Morphology of Compatibilized Ternary Blends

In this work, the evolution of the morphology of polypropylene/polystyrene/poly(methyl metacrylate) (PP/PS/PMMA) blends to which graft copolymers polypropylene-graft-polystyrene (PP-g-PS) of 2 compositions (55/45 and 70/30), polypropylene-graft-poly(methyl metacrylate) (PP-g-PMMA), or styrene-block-(ethylene- co-butadiene)-block-styrene (SEBS) was added has been studied. The ternary blends morphologies were predicted using phenomenological models that predict the morphology of ternary blends as a function of the interfacial tension between the blend components (spreading coefficient and free energy minimization). All blends studied presented a core-shell morphology with PS as shell and PMMA as core. The addition of PP-g-PS or SEBS resulted in a reduction of the size of the PS shell phase and, the addition of PP-g-PMMA did not seem to have any effect on the diameter of PMMA. The difference observed between the different morphologies relied on the number of droplets of core within the shell. All the phenomenological models predictions corroborated the experimental results, except when PP-g-PMMA was added to the blend.     

Interfacial tension and acid‐base approaches to polymer interactions

A significant correlation has been shown to exist between the interfacial tension of polymer pairs and their acid‐base pair interaction. The relationship is inverse, with interfacial tensions decreasing as acid‐base interactions increase. Interfacial tensions, frequently used as an indicator of polymer compatibility, were measured by the breaking thread method at temperatures in the vicinity of 200 °C. Acid‐base pair interaction values were measured by inverse gas chromatography over wide temperature ranges. The observed correlation confirms the important contribution made by short‐range, acid‐base interactions to the observed value of interfacial tension and supports the prediction of equations based on fundamental definitions of surface forces. A collateral finding of this work is the decrease of acid‐base functionality with rising temperature for all polymers studied. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2096–2104, 2000     

The influence of partial emulsification on coalescence suppression and interfacial tension reduction in PP/PET blends

This study examines how the relative role of coalescence suppression and interfacial tension reduction influence the particle size at various levels of in situ compatibilization. The polymers studied are polyethylene terephthalate (PET) as matrix and a polypropylene (PP) as dispersed phase compatibilized by a triblock copolymer of poly(styrene–hydrogenated butadiene–styrene) (SEBS) grafted with maleic anhydride. The interfacial tension was studied by the breaking‐thread method, and it was used along with the morphology to characterize the emulsification efficacy of the copolymers. By modifying the concentration of MA grafted on the SEBS, different levels of emulsification of the blends were obtained. A comparison of 1/99 and 10/90 PP/PET blends compatibilized by SEBS‐g‐MA allows one to distinguish the relative role of interfacial tension and coalescence suppression in diminishing particle size. It is shown that varying degrees of residual coalescence remain, depending on the level of %MA in the copolymer. A detailed study of the 2%MA system below interfacial saturation was carried out to shed further light on the dependence of coalescence suppression on emulsification level and interfacial coverage. After separating out the contribution of interfacial tension on particle size reduction, it is shown that coalescence suppression for this system increases gradually with areal density of modifier at the interface right up to the region of interfacial saturation. Finally, the interfacial and morphological data were used to test the ability of the Lee and Park model to describe coalescence in polymer blends. Reasonable agreement was found between the parameter c₁, describing the coalescence in that model, and the trends related to residual coalescence from this study. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 939–951, 1999     

On the wall slip of polymer blends

The slip flow of the polypropylene (PP)/poly[ethylene‐co‐(vinyl acetate)] (EVA) system was studied in a capillary rheometer for shear rates of 40–1000 s^?1 at four temperatures. Three dies made of aluminum with a length/diameter (L/D) ratio of 15 and diameters of 1.59, 1.19, and 0.79 mm provided the flow data. Calculations of the slip velocity by the Mooney method showed power‐law behavior with the stress. Blends were prepared at various proportions of PP and EVA for observation of the variation of the slip velocity for different compositions and temperatures. Direct microscopic observations of the slip layer on extruded samples showed domains of the dispersed phase unevenly distributed between the slip layer and the core and provided estimates of the thickness of the layer adjacent to the capillary wall. Results showed that the viscosity in the slip layer was 10–100 times lower than that in the bulk for the same value of the shear stress. In terms of the extrapolation length, the development of the slip layer was the result of different disentanglement dynamics of the molecules in the slip layer in comparison with those in the bulk. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 303–316, 2002     

