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A Short Guide to Gluing Plastics

Published : 2016-07-12 16:14:51
Categories : Blog

When working with plastic, you have several options for joining pieces together; however, one of the fastest and most convenient options is to use an adhesive of some kind. 

There are many kinds of suitable adhesives for plastics, all of which work in slightly different ways.  Here is a short rundown on the most common types of adhesives to help you understand how they work.

Epoxy (Polyepoxides) 

Epoxy resins are a class of reactive prepolymers and polymers that contain epoxide, a highly reactive chemical.  These glues are created by mixing two starting compounds; the epoxide resin and the polymer hardener.  The hardener acts as a catalyst for the resin, starting a chemical reaction that makes the resin harden.  This process is known as curing,

During this chemical process, molecular chains in the hardener react with the resin, creating an exothermic reaction (a process that produces heat).  Chemical bonds are created between the substances, causing them to harden. 

Different ratios of resin and hardener can be used to achieve different results.  More hardener would result in a stronger compound that takes longer to cure.

There are many types of epoxy adhesives available, with differing levels of rigidity and strength.  Some epoxies also have qualities that make them ideal for certain applications, such as; water-resistance, heat resistance, and chemical resistance. 

Some of the most common epoxy products on the market include Loctite® Epoxy Plastic Bonder, Super Steel epoxy glue, Gorilla epoxy glue, J-B Weld PlasticWeld and Smooth-On Metalset A4.

Cyanoacrylate

Cyanoacrylates are very fast-acting adhesives that are found in most brands of “superglue”.  In technical terms, Cyanoacrylate is an acrylic resin that hardens in the presence of hydroxide ions (condensed water vapor).  The moisture in the air and presence of moisture on the objects being joined is enough for Cyanoacrylate to form a bond.

Because moisture plays a role in how quickly the glue sets, it can bond extremely quickly when used in humid environments.  This glue is very useful for forming bonds between two stationary pieces of plastic; however, it can weaken if used in an environment with frequent temperature changes.

Methacrylate

Methacrylate is an acrylic adhesive that is incredibly strong and simple to use.  This type of glue uses a curing agent and resin, which are mixed together to force a chemical reaction.  Once mixed, chemical bonds are formed between the curing agent and resin, creating a strong bond.  The key difference to epoxies is that Methacrylate does not need to be well mixed to create a strong bond.

Hot Melt Adhesive 

Hot Melt Adhesive is a form of thermoplastic adhesive that is melted using an electric hot glue gun.  The adhesive comes in solid cylindrical sticks that become fluid when heat is applied.  The gun used to heat the material has a very hot heating element that turns the adhesive into a fluid as it flows past.

Hot melt adhesive is often used in industrial applications because it has certain advantages over solvent-based adhesives.  The adhesive material has a long shelf life, it is less dangerous than many solvent adhesives, there are less volatile organic compounds involved and it can be disposed of more easily.  Hot melt adhesive also avoids a lengthy curing phase and there is no mixing required.  The only disadvantages of hot melt adhesive are the energy required for its application and the fact that it can lose its bond in environments with high temperatures.

Urethane Glues

Urethane glues are capable of making strong bonds between objects while remaining elastic.  This elasticity makes urethane glues ideal for applications where an object is exposed to different loads or temperatures that cause the object to expand or contract.

These glues are frequently used in woodworking but are also ideal for joining plastics or metals.  Urethane glues are available in two different forms, moisture curing and heat curing.  They are convenient to use, useful for bonding porous objects together, quick to set and require no mixing.

Solvent Cement Glues

Solvent glues melt the surface of the plastic, creating a bond and fusing pieces together.  They create a very strong bond that is both temperature and water-resistant.  There are specific solvents for different types of plastics including PVC and ABS.  Care should be taken when using solvent cement glues because many are toxic and flammable.

Plenty Of Options!

As you can see, there are plenty of options for gluing plastics!  Remember to be very careful when gluing plastics together and always use a glue that is appropriate for the type of plastic you are working with.  If you are unsure, read the manufacturer’s directions.

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