Jørgen Lyngaae-Jørgensen

Phase continuity and inversion in polystyrene/poly(methyl methacrylate) blends

Dual-phase continuity and phase inversion of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends processed in a twin-screw extruder was investigated using a selective extraction technique and scanning electron microscopy. Emphasis was placed on investigating the effects of viscosity ratio, blend composition, processing variables (mixing time and annealing) and diblock copolymer addition on the formation of bi-continuous phase structure (BPS) in PS/PMMA blends. The experimental results were compared with the volume fraction of phase inversion calculated with various semi-empirical models. The results showed that the formation of a BPS strongly depends on the blend composition and the viscosity ratio of the constituent components. Furthermore, BPS was found in a wide volume fraction interval. Increasing the mixing time and the addition of diblock copolymer, both led to a narrowing range of volume fraction in which BPS exists. Quiescent annealing coarsened the structure but indicated no qualitative changes. Some model predictions for phase inversion could predict qualitative aspects of the observed windows of co-continuity but none of the models could account quantitatively for the observed data.

Structuring polymer blends with bicontinuous phase morphology. Part II. Tailoring blends with ultralow critical volume fraction

Abstract A hypothesis providing a guideline for the development of immiscible polymer blends with co-continuous phase structure at very low critical volume fraction of one component is postulated and experimentally verified. Based on a number of simplifying assumptions the following relation was derived: φ cr =k(λ γ ) 1−z /(θ b ∗ ) z where λ γ is a Deborah number and θ b ∗ is a dimensionless break-up time. The equation parameters, k and z are constant that depend on the flow field hence on the blending equipment. For the studies an internal mixer with Walzenkneter-type 30 mixing shafts was used. For this equipment the experimental values of the equation parameters, k=1801 and z=2.01, were found.

Coalescence in an interface-modified polymer blend as studied by light scattering measurements

Abstract The influence of A—B diblock copolymers on coalescence in A:B blends has been studied by rheo-optical measurements and electron microscopy. Divergent criteria and experimental evidence appear in the literature on the block copolymer (BC) molecular weight (MW) and volume fraction (ϕbc) when the requirement is the BC to reside at the interface. In the present study the block chain lengths were chosen shorter than the corresponding homopolymers as a starting point. For selected model systems it was found that symmetrical diblock copolymers with ϕbc ≥ 1% were most effective for inhibiting coalescence. However, rheo-optical measurements revealed that the stabilization effect is not unconditional during the flow; coalescence is prevented for a time which decreases with increasing shear rate due to removal of the BC away from the interface. The origin of the observed behaviour is discussed based on various mechanisms: shear-induced mutual compatibility between components, squeeze-out/drainage of the interfacial layer, frictional pull-out of BC chains, collision-induced entrapment of BC between interfaces, encapsulation of the BC based on the concept of elastic interfacial curvature.

Polypropylene and polyethylene blends

SummaryThe flow behaviour of blends of an isotactic polypropylene (PP) and a high density polyethylene (PE) in the molten state was studied as a function of composition, temperature and shear rate to examine the degree of compatibility under shear. PP and PE were melt blended in a laboratory single screw mixing extruder at the compositions 0, 25, 50, 75 and 100 percentage of PE by weight and shear stress versus shear rate data were obtained using an Instron capillary viscometer at different temperatures. Viscosity-shear rate data of PP-PE blends at different temperatures constitute “master curves” at constant blend composition, when plotted as η/η0 versus

Bonding at Compatible and Incompatible Amorphous Interfaces of Polystyrene and Poly(Methyl Methacrylate) Below the Glass Transition Temperature

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Autoadhesion of high-molecular-weight monodisperse glassy polystyrene at unexpectedly low temperatures

η0/T. This type of behaviour is commenly observed for homopolymer systems. Therefore these experimental findings indicate that the PP-PE system forms either a compatible blend in the molten state under shear flow conditions or a morphology which is independent of temperature.ZusammenfassungEs wurde das Fließverhalten von Mischungen eines isotaktischen Polypropylens (PP) und eines Polyäthylens mit hoher Dichte (PE) im Schmelzzustand untersucht in Abhängigkeit von der Zusammensetzung, der Temperatur und der Schergeschwindigkeit. Damit sollte der Grad der Kompatibilität unter Scherbeanspruchung geprüft werden. PP und PE wurden in einem Labor-Einschnecken-Misch-Extruder mit Anteilen von 0, 25, 50, 75 und 100 Gewichts-Prozent PE zusammengemischt. Die Fließkurven wurden bei verschiedenen Temperaturen in einem Instron-Kapillar-Rheometer gemessen. Die Viskositätsverläufe als Funktion der Schergeschwindigkeit bei verschiedenen Temperaturen lassen sich bei konstantem Mischungsverhältnis zu „Masterkurven“ zusammenfassen, wenn man η/η0 gegen

Domain Stability During Capillary Flow of Well Dispersed Two Phase Polymer Blends. Polystyrene/Polymethylmethacrylate Blends

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