Structure–property relation in varieties of acid dye processed silk fibers H. Somashekarappa a , V. Annadurai b , Sangappa a , G. Subramanya c , R. Somashekar d, * a Department of Physics, Yuvaraja’s College, University of Mysore, Mysore-570 005, India b Department of Physics, BIET, Davanagere-577 004, India c Department of Sericulture, University of Mysore, Manasagangotri, Mysore-570 006, India d Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore-570 006, India Received 4 May 2001; accepted 10 June 2001 Abstract The changes in microstructural parameters in varieties of acid dye processed (Bombyx mori and Antheraea) silk fibers have been studied using wide angle X-ray scattering (WAXS) method. The crystal imperfection parameters like crystal size hN i, lattice strain ( g) and enthalpy (a*) have been determined by profile analysis using Fourier method of Warren. These results were crosschecked with the one obtained by matching the simulated intensity profile obtained from one-dimensional Hosemann’s paracrystalline model. In all this computation, we have used (201) reflection observed in these silk fibers. We have also computed volume-weighted and surface-weighted crystal sizes and compared the changes in these parameters with the measured physical properties like tensile strength and percentage of elongation at break in these fibers. D 2002 Elsevier Science B.V. All rights reserved. PACS: 61.10.i; 61.10.Eq; 61.41. + e; 61.43.Bn Keywords: Wide angle X-ray scattering (WAXS); Crystal imperfection parameters; Tensile strength; Percentage of elongation at break 1. Introduction Silk fiber is a semicrystalline polymer [1,2]. It is one of the most important materials extensively used in the textile industry. It is quite important to know the microstructural changes in silk fibers due to dye processing as these parameters determine the property and strength of the fibers. Enormous work has been carried out and reported on the effect of various solvents on silk fibers [3–5]. However, the changes in crystal imperfect parameters like surface-weighted, volume-weighted crystal sizes in wild silk fibers like Muga (Assama) and Tassar (Mylitta) have not been studied so far. Hence, in this paper, we have carried out X-ray analysis on varieties of acid dye processed silk fibers to determine the micro-paracrystalline parame- ters from the intensity profile of a fairly clear (201) X- ray reflection. For this purpose, we have used Warren’s Fourier method [6,7] and also Hosemann’s paracrystal- line modelling method [8]. The obtained parameters analyzed by comparing with the measured physical parameters like tensile strength and percentage of elongation at break. 0167-577X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0167-577X(01)00517-1 * Corresponding author. E-mail address: rs@uomphysics.net (R. Somashekar). www.elsevier.com/locate/matlet April 2002 Materials Letters 53 (2002) 415 – 420