Study On Mechanism Of Flame Retardant Microcapsules By Multiple Emulsion Method

In this paper, the microcapsules were synthesized by W/O/W multiple emulsion method, with DMMP as the core material and the acetual product of polyvinyl alcohol (PVA) and glutaraldehyde (GA) as the shell material.The work mainly consisted of four parts. In the beginning, research was focused on the stability of W/O emulsion. Then factors affecting the average particle size and distribution of microcapsules were discussed. Then, the migration mechanism of polyvinyl alcohol (PVA) and glutaraldehyde (GA) was deduced. Finally, ignited cigarette test on canvas was conducted.Based on the stability tests of W/O emulsion, the optimal technical-parameters for preparation of W/O emulsion were confirmed as follows, water content: 60 %vol; ratio of Span80 and Tween80: 4/1(v/v); amount of surfactant: 3.5 %vol; pH value of water phase: 1.05; emulsification temperature: 40℃; time of emulsification: 20min; emulsification intensity: 1500rpm.Premised on the single-factor experiments of microcapsule preparation, factors affecting the average particle size and distribution of microcapsules were formulated. Those factors included water content, amount of surfactant, amount of catalyst HCl, concentration of PVA, time of emulsification and solidification, intensity of emulsification and solidification. However, affecting regularity of GA amount was not detectable.By the comparison of average particle size among inner phase droplets, W/O emulsion droplets, W/O/W multiple emulsion droplets and microcapsules, the migration mechanism of PVA and GA was found. The shell of microcapsules was formed at the interface between middle phase and outer water phase by the acetual reaction of GA with PVA as GA passed through middle phase to outer water phase.