J. Phys. IV France
Volume 125, June 2005
Page(s) 383 - 386

J. Phys. IV France 125 (2005) 383-386

DOI: 10.1051/jp4:2005125089

Open Photoacoustic Cell study of thermal diffusivity of Nafion® as a function of water content

D.T. Dias1, J. Mura1, M.L. Baesso1, A.N. Medina1, A.C. Bento1 and J. Shen2

1  Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, Maringá-Paraná 87020-900, Brazil
2  National Research Council of Canada, Innovation Centre, 3250 E Mall, Vancouver, BC V6T 1W5, Canada

The Dupont Nafion® (acid polymer perfluorsulfonic/PTFE copolymer in an acid form H+) is derived from Teflon® (PTFE) and both present great similarities. In order to study thermal properties of the Nafion®, we used the open photoacoustic cell (OPC) to measure the longitudinal $\alpha_{\perp}$ and the thermal lens technique (TLS) for the planar direction, $\alpha_{/\!/}$. From OPC experiment it was found an averaged (Nafion® in nature) value $\alpha_{\perp} = (6.5 \pm 0.4) \times 10^{-4}$ cm2/s whilst TLS gave $alpha_{/\!/} = (7.0 \pm 0.2) \times 10^{-4}$ cm2/s. The value found, $alpha_{\perp}\sim \alpha_{/\!/}$, means that there is no significant anisotropy in the Nafion® foil. Water content dependence of thermal diffusivity for ten samples dipped in water showed a minimum near 4 h ( $\sim 4.5 \times 10^{-4}$ cm2/s) and goes to a saturating value after 28 h ( $\sim 5.5 \times 10^{-4}$). On the other hand, in experiment where the sample is left to dry in the ambient air, $\alpha_{\perp}$ present a transitional behavior near 5 h off water ( $\sim 6.0 \times 10^{-4}$) and diminish monotonically after 28 h. It is believed that thermal diffusivity can be related with water content and it may be helpful in the understanding of permeation in the Nafion® membrane.

© EDP Sciences 2005