2.1 Introduction

Most polymers contain quite complex additive systems which are incorporated during manufacture to impart beneficial properties during manufacturing operations, e.g., protective antioxidants, slip agents, etc., and during end-use, e.g., antioxidants, ultraviolet (UV) stabilisers, plasticisers and antistatic agents, flame retardants, antioxidants and thermal stabilisers. The first stage in the examination of a polymer, either from the point of view of identifying the polymer or identifying and determining additives present must be to separate gross polymer from gross additives. It may then be necessary to separate the gross additive fraction into individual additives by a chromatographic procedure in order to facilitate the identification of individual additives.

Separation of gross polymer from gross additives is necessary so that examination of the polymer is not affected by interference from the additives present and also vice versa. Many different procedures have been studied for the removal of gross additives from the polymer and some of these are discussed next.

The main extraction procedures used are summarised in Table 2.1 and although most of them can be carried out on material cut to a particle size of less than 2 mm diameter, it is often advantageous to produce material of a smaller size and with a larger surface area to mass ratio. This is conveniently done by grinding at the temperature of liquid nitrogen using an efficient and easily cleaned cutter mill.