Glues for Plastic: How to Choose the Right Adhesive

 

Jan
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Weld-On Glues for PlasticsPlastic 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!

What questions do you have about glues for plastic? Ask in the comments below. We’re here to help.

11 Responses to “Glues for Plastic: How to Choose the Right Adhesive”

  • keith exelby says:

    April 29, 2012 at 8:40 am

    I need a glue for cracks in my plastic ( double grazed caravan windows) Maybe a self seeking type would be best
    can you advise me please
    many thanks
    keith



      Pam Aungst says:

      April 30, 2012 at 2:01 pm

      Hi Keith,

      Thanks for your comment. Usually vehicles don’t have windows that are entirely made of plastic. If you’re sure that it is, give IPS Corporation a call. They should have some good advice for you. Their tech support line is (877) 477-8327.



  • Jimmy Dean says:

    May 20, 2012 at 10:30 pm

    Could you please recommend a good adhesive? I plan to glue a sheet of EVA foam padding to the fiberglass swim platform on my boat. HOWEVER, the foam will probably need to be replaced every oher year or two, due to my dogs’ claws, which will wear it out rather quickly. So, the adhesive should allow me to separate the two materials and get cleaned off reasonably easily, using a solvent or heat, rather than a ton of elbow grease. And, of course the glue should stand up well to water and 100 degree temperatures. Thanks for your help and expertise! JD



    James Melton says:

    August 8, 2012 at 7:50 pm

    I am working on the inside of an automobile door panel which has plastic catches that holds switches, etc. I have one that is broke and need to reglue. Super Glue will not do, I tried it and thought it worked until I put a little pressure on it an it came right apart again. Once it came apart the surfaces taht I put glue on looked as though none had ever been applied.
    Pleas helpwith this project.



      Pam Aungst says:

      August 13, 2012 at 3:46 pm

      Hi James,

      Thanks for your comment. Unfortunately, without knowing what the part is made of, it’s difficult to recommend a glue or solvent.



    Dennis Glover says:

    August 15, 2012 at 3:48 pm

    I need to bond two pieces of 1/2 inch cast acrylic sheet. Each sheet is 12in x 12in and I need to bond across the flat face (1 square ft of bonding). Which glue do you recommend? Will the capillary process reach completely into the 1 square ft.?

    Thank you



      Pam Aungst says:

      August 15, 2012 at 4:20 pm

      Hi Dennis!

      Thanks for reading our blog. For that you should be able to use either Weld-On number 3 or Weld-On number 4. Number 4 sets up slightly slower, so that may be preferred.

      Good luck with your project!



    Gil Cray says:

    September 15, 2012 at 9:34 am

    Hi
    I’m making a rain collector out of two 30 gal. plastic barrels. I don’t know what type of plastic they are. I want to glue them flat end to flat end. What glue would you recommend?
    Thanks



      Pam Aungst says:

      September 17, 2012 at 10:41 am

      Hi Gil,

      Unfortunately, without knowing what the part is made of, it’s difficult to recommend a glue or solvent.



    Neil MacInnes says:

    September 4, 2013 at 8:53 am

    I have broken the frame of my dive-mask (unfortunately with expensive prescription lenses!) and the Mares manufacturer advises the model is made of Polycarbonate plastic (and no longer made). It is hard and barely flexible. I have tentatively tried Evostik ‘Sticks-Like’ but the bond can be peeled apart in spite of its claims. Could you suggest an appropriate adhesive (+/- primer?)
    Thanks



      Administrator says:

      September 6, 2013 at 11:03 am

      Hello Neil, I’m sorry to hear about your dive-mask I would need to know exactly what you are gluing to what, is it Polycarbonate to Polycarbonate? or is it to Polyurethane, etc?



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