The Research On "Phase Inversion" Mechansion Of Preparing PA6 And PA6/12 Microspheres

A novel method has been developed for the synthesis of PA6/PS, PA6/12/PS blends based on polystyrene (PS) and lactam (caprolactam-CL, lauryllactam-LL) via successive in-situ free radical polymerization and anionic ring-opening polymerization. Various characterization methods, such as FTIR, SEM, DSC were carried out to investigate the morphological structure, thermal properties and so on. The main results are as follows:(1) The morphology of PA6/PS blends reveals that phase inversion occurs at extremely low PS content, the morphology characteristic of the blends transferred from "dispersed PS minor phase/PA6 matrix" to "dispersed PA6 minor phase/PS matrix", in which PA6 finely dispersed in PS continuous phase. Since the viscoelastic difference between PS and PA6, dynamic asymmetry became the characteristic feature of the system studied, which leads to the formation of special morphology in anionic ring-opening of CL in the presence of PS.(2) The molecular weight of PS has a strong effect on morphology in anionic ring-opening of CL. Onset of the phase inversion changes with the molecular weight of PS, the lower the PS molecular size, the lower the PS content at which the PA6 finely dispersed droplet phase is generated. Furthermore, the particle size of PA6 microspheres will change with the molecular weight of PS.(3) Polymerization temperature has a certain influence on the morphology of PA6/PS. when the polymerization temperature rise, the polymerization and phase separation rate will rise as well. Moreover it will enhance the effect of polymerization induced phase separation and destroys the structure of "dispersed PA6 minor phase/PS matrix".(4) Rising of the concentrations of initiator and activator will make the polymerization rate accelerate as well. The great dynamic asymmetry between PA and PS will breach the regularity of PA6/PS morphology.(5) PA6/12 microspheres with tunable diameters are prepared based on in-situ PA6/12/PS blends with "dispersed PA6/12 minor phase" morphology feature.