Polyvinyl chloride (PVC) can be a versatile and resource efficient thermoplastic using the widest selection of uses of any one of the plastics family so that it is valuable in practically all regions of human activity.
Without additives pvc compound would not be an especially useful substance, but its compatibility with a variety of additives – to soften it, colour it, ensure it is more processable or longer lasting, results in a broad range of potential applications from car underbody seals and flexible 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 family of products tailor-made to suit the needs of each application. Unlike the majority of thermoplastics, nearly all PVC applications have a lifetime of between 10 and a hundred years. This involves proven durability and stabilisers play an important part in achieving such performance. All polymers require stabilisers of merely one sort or other; PVC is no different in this respect.
Before PVC can be done into products, it has to be put together with a range of special additives. The fundamental additives for all those PVC materials are stabilisers and lubricants; with regards to upvc compound, plasticisers will 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. Once the additives have already been selected, they may be mixed with the polymer in a process called compounding. One strategy uses an intensive high-speed mixer that intimately blends all of the ingredients. The end result is a powder, referred to as a ‘dry blend’, which happens to be then fed to the processing equipment.
The 2nd method is to blend the components either in a small or high-speed mixer after which transfer the powder into a melt compounder. This may either be a compounding extruder, or some other special equipment for producing pvc compound. These develop a melt which, when cool, is cut into granules ready for processing. Within a specialised process, liquid compounds known as plastisols, are designed as dispersions of very fine PVC polymer particles in liquid organic media. PVC compounds are made into products using various processing methods that include extrusion, injection moulding, blow moulding, calendering, spreading and coating.