Solid state C-13 NMR spectroscopy on EPDM/PP/oil based thermoplastic vulcanizates in the melt

C-13 NMR and EPR methods are employed to quantitatively determine the compo sition of thermoplastic vulcanizates (TPVs) based on ethylene-propylene-die ne rubber (EPDM), polypropylene (PP) and extender oil, with and without tal cum filler. The oil has a strong influence on both the processing and the m echanical properties of TPVs, and the specific aim of this study is to dete rmine the location of the oil in the melt. C-13 NMR of the pure oil reveals that it closely resembles a low molecular weight EPM with M-n = 800 g/mol and an ethylene content of 70 wt%. EPR shows that traces of paramagnetic Mn 2+ ions are present in the talcum filler. The Mn2+ ions appear to suppress a substantial fraction of similar to 30% of the oil 13C NMR response. In co ntrast, the paramagnetic ions do not significantly affect the PP/EPDM ratio . Taken together, the NMR and EPR results provide strong evidence that in t he melt about one third of the oil is neither mixed with EPDM nor PP. The d ata indicate that it may form a thin layer of similar to0.05 mum characteri stic thickness around talcum filler particles. (C) 2001 Elsevier Science Lt d. All rights reserved.