Risks in plastics

Plastics are indispensable to modern life. The cars we drive, the computers we use, the utensils we cook with, the clothes we wear and the houses and buildings we live and work in all include important plastic components.

The past 50 years have seen plastic become the main substitute for may other materials, such as wood and metal. The advantage plastic has over other materials is that it can be made as hard as stone, as strong as steel, as transparent as glass, as light as wood, and as elastic as rubber.

Plastics are also lightweight, waterproof, chemical resistant, and can be produced in almost any colour. There are more than 50 types of plastic and new types are constantly under development.

The UK plastics industry is a major player in the global market and is viewed as being at the forefront of research and development. This, combined with the flexibility of plastic materials, has created an industry that now accounts for annual sales of approximately £17.5bn (2.1% of UK GDP) and employs 230,000 people in 6,580 companies.

These companies not only vary considerably in the products they manufacture, but also in size from small to medium enterprises to multinational companies. This makes the plastics industry an exceptionally diverse segment of the economy and one that isn't easy to categorise as representing only a certain type of risk.

The wide range of products manufactured and the number of different processes involved within the plastic industry mean that there are a variety of underwriting issues to be considered.

A thermoplastic is a plastic that softens when heated and hardens again when cooled. Thermoplastics can generally go through many melt/freeze cycles with no appreciable chemical change, making them suitable for recycling. Examples are PVC, polystyrene, polycarbonates, nylon, etc.

Thermosetting plastics refer to a range of polymer materials that cure, through the addition of energy, to a stronger form. The energy may be in the form of heat, through a chemical reaction or irradiation. Thermoset materials are usually liquid or flexible prior to curing, and designed to be moulded into their final form or used as adhesive. After being fully cured, thermosets cannot be re-softened by heat. Examples are polyurethane and phenolics.

Plastic products can be manufactured using a number of different processes, though a common feature of all processes is that the plastic material must be sufficiently softened or liquefied to allow it to be shaped.

Plastic powder, granules or small pellets are melted in a heated barrel and then forced under pressure either by a screw or ram into a cold mould. When the contents of the mould have cooled, the mould is then opened and the moulding removed.

Injection moulding can be used for both thermoplastics and thermosets. It is used to produce a wide range of identical items from precision engineering components to disposable consumer goods.

Injection moulding
There are two basic types of technology: extrusion blow moulding and injection blow moulding. In extrusion blow moulding a tube is produced by extrusion.

A mould is then closed around the tube and the product is blown into the shape of the mould with compressed air. In injection blow moulding two moulds are used. A mandrel or blowing stick is placed in the first mould, and the thermoplastics material is then injected into the mould flowing around the mandrel to create a tube.

The tube is then transferred to the second mould where air is introduced to expand it to the shape of the mould. Bottles of all shapes and sizes are typically produced by this method.

On the face of it, plastics' risks can be difficult to underwrite. It is important to understand the various levels of hazard from low hazard general fabrication and medium hazard plastic bag manufacturers to higher hazard fibre-glass moulding.

As plastics are combustible, storage arrangements for both raw materials and finished products are important. Concentration of goods can give rise to a heavy fire load and lead to a heavy spreading fire risk. External storage close to buildings should be avoided. Internal storage should be tidy, properly controlled and appropriately protected, and fire protection needs to be adequate.

Some of the processes and raw materials used are potentially hazardous and present a risk to both individuals and property. Consideration needs to be given to the process involved, materials used, type of machinery, maintenance programmes, provision of suitable protective equipment, risk management, housekeeping and waste management.

Given that plastics are used in so many products and can be safety critical and/or constitute high risk items, the end use and customer and implications of any product failure need to be fully understood.

It is important to take time to understand your client's needs and expectations and to consider each potential hazard, placing emphasis on risk management and the client's processes. IT

' Paul Sowden is corporate management trainee at Allianz
What are plastics
Plastics are very long molecules each composed of carbon atoms linked in chains.

It is the long chains of molecules that give plastics their unique properties and distinguish plastics from materials (such as metals) that have short, crystalline structures.

While the structure of each type of plastic is different according to its unique properties, all plastics can be divided into two groups: thermoplastics and thermosetting plastics. These terms refer to the different ways these types of plastics respond to heat.