TABLE OF CONTENTS Infrared (IR) spectra of thin films of a polymer in the region up to 2.5 ?m are characteristic of the polymer. Computerised retrieval from data in a library of standard polymers has been used in the IR fingerprinting technique to facilitate polymer identification [1].
Alexander [2] has described a method for obtaining spectra of thin films of polymer that are free of interference fringes.
Various methods have been used to prepare polymers for IR spectroscopy:
Potassium bromide discs [3]: the spectra were run either as potassium bromide discs (1.5 2 ?g polymer per 400 mg potassium bromide) or as polymer films of varying thickness, up to 12 ?m, using a sodium chloride prism.
Hot pressed film [4]: Osland [5] has described a heated press for the preparation of plastic films for analysis by IR spectroscopy. The press can produce films of reproducible thickness, as thick as 500 ?m.
Alternatively, the sample material can be dissolved in a suitable organic solvent and a film cast onto glass or a cell window.
A new sample handling accessory with which films of constant thicknesses can be prepared has been introduced by Phillips Analytical. The plastic film press contains a thermostatically controlled oven unit that is calibrated up to 300 C. It also contains a cooling facility which may be connected to a low-pressure compressed air supply to cool the prepared films rapidly. Reproducible thickness is ensured by using a set of brass dies that can...
