A water-insoluble dye (BL-S) was used as a probe to study the influence of some factors on the process of nucleation and nucleation mechanism in seeded semi-continuous emulsion polymerization.Some parameters were analysed for quantitative study on nucleation mechanisms

the parameters include the amount of dye incorporated into the resultant latex particles (Pdye)

number of the resultant latex particles (Ncp) and the different numbers of particles which are formed by micellar nucleation (Nm) and homogeneous nucleation (Nh).The results of the study and analysis show that Pdye

Nh

Nm and Nh/Ncp all increase with increasing initiator concentration ［I］

but Nm/Ncp decreases as Nm/Ncp=-0.0262［I］+0.8833

which can illuminate the proportion of homogeneous nucleation increases while micellar nucleation decreases with increasing ［I］.The influence of the emulsifier concentration ［E］ on nucleation mechanisms is different at different concentration range

when ［E］ equals to 0.7216×10-2 mol·L-1

the proportion of homogeneous nucleation is equal to micellar nucleation

both of them are 50%.When ［E］ is greater than 0.7216×10-2 mol·L-1

the nucleation time t1

2 decreases and Nm/Ncp increases with increasing ［E］

Nh/Ncp decreases accordingly

and the proportion of micellar nucleation is larger than homogeneous nucleation

so that the micellar nucleation mechanism predominates gradually in the particle nucleation process; when ［E］ is less than 0.7216×10-2 mol·L-1

the proportion of micellar nucleation is less than homogeneous nucleation

the main nucleation mechanism becomes to homogeneous nucleation.In the system of MMA/BA copolymerization

when fMMA increases from zero to 06

the value of Nm/Ncp decreases from 80.93％to 50％

which means that the proportion of micellar nucleation is larger than that of homogeneous nucleation

so that micellar nucleation plays a key role in the particle formation period.When fMMA increases from 0.6 to 1

Nm/Ncp is reduced to 40% and Nh/Ncp is raised to 60％

but homogeneous nucleation is more important than micellar nucleation in this system.In addition

the t1

2 is 12 min and 6 min for the conventional and seeded semicontinuous emulsion polymerization

respectively

but Pdye change is less.All these show that the both semicontinuous emulsion polymerization techniques only have some effect on the formation process of particles and the neculeation time

but little effect on their specific nucleation.