Blending of immiscible polymers in a mixing zone of a twin screw extruder—effects of compatibilization

Abstract

The dependence of the morphology development of physical as well as of reactive compatibilized polypropylene/polyamide 6 (PP/PA6) blends in a mixing zone of a co‐rotating twin screw extruder on blend composition and screw rotational speed was investigated. A special process analytical set‐up based on a co‐rotating twin screw extruder was used, which allowed melt sampling from different positions along the operating extruder in time periods less than 10 seconds. It has been shown that the disperse particle sizes in physical blends depend crucially on the blend composition because of the increasing influence of coalescence with an increasing concentration of the disperse phase. Furthermore, the morphology of physical PP/PA6 blends depends strongly on their rheological properties. In contrast, the influence of the screw rotational speed on the morphology is minor. The resulting particle size in a mixing zone is achieved already after a short screw length. The particle size of compatibilized blends is significantly smaller than in physical blends because of the better conditions for drop break‐up and the suppression of coalescence effects. Due to this, compatibilization has a stronger influence on the blend morphology than a variation of process or rheological conditions with physical blends. Furthermore, the compatibilization leads to a concurrent crystallization of the PA6 phase with the PP phase.

Effect of the dispersed phase fraction on particle size in blends with high viscosity ratio

“…I t is known that addition of compatibilizer reduces coalescence of particles in polymer blends (9,14,57). This provides a n approach to study the pure deformation and breakup effect during mixing while coalescence is suppressed.…”

“…However, it has been also reported that at high dispersed phase fractions, particle sizes of blends with high viscosity ratio (i.e. the ratio of the viscosity of the dispersed phase to the viscosity of the matrix phase) are smaller than those of blends with low viscosity ratio (14,15). This was explained based on the small deformation theory (16,17).…”

“…any researchers have shown that the size of the M dispersed phase in polymer blends increases with the increase of the dispersed phase fraction (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). However, it has been also reported that at high dispersed phase fractions, particle sizes of blends with high viscosity ratio (i.e.…”

Tensile Behaviour and Morphology of Polypropylene/Polycar-bonate/Polypropylene-graft-maleic Anhydride Blends

“…The increase in fineness of particles led to higher tensile strength and modulus [3]. In comparison, compatibilization effect has a stronger influence towards polymer blend morphology than a process variation or rheological conditions with physical blends [16]. Besides compatibilization, some works reported studies on PP/PC blends integrated with other substance.…”

Polymer Blends

“…Only a weak dependence of R on processing parameters was quite frequently observed (70,(127)(128)(129), apparently due to a non-Newtonian character of the matrix, increase in temperature in a mixer at growing mixing rate, and increasing P c with decreasing R. Mostly, quite fine morphology is readily achieved after a short time of mixing in batch mixers or in first zones of extruders (64-68, 70,128-130). On the other hand, large particles of dispersed phase with high viscosity surrounded by material with fine phase structure were found in blends with low interfacial tension (94,(131)(132)(133).…”