Effects of the shear flow on a homogeneous polymeric reaction

Abstract

The reaction kinetics of the postamidation of polyamide 6 in the melt was studied by a new rheological method, and the reaction rate constant was calculated to be about 0.087 kg/mol min at 2508C. To study the effects of the shear flow on a homogeneous polymeric reaction, a more practical technique was used to select the data that responded only to the reaction without the effect of different shear flows. The experimental results showed that the reaction rate constant decreased with an increase in the shear rate. Moreover, the decreases in the rates were different under different shear modes: the reaction rate constant decreased slightly under oscillatory shear but strongly under steady shear. Possible reasons for these phenomena were examined.

Flow Accelerates Interfacial Coupling Reactions

“…This suggests that dynamic shear can promote the coupling reaction when the initial interface has only a low coverage of block copolymer. However, the dramatic viscosity increase reported by Kim et al and Xie et al was not observed for the PS/PMMA bilayer, as discussed in the Appendix. − ,− …”

“…SM640 was also sheared dynamically under various conditions, with frequencies ranging from 0.05 to 10 rad/s and strain amplitudes from 0.05 to 15%. The reaction conversion did not change significantly. , Kim et al and Xie et al reported that dynamic shear could have significant effects on coupling reactions. − ,− However, the samples used in their studies were laminated rather than extruded, and little reaction happened during the lamination process. Therefore, we speculate that the minimal reaction observed with SM640 under dynamic shear was due to the interface already being highly covered with block copolymer.…”

“…37,44 Kim et al and Xie et al reported that dynamic shear could have significant effects on coupling reactions. [9][10][11][19][20][21] However, the samples used in their studies were laminated rather than extruded, and little reaction happened during the lamination process. Therefore, we speculate that the minimal reaction observed with SM640 under dynamic shear was due to the interface already being highly covered with block copolymer.…”

“…However, the dramatic viscosity increase reported by Kim et al and Xie et al was not observed for the PS/PMMA bilayer, as discussed in the Appendix. [9][10][11][19][20][21]…”

“…The graft or block copolymers formed in situ by coupling of functional polymers stabilize the blend morphology and improve mechanical properties. During the past two decades, many aspects of reactive blending have been investigated, − for example, reactivity, architecture, molecular weight, , and concentration of functional polymers as well as molecular weight and thermodynamics of matrix polymers . For most of those studies, a bilayer sample geometry with a flat interface was annealed quiescently in order to separate reaction kinetics from interfacial area generation caused by the complex flows during melt blending.…”