【摘要】 本文報告測定本所合成研究室用乳液聚合在50°時所製備的丁苯橡膠分子量分佈的結果。我們在1％苯溶液中,加入甲醇作沉澱劑經分級沉澱後,用粘度法測定各級份的分子量。所得分子量分佈曲線,在分子量等於50,000處有一個明顯的高峯,與前人的結果相符合。特性粘數[η]>3的級份,從它們的溶解度和在甲苯溶液中的粘度數據,我們認為有顯著的支鏈和交聯的存在,約佔試樣的25％。甲苯溶液的粘度數據指示在[η]<3時,k′=0.36,與分子量無關,而且k′+β=1/2;當[η]>3時,k′值顯著地增大,而且k′+β>1/2。 這些差異的大小,我們認為可以看作丁苯橡膠分子支鏈或交聯程度的一種量度。 從本實驗所得的丁苯橡膠的分子量分佈曲線,我們建議同時用■和■來做橡膠的品質指示。更多还原

【Abstract】 A sample of butadiene-styrene copolymer obtained from emulsion polymerization at 50℃ with 80% conversion has been doubly fractionated into fractions by adding successive amounts of methanol at 25℃ into a 1% solution of the polymer in benzene. From the weight and intrinsic viscosity of each fraction obtained, an integral weight distribution curve was drawn according to the method of Schulz and Dinlinger. The differential distribution curve exhibits a rather sharp maximum around the molecular weight of 50,000, in agreement with many published results including one obtained from ultracentrifuge data. The fractions with [η]>3, i.e., M>500,000 took a couple of weeks to go into solution, indicating an appreciable degree of branching or slight cross-linking of the macromolecules. The viscosity data of the fractions in toluene at 30℃ show that the values of k’ snd β of the equations Inη_r/C = [η] - [β] [η]²C η_sρ/C = [η] + k’ [η]²C are constant, k’=0.36, being independent of molecular weight and k’ + β = 1/2 for fractions with [η]>3. For fractions with [η]>3, k’>0.36, in conformity with the findings of Cragg and others that k’ increases rapidly with the presence of branching or cross-linking. Besides, we found that for these fractions, k’+β>1/2, which relationship can also be used for the detection of branching in butadiene-styrene copolymer.更多还原