Synthesis and characterization of polyurea microcapsules containing leuco dye

Abstract

This thesis synthesized polyurea microcapsules containing leuco dye by interfacial polymerization. Wall materials and the ratios of core-to-wall were investigated to improve the characteristics of the microcapsules. The effect of core-to-wall ratio, wall material types (HDI, MDI and EDA) on the morphologies, particle size distribution of the resultant microcapsules, thermal properties and encapsulation efficiency were investigated. Image intensity on the dye acceptor coated paper was determined. Insufficient wall materials were found to yield and incomplete encapsulation. The factors affecting characteristics of the microcapsules depended on the structure of diisocyanate and amount of EDA. The MDI-based polyurea microcapsules had a wider particle size distribution, a much rougher surface than the HDI-based polyurea microcapsules because of the rapid wall forming of MDI. The higher decomposition temperature of MDI-based microcapsules seemed to be related to the wall thickness, strong urea linkage from the rapid reaction and stiff chains of polyurea. EDA was utilized as a hardening agent for the microcapsule wall and which enhanced the microencapsulation efficiency. The sufficient amount of EDA added provided the better image intensity. This research explained the possible causes of microencapsulation and their relationship to the intensity of the images.

This thesis synthesized polyurea microcapsules containing leuco dye by interfacial polymerization. Wall materials and the ratios of core-to-wall were investigated to improve the characteristics of the microcapsules. The effect of core-to-wall ratio, wall material types (HDI, MDI and EDA) on the morphologies, particle size distribution of the resultant microcapsules, thermal properties and encapsulation efficiency were investigated. Image intensity on the dye acceptor coated paper was determined. Insufficient wall materials were found to yield and incomplete encapsulation. The factors affecting characteristics of the microcapsules depended on the structure of diisocyanate and amount of EDA. The MDI-based polyurea microcapsules had a wider particle size distribution, a much rougher surface than the HDI-based polyurea microcapsules because of the rapid wall forming of MDI. The higher decomposition temperature of MDI-based microcapsules seemed to be related to the wall thickness, strong urea linkage from the rapid reaction and stiff chains of polyurea. EDA was utilized as a hardening agent for the microcapsule wall and which enhanced the microencapsulation efficiency. The sufficient amount of EDA added provided the better image intensity. This research explained the possible causes of microencapsulation and their relationship to the intensity of the images.

This thesis synthesized polyurea microcapsules containing leuco dye by interfacial polymerization. Wall materials and the ratios of core-to-wall were investigated to improve the characteristics of the microcapsules. The effect of core-to-wall ratio, wall material types (HDI, MDI and EDA) on the morphologies, particle size distribution of the resultant microcapsules, thermal properties and encapsulation efficiency were investigated. Image intensity on the dye acceptor coated paper was determined. Insufficient wall materials were found to yield and incomplete encapsulation. The factors affecting characteristics of the microcapsules depended on the structure of diisocyanate and amount of EDA. The MDI-based polyurea microcapsules had a wider particle size distribution, a much rougher surface than the HDI-based polyurea microcapsules because of the rapid wall forming of MDI. The higher decomposition temperature of MDI-based microcapsules seemed to be related to the wall thickness, strong urea linkage from the rapid reaction and stiff chains of polyurea. EDA was utilized as a hardening agent for the microcapsule wall and which enhanced the microencapsulation efficiency. The sufficient amount of EDA added provided the better image intensity. This research explained the possible causes of microencapsulation and their relationship to the intensity of the images. This thesis synthesized polyurea microcapsules containing leuco dye by interfacial polymerization. Wall materials and the ratios of core-to-wall were investigated to improve the characteristics of the microcapsules. The effect of core-to-wall ratio, wall material types (HDI, MDI and EDA) on the morphologies, particle size distribution of the resultant microcapsules, thermal properties and encapsulation efficiency were investigated. Image intensity on the dye acceptor coated paper was determined. Insufficient wall materials were found to yield and incomplete encapsulation. The factors affecting characteristics of the microcapsules depended on the structure of diisocyanate and amount of EDA. The MDI-based polyurea microcapsules had a wider particle size distribution, a much rougher surface than the HDI-based polyurea microcapsules because of the rapid wall forming of MDI. The higher decomposition temperature of MDI-based microcapsules seemed to be related to the wall thickness, strong urea linkage from the rapid reaction and stiff chains of polyurea. EDA was utilized as a hardening agent for the microcapsule wall and which enhanced the microencapsulation efficiency. The sufficient amount of EDA added provided the better image intensity. This research explained the possible causes of microencapsulation and their relationship to the intensity of the images.