The relative role of coalescence and interfacial tension in controlling dispersed phase size reduction during the compatibilization of polyethylene terephthalate/polypropylene blends

The breaking thread and the sessile drop methods have been used to evaluate the interfacial tension between a polypropylene (PP) and a polyethylene-terephthalate (PET). An excellent correlation was found between the two. The breaking thread technique was then used to evaluate the interfacial tension of these blends at various levels of a styrene-ethylene butylene-styrene grafted with maleic anhydride (SEBS-g-MA) compatibilizer. In order to evaluate the relative roles of coalescence and interfacial tension in controlling dispersed phase size reduction during compatibilization, the morphology of PP/PET 1/99 and 10/90 blends compatibilized by a SEBS-g-MA were studied and compared. The samples were prepared in a Brabender mixer. For the 10/90 blend, the addition of the compatibilizer leads to a typical emulsification curve, and a decrease in dispersed phase size of 3.4 times is observed. For the 1/99 blend, a 1.7 times reduction in particle size is observed. In the latter case, this decrease can only be attributed to the decrease of the interfacial tension. It is evident from these results that the drop in particle size for the 10/90 PP/PET blend after compatibilization is almost equally due to diminished coalescence and interfacial tension reduction. These results were corroborated with the interfacial tension data in the presence of the copolymer. A direct relationship between the drop in dispersed phase size for the 1/99 PP/PET blend and the interfacial tension reduction was found for this predominantly shear mixing device. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2271–2280, 1997     

Interfacial tension coefficient from the retraction of ellipsoidal drops

A new method for the determination of the interfacial tension coefficient between two immiscible fluids is proposed. The method is particularly useful for the binary polymer blends. The deformed drop retraction method, DDRM, makes it possible to determine the dynamic interfacial tension coefficient, ν, from the time evolution of a distorted fluid drop toward its equilibrium form. Analysis of this interfacial tension-driven process led to a theoretical relation between the shape retraction rate and the system's geometrical and rheological characteristics. Measurements of either low viscosity model systems or high viscosity industrial polymer mixtures led to a good agreement with values obtained from the widely used breaking thread method. DDRM enables to measure ν in polymeric blends of commercial interest—the high viscosity systems that would be very difficult to characterize by other techniques. Furthermore, for the first time it is possible to follow the time dependence of the interfacial tension coefficient, thus unambiguously determine the dynamic and equilibrium values of ν₁₂. For example, in low density polyethylene blends with polystyrene, LDPE/PS, ν decreased with the polymer-polymer contact time, t_c, from ν = 6.9 mN/m at t_c = 12 min, to ν = 5.2 mN/m at t_c ≥ 75 min—the latter may represent the true thermodynamic equilibrium value, ν₁₂. However, it is not clear whether such a reduction is exclusively due to the thermodynamically driven migration of chain-ends, low molecular weight fractions and additives, or by the thermal degradation as well. The contact time dependence of ν explained some of the differences reported for the data obtained using different measurement techniques, viz. pendant drop, capillary breakup, or ellipsoid retraction techniques. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1393–1403, 1997     

热致液晶／PEEK／嵌段共聚物共混体系的结构与性能

用ＷＡＸＤ、ＳＥＭ及力学性能测试等研究热致液晶／ＰＥＥＫ／嵌段共聚物三元共混体系形态、结构和性能。结果表明嵌段共聚物的加入，使体系具有一定的相容性和较好的界面粘接，共混物的强度、模量有一定的提高，对共混物的结晶行为具有明显的影响，当热致液晶含量高时，基材与液晶两相间出现明显的分离现象，即“皮－芯”结构．     

Biosourced Poly(lactic acid)/polyamide-11 Blends: Effect of an Elastomer on the Morphology and Mechanical Properties

