Thermal conductivity of stretched and annealed poly ( p-phenylene sulfide) films Luc Langer a,1 , Denis Billaud b, * , Jean-Paul Issi a a Universite ´ Catholique de Louvain, Unite ´ PCPM, 1 Place Croix du Sud, B-1348 Louvain-la-Neuve, Belgium b LCSM, Universite ´ Henri Poincare ´ Nancy I, BP 239-54506 Vandoeuvre les Nancy Ce ´dex, France Received 20 November 2002; accepted 28 January 2003 by P. Burlet Abstract The temperature variation of the thermal conductivities of as-prepared, mechanically stretched, as-prepared and then annealed PPS samples are presented. Unusually high thermal conductivity values are observed as compared to other polymeric materials. In agreement with the X-ray diffraction observations, the thermal conductivity of the oriented film is higher than that of the as-prepared or annealed films. The differences observed after stretching are comparable to those previously reported for polyethylene and polyacetylene films for the same draw ratios. These unusually high thermal conductivity values justify the use of PPS in devices where efficient heat dissipation, associated with electrical insulation, is required. q 2003 Published by Elsevier Science Ltd. PACS: 61.10. 2 i; 61.25.Hq; 44.50. þ f Keywords: A. Polymers, elastomers, and plastics; C. X-ray diffraction; D. Heat conduction 1. Introduction Poly( p-polyphenylene sulphide), abbreviated as PPS, is witnessing increasing interest nowadays due to its various technical applications. This is mainly due to its resistance to relatively high temperatures and mechanical stresses. It is currently used in connections between electrical cables and optic fibers or to encapsulate electronic components. In order to estimate heat dissipation in electrical devices it is necessary to know the value of the thermal conductivity of the material around room temperature. Since the macro- scopic properties, and more specifically the thermal conductivity, are directly related to sample structure and history, it is also important to know about the crystallinity of PPS and its morphology. It was shown that by acting at the molecular level one may tailor the lattice thermal conductivity of polymeric materials to a desired level [1]. In some cases, one may improve the thermal conductivity of some polymeric materials signifi- cantly [2,3]. On one hand, the magnitude and the temperature dependence (see below) of the lattice thermal conductivity of polymeric materials are both very sensitive to crystallinity. For example, for isotropic polyethylene, the room tempera- ture thermal conductivity varies from.15 to.67 W m 21 K 21 when the crystallinity ratio varies from.4 to.9. On the other hand, by stretching and aligning the polymeric chains, one may considerably increase the thermal conductivity of polymeric materials along the stretching direction [2,3]. This was shown to be the case for highly oriented polyethylene fibers [2] and for oriented polyacetylene films [3], where thermal conductivities comparable to those of metallic alloys were obtained. Crystallization kinetics of PPS have been studied using classical tools [4]. We propose here to use the temperature variation of the thermal conductivity as a complementary tool to get an insight into sample crystallinity and morphology, as is the case for other polymeric materials 0038-1098/03/$ - see front matter q 2003 Published by Elsevier Science Ltd. doi:10.1016/S0038-1098(03)00110-8 Solid State Communications 126 (2003) 353–357 www.elsevier.com/locate/ssc 1 Present address: BRONTES sprl, Rue de la Bruye `re 11, B-1315 Opprebais, Belgium. * Corresponding author. Tel.: þ33-3-83-684622; fax: þ33-3-83- 684623. E-mail address: denis.billaud@lcsm.uhp-nancy.fr (D. Billaud).