There are thousands of distinctively different kinds of plastics produced in the world – each is a unique complex formulation of gases, chemicals, minerals, plant and animal by-products, as well as other ingredients. A given formulation possesses specific properties that make it perfect for certain applications, but often unusable for others.
Complex Formulation of Plastics
To understand this better, let’s examine some of the plastics used in extrusion blowmoulding. Polyethylene, or P.E., is probably the most common type of blowmoulded plastics.
A harsh substance like bleach can be packaged in polyethylene because of its chemical resistance properties. Other substances like shampoo, motor oil, and laundry detergent take advantage of the lightweight and fairly strong characteristics of PE. Blowmoulded containers made from natural PE are normally off-white or opaque, similar to the virgin pellets, and have a dull surface appearance.
Another material that is commonly used in the industry is polypropylene. Polypropylene is similar to PE, but has increased chemical and heat resistance. PP is also off-white and opaque in its virgin form. Natural polypropylene products look similar to finished PE containers cut are usually much shinier.
PE and PP Material Product
When it is desirable to blowmould a product that has a clear, glossy, glass-like appearance, the material polyvinylchloride, or PVC, is often selected as the resin of choice. PVC moulds into strong and impact resistant structures that are transparent and very shiny. Because of its transparency, the product inside the PVC container can be clearly seen – unlike PE or PP containers. In its virgin state, polyvinylchloride pellets appear bluish in colour and are somewhat transparent.
PVC Product
Although the three resins mentioned are the major materials used in continuous extrusion blowmoulding, there are other resins used. New materials are constantly being developed and introduced to the blowmoulding industry to produce superior products.
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