Fully biobased polylactide (PLA)/polyamide-11 (PA11) blends were prepared by melt mixing with an elastomer intermediate phase to address the low elasticity and brittleness of PLA blends. The incorporation of a biobased elastomer made of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene oxide (PEO) copolymers was found to change the rigid interface between PLA and PA11 into a much more elastic/deformable one as well as promote interfacial compatibility. The interfacial tension of the polymer pairs and spreading coefficients revealed a high tendency of PEO to spread at the PLA/PA11 interface, resulting in a complete wetting regime (interfacial tension of 0.56 mN/m). A fully percolated rubbery phase (PEO) layer at the PLA/PA11 interface with enhanced interfacial interactions and PLA chain mobility contributed to a better distribution of the stress around the dispersed phase, leading to shear yielding of the matrix. The results also show that both the morphological modification and improved compatibility upon PEO addition (up to 20 wt %) contributed to the improved elongation at break (up to 104%) and impact strength (up to 292%) of the ternary PLA/PA11/PEO blends to obtain a super-tough multiphase system.     

Influence of hyperbranched polymers on the interfacial tension of polypropylene/polyamide‐6 blends

The compatibilizing effect of polypropylene (PP) grafted with hyperbranched polymers (PP–HBP) has been investigated in PP/polyamide‐6 (PA‐6) blends. Because of its high reactivity and diffusitivity, PP–HBP has been shown to be a more effective compatibilizer in decreasing the interfacial tension than the commonly used maleic anhydride–grafted polypropylene (PP–MAH). This article describes the influence of PP–HBP and PP–MAH on the interfacial tension between PP and PA‐6, as measured by the deformed drop‐retraction method (DDRM). Overall, PP–HBP yielded lower interfacial tension values between PP and PA‐6, which resulted in a finer particle size of the secondary phase. The time dependence of the interfacial tension can be monitored by DDRM, enabling evaluation of the diffusitivity and reactivity of the compatibilizer. A model based on particle coarsening has been developed to describe the time dependence of the interfacial tension. This model showed that the diffusitivity and reactivity for PP–HBP was higher than that of PP–MAH. Therefore, PP–HBP has strong potential as a compatibilizer in diffusitivity‐dependant processes such as film coextrusion and fusion bonding. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2069–2077, 1999     

Preparation and interfacial properties of a novel biodegradable polymer surfactant: poly(ethylene oxide monooleate-block-DL-lactide)

In this paper, we report a novel synthesis of poly(ethylene oxide monooleate-block-DL-lactide) (MOPEO-PLA) in the presence of stannous 2-ethylhexanoate catalyst. By utilizing the surfactant property and the reactive double bond of the amphiphilic MOPEO-PLA, various characteristics of PLA microspheres, such as surface and internal structure, surface morphology, release property, and so on, may potentially be controlled. MOPEO-PLA was found to be hydrophobic enough to prevent loss by dissolution into aqueous solution, which is often a problem for MOPEO. Furthermore, the interfacial tension measurements of a MOPEO-PLA/toluene/water system revealed that MOPEO-PLA had a good surface activity almost equal to that of MOPEO. The MOPEO-PLA/PLA blend films were prepared by solvent casting on a water layer. Contact-angle measurements of MOPEO-PLA/PLA blend films confirmed that the hydrophilic PEO segments were selectivity accumulated at the oil/water interface. Moreover, the surface free energy on the 'water side' of the MOPEO-PLA/PLA blend films was increased because of the increase in polar components as a result of the ether bonds of the PEO segments. Schematic illustration of the adsorption property of a) MOPEO-PLA with a high-molecular-weight PLA segment and b) MOPEO-PLA with a low-molecular-weight PLA segment at an ethyl acetate/water interface.     

Rheo-optical determination of the interfacial tension in a dispersed blend

In this work, we present two novel methods to determine the interfacial tension of a disperse polymer blend through rheo-optical measurements of flow-induced single drop distortions. A counter-rotating shearing device with transparent plates is used to measure drop distortions. The cell geometry allows for a top view of the deforming drop, i.e., along the velocity gradient direction. Such a view is the only possible option for all currently available commercial rheo-optical instruments. Two different quantities are monitored, namely, the drop axis along the vorticity direction, and the rotation period of the drop surface. We use drops of a polyacrilamide aqueous solution (a shear thinning liquid) immersed in a polyisobutene matrix. Experimental results are interpreted in terms of theories for Newtonian liquids, where the relevant parameter is the Capillary number. If an appropriate viscosity ratio is chosen, that accounts for the shear thinning behaviour of the drop phase, good agreement is found between measurements and theoretical predictions. As a result, a robust estimate of the blend interfacial tension, that makes use only of the information acquired from top view experiments, is obtained.     

