通过高斯加权的1H CPMG弛豫曲线测定橡胶交联密度

摘要

CPMG (Carr-Purcell-Meiboom-Gill)回波法是测量橡胶交联密度[常用交联点之间的分子量(Mc)表示]的一种常用核磁共振(NMR)技术,但实验发现通过该技术获得的Mc对于CPMG序列中脉冲间隔时间具有较强的依赖性,导致交联密度NMR测量值与橡胶材料硬度的相关性低.为了克服这一缺点,本文对不同脉冲间隔时间下CPMG实验测得的质子横向驰豫曲线进行高斯加权.通过对高斯加权求和后的质子横向驰豫曲线进行处理分析,实现了对橡胶交联密度更加准确地测量,大幅提升了天然橡胶交联密度NMR测量值与材料硬度的相关性.本文方案测量能获得与1H DQ NMR方法相当,或比之更佳的交联密度-硬度相关性.同时,本文方案比1H DQ NMR方法更为高效,整体测量时间缩短为1H DQ NMR实验时间的1/10.%CPMG sequence is widely used to measure crosslink density of rubber.However,the crosslink density obtained by this technique has a strong dependence on the interval times between the pulses in CPMG sequence,and the results measured have only a weak correlation with rubber hardness.To overcome this shortcoming,we proposed in this work to construct a 1H T2 relaxation curve by summing Gaussian-weighted CPMG relaxation curves acquired at by varying the interval time between the pulses in CPMG sequence.Using the multi-echo Gaussian-weighted relaxation curve to calculate the crosslink density gave results that had greatly improved correlation with the rubber hardness.The new method was also fast and efficient,as it took only one-tenth of the experimental time required for the conventional 1H double quantum NMR (1H DQ NMR) experiment.