3 Plastic Joining Methods You Should Consider During Fabrication

3 Plastic Joining Methods You Should Consider During Fabrication

After successful plastic fabrication, probably you like to join parts.

This guide covers the most common and effective plastic joining methods and techniques. In each case, you will learn how the process works, benefits and limitations.

Let’s look at some common ways of joining plastic parts.

Plastic Joining Process
Plastic Joining Process

1. Solvent Bonding Plastic Parts

This method is also known as adhesive bonding. Here, you will coat the pieces of plastic you want to join with a special solvent.

The solvent will evaporate after some time leaving the plastics bonded. This is a chemical process used to mainly join thermoplastics.

Solvent Bonding Diagram Illustration
Solvent Bonding Diagram Illustration

Advantages Of Solvent Bonding Technique

  • It is a fast and simple method to join plastics.
  • It is a cheap technique.
  • Results in smooth joint plastic surfaces.
  • Mechanical stress over the joint is uniform.
  • This method can also be used to join unlike materials.
  • Results in a properly sealed joint with no gaps.

Disadvantages Of Solvent Bonding Plastic Parts

  • Time-consuming as mixing and curing will take time.
  • Extensive surface preparation is required.
  • The joined pieces must be clamped together during curing process.
  • It is difficult to disassemble the parts once joined.
  • This process is limited to service temperature and the surrounding environment.

Stages Of Solvent Bonding Plastic Parts

Solvent bonding plastic parts is straightforward and simple.

i. Adhesive Selection – you will select the solvent/adhesive appropriate for the plastics

ii. Surface Preparation – you will clean the plastic surfaces and have them abraded

iii. Solvent Application – apply solvent on the plastic surface you would like to join

iv. Assembly of the plastic pieces to be joined

v. Clamping the plastics together

vi. Curing- the molecules within the solvent link thus creating a strong joint

2. Welding Plastic

Welding basically involves joining materials at a high temperature. There are many types of welding. However welding is divided into two types.

Vibration Welding Plastic Material

Join the two plastic pieces you wish to bond and vibrate one of them. This vibration will cause friction which would in turn create heat. The heated plastics eventually fuse together.

Vibration Welding
Vibration Welding

Induction Welding Plastic

Run the plastics through a magnetic field. They will heat up and fuse together.

Advantages Of Welding

  • It is a simple and affordable method
  • Results in permanent and durable joints

Disadvantages Of Welding

Some of the main disadvantages of plastic welding are:

  • It is difficult to dismantle the joint once welded
  • Welding requires skilled labor
  • It is impossible to weld without electricity
  • It is hazardous thus safety measures must be adhered to
Induction Welding Set Up
Induction Welding Set Up

3. Mechanical Fastening and Joining Plastic

This involves joining two or more plastic materials mechanically using mechanical fasteners. You should note that this method is only suitable for strong plastics which can withstand the strain during insertion of fasteners.

Mechanical fasteners can be broadly classified into permanent and non-permanent fasteners.

Mechanical Fastening
Mechanical Fastening

Examples Of Non-Permanent Mechanical Fasteners

  • Screws
  • Nails
  • Rivets
  • Nuts
  • Bolts
  • Washers

These ones can be removed, reused or replaced as many times as possible. Snap-fits and rivets on the other hand are examples of permanent fasteners.

Mechanical Fastening Methods for Joining Plastic

They include the use of:

  • Integral Fasteners – These fasteners hardly vibrate or loosen. They are used to make a more stronger and permanent joint.
  • Threaded Fasteners – This method is suitable for thick plastics and in cases where disassembly and reassembly of the joined parts may be required. Suitable fasteners for this method are screws, nuts and bolts.
  • Non-Threaded Fasteners – This method provides a more permanent joint than when threaded fasteners are used. It is thus unsuitable in a case where disassembly might be required. Rivets, pins and washers can be used here.

Advantages Of Mechanical Fastening Plastic Parts

  • It can be automated.
  • No special prior preparation is required.
  • It can easily be combined with solvent bonding technique for better outcome.
  • Permanent fasteners provide stronger joints than the non-permanent ones.

Disadvantages Of Mechanical Fastening Plastic Material

  • Produces a weaker connection compared to those made through welding and solvent bonding methods.
  • Refastening can be time consuming.
  • Mechanical fasteners are prone to corrosion.


As you can see, there are many ways of joining plastic material. Depending on the plastic parts you wish to join – choose solvent, welding or mechanical joining techniques.

For any questions or inquiries on plastic fabrication, contact us now.

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