Application of the ISM EoS for polymer solutions and blends

A method for predicting an analytical equation of state for polymer mixtures and blends from surface tension and liquid state density at normal (ordinary) temperature (γ_n, ρ_n), as scaling constants, is presented. B₂(T) follows a promising corresponding-states principle. Calculation of (T) and b(T), the two other temperature-dependent constants of the equation of state, are made possible by scaling. As a result, γ_n and ρ_n are sufficient for determination of thermophysical properties of polymer mixtures and blends.

We applied the procedure to predict liquid density of poly(ethylene glycol) (PEG-200) + 1-octanol solutions and poly(propylene glycol) (PPG) + poly(ethylene glycol) (PEG-200) blends at compressed state with temperature range from 298.15 to 338.15 K and pressures up to 40 MPa. In this work, the ISM EoS is extended to polymer mixtures and blends as well as pure case without proposing any mixing rule.     

Viscoelastic properties and interfacial tension of polystyrene–polyethylene blends

The linear viscoelastic properties of polystyrene polyethylene (PS/PE) blends have been investigated in the molten state. For concentrations of the dispersed phase equal to 30 vol %, the blends exhibited a droplet‐matrix morphology with a volume‐average diameter of 5.5 μm for a 70/30 PS/PE blend at 200 °C and 14.7 μm for a 30/70 PS/PE blend at 230 °C. Enhanced elasticity (G′) for both blends, in the terminal zone, compared to the modulus of the matrix (PS and PE, respectively) was observed. This is related to the deformation of the droplets in the matrix phase and hence to the interfacial forces between the blend components. The results for these uncompatibilized blends are shown to be in agreement with the predictions of the emulsion model of Palierne. These predictions were used to obtain the interfacial tension between PS and PE, which was found to be between 2 and 5 mN/m at 200 °C and 4 ± 1 mN/m at 230 °C. Independent interfacial tension measurements using the breaking‐thread method resulted in a value of 4.7 mN/m and 4.1 mN/m at 200 °C and 230 °C for the respective blends. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1359–1368, 2000     

Temperature and molecular weight dependence of interfacial tension between immiscible polymer pairs by the square gradient theory combined with the Flory–Orwoll–Vrij equation-of-state theory

Interfacial tension between immiscible polymer pairs was predicted by using a square gradient theory in conjunction with the Flory–Orwoll–Vrij equation-of-state expression for the free energy of mixing. The contact interaction parameter was determined by fitting the equation-of-state theory to experimental cloud points taken from the literature, and the square gradient coefficient was estimated from the relation derived from a scattering function. The modified square gradient theory could successfully predict both the magnitude and temperature dependence of interfacial tension between polystyrene and poly(methyl methacrylate), although no adjustable parameters were used in calculating interfacial tension. The molecular weight dependence of interfacial tension was also successfully predicted. The contribution of free volume on interfacial tension is analyzed for two systems: polystyrene/poly(methyl methacrylate) and polystyrene/poly(dimethyl siloxane) blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2683–2689, 1998     

pH dependence of the kinetics of interfacial tension changes during protein adsorption from sessile droplets on FEP-Teflon

