Introduction

PVC is one of the most widely used plastics in the world. It offers a diverse and varied range of properties, and contributes significantly to the modern lifestyles that we enjoy.

Plastics are also called ‘synthetic resins’. This name refers to the fact that, in their semi-liquid state, they have the property of plasticity. They are broadly classified into two categories; thermosetting resins and thermoplastic resins.

Thermosetting resins include phenolic resin and melamine resin, which are thermally hardened and never become soft again. Thermoplastic resins include PVC, polyethylene (PE), polystyrene (PS) and polypropylene (PP). These can be re-softened by heating and will harden again as they cool.

Once manufactured as a processable material, PVC is supplied downstream to companies collectively known as ‘converters’.

Various additives, including stabilisers and plasticisers, need to be added to PVC resin to create a compound that meets the requirements of the end product and of the processing technology to be used. Compounding may be carried out by the converters themselves or by separate ‘compounders’ who supply ready-made blends for processing. The PVC compound is then ‘converted’ by processes such as extrusion, moulding and calendering.

Click image to enlarge