Migration phenomena of surfactants in polyethylene film

Migration diffusion coefficients of two surfactants (sorbitan laurate, SPAN -20 and sorbitan palmitate, SPAN-40) in polyethylene blend are calculated i n the desorption process by means of Fourier transform infrared (FT-IR) spe ctroscopy technique at 25 degrees C. They are 2.31 and 2.24 x 10(-11) cm(2) /s, respectively, which show no significant dependency of molecular weights of the surfactants on diffusion. The composition of LLDPE (linear low-dens ity 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 semicrystal line LLDPE blend. Incorporation of 20 wt% EAA in the LLDPE blend retards th e migration rate of the surfactants by reducing the diffusion coefficients to be 9.6 and 7.7 x 10(-12) cm2/s and this is believed to the blocking effe ct of EAA. Although the diffusion coefficient was varied from system to sys tem, the migration kinetics of the surfactants in short times obeys the Fic kian behavior if the experimental error is allowed. (C) 1999 John Wiley & S ons, Inc.