STUDY OF THE AMOUNT OF SURFACTANT IN THE CORE-SHELL EMULSION POLYMERIZATION

Abstract

In order to prepare a core-shell structure latex with a narrow size distribution and without the secondary nucleation to form new latex particles,a method was given for calculating the amount of surfactant,sodium dodecyl sulfate(SDS),in the process of multi-step seeded semi-continuous emulsion polymerization.From the total area of soap adsorbed particles and the effective molecular surface area of the soap,the above quantities can be calculated.In this method,the number of particles was the weight of monomer divided by the average particle weight,the seed particle density and average particle size could be measured by weighing strips of particles of measured volume and TEM,and the effective molecular surface area of the soap could be determined by soap titration.The influence of the amount and dropping speed of surfactant in every polymerization stage on the particles structure was studied.The amount of surfactant needed in the second and third polymerization stage was decided by both the amount surfactant added in the seeded polymerization and the particle size of seeds.A core-shell latex was synthesized with a narrow size distribution and without secondary nucleation when the amount of monomer for the seed,core and shell was 12 g,50 g and 50 g,the amount of surfactant was 0.4 g,0.64～2.07 g and 0.04～2.12 g,respectively,and the dropping speed of pre-emulsified monomer was below 0.021 mol/min.The core-shell morphology,size distribution of the final latex were confirmed by TEM analysis.