What are plastics and their bonding?

Plastics are materials that consist of synthetic polymers (not found in nature. They have been artificially created by man) or modified natural polymers, e.g. heat stabiliser, UV light or powder fillers. They are so abundant in the world because the cost of production is low and the whole process of making them is relatively easy. Plastics have a very wide range of applications and are used in almost every area of life. They are a great material for construction and are chemically durable. They can be recycled many times, have a low processing temperature and are a very good construction material. 

man welding plastics

We can combine plastics in several ways: 

  • Bonding; 
  • Welding; 
  • Manual welding (otherwise known as hot air welding); 
  • Extrusion welding. 

Methods of joining plastics - welding and sealing 

Welding and welding are among the methods used to join plastics. 


Manual welding, for which we use a welding machine, involves hot air (which enters the nozzle through the welder) heating the material to be joined and the welding wire permanently joining the parts.  

Extrusion welding is used to join thicker materials. The component to be welded is heated, and plasticised material is fed into the joint through a so-called welding shoe (this shapes the weld to the correct size). 

Welding is a very common method of joining thermoplastics. In the simplest terms, it is the plasticisation of the joining material (welding rod, filler metal) with the surface to be joined using pressure and heat. The heated surface is above its melting point and is fused in such a way as to form as homogeneous a weld as possible. In the process, diffusion of the material molecules takes place. When it cools down, a cohesive joint is formed. Plastic welding is used with thermoelectric and thermoplastic materials. Welding of plastics is used for, among other things: 

  • When welding film; 
  • Lids for containers; 
  • Making the plating tank from polypropylene; 
  • Welding of bars, window frames; 
  • Welding of tubes and plates and cylinders; 
  • In automotive: repair of covers, spoilers, bumpers. 


man standing by two pipes

Welding is the second method, next to welding, of joining plastics. It is joined by applying pressure to the plasticised material. The plasticisation takes place under the influence of heat, which is supplied from outside or generated inside the material (by mechanical energy or electricity). A distinction is made between electrofusion welding and butt welding. 

Electrofusion welding is a way of joining polyethylene pipes using specialised fittings equipped with built-in heating parts. This welding can only be carried out under certain conditions and the welding site must be properly prepared.  

Another method of joining pipes is butt welding. It is used, for example, in the construction of pipelines. It can also be used on plates to join them into a larger area. This is then carried out on a special machine.   

Both welding and heating methods fall under ISO 13067, or EN 13067, which is the European standard that defines the method to test the knowledge and skills of welders and welders.