TABLE OF CONTENTS Fractional extraction can be used in three ways, depending on the substance under examination:
Finely shredded solid plastics are extracted one-by-one in a Soxhlet apparatus with solvents, of increasing solvent power.
To ensure that the plastic particles are fine enough to allow the components to be extracted to diffuse sufficiently quickly, a solution or dispersion of the plastic is poured over an inert carrier, such as silica gel or Sterchamol, the solvent is allowed to evaporate and the carrier is then extracted in a heatable column with solvents of increasing solvent power.
The components of a plastic are distributed between two non-miscible liquids in separating funnels or a distribution apparatus.
Most of these procedures 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 large 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.
The extraction of additives strongly adsorbed or chemisorbed on the polymer - filler matrix must be carefully observed by the analyst, as a change of the method of manufacture of, for example, the filler or in the method of compounding the plastic formulation, can also markedly alter the degree of adsorption being produced and hence invalidate an established quantitative extraction procedure. The use of stronger ...
