Bonding to Plastics - Part 2

Wednesday, November 25, 2020
Bonding to Plastics: Part 2

Part II: Common Types of Plastics 

This blog will cover the most common types of plastics used in manufacturing and the adhesives needed to bond to them.

Categories of Plastics

Polyvinyl chloride (PVC)
  • Water piping
  • Electrical wiring
  • Windows
  • Raincoats
  • House siding
  • Various household & auto products
Commonly known as PVC, polyvinyl chloride has a wide range of uses.  PVC water piping will be the first thing that pops into most people’s heads.  Most super glues do, in fact, work on PVC plastic and can even be used for water piping with a waterproof option.  RapidFix Dual Adhesive system is a waterproof variant that can also hold up under extreme heat and bonds well with PVC.

Polypropylene (PP)
  • Tote bags
  • Luggage bags
  • Upholstery
  • Food containers
  • Various toys      
  • Some bottle caps
Polypropylene is one of the most common plastics due to its availability and all-around usefulness.  As mentioned earlier, polypropylene has low surface energy making it difficult for glues to attach too.  While the bond will not reach 100% strength, it may suffice for lighter applications.
One option is to use sandpaper to create a rougher surface that allows the glue or adhesive to grab on.  This may not benefit cheaper cyanoacrylates, but higher-end options should work.  If these do not work, several plastic specific glues or epoxies on the market may get the job done.  The product labels should identify their ability to work with PP.

Polyethylene – Low Density or High Density (PE, LDPE, HDPE) 
  • Soda bottles
  • Microwaveable trays
  • Water bottles
  • Shopping bags
  • Medical packages
  • Shrink films
           
Polyethylene is the most difficult to use with super glue.  In most cases, it simply will not bond without a primer or accelerator.  Use a primer when you can easily apply it to whatever surface you are about to bond.  The primer chemically changes the surface it is applied to and allows the adhesive to grab hold easier.  Use an activator when you want the curing time (dry time) to speed up.
For plastics, applying a primer is the best option.  Clean the surface, apply a cyanoacrylate-based primer, and then use the adhesive to finish the job.  Other options include plastic friendly epoxies, melting them together or using a plastic friendly glue or tape.

Poly(methyl methacrylate) (PMMA)
  • Acrylic
  • Retail signs
  • Plexiglass windows
  • Greenhouse panels
  • Aquariums         
  • LED Screens
Finally, another plastic we can work with!  Acrylic can be tricky to work with because typically you want something that is waterproof and that will dry clear.  It seems that in the professional industry, people prefer an acrylic cement or solvent bonding.  However, if you do not have these on hand, MOST super glues should do the job, but there are some that may not hold up over time.  You may need to ask the specific brand that you are buying from, but as far as RapidFix, it is waterproof and holds up over time.  It is also FDA approved for being non-toxic.

Acrylonitrile butadiene styrene (ABS)
  • 3D prints
  • Pipe fittings
  • Legos
  • Gaming accessories
  • Various auto parts          
  • Various Appliances
One of the most common materials in 3d printing, ABS plastic is increasing in use.  It is easy to paint and glue, it is chemical and impact-resistant, and it performs well in most temperatures.   Cyanoacrylates work great with ABS and are extremely fast setting.  RapidFix Adhesives also work very well with ABS plastics and you could also use the welding powder to fill in small holes and crack that might have been missed during a 3D print.  It is also fairly common to use acetone to weld ABS plastics together, although this takes a bit more skill and might take longer to fully cure.
Polylactic Acid (PLA)
  • 3D printing
  • Films
  • Biodegradable medical products
  • Auto applications
  • Short-term food storage
  • Textile fibers
Polylactic acid is most commonly found in 3D printing or packaging of sensitive food products.  PLA is common in 3D printers because it does not require a heat bed and can be printed at a relatively low temperature.  Cyanoacrylates work the same on PLA as they do one ABS plastic, but many people still use the acetone bonding route as mentioned in the ABS section above.

Polycarbonate (PC)
  • Eye protection/lenses
  • CDs/DVDs
  • Shatterproof windows
  • Electrical sockets
  • Appliances
  • Phone cases
Polycarbonate is extremely useful due to its ability to let light in while also being stronger than most other plastics.  It can even be used as bullet-resistant glass.  Cyanoacrylates are one of the best options when it comes to this plastic.  There are polycarbonate cements also on the market that might produce a slightly better bond quality, but these are typically only used on higher-end projects.

Polystyrene (PS)
  • Styrofoam
  • Disposable plates
  • Packaging
  • Surfboards
  • Disposable cups
  • Model planes
Unfortunately, typical cyanoacrylates do not work on Styrofoam because they just melt right through it.  However, it is possible to use a UV light cyanoacrylate if you can shine a UV flashlight on to whatever surfaces you are gluing together. Other options for polystyrene include construction adhesives, original white or thicker glues, or foam sealant.

Have a question specific to your project? Give us a call at 800.542.3697
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