凝胶色谱法测定顺丁橡胶平均分子量及其分布的研究

Study on Determination of Molecular Weight Averages and Molecular Weight Distribution of Polybutadiene by GPC

通过一系列的条件试验，包括样品浓度、样品量及流动相流速对柱效的影响，确定了最佳的凝胶色谱（ＧＰＣ）试验条件；采用普适校正法将聚苯乙烯（ＰＳ）标定曲线转换成顺丁橡胶（ＰＢ）标定曲线，并对Ｍａｒｋ－Ｈｏｕｗｉｎｋ方程式中Ｋ，α值的选择进行了讨论；采用４种分子量加宽方程对色谱柱加宽效应进行改正计算，通过比较，选定适合本试验系统的加宽效应的改正方法；用粘度法测得的顺丁橡胶特性粘度（η）吻合ＧＰＣ所测得特性粘度值，证明了方法的可靠性。

In this paper, optimum conditions and various factors that influence the determination of molecular weight of polybutadiene (PB) are discussed. Suitable PB concentration(1g/L) and flow rate of mobile phase (1mL/min) have been found in accordance with theoretical plate number. Elution volume increases as sample concentration increased. It makes unacceptable error if the concentration is up to 3g/L, especially for high molecular weight PB. It has demonstrated that there is a limiting sample size in GPC column. These data indicate that 150μg of PS is the suitable sample size for our GPC column. Four methods of molecular weight (MW) correction are used in this test. However, the relative error is 219% for Mn,90% for Mw if MW is calculated without correction. It is shown in comparision with four corrections that the correction method recommended by ASTM D3593 is a simple and accurate method. Six sets of K,a have been used to establish calibration curves of PB. It is clear that MW and its distribution calculated by the six sets of K,a are quite different, so it should be more careful to choose values of K,a obtained from references. The validity of this method is determined for the same PB by comparing the calculated intrinsic viscosities with the actually measured intrinsic viscosities using Test Method ASTM D2857. The fact of calculated and measured intrinsic viscosities agrees within statistical limits confirmed that this method is valid for PB. The method is applied to compare the MW and its distribution of PB from Japan and from Gaoqiao.