Viscoelastic Behavior of Polyacrylonitrile/Dimethyl Sulfoxide Concentrated Solution during Thermal-Induced Gelation

摘要

Thermal-induced gelation of polyacrylonitrile(PAN)/dimethyl sulfoxide(DMSO)concentrated solution has been Theologically investigated in relation to temperature and aging.Phase behavior of PAN/DMSO solution was studied through examining the intrinsic viscosities[eta].The gelation temperature T_g,gel time t_g,and the critical values of relaxation exponent n were obtained by measuring the viscoelastic functions(G',G",tan 5,and eta*)based on the Winter and Chambon theory.The solution with higher PAN concentration was found to be more sensitive to the temperature,which makes it gel at a higher temperature.The n value,however,changes little with varied concentration.The gel strength S was found to depend on the concentration of the solution.Gelation of the 23 wt % PAN/DMSO solution occurs after being aged at 25 °C for a period of time,i.e.,gel time t_g.The critical n value(S value)at t_g was larger(smaller)than that at T_g in the cooling process,attributed to the different critical feature of the PAN gels formed in different conditions.The power law relations eta_0 propor.to epsilon~(-gamma)and G_e propor.to epsilon~z were found to be valid for PAN/DMSO solution before and beyond the gel time ts,respectively.