129Xe-NMR of carbon black filled elastomers

Journal of the Brazilian Chemical Society

Gerhard-Mercator-University, Duisburg, Germany¹  Sperling-Ischinsky, K.¹  Veeman, W.S.¹ 

关键词: carbon black;    elastomers;    filled elastomers;    129Xe-NMR;   

DOI  :  10.1590/S0103-50531999000400008

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

129Xe-NMR spectroscopy has proven to be a valuable tool for the study of microporous solids. Xe atoms with their diameter of 4.4 Ã… can be sorbed in many porous materials, ranging from crystalline materials like silicates to amorphous polymers1. The advantage of Xe as a NMR probe is the extraordinary sensitivity of the Xe chemical shift to the interaction between the Xe atoms and the material in which they are adsorbed. For most materials the Xe chemical shift varies between 0 and 250 ppm, when the resonance of free Xe gas is taken as 0 ppm. A strong Xe-wall interaction results in high chemical shifts, a weak interaction in small shifts. In rigid microporous materials with pores of which the diameter exceeds the Xe atom diameter, the Xe atoms are thought to rapidly exchange between an adsorbed and a pseudo-gas state in which the atoms are more or less free. In such a situation the experimentally found chemical shift d results from the equilibration of the Xe atoms between the adsorbed state with shift da and free state with a shift of 0 ppm. In most amorphous polymers the situation seems to be different. The Xe atom usually is not small compared to the local free volume and the mobility of the Xe atoms is largely determined by the polymer chain mobility. Here we want to report experimental 129Xe-NMR results of elastomers filled with carbon black fillers. In filled polymers, rigid microporous materials like carbon blacks are combined with amorphous polymers and we were interested to see how the 129Xe-NMR parameters of Xe in filled polymers are related to those parameters in the unfilled polymers and in the filler itself.   Experimental The 129Xe-NMR experiments were performed on a Bruker CXP200 (129Xe frequency 55.345 MHz) using 30° rf pulses (pulse length 4-5.5 ms) and between 10000 and 32000 scans. The NMR tubes, filled with the sample, are first evacuated for two hours at a pressure below 5x10-9 bar. In

【 授权许可】

Unknown