Interfacial tension changes during protein adsorption at both the solid-liquid and the liquid-vapor interface were measured simultaneously by ADSA-P from sessile droplets of protein solutions on fluoroethylenepropylene-Teflon. Four globular proteins of similar size, viz. lysozyme, ribonuclease, -lactalbumin and Ca²⁺-free -lactalbumin, and one larger protein, serum albumin, were adsorbed from phosphate solutions at varying pH values (pH 3-12). The kinetics of the interfacial tension changes were described using a model accounting for diffusion-controlled adsorption of protein molecules and conformational changes of already adsorbed molecules. The contribution of conformational changes to the equilibrium interfacial pressure was shown to be relatively small and constant with respect to pH when compared to the contribution of adsorption of the protein molecules. The model also yields the diffusion relaxation time and the rate constant for the conformational changes at the interface. Around the isoelectric point of a protein the calculated diffusion relaxation time was minimal, which is ascribed to the absence of an energy barrier to adsorption. Energy barriers to adsorption become larger at pH values away from the isoelectric point and can therefore become rate-limiting for the adsorption process. The rate constants for conformational changes at the liquid-vapor interface were maximal around the isoelectric point of a protein, suggesting a smaller structural stability of the adsorbed protein. At the solid-liquid interface the rate constants were smaller and independent of pH. indicating that conformational changes more readily occur at the liquid-vapor than at the solid-liquid interface.     

Cure kinetics of epoxy resin and thermoplastic polymer

The cure kinetics and morphology of diglycidyl ether of bisphenol A (DGEBA) modified with polyvinyl acetate (PVAc) using diaminodiphenylmethane (DDM) as hardener were investigated through differential scanning calorimetry (DSC) and environmental scanning electron microscopy (ESEM). Isothermal curing measurements were carried out at 150, 120 and 80°C. The kinetic parameters were obtained using the general autocatalytic chemically controlled model. The comparison of the kinetic data indicates that the presence of PVAc does not change the autocatalytic nature of the cure reaction. Two T _g’s were observed in the fully cured samples of the modified systems. ESEM micrographies confirm the biphasic morphology.     

A differential approach to calculating osmotic equilibrium for multisolvent systems

A differential approach to the calculation of osmotic pressure of multisolvent systems within the Lewis–Randall framework is presented in this paper. Exact differential equations relating the osmotic pressure and the system composition along paths of constant solvent chemical potential are obtained and numerically solved. Although even for the simple case of an ideal solution no analytic expression for the osmotic pressure can be obtained, the system of differential equations does not pose numerical difficulties to be solved. Examples of the use of the proposed methodology are presented using the two-suffix Margules and Flory–Huggins equations, allowing an assessment of the influence of liquid-phase non-ideality on the performance of the method, and showing that it can be applied even for systems wherein liquid–liquid phase equilibrium occurs.     

A review on ternary immiscible polymer blends: morphology and effective parameters

In this paper a review of studies on ternary polymer blends, reported in the period from 1980s to 2007, is presented. This review covers the investigations carried out on the formation of morphologies observed in ternary blends including separated disperse, core–shell and co‐continuous morphologies; and also the parameters affecting the type of morphology and its distribution state. Copyright © 2008 John Wiley & Sons, Ltd.     

Fast FTIR imaging: A new tool for the study of semicrystalline polymer morphology

The distribution of chemical species and the degree of orientation in semicrystalline polymer systems have been studied using fast Fourier transform infrared (FTIR) imaging. A variety of poly(ethylene glycol) systems, including pure polymer, high and low molecular weight blends, and blends with amorphous polymers, were studied. It is shown that fast FTIR imaging can be used to determine the distribution of species with different molecular weights and can be used to determine the degree of segregation of different components in blends with amorphous polymers. Additionally, by employing an infrared polarizer, the degree of orientation was determined in these systems by the generation of spatially‐resolved dichroic ratio images. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2353–2359, 1999     

Calculation of polymer blend compositions from vibrational spectra: A simple method

In this work, the application of a new approach for quantitative analysis, originally developed for Raman spectroscopy, is extended to IR spectroscopy. The attractive features of this methodology are its simplicity and ease of use in comparison with traditional approaches. Unlike other methods, rich spectral information containing several overlapped peaks can be used in the calculations. A robust and well‐conditioned calculation scheme renders precise results, which are independent of the operator's decisions. The method was applied to study the chemical compositions of homogeneous polymer blends made of polystyrene and poly(vinyl methyl ether). Raman and IR blend spectra were acquired with confocal Raman microspectroscopy and attenuated total reflection/Fourier transform infrared, respectively. The blend compositions were calculated from the corresponding vibrational spectra with the proposed strategy, and excellent agreement between those values and the true ones was found for both techniques. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1144–1151, 2005