FUNCTIONALIZATION OF POLYPROPYLENE WITH OXAZOLINE AND REACTIVE BLENDING OF PP WITH PBT IN A COROTATING TWIN-SCREW EXTRUDER

The aim of this study was to prepare a compatibilized PP/PBT blend in a twin-screw extruder, using oxazoline-functionalized PP. First we pre pared the functionalized PP (PP-g-OXA), and then we used it as a compa tibilizer in the subsequent reactive blending stage. Polypropylene was successfully functionalized by ricinoloxazoline maleinate in a corota ting twin-screw extruder using a melt free radical grafting technique. Grafting yields up to 2.1 phr were achieved. This functionalized PP u sed as a compatibilizer markedly improved the mechanical properties of the uncompatibilized PP/PBT (PET content 30 wt %) blend. Significant improvements were observed, especially in impact strength ( Charpy) an d elongation at break: of the compatibilized blends. The increased int eractions between the phases were characterized by SEM analysis, DMTA, and DSC experiments. The properties of the blend greatly depended on the degradation of the PP during grafting. An optimal content of compa tibilizer exists, which is dependent on the degradation of PP, graftin g yield of oxazoline monomer, and on the amount of free, ungrafted mon omer present in the compatibilizer. These factors can be adjusted by p roperly choosing the processing conditions and chemical parameters. (C ) 1997 John Wiley & Sons, Inc.