热敏显色微胶囊的制备与表征

热敏显色微胶囊是用于传真、条形码系统、医用图像、各种打印等领域的重要材料，它是一种内部含有染料隐色体的球形胶囊。染料隐色体是一种内酯结构的无色染料，在一定条件下，与显色剂发生显色反应。由于染料隐色体的化学惰性不够理想，易受外界因素的干扰，因而在应用中受到一定限制，所以为了克服其存在的不足，常将其微胶囊化。微胶囊的芯壁结构可以将芯材与外界隔离,提高芯材的稳定性,同时保留芯材原有的化学性质。当环境温度在微胶囊的玻璃化温度以上时，由于形成微胶囊壁的物质透过性显著增加，因此显色成分接触而发生显色反应。本文利用界面聚合法，以聚乙烯醇为保护胶体，曲拉通X-100为表面活性剂，聚氨酯为壁材，染料隐色体为芯材，合成了聚氨酯热敏显色微胶囊。研究了三个主要因素对微胶囊的粒径及其分布、表面形貌和热敏显色性能的影响。结果表明，增大保护胶体浓度，提高乳化速度，增加乳化剂用量，微胶囊的平均粒径变小，粒径分布变窄，表面变得光滑而且致密，具有较高的热敏显色密度。利用红外光谱仪确认了微胶囊的结构，在最优条件下，所制备的微胶囊玻璃化温度为131 ℃，并具有良好的热稳定性。

Preparation and Characterization of Heat Sensitive Color‐developing Microcapsules

Heat sensitive color‐developing polyurethane microcapsules containing leucocompounds were prepared by interfacial polymerization. The effects of three determinative process parameters on the particle size distributions, surface morphologies, and heat sensitive color‐developing behavior of the microcapsules were investigated. As a result, the polyurethane microcapsules with a narrower distribution, rounder shape and better heat sensitive color‐developing property were prepared with increasing of the protective colloid content, emulsifying rate and emulsifier content. This was related with the surface roughness of the microcapsules.