NONDEGRADATIVE MELT FUNCTIONALIZATION OF POLYPROPYLENE WITH GLYCIDYL METHACRYLATE

The melt grafting of glycidyl methacrylate (GMA) onto powdered isotact ic polypropylene (PP) in a Haake Rheocord RC90 mixer was studied. Graf ting degrees were determined by nonaqueous back titration of trichloro acetic acid with sodium hydroxide. The extent of degradation and cross linking of PP during grafting was indicated by the melt-flow rates (MF R) of the grafted samples. The influences of GMA concentration, initia tor type and concentration on grafting degree, reaction efficiency, an d degradation were evaluated. A novel method was developed to obtain a high grafting degree with little degradation of PP using acrylamide ( AM) as the initiating agent. The grafting process occurred before or d uring the melting of PP (i.e., solid-state grafting), at which tempera ture crosslinking is preferred over chain scission. Primary free radic als generated from the rapid decomposition of AM have a higher tendenc y to attack GMA molecules than PP chains. At the same estimated amount of primary radicals, both grafting degree and grafting efficiency inc rease with decreasing decomposition temperature of the initiator (for the same decomposition half-life) in the order of AM > benzoyl peroxid e (BPO) > 2,5-di(t-butylperoxy)-2,5-dimethyl-3-hexyne (LPO). Functiona lized PP with the desired grafting degree and little degradation of PP could be obtained by the use of mixed initiators. (C) 1998 John Wiley & Sons, Inc.