Polyvinyl chloride (PVC) is a versatile and resource efficient thermoplastic using the widest range of applications of any one of the plastics family which makes it useful in almost all aspects of human activity.
Without additives pvc compound would not really a really useful substance, however its compatibility with an array of additives – to soften it, colour it, allow it to be more processable or longer lasting, generates a wide range of potential applications from car underbody seals and versatile roof membranes to pipes and window profiles. PVC products may be rigid or flexible, opaque or transparent, coloured and insulating or conducting. There is not only one PVC but a whole group of products tailor-designed to suit the needs of each application. Unlike many other thermoplastics, virtually all PVC applications have a lifetime of between 10 and 100 years. This calls for proven durability and stabilisers play an essential part in achieving such performance. All polymers require stabilisers of one sort or another; PVC is not any different in this respect.
Before PVC can be made into products, it has to be coupled with a selection of special additives. The main additives for all those PVC materials are stabilisers and lubricants; with regards to upvc compound, plasticisers can also be incorporated. Other additives which can be used include fillers, processing aids, impact modifiers and pigments. Additives pvcppellet influence or determine the mechanical properties, light and thermal stability, colour, clarity and electrical properties of the product. As soon as the additives have already been selected, they are together with the polymer in the process called compounding. One strategy uses an intensive high-speed mixer that intimately blends all the ingredients. The effect can be a powder, known as a ‘dry blend’, which is then fed to the processing equipment.
The second strategy is to blend the constituents in either a low or high-speed mixer after which transfer the powder to some melt compounder. This will either be a compounding extruder, or any other special equipment for creating pvc compound. These create a melt which, when cool, is cut into granules ready for processing. In a specialised process, liquid compounds called plastisols, are made as dispersions of very fine PVC polymer particles in liquid organic media. PVC compounds are produced into products using a variety of processing methods such as extrusion, injection moulding, blow moulding, calendering, spreading and coating.