The effectiveness of solid-state MRI with dipolar refocusing techniques was tested to improve the sensitivity and spatial resolution for the investigation of various solid polymers. The comparison of dipolar refocusing methods with conventional SPI was undertaken. As an alternative, gas-phase MRI experiments with thermally polarized SF6 and hyperpolarized xenon were performed. The performance of SF6 was found to be equivalent to solid-state methods. The possibility of achieving a significant increase in imaging efficiency by use of the hyperpolarization technique is demonstrated. The effects of embedding gaseous SF6 into EPDM rubber were investigated using NMR methods. A strong correlation was found between EPDM cross-linking and the transversal relaxation time of embedded SF6.