TABLE OF CONTENTS Polyethylene (PE) (sometimes known as polythene) was discovered in 1933 by Reginald Gibson and Eric Fawcett at the British industrial giant, Imperial Chemical Industries (ICI). Although it is more than 70 years since it was first produced, it is still a very promising material. This widely used plastic is a polymer of ethylene, CH 2=CH 2, having the formula ( CH 2CH 2 ) n. It is produced at high pressures and temperatures in the presence of any one of several catalysts, depending on the desired properties of the end-use product. Other structures (leading to long and short branches) may be present, depending on the procedure used in the synthesis. PE is the largest volume polymer consumed in the world. It is a versatile material that offers high performance compared to other polymers and alternative materials such as glass, metal or paper.
Despite ethylene s simple structure, the field of PE is a complex one with a wide range of types and many different manufacturing processes, which offer the possibility of a versatile tailor-made range of products.
The polymerisation processes are classified with respect to the physical state of the medium, namely in suspension, in solution, in gaseous phase, and in bulk, and with respect to the reactor type, as in autoclave, tubular, loop, or fluidised bed (Table 1.1). The first three processes occur at low pressure (~10 MPa) by a coordination mechanism, while the last one occurs at high pressure (~100 MPa) in...
