ON THE CHARACTERIZATION OF POLYMER-FILMS AND COATINGS FOR PHOTOCONDUCTING FIBERS PREPARED FROM ADDITION-CROSS-LINKING SILICONE

The crosslinking behaviour of addition-crosslinking Wacker SilGel 600 silicone was investigated in the temperature range of 50 to 90-degrees-C with respect to its dependence on heating time. Measurements of the swelling of thin polymer films on special paper (Pecozet Z10) allow the observation of the swelling process which reaches the swelling equilibrium within a few minutes, the selection of a suitable swelling agent, and the rapid determination of the temperature dependence of the degree of swelling Q. Aside from Q, the "solubility parameter" of the polymer network, the rate constants, and the activation energy of the crosslinking process can be obtained. Measurements of the swelling combined with determination of Huggins' interaction parameter additionally provide the possibility of determining the density of crosslinking of the polymer films. On the basis of these investigations, a rapid method for characterizing the sheathing of optical fibres could be developed. The cylindrical polymer films detach from the glass core during swelling in toluene (25-degrees-C). After 5 min the degree of swelling of the sheathing can be measured.