Interfacial reactive blending, effect

Marie et al. (2001) have studied PA blends with poly(dimethylsiloxane) (PDMS) either in binary blends of the functionalized polymers or in ternary blends with a functionalized styrene copolymer. The efficiency of copolymer formation concurrent with morphology development and stabilization was studied for reactions between PA-amine and PDMS-anhydride, between PA-amine and PDMS-epoxy, and between PA-carboxylic acid and PDMS-epoxy. The effects of relative melt viscosities on interfacial reactivity and resulting morphology were noted. 

Figure 3.9 Effect of the interfacial reaction on the morphology development of non-reactive and reactive blends of PS/PMMA (60/40) as a hmction of time [58]...

Nevertheless, there are many similarities in morphology development of reactive and non-reactive blends. Indeed, much of our knowledge concerning reactive blends has been obtained through comparison with or extension fi om knowledge of non-reactive blends. The discussion, which follows thus, generally applies to both types of blends, with special emphasis on the effects of the interfacial chemical reaction. 

The interfacial chemical reaction changes the dynamics of the phase inversion process. Sundaiaraj et al. [25] systematically studied the phase inversion process in a reactive polyarylate/ethylene-ethyl acrylate-glycidyl methacrylate rubber blend where the extent of interfacial chemical reaction was controlled by the addition of stearic acid. The primary effects of the interfacial reaction were to delay phase inversion and increase the mixing torque rise associated with it. Figure 5.6 illustrates both of these points. They attributed these effects to the fact that in reactive blends steric stabilization of the... 

Suppression of domain coalescence in the melt flow regime is one of the most important effects of the interfacial reaction on morphology and morphology development. Simdararaj and Macosko [33] have conducted a careful study of morphology as a function of dispersed phase voliune fraction in reactive and non-reactive blends to discern the influence of the reaction. Figure 5.9 illustrates the dependence of the dispersed phase domain size on the dispersed phase concentration for typical uncompatibilized blends. At dispersed phase concentrations less than about 0.5 wt.% the system is dilute enough that coalescence is insignificant due to the very low frequency of dispersed phase domain... 

As described above in the section on morphology development, there are several separate mechanisms responsible for the effects of the interfacial reaction on the final morphology. Empirical means may be used to separate some of these simultaneous effects. For example, Scott and Macosko [41] successfully separated the effects of increased mixing torque and changing component rheologies as a fimction of temperature from other effects of the chemical reaction. They utilized Wu s [55] empirical equation for rubber particle diameters in reactive blends with polyamide 66 and poly(ethylene terephthalate) prepared in twin screw extruders ... 

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