电解质和酸碱性对天然鲜胶乳电动特性的影响

Effect of Electrolytes and pH on the Electrophoretic Characteristics of Fresh Natural Rubber Latex

采用高速冷冻离心处理天然鲜胶乳制备离心胶乳,通过改变胶乳中酸碱度和电解质,结合激光多普勒技术、扫描电子显微镜以及电感耦合等离子体质谱仪等仪器对处理前后的胶乳进行电动特性、形貌及金属离子含量分析。结果表明pH值的降低能使胶乳电泳迁移率的正负发生反转。增加电解质浓度,天然鲜胶乳负的电泳迁移率随之降低,相同浓度条件下阴离子电解质对天然胶乳电泳迁移率与电导率的影响顺序为NaCl>NaBr>NaNO3>SDS(十二烷基硫酸钠)。金属阳离子压缩天然胶乳双电层效率由大到小依次为Al 3+>Fe3+Fe2+>Cu2+Mn2+>Co2+>Ca2+>Na+。高价金属阳离子如铜离子、铁离子与铝离子能使胶乳带电性质反转,酸碱度及形貌分析表明这些电解质会改变胶乳pH值环境,使胶乳发生团聚甚至破乳现象。

Fresh natural rubber latex was used to prepare centrifuged latex through high-speed refrigerated centrifuge. Combining laser Doppler electrophoresis, scanning electron microscope and inductively coupled plasma mass spectrometer and other instruments, the writer analyzed the electric properties, morphology and metal ion content of freshed and centrifuged natural rubber latex by changing the pH and electrolyte. The results showed that as the pH was lowered, the plus or minus of latex electrophoretic mobility was inverted. With the increasing electrolyte concentration, the negative electrophoretic mobility of natural fresh latex decreased accordingly. Under the same condition of concentration, the order of anions＇ effects on natural rubber latex＇s electrophoretic mobility and conductivity was NaCl〉NaBr〉NaNO3〉SDS （sodium dodecyl sulfate sodium）. The descending order of compressing the electric double layer efficiency of metal cation was Al^3＋〉Fe^3＋〉〉Fe^2＋〉Cu^2＋〉Mn^2＋〉Co^2＋〉Ca^2＋〉Na^＋. There was a special situation that high metal cations such as copper ions, iron ions and aluminum ions could invert the latex＇s charged nature. pH and electrolyte and the Morphology analysis showed that these electrolytes change latexrs pH environment, leading to latex agglomeration, even emulsion breaking.