Chemorheological studies on a dicyanate resin modified with polyethersulfone

Abstract

The chemorheology of a dicyanate resin modified with a polyethersulfone (PES) was investigated. The rheological and dielectrical property changes during curing of the dicyanate resin system catalyzed by an organic metal salt were monitored by a rheometer and dielectric analyzer, respectively, and used to investigate the curing behavior and chemorheology of the resin system. The curing rate of the dicyanate resin system decreased as the PES content was increased. A function that can describe the viscosity change of the dicyanate resin system during curing was determined by a nonlinear regression method using the rheometer data. The gelation time of the dicyanate resin system decreased with increasing isothermal curing temperature and with decreasing PES content. The curing behavior of the dicyanate resin system monitored by the dielectric analyzer coincided fairly well with that measured by the rheometer Copyright © 2004 Society of Chemical Industry

A Reactive Blending Method for Preparation of Polyvinyl Chloride/Thermosetting Polyurethane Blends

“…Temperature affects the viscosity of a curing thermoset in two opposing ways. Raising the temperature will cause the viscosity to drop but will also raise the reaction rate, causing an increase in the viscosity [27] . In this heating period, the viscosity increase due to reaction progression is not high enough to counter the dilution effect of temperature on the viscosity.…”

“…2, a steep increase of the complex viscosity is observed. The gel time can be determined as the time when the viscosity of the reacting system tends to infinity [27] ; however, it is not easy to determine the exact time of the abrupt viscosity rise. The curing of thermosets has been monitored by recording the evolving values of G 0 and G 00 during cure, and the gel time has also been determined as the point at which the curves of storage and loss modulus cross each other [23,27,28] .…”

“…The gel time can be determined as the time when the viscosity of the reacting system tends to infinity [27] ; however, it is not easy to determine the exact time of the abrupt viscosity rise. The curing of thermosets has been monitored by recording the evolving values of G 0 and G 00 during cure, and the gel time has also been determined as the point at which the curves of storage and loss modulus cross each other [23,27,28] . For instance, the evolution of G 0 and G 00 at the temperature of 120 C, the strain of 1%, and the frequency of 10 s À1 is plotted against time in and G 00 intensifies as a result of formation of a threedimensional network throughout the system until the curves of viscoelastic moduli cross each other [29] .…”

“…The gelation temperature, T gel , has been determined from dynamic temperature ramp (temperature sweep) experiments. The temperature corresponding to the chemical gelation is manifested by a dramatic increase of the viscosity and viscoelastic moduli (storage modulus [G 0 ] and loss modulus [G 00 ]) [26,27] . Figures 1a and 1b depict the results of temperature sweep experiment at the strain amplitude of 1% and frequency of 10 s À1 .…”

“…The gelation temperature has been essentially determined from the inflection point of the elastic moduli curve in the temperature corresponding to its sharp increase (T gel-inflection ) [26] . Moreover, the gelation temperature has been determined as the point at which G 0 and G 00 crossover takes place (T gel-crossover ) [27] . In the present research work, the gelation temperatures, which were calculated using both criteria, are marked in the curves of G 0 and G 00 versus temperature.…”