PLASTIC WELDING

                        Plastic welding is welding for semi-finished plastic materials, and is described in ISO 472 as a process of uniting softened surfaces of materials, generally with the aid of heat (except solvent welding). Welding of thermoplastics is accomplished in three sequential stages, namely surface preparation, application of heat and pressure, and cooling. Numerous welding methods have been developed for the joining of semi-finished plastic materials. Based on the mechanism of heat generation at the welding interface, welding methods for thermoplastics can be classified as external and internal heating methods. Plastics are typically organic polymers of high molecular mass usually synthetic or semi-synthetic organic compounds that are malleable and can be often molded into solid objects. Plasticity is a property of all materials that are able to irreversibly deform without breaking. Relatively low cost, ease of manufacturing, versatility and other factors has already found many applications in the field of automotive, medical, food, packaging etc. Best alternative for traditional materials like wood, stone, metal, glass, ceramic, paper, leather etc. Plastic welding is the process of uniting Softened surfaces of materials, generally with the aid of heat. Welding can be used to produce bonded joints with mechanical properties that approach to those of parent material. 

   

                                   Thermoplastics like Polyethylene, Polypropylene, Polyvinyl Chloride, Polyurethane and Acrylonitrile Butadiene Styrene (ABS) are frequently used in plastic welding. Plastics that can be welded are called “thermoplastics” and when they are heated to a sufficiently high temperature they will soften and welded.

CLASSIFICATION OF PLASTIC WELDING

Welding process are categorized by the heating method that is used. Two general categories  are

 1. External heating

              2. Internal heating

External heating: It rely on convection & conduction to heat the weld surface. Hot tool, hot gas, extrusion, implant induction, implant resistance welding

Internal heating: It rely on conversion of mechanical energy into heat through surface friction. Further divided into internal mechanical, Internal electromagnetic heating

A plastic welding rod, also known as a thermoplastic welding rod, is a rod with circular or triangular cross- section used to bind two pieces of plastic together. They are available in a wide range of colours to match the base material's colour. Spooled plastic welding rod is known as "spline".

HOT PLATE WELDING

It is the simplest of the mass production techniques to join plastics. A heated plate is clamped between the surfaces to be joined until they soften. The plate is then withdrawn and the surfaces are brought together again under controlled pressure for a specific period. The fused surfaces are allowed to cool, forming a joint. The tool is often coated with non-stick material (Teflon) to act as a release agent. Hot plate welding includes two kinds,

1. High temperature hot plate welding

2. Non-contact hot plate welding.