Changes in molecular dynamics during the bulk polymerisation of an epoxide/boroxine mixture as studied by dielectric relaxation spectroscopy, revealing direct evidence for a floor temperature for reaction

Chain Dynamics in Solid Polymers and Polymerizing Systems as Revealed by Broadband Dielectric Spectroscopy

“…an elastomer is formed. Williams and coworkers [86] demonstrated that there was a Floor Temperature T Floor at 72 8C for this reaction mixture. For T cure > T Floor sustained molecular mobility during reaction allows it to go to chemicalcompletion, so an elastomer is formed.…”

“…They applied a modification of the KWW-function to their curing data and determined how tðt c Þ h ivaried with cure-time t c at different cure-temperatures T cure . These and related studies show [81][82][83][84][85][86] that a reaction becomes diffusion-controlled at long times, through the reduced mobility of chains, and leads to the formation of a polymer glass. Fournier and coworkers [85] proposed a kinetic theory for diffusion-controlled step-polymerization reactions to quantify their extensive real-time BDS data for an epoxide-amine thermosetting system.…”

“…This is the preferred route to obtain practical materials in the form of adhesives and electrical insulators. Williams and coworkers [86] made real-time multi-frequency BDS studies of an epoxide/boroxine mixture of a fixed composition, at cure-temperatures in the range 60-120 8C. Figures 6a and 6b show the 3D-plots of e 00 vs. {log f/Hz, temperature / 8C} for T cure equal to 65 8C and 75 8C, respectively.…”

“…On the basis of their results, Williams and coworkers [86] proposed an extension to the well-known TTT contour-diagram of Gillham [87,88] for the temperature-time behaviour of bulk thermosetting reactions to include T Floor . This is shown schematically in Figure 7.…”

Real time dielectric monitoring of glass transition in n-vinyl pyrrolidone polymerization

“…Studies by Shephard and Senturia [1], Kranbuehl et al [2,3], Johari [4][5][6], Rolla [7] Williams [8][9][10], Mijovic [11][12][13] and Friedrich [14] were mostly devoted to epoxy systems and their modifications. These works established the dipolar aspects of molecular dynamics, a-and b-relaxation kinetics, and the contribution of different relaxation processes to the dielectric function.…”