape the product in minutes to replicate curves and bends.
  • The formulation allows the putty to stay consistent, preventing it from shrinking after application.
  • It provides a permanently durable material.

What makes Bondo such a great product is its ability to work on multiple surfaces. You can repair any fiberglass material with it, especially when you select one of its resins or repair kits. These items are 100% waterproof and don’t shrink, making them an excellent sealer.

Bondo’s fiberglass resins are sandable in two hours or less, compatible with all paint types, and create a long-lasting bond.

You can also use Bondo on wood, galvanized metal, and many other surfaces.

How to Make Fiberglass Stick to Plastic Surfaces

Fiberglass and plastic are two common building materials found in numerous industries and trades. Both options mold to almost infinite sizes and shapes, which makes them useful for plumbing, infrastructure needs, marine applications, and automobiles.

You can see mixed-media artists combining plastics and fiberglass into their sculptures, so it only makes sense that the two materials can work together to create an effective repair.

If you want to place fiberglass over plastic to create a strong bond, here are the steps you’ll need to take to have a successful experience.

  • Clean the bonding surface on both materials. It helps to use microfiber cloths dampened with a high-quality solvent for this step.

When you soak the cloth in the solvent, your best options are to use acetone or isopropyl alcohol. If you don’t have either choice, you can use lighter fluid.

  • Roughen the surfaces of the plastic and the fiberglass with a fine-grit sandpaper.

By roughing up the surfaces, you’re creating places where the adhesive can adhere on both sides. You’ll want to wear protective gear for this step, including a respirator, to prevent inhaling plastic or glass particles.

The scratches don’t need to be visually noticeable to be effective, but you will need to put some elbow grease into the work to obtain a solid seal.

  • Mix your adhesive according to the container’s instructions.

If you want to place fiberglass over plastic, the best adhesive to use is epoxy. Each brand has different instructions to follow based on the type and drying duration of the product. A thorough mixing of the resin with the hardener is necessary to achieve a positive result.

Although some products cure in as little as five minutes, it usually works better to have a solid result in six to eight hours for a strong bond. When you use the West System 105 and 205 Combination for this step, you’ll achieve working strength in one to four days.

  • Apply a thin, even coat of epoxy.

When applying your epoxy mixture, try to avoid using too much of the product. A thin layer delivers a strong bond, but a thick one will create weakness when placing fiberglass over plastic.

  • Press the fiberglass and the plastic together.

You’ll need to press the two surfaces together for about three to five minutes to ensure that the items can start bonding together. This step might cause some of the adhesive to come out the edges of your repair. A damp cloth will help you get everything cleaned up before the product sets.

  • Place the bonded pieces into a vice clamp.

Since the West System 105/205 epoxy requires six to eight hours to form a secure bond, you’ll need to clamp the fiberglass and plastic together. Tighten the clamp by rotating the arm clockwise.

You don’t want to place too much pressure on the fiberglass or plastic because the materials could crack.

There could be more epoxy that comes out of the repair area as you tighten the clamp. Use a damp cloth to keep the edges clean.

  • Allow the repair to sit undisturbed.

Most epoxy products have a thermosetting feature that lets you achieve a working hold in less time. If you blow warm air from a blow dryer or expose the product to a high-temperature space heater or heat lamp, you can achieve a faster cure without creating weakness.

If you allow the 105/205 epoxy from West System to cure at its regular pace, it can take up to four days to achieve working strength. You can still take the product out of the clamps after eight hours.

Precautions to Consider When Working with Epoxy

When working with any epoxy product, you should be in a well-ventilated area. You don’t want to inhale any fumes, no matter what brand you choose to use.

You don’t want the epoxy to come into contact with your skin at all. If it does, do not attempt to rip it away as this action could cause a significant injury.

It is much easier to remove uncured epoxy, so act quickly if some gets on your skin. In most instances, soapy water and a little scrubbing are enough to take care of the situation.

If water and soap don’t work, the acidic pH found in industrial-strength white vinegar can help you remove the epoxy. Gently rub the area until the resin softens so that it can be peeled away.

Citrus-based cleaners can also remove some epoxy products from the skin.

Once you’ve removed the epoxy, you will need to wash the area thoroughly and use lotion to soothe the contact dermatitis that often occurs.

It helps to wear a safety apron, safety glasses or goggles, and a respirator to ensure you receive protection from epoxy exposure. Gloves are helpful, but they could be too bulky for some fiberglass over plastic applications. Disposable products are a reasonable compromise.

Is It Worth Putting Fiberglass Over Plastic?

When plastic requires repair, fiberglass is an essential option. The stronger material works as a splint to shore up any weakness found in the damaged product. You can also use this technique when your goal is to create a stronger barrier for vehicles, boats, and other modes of transport.

Placing fiberglass over plastic is a useful way to create a fast, strong repair without going through a complete retrofit.

One of the first things I purchased after moving away from home was a boat. I can’t say why, but I always wanted one.

I knew that I couldn’t afford something fancy, so I searched the local listings for a fixer-upper. One with a cracked plastic hull came up, so I jumped on it instantly.

After filling the cracks with Bondo, I found a beautiful fiberglass piece to place around the hull. I decided to put it over the plastic across the entire vessel to create a consistent look. Although the work took me about a month to complete, it wasn’t recognizable after I was finished with the repair.

We still use that boat today, all these years later. It won’t win a race, but it’s the perfect float for a day of fishing on the lake.

If you have a plastic surface to repair, I highly recommend looking at fiberglass to complete the job.


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