Dissolution of viscose rayon multifilament yarn in the ionic liquid 1-ethyl-3-methylimidazolium acetate studied using time–temperature superposition

Wide-angle X-ray diffraction (WAXS) and mechanical testing techniques are used to track the dissolution of a viscose rayon multifilament yarn in the ionic liquid 1-ethyl-3-methyl-imidazolium acetate [C 2 mim] + [OAc] − for different times and temperatures. In the dissolution process, the oriented cellulose II crystals in the regenerated cellulose fibres dissolve and then reform into randomly oriented crystals to form a matrix phase, and this change in orientation enables us to follow the dissolution process using WAXS, and hence determine the dissolved matrix volume fraction v_m . The change in the average molecular orientation P_2 determined from an azimuthal (α ) X-ray scan, allows the growth of the matrix volume fraction v_m to be calculated with time and temperature. The growth of v_m was found to follow time temperature superposition, with an Arrhenius behaviour, giving a value for the activation energy of E a = 149 ± 4 kJ/mol. Young’s modulus was measured on all the resulting processed composites. The fall of Young’s modulus with dissolution time and temperature was also found to follow time–temperature superposition, with an Arrhenius behaviour giving a value for E a = 198 ± 29 kJ/mol. The Young’s Modulus results plotted against v_m determined from the WAXS measurements fitted well to the Voigt upper bound parallel Rule of Mixtures .