The interface in binary mixtures of polymers containing a corresponding block copolymer: Effects of industrial mixing processes and of coalescence

Abstract

In theories of the minor phase (domain) formation in polyblends rendered as emulsions it is usually assumed that the size and shape of the domains are the result of melt viscosity effects (Taylor, Wu) or viscoelasticity effects (VanOene, Elmendorp) being balanced by interfacial tension. This assumption would predict a monotonic decrease of the domain size to a final limiting size with increasing energy of mixing. However, a systematic study of the dependence of domain morphology on industrial mixing processes which was carried out on a "model" LDPE/PS (2/1) mixture and the related polyalloy (i.e., the same mixture with a corresponding block copolymer as compatibilizer) does not support this expectation. Domain size was found to go through a minimum a s mixing energy was increased. A similar minimum was seen in data on specific volume of the melt vs. mixing energy, which indicates a correlation between melt specific volume and domain size. Calculation of the approximate surface area of the domains using a simple model of domain shape indicated that total interfacial energy in the polyblend and/or polyalloy is a trivial part of the mixing energy introduced. These calculations also indicated that if compatibilizer was located entirely at the interface, the surface layer would have a thickness of about 90 nm. Some micrographs seem to show such a surface layer. We propose that a n abrasion mechanism is responsible for the early stage of the dispersion process, and that the final domain size may be controlled by a dispersion-coalescence equilibrium. This is compared with the theories of final particle size proposed by VanOene and Wu. A. P. Plochocki, S. S. Dagli, a n d R. D. A n d r e w s groups the larger domains in the vicinity of the extrudate courtesy of M . J . Doyle, Exxon Corp. center (right hand side of the photograph) (cf. 31 b).

Mixing of viscous immiscible liquids. Part 1: Computational models for strong–weak and continuous flow systems

“…The average size increases with increasing interfacial tension, while the width of the distribution appears to be una ected. The trend in the average size agrees with experiments from the literature (Wu, 1987;Plochocki, Dagli, & Andrews, 1990), however, there are no experimental data to compare with the width of the distribution. Based on the local processes, explanation of this trend is as follows:…”

Influence of compatibilizer addition on particle size and coalescence in TPU/PP blends

“…has been studied. 8,18,19 For surfactants in Newtonian systems, coalescence is suppressed by steric hindrance of the surfactant located at the interProcessing face between two liquid components. 20 A similar mechanism has been proposed by Sundararaj…”

Electrical and mechanical properties of grafted and ungrafted polyacrylamide-rubber blends

“…5 Several strategies have been employed to minimize the phase separation and to increase the interfacial adhesion that include the addition of physical or chemical comatibilizers. 6,7 Even though blending is an easy method for the preparation of thermoplastic elastomers (TPEs), most of the TPE blends are immiscible. Very often, the resulting materials exhibit poor mechanical properties due to the poor adhesion between the phases.…”