D_4单体细乳液的稳定性探讨

Stability of monomer miniemulsions of octamethylcyclotetrasiloxane(D_4)

以八甲基环四硅氧烷(D4)作为模型单体,分别使用高速分散机、超声波仪和高压均质机制备了D4细乳液,使用多重光散射稳定性分析仪(MLS)分析比较了不同方法制备的D4细乳液的稳定性,并通过稳定性的分析,研究了均质压力和乳化剂浓度对单体细乳液的稳定性的影响。结果表明,在同样的乳化剂浓度下采用高压均质机制备的细乳液稳定性最好,能够稳定进行细乳液聚合;随着均质压力(10～110 MPa)增大,D4细乳液的稳定性先增强后减弱,在90 MPa下制备的细乳液稳定性最好,乳液粒径增长速率仅为0.342 nm/min;随着DBSA浓度(0.0092～0.0460 mol/L)增大,在相同均质条件下(90 MPa下均质4次)制备的单体细乳液稳定性增强,粒径增长速率都小于0.505 nm/min,具有较好的稳定性。

Using octamethylcyclotetrasiloxane（D4） as a model monomer,miniemulsions have been prepared using a rotor-stator system,ultrasonication and a high-pressure homogenizer.The stabilities of the monomer miniemulsions prepared using different methods were characterized by multiple light scattering（MLS）.The results showed that with the same concentration of dodecylbenzenesulfonic acid（DBSA） as emulsifier,the monomer miniemulsion prepared using the high-pressure homogenizer had the best stability and was most suitable for miniemulsion polymerization.The MLS data showed that with increasing homogenization pressure（in the range 10-110MPa）,the stability of the D4 miniemulsion increased at first and then decreased.The monomer miniemulsion prepared under a pressure of 90MPa had the best stability.The rate of increase of the size of monomer droplets prepared under this pressure was only 0.342nm/min.The influence of the emulsifier concentration on the stability of the monomer emulsion was also quantitatively characterized by MLS.Under the same homogenization conditions（carried out four times under a pressure of 90MPa）,the monomer miniemulsions showed good stability with the rate of increase of the size of monomer droplets being less than 0.505nm/min in the DBSA concentration range from 0.0092mol/L to 0.0460mol/L.The miniemulsion stability was enhanced with increasing concentration of DBSA.