Migration phenomena of surfactants in polyethylene film

Abstract

Migration diffusion coefficients of two surfactants (sorbitan laurate, SPAN-20 and sorbitan palmitate, SPAN-40) in polyethylene blend are calculated in the desorption process by means of Fourier transform infrared (FT-IR) spectroscopy technique at 25°C. They are 2.31 and 2.24 × 10−11 cm2/s, respectively, which show no significant dependency of molecular weights of the surfactants on diffusion. The composition of LLDPE (linear low-density polyethylene) and LDPE (low-density polyethylene) in LLDPE blend is a 7 : 3 ratio, and ethylene acrylic acid (EAA) copolymer is used to verify its role as a migration controller. The key factor affecting the diffusion of the surfactant is suggested to be the segmental mobility by the semicrystalline LLDPE blend. Incorporation of 20 wt% EAA in the LLDPE blend retards the migration rate of the surfactants by reducing the diffusion coefficients to be 9.6 and 7.7 × 10−12 cm2/s and this is believed to be due to the blocking effect of EAA. Although the diffusion coefficient was varied from system to system, the migration kinetics of the surfactants in short times obeys the Fickian behavior if the experimental error is allowed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1387–1395, 1999