Thermoplastics

This plastic has a disordered structure, also known as an amorphous structure. Amorphous thermoplastics are easy to glue and can be reshaped when warm in a wide range of temperatures. When such a plastic is heated, the chains become more mobile and they detach from each other. The plastic can then be reshaped. When the plastic cools down again, the chains become less mobile and the material hardens again.

The word crystalline here has nothing to do with the word crystal. Crystalline in this context means ‘ordered’ or ‘regular’. Crystalline plastics are usually tough, impact-resistant plastics with good resistance to chemicals, which are difficult to glue and difficult to heat mould. They are, however, easier to weld. Thermoplastics can be welded once they have been heated to the plastic or thick liquid state. The plastic parts are pressed together with a certain amount of force, causing the macromolecules of both materials to intertwine. The force of physical bonding causes the two materials to form a whole.