Fickian diffusion of erucamide (13-cis-docosenamide) in poly(laurolactam) (Nylon 12) (PA-12)

Diffusion of erucamide (13-cis-docosenamide) [H3C-(-CH2-)u-HC=CH-(-CH2-)(7) -CO-NH2] (eru) in poly(laurolactam) (Nylon 12) (PA-12) has been studied in a temperature range from 343 to 353 K. In previous investigations on the di ffusion of eru in isotactic poly(propylene) (i-PP) it was found that the di ffusion took place by a non-Fickian mechanism. This feature was explained b y taking into account the microstructure of i-PP films and the incompatibil ity of eru and i-PP. The same experimental method to determine the concentr ation profiles was previously employed in this system. The experimental pro files have been compared with theoretical curves based on solutions of Fick 's diffusion equation for the best fitting, with the appropriate boundary c onditions. The measured concentration profiles show a good agreement with t he Fickian law. Values of the diffusion coefficient D in the range from 10( -10) to 10(-11) cm(2) . s(-1) have been obtained. The activation energy for diffusion (Ed) has been calculated from the D values in the temperature ra nge investigated assuming an Arrhenius-type behaviour. The activation energ y has been calculated as E-d = 156 kJ . mol(-1). The values of diffusion co efficients and activation energy are in the range found for some other addi tives. By using Fujita's equation a good correlation between diffusion coef ficient and free volume fraction estimated by means of the Williams-Landel- Ferry equation have been found.