Crosslinking of elastomers resulting from ageing:: use of thermoporosimetry to characterise the polymeric network with n-heptane as condensate

Thermoporosimetry has been used to characterise the network generated by UV-irradiation of Ethylene-Propylene-Diene-Monomer (EPDM) samples. The technique was calibrated by using well characterised monodisperse silica gel samples. In the case of n-heptane, the following relationship between the freezing point depression (AT) of the solvent and the radius of the pore in which it crystallizes is found: R-p(Adegrees) = -587.4/DeltaT + 2.4 with -40 < ΔT < 0degreesC The use of n-heptane as swelling solvent permits the determination of the precise mesh size distribution (MSD) of the network generated by crosslinking of the elastomer. The more crosslinked the elastomer, the narrower its MSD and the smaller the mean mesh size of its network. This method can be generalised to any polymer crosslinked by any technique (UV, gamma, chemical,...) provided an appropriate swelling solvent and a corresponding calibration can be obtained. (C) 2003 Elsevier Science Ltd. All rights reserved.