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

C-13 NMR and EPR methods are employed to quantitatively determine the composition of thermoplastic vulcanizates (TPVs) based on ethylene-propylene-diene rubber (EPDM), polypropylene (PP) and extender oil, with and without talcum filler. The oil has a strong influence on both the processing and the mechanical properties of TPVs, and the specific aim of this study is to determine 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 Mn2+ 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 contrast, the paramagnetic ions do not significantly affect the PP/EPDM ratio. Taken together, the NMR and EPR results provide strong evidence that in the melt about one third of the oil is neither mixed with EPDM nor PP. The data indicate that it may form a thin layer of similar to0.05 mum characteristic thickness around talcum filler particles. (C) 2001 Elsevier Science Ltd. All rights reserved.