Wasting the Nation.indd - Groundwork

Chapter 4: The toxic cradle of productionBox 16: Making plasticPlastics are produced from polymers which, in turn, are produced from monomers.Monomers are composed of simple chemical molecules. Catalysts and energy areused to produce long chain molecules that make up polymers. Thus, ethylene is acommon monomer and the basic molecules can be joined up to create the polymerpolyethylene. Pure polyethylene is called a homopolymer because it is made from asingle monomer. However, not all polyethylenes are the same: the longer the chaincomposing the molecule, the higher the density of the polyethylene. High densitypolyethylene is used to make thicker and more rigid plastics while low densitypolyethylene is generally used to make flexible light products like film-wrap.There are a great number of monomers. Apart from ethylene, the most commonare vinyl, styrene and propylene. Where a polymer is made from two or moremonomers it is called a copolymer. Thus, ethylene combined with vinyl acetatemakes EVA commonly used for electric plugs or foamed to make padding forsports equipment. Polymers are also combined with other chemicals. Chloride, forexample, is commonly combined with polymers as in polyvinyl chloride (PVC).Finally, various other chemicals can be added in the process of producing polymersor plastics. Thus, plasticisers such as phthalates are used to add flexibility, pigmentsare added for colour and flame retardants are added to products subject to heat. Themix is called a resin and is sold in the form of liquids, solid rods or pellets, as theraw material for plastic fabricators or ‘converters’.The result is that plastic can be given almost any physical characteristic desiredby the manufacturer and it can be moulded, extruded or blown into just aboutany shape. The first plastics were made from naturally occurring polymers but,as Heather Rogers observes, the invention of synthetic plastic made from theapparently limitless flow of petrochemicals freed industrial production from thelimits of nature. During the 20 th Century it was progressively used to substitutefor wood, glass, paper, metal and pottery goods. Plastics are now used in almostall manufacturing sectors – in cars, aeroplanes, guns, garments, ropes, computers,household appliances and buildings. They are used for making plates and cups, thesoles of shoes, tyres and rubbers. And, in the form of plastic bags, film-wrap, jars,jugs and bottles, they are now the most common form of packaging.Wasting the Nation - groundWork - 109 -