The influence of thermal aging on dispersion stability and mechanical stability of styrene butadiene latex(SBL) was studied.It was found that with increasing the aging temperature

the SBL particles are easy to coagulate together and to form a solid gel within a short time period.However

the gelation ratio determined by Maron test showed that the mechanical stability remarkably increased for the thermal aged samples.To clarify the mechanism of the abnormal phenomenon

FTIR

GPC

as well as stress-strain behavior of the thermal aged SBL system were investigated.It is found that the reduction of dispersion stability is mainly due to lowering the barrier energy between the latex particles

and thermal degradation of poly(styrene-butadiene) in the colloid state is not oxidized into carbonyl group at the double-bond site

but turns into cross-linking between the macromolecules

resulting in an increase of mechanical strength of the SBL film.Correlation of the tensile modulus at 300% strain to the gelation ratio demonstrated that the improvement of the mechanical stability was originated from crosslink-induced high tensile modulus of the SBL particles.