Film Formation of High Tg Latex Using Hydroplasticization: Explanations from NMR Relaxometry
Film Formation of High Tg Latex Using Hydroplasticization: Explanations from NMR Relaxometry
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利用氢塑化形成高 Tg 乳胶的成膜：NMR 弛豫测量的解释
DOI：
10.1021/acs.langmuir.9b01353
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发表时间：
2019
期刊：
影响因子：
3.9
通讯作者：
O. Adan
中科院分区：
文献类型：
--
作者：
Benjamin Voogt;H. Huinink;S. Erich;J. Scheerder;P. Venema;J. Keddie;O. Adan
用加菲尔德1H核磁共振仪研究了不同相对湿度(RH)下甲基丙烯酸(MAA)对不同羧酸含量的丙烯酸酯乳液分散体系成膜的影响。玻璃化转变温度在26℃到50℃之间的聚合物颗粒由于水化作用在室温下形成薄膜。结果表明，随着相对湿度的降低，干燥速率增大，水的蒸发通量受到乳胶聚合物的限制。只是在干燥的第二阶段，随着MAA含量的增加，这一现象更加明显。用~1H核磁共振弛豫法研究了薄膜形成和硬化过程中氢迁移率的变化。这表明干燥速度本身对通过T2弛豫时间测量的乳胶膜中的氢迁移率没有影响。水和可流动聚合物相的氢迁移率只有在大部分水蒸发后才会显著降低。这意味着聚合物的刚性随着水的蒸发而增加，否则水会通过与羧酸基团的氢键来塑化聚合物。聚合物相的这种硬化对于涂层的应用是必不可少的。氢的迁移率受MAA浓度的影响。随着MAA含量的增加，可移动氢的密度增加。如果移动质子包含在MAA基团中，这是预期的。这一结果证实了羧酸基在共聚物的氢键和塑化过程中的作用。然而，氢的迁移率随着MAA含量的增加而降低，这被认为是由于仍然保持水分的羧酸基的二聚体的形成所致。由于水化作用，它们仍然能够实现短距离聚合物的氢迁移，但由于羧酸基团之间的相互作用，限制了长距离聚合物的迁移。
The film formation of acrylic latex dispersions, containing different amounts of carboxylic acid functional groups by the incorporation of methacrylic acid (MAA), was studied with GARField 1H NMR at various relative humidities (RH). Polymer particles with glass-transition temperatures in the range from 26 to 50 °C formed films at room temperature because of hydroplasticization. It was found that with an increased drying rate due to lower RH, the evaporation flux of water was limited by the latex polymer. Only in the second stage of drying this phenomenon was more obvious with increasing MAA content. 1H NMR relaxometry was used to study the change of hydrogen mobilities during film formation and hardening of the films. This showed that the drying rate itself had no impact on the hydrogen mobility in the latex films as measured via the T2 relaxation time. Hydrogen mobilities of water and the mobile polymer phase only significantly decrease after most water has evaporated. This implies that the rigidity of the polymers increases with the evaporation of water that otherwise plasticizes the polymer through hydrogen bonding with the carboxylic acid groups. This hardening of the polymer phase is essential for applications in a coating. The hydrogen mobilities were affected by the MAA concentration. Densities of mobile hydrogens increase with increasing MAA content. This is expected if the mobile protons are contained in the MAA groups. The result thus confirms the role of carboxylic acid groups in hydrogen bonding and plasticization of the copolymers. Hydrogen mobilities, however, decrease with increasing MAA content, which is hypothesized to be caused by the formation of dimers of carboxylic acid groups that still hold water. They still enable short-range polymer hydrogen mobility due to hydroplasticization but limit long-range polymer mobility due to interaction between the carboxylic acid groups.
DOI：
10.5860/choice.41-0674
发表时间：
1970-02
期刊：
--
影响因子：
--
作者：
J. Kroschwitz;H. Mark
通讯作者：
J. Kroschwitz;H. Mark