The coalescence of multiphase polymer systems is a process which effective collision and coarsening behavior of dispersed particles happened after phase separation of thermodynamics incompatible polymer blending systems. In this paper

the phase coalescence mechanism and research methods of multiphase polymer systems and the coalescence behavior during processing were summarized. The coalescence process could happenned either in annealing conditions or in shearing conditions. Static coalescence means the aggregation of dispersed particles caused by multiphase polymers’s annealing under molten status. Flow driven coalescence means the aggregation of dispersed particles caused by polymers’s shearing flow under certain flow conditions. SALS (small-angle laser light scattering) is a in situ and in real time on-line observation technique

which is fit for theoretical research. Because it is inconvenient to use light scattering method in injection and screw

on-line sampling method was mainly used to research the coalescence of multiphase polymers during processing by TEM and SEM. Current coalescence researches were mainly focused on theoretical method of rheometer. Researches on coalescence behavior during processing were few although its was more significant in practice. Not only the research of regularity

mechanism and dynamical equation of coalescenceduring processing

but also the design of appropriate interfacial structure and processing technology to control the coalescence behavior of processing could achieve the stability of phase structure.