Rheokinetics and Characteristics of Resulted Gels during Isothermal Gelation Process for Lower Concentrated PAN/DMSO/H₂O Solutions

Isothermal gelation processes for relatively low concentration PAN/DMSO/H₂O solutions are studied by rheology. Winter–Chambon criterion is unitedly used to investigate the rheological kinetics and the structural and mechanical characteristics of the resulted gels are evaluated. It is found that during the isothermal gelation procedure, two coincident points appear sequentially, where loss tangent tan δ is independent of frequency. The occurrence of two coincident points suggests that the critical gel forms first, then it evolves into the second self-similar structure, and the average distance between crosslinks of network becomes shorter. The results also show that decreasing temperature, increase of PAN concentration or H₂O content will lead to faster gelation kinetics and formation of more elastic and compact critical gel and the second self-similar structure. At the same temperature, the later formed second self-similar structure is always more elastic and compact than the critical gel, and the corresponding gel stiffness is stronger.