Abstract
Control of the phase structure evolution in flowing immiscible polymer blends during their mixing and processing is fundamental for tailoring of their performance. This review summarizes present state of understanding and predictability of the phase structure evolution in flowing immiscible polymer blends with dispersed structure. Results of the studies of the droplet breakup in flow, important for determination of the droplet breakup frequency and of the size distribution of the daughter droplets, are reviewed. Theories of the flow-induced coalescence providing equations for collision efficiency are discussed. Approximate analytic expressions reliably describing dependence of the collision efficiency on system parameters are presented. Available theories describing the competition between the droplet breakup and coalescence in flow are summarized and approximations used in their derivation are discussed. Problems with applicability of available theories on prediction of the droplet size evolution during mixing and processing of immiscible polymer blends, which have not been broadly discussed so far, are addressed.
Highlights
End-use properties of immiscible polymer blends are strongly affected by their phase structure, which is formed during their preparation and processing
The aim of this paper is to present theories of the droplet breakup, coalescence, and the competition between them which can be utilized for understanding and evaluation of the phase structure formation in polymer blends
The use of effective interfacial tension or the above concept of the dynamic equilibrium between the deforming and deformation-resisting forces for viscoelastic systems leads to the same qualitative conclusion: Cac increases with N1,d (G’d ) but decreases with increasing N1,m (G’m ) of the matrix with respect to the related Newtonian system
Summary
End-use properties of immiscible polymer blends are strongly affected by their phase structure, which is formed during their preparation and processing. An important group of polymer blends are blends with droplets in matrix morphology (e.g., plastics with impact strength enhanced by the addition of elastomers) For this type of blends, micro-rheological events controlling the size of dispersed droplets are qualitatively understood. I.e., time-independent droplet size distribution, is achieved after long enough steady flow of the blend when the blend components degradation is avoided. It relates to long enough mixing of a blend with properly stabilized components in batch mixers. The aim of this paper is to present theories of the droplet breakup, coalescence, and the competition between them which can be utilized for understanding and evaluation of the phase structure formation in polymer blends. The further aim is a discussion of the plausibility of available approximate theories for the prediction of the droplet size formed by mixing and processing of polymer blends
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