Morphology and Texture Development of Uniaxially Stretched Poly(ethylene naphthalene-2,6-dicarboxylate) A. Douillard, 1 C. Hakme, 1 L. David, 1 I. Stevenson, 1 G. Boiteux, 1 G. Seytre, 1 T. Kazmierczak, 2 A. Galeski 2 1 Laboratoire des Mate ´riaux Polyme `res et des Biomate ´riaux, UMR CNRS 5627, Universite ´ Claude Bernard–Lyon 1, Bat. ISTIL, 43, Bd du 11 novembre 1918, 69622 Villeurbanne cedex, France 2 Centrum Badan Molekularnych I Makromolekularnych, 90-363 Lodz, ul.Sienkiewicza 112 Poland Received 22 February 2006; accepted 14 April 2006 DOI 10.1002/app.24758 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The texture development of PEN films with different semicrystalline morphologies have been studied by X-ray diffraction. These different structures have been obtained by uniaxially stretching PEN amorphous films at 100 and 1608C (below and above T g ) at different drawing ratios. Samples have also been characterized by DSC to deter- mine the crystallinity ratios, the crystallization, and melting temperatures. To define the orientation of crystallites in the oriented samples, pole figures have been constructed, as a function of temperature and drawing ratio (DR) in the range 1.5–4. In the range from DR ¼ 2 to 4 the orientation is clearly uniplanar-axial. At T draw ¼ 1008C the crystallinity shown by DSC analysis is higher than the sample stretched at 1608C. The orientation is also higher when samples are stretched at 1008C. The naphthalene rings mainly stay in the plane of the film with a lower fraction perpendicular to the plane of the film. Ó 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 395–401, 2007 Key words: morphology; X-rays; pole figure; texture; orien- tation; poly(ethylene naphthalene-2,6-dicarboxylate) (PEN); differential scanning calorimetry (DSC) INTRODUCTION As poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) is largely used in the form of thin films which can be obtained by uniaxial or biaxial stretching, the under- standing of the evolution of its morphology and ori- entation with temperature and stretching conditions is essential to adjust its properties for a given appli- cation. 1–4 The complex orientation of industrially stretched PEN during a two step biaxial process was studied by the building of pole figures in a previous paper. 5 The establishment of relationships between microstructure and properties (dielectric or mechani- cal) is not straightforward, due to the complexity of the morphology. Moreover, the morphology itself is diffi- cult to interpret as a function of processing parameters. The aim of this work is to study the effect of a home- made uniaxial stretching on PEN films. This can be viewed as a thermomechanical treatment yielding a more simple morphology, but also the first step of a more complicated biaxial stretching. During the last decade, several papers have been devoted in literature to the microstructure of uniaxially drawn PEN. Murakami et al. 4 have studied orientation and structural change of amorphous PEN during uni- axial drawing and/or heating. Stretching at tempera- ture lower than T g (1208C) produces oriented structure with neck formation. On the other hand, drawing at 1508C(> T g ) gives directly a crystalline fibrous struc- ture with uniaxial planar orientation in which the naphthalene ring is parallel to the film plane. EXPERIMENTAL PEN samples were obtained from Du Pont de Nemours (Luxembourg) as amorphous films with a thickness of 300 mm. These films were stretched uniaxially at an ini- tial speed of 0.02 s À1 (50 mm/min with a distance between clamps of l o ¼ 40 mm) using a tensile test machine (MTS 2/M) equipped with a thermoregulated chamber at two different drawing temperatures, below and above T g , respectively, at 100 and 1608C. Four mac- roscopic drawing ratio (DR ¼ l/l o ) were applied: 1.5, 2, 3, and 4. The DR of the different samples was evaluated at a more local scale by means of the deformation of a fine grid stamped on the films. 6 The correspondence between macroscopic and experimentally measured drawing ratios is reported in Table I. The WAXS system used to obtain pole figures has been described elsewhere, 5 including the POD soft- ware. The slit opening allowing to collect scattered beam was within 60.1558 around the fixed 2y angle. As in Ref. 5, DSC measurements were carried out using a 2920 TA Instruments (range from 50 to 3008C with a heating rate of 10 K/min, with samples of about 5 mg). Correspondence to: I. Stevenson (isabelle.stevenson@univ- lyon1.fr). Contract grant sponsor: MIRA. Journal of Applied Polymer Science, Vol. 103, 395–401 (2007) V V C 2006 Wiley Periodicals, Inc.