Plastic is a popular material for contractors, fabricators and hobbyists because it’s shatterproof, lightweight and temperature resistant, as well as relatively inexpensive. Detailed instructions on how to build with plastic are easy to find on the Internet as well as in books and magazines. Before you begin working with plastic, it’s important to choose the right adhesive and learn how to apply it correctly. This article will give you a quick overview on glues for plastic and some tips on assembling plastic parts. Links to other WebPages are provided where more detail may be helpful.
Step One – Identify the Type of Plastic
There are many types of decorative, industrial, and specialty plastics, each with its own distinct physical properties. Acrylic (aka Plexiglas), polycarbonate, PVC and polystyrene are examples of popular plastics for commercial and home applications.
To learn which of the glues for plastic will work best for your project, first identify what type of plastic(s) you are working with and find out if you need to bond different plastics together or glue plastic to another material, such as metal or wood. Joining pieces of the same type of plastic is generally easy to do with the right adhesive, however, some dissimilar plastics will not bond together regardless of what glue is used. Check this excellent adhesive cross-reference chart (PDF) published by Weld-On® Adhesives to see which plastics and materials can be bonded together.
Step Two – Choose an Optimal Work Environment
Temperature and humidity are key factors in how well your plastic pieces will adhere. Temperatures between 70°F and 75°F with low relative humidity are recommended to minimize drying time and achieve a solid bond.
Many glues for plastic are highly volatile and may be flammable. Working indoors makes it is easier to control conditions, but be sure to keep the area well ventilated to avoid exposure to toxic fumes and minimize risk of fire. Use a vapor removal system if opening windows is not an option. Or consider working outside or in a garage if the temperature and humidity levels there are favorable.
Step Three – Select the Right Glue for Plastic
Bonding plastics can present a special problem with some adhesives because the solvents in the adhesive can dissolve the plastic, therefore it’s critical to choose an adhesive that won’t react with the plastic. Where the finished project will be used is another consideration when choosing glues for plastic, since temperature and climate stress can affect the bond.
There are two primary types of adhesives used to bond plastics: reactive adhesives and non-reactive adhesives, also called solvent cements.
Reactive adhesives – These glues for plastic contain two or more components (a base resin and a catalyst) which chemically react when mixed together. When cured, the components harden and adhere. To apply, the user mixes the components together, per the manufacturer’s directions. The adhesive is applied to either one or both of the materials being bonded. The pieces are aligned and pressure is added to aid in adhesion and rid the bond of air bubbles. Reactive adhesives are generally more difficult to use and apply.
Non-reactive adhesives (or solvent cements) – A non-reactive adhesive, such as an epoxy, does not require a chemical reaction for adhesion. Solvent cements are usually packaged in tubes and are easier to handle and apply. Popular solvent cements used in bonding plastics include polystyrene (poly) cement used by model makers working with rigid polystyrene plastic; vinyl adhesive (like Weld-On® 66) which forms a strong, waterproof bond on many plastics; and acrylic solvents (like Weld-On® 3), which are actually not adhesives but act by melting the acrylic bonding surfaces, fusing them together at the joint.
This overview provided by Weld-On® Adhesives reviews which adhesives and cements (PDF) are recommended for the most popular plastics.
Step Four – Proper Prep and Assembly Ensures a Good Bond
To ensure a good bond, properly prepare the edges of the plastic parts by cleaning all pieces with plastic cleaner (PDF) and making sure they fit together accurately and smoothly without being forced. Masking tape or clamps can be used to hold the pieces together while the adhesive cures. The procedure for assembly, gluing and curing the plastic parts varies and is based on the type of adhesive you are using (reactive or non-reactive). Click here for an in-depth article in Plastics Distributor and Fabricator magazine that details proper assembly procedures for each type of adhesive and read the label on the adhesive for the manufacturer’s instructions on how to apply that particular product.
Following these steps will help to ensure that your finished project is a success. If in doubt about the type of plastic or adhesive you are working with, always check with the manufacturer. If you have a specific question about glues for plastic, use the “Comment” section below and one of our experts will help you.
Step Five – Proper Storage of Glues for Plastic
Always read and follow the instructions on the adhesive container to maximize the useful life of the adhesive. Different varieties of plastic glues need different storage environments; some even need to be refrigerated. Following the storage instructions will help reduce the chances of the adhesive losing its effectiveness over time. Even with proper storage, all glues for plastic have a shelf life, so be sure to note the expiration date on the container as well.
Ask Us Your Questions About Glues for Plastic!
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