REACTIVE PROCESSING OF LLDPES WITH PEROXIDES IN COUNTER-ROTATING NONINTERMESHING TWIN-SCREW EXTRUDER .4. EFFECTS OF MOLECULAR-STRUCTURE OF LLDPES

The effects of reactive extrusion with peroxide have been compared for two linear low-density polyethylenes (LLDPEs). Resin C is a butene co polymer, while Resin B is an octene-ethylene copolymer. Both have simi lar molecular weight distributions, but Resin B is significantly riche r in terminal vinyl groups. Under the same reactive extrusion conditio ns, Resin B is much more reactive. Resin C is easier to process in thi s system, producing products clean of microgel. Concurrently, however, a given peroxide level produces less molecular weight enhancement and long-branch formation in Resin C. Reactive extrusion with peroxide is suitable to effect improvements in the processability of LLDPEs for f ilm applications, provided that the choice of peroxide and the process details are tailored to the characteristics of the particular LLDPE. (C) 1996 John Wiley & Sons, Inc.