Lignin–polypropylene composites. II. Plasma modification of kraft lignin and particulate polypropylene

Indulin kraft lignin and polypropylene were subjected to plasma treatments in a rotating electrodeless plasma reactor at 13.56 MHz radio frequency, with the goal of improving the strength properties of the composites made from these materials. It was shown that efficient surface modification could be achieved by these plasma treatments, avoiding long reaction times and large volumes of reactants for modification by conventional wet chemistry. SiCl₄-plasma treatments of lignin at 100 and 200 W resulted in silicon implantation in the range of 4–10% that depended on the treatment time. However, the effect of power in the treatments was minimal, given that changes in silicon implantation were not observed for changes in this parameter. SiCl₄-plasma treatment of polypropylene at 80 W, 1 and 10 min, resulted in silicon implantation in the order of 10–15%, for the two different treatment times, showing that low power and short treatment times were sufficient to significantly alter the polypropylene surface. However at high power (250 W), the longer treatment time of polypropylene apparently led to formation of oligohalosilanes. Other plasma treatments in the rotating reactor such as plasma-induced copolymerization of acryloyl chloride on both lignin and polypropylene, and plasma-state polymerization of acryloyl chloride on polypropylene under pulsing conditions, resulted in thin film depositions. Evaluation of composites from these treated materials is described in the next contribution (Part III) from this series. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1920–1926, 2004