Palierne Model Research Articles

Miscibility analysis, viscoelastic properties and morphology of cyclic olefin copolymer/polyolefin elastomer (COC/POE) blends

Miscibility of cyclic olefin copolymer/polyolefin elastomer (COC/POE) blends over full composition range was investigated through determination of viscoelastic characteristics both at melt and solid state as well as by direct morphological analysis using experimental and theoretical approaches. The melt viscosity, storage modulus and Han diagrams were used for analyzing the rheological behavior. It was found that the storage modulus of neat COC was higher than that of neat POE, while the modulus of the blends were in between the modulus of the neat components. Palierne and Gramspacher–Meinssner models were used in order to predict the storage and loss moduli of COC and POE. Better correspondence of Palierne model with the experimental results was observed as compared to the other model. Contrary to the Veenstra model, the calculated modulus via Coran model was reasonably in good agreement with the experimental results for blends with co-continuous morphology. Dynamic mechanical investigations have revealed that COC/POE blends were immiscible which firmly supported the morphological and rheological findings.

Rheological behavior of a LDPE/PS/SBS blending melt

The dynamic rheological behaviors are measured by small amplitude oscillatory shear on a rotational rheometer for a low-density polyethylene (LDPE)/polystyrene (PS)/styrene–butadiene–styrene (SBS) block copolymer blend with the tool of cole–cole plot. The morphology of the blend is measured by scanning electron microscope (SEM) micrograph, the storage moduli–angular frequency (G′–ω) data are fit by the Palierne model, and the relaxation time spectrum is investigated. The storage modulus and loss modulus of the LDPE/PS/SBS blend at low frequency increase when the weight ratio LDPE/PS increases from 10/90, reaches a maximum of 30/70, and drops thereafter. The cole–cole plots of some blends (10/90/3, 70/30/3, 90/10/3 and 100/0/3) have only one main arc due to compatibilizing effect of the SBS, and those of other blends (0/100/3, 30/70/3 and 50/50/3) have a second arc or a long tail besides the main arc probably due to phase separation. The SEM micrographs of the LDPE/PS/SBS = 10/90/3, 30/70/3, 50/50/3 show sea-island, semi-co-continuous and co-continuous structure, respectively. G′–ω curve of two LDPE/PS/SBS = 30/70/3 and 50/50/3 blends shows a power law, and the power index is much lower than one (0.748 and 0.817), respectively, showing a co-continuous morphology also verified by the SEM micrographs. The experimental data of G′–ω curve of the LDPE/PS/SBS blends are fit by Palierne model, the deviation between the fit line and the experimental data increases gradually as the LDPE/PS weight ratio decreases from 90/10 to 10/90. For the LDPE/PS/SBS blends, the weighted relaxation spectra τH (τ)–τ show a main as well as a second arc or tail; the former corresponding to the relaxation of PS phase and the latter corresponding to that of LDPE phase. Due to the compatibilizing effect of SBS the relaxation time and spectrum strength of LDPE/PS = 50/50 (wt) blends are both increased.

Morphology development, melt linear viscoelastic properties and crystallinity of polylactide/polyethylene/organoclay blend nanocomposites

ABSTRACTPolylactide/polyethylene blends (PLA/PE) and their nanocomposites were prepared via the melt blending process. The effects of organoclay, compatibilizer (PE‐g‐MA), and PE content on morphology, linear viscoelastic properties of the melt and cold crystallization of the samples have been studied. The Palierne model is applied to predict the rheological behavior of unfilled blends. It implies that there is a quantitative agreement between model and experimental data for low PE content blend. From WAXD and the rheological behavior, it is shown that organoclay exhibits a higher extent of intercalation and dispersion in PLA/PE/organoclay nanocomposite than in PLA/organoclay nanocomposite. The DSC results present that the addition of compatibilizer into blend nanocomposite increases cold crystallization temperature of PLA by about 3°C. This can be explained by the role of compatibilizer in transfer of a part of organoclay from PLA matrix to droplets resulting in increase of PLA chain mobility and, therefore, slightly greater cold crystallization temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41300.

Rheology of multiphase polymer blends with and without reactive compatibiliser: evaluation of interfacial tension using theoretical predictions

The phase morphology and rheology of polyamide 12/polypropylene (PA12/PP) blends have been studied. Effects of blend ratio and reactive compatibilisation on the rheological properties of compatibilised and uncompatibilised blends were analysed. The viscosity ratio between the polymers was found to be sensitive to frequency. The complex viscosity and dynamic modulus increased with increase in the amount of compatibiliser, up to critical micelle concentration. The interfacial tension between the polymers was calculated from the storage modulus of the blends using Palierne and Choi-Schowalter models. It was found that the rheological properties of both compatibilised and uncompatibilised blends are intimately related to their phase morphology.

Effect of fat hardness on large deformation rheology of emulsion-filled gels

The aim of this work was to investigate the impact on the texture properties of emulsion-filled gels when saturated solid fat is replaced by unsaturated liquid oil. Whey protein aggregate, gelatin and micellar casein, were chosen to form different types of gel matrices and the fat hardness was varied by selection of the fat type and variation of the temperature. As emulsifier, either whey protein aggregates, whey protein or sodium caseinate was used. Texture properties of the filled gels were investigated by uniaxial compression. The fracture properties were affected by the presence of emulsion droplets, however the effect of fat hardness was small. The presence of emulsion droplets (either liquid or solid) increases the gel stiffness as compared to the emulsion-free gel, indicating that the droplets are an active part of the gel. An increase in solid fat content led to a moderate increase in gel stiffness for whey protein aggregate gels, which was in agreement with predictions according to the Palierne model for the effect of fat hardness on the stiffness of the filled gels. For the gelatin and micellar casein gels, the magnitude by which the gel stiffness increased as a function of the solid fat content was much larger than expected on the basis of this model. Microscopical observation suggested that this was caused by an inhomogeneous distribution of the fat droplets, due to droplet aggregation or/and concentration of the droplets in gel strands, which increases the effective volume fraction of the droplets in the matrix.

Phase behavior actuating morphology and rheological response of polybutadiene/polyisoprene blends under small amplitude oscillatory shear

The morphology evolution and the corresponding linear viscoelastic behavior of the phase-separating polybutadiene (PB)/low vinyl content polyisoprene (LPI) blend have been investigated by phase contrast optical microscopy (PCOM), small-angle light scattering (SALS) and rheometry. Two kinds of structure evolutions and rheological responses have been observed. It is found that the co-continuous structure generally gives a power law behavior of the dynamic storage modulus versus frequency and the coarsening of co-continuous structure leads to a decrease of the storage modulus. For the droplet-matrix structure, a platform modulus is observed at the mediate frequencies, followed by the typical terminal relaxation behavior of storage modulus at the extremely low frequencies. The decreasing platform modulus and increasing terminal modulus with the growth of droplets are observed and can be well interpreted by the simplified Palierne model. The platform modulus and terminal modulus at a given frequency are found to be scalable with the phase separation time. Besides, the characteristic relaxation time and domain size of the droplets have been obtained by rheology. And it seems that the rheologically determined droplet dimensions are consistent with the ones determined by PCOM and SALS.

Morphology, interfacial and mechanical properties of polylactide/poly(ethylene terephthalate glycol) blends compatibilized by polylactide-g-maleic anhydride

Polylactide/poly(ethylene terephthalate glycol) (PLA/PETG 80/20wt) blends compatibilized with polylactide-g-maleic anhydride (PLA-g-MAH) were prepared by melt blending and the rheological, morphological and mechanical properties of the blends were studied. PLA/PETG (80/20wt) blend formed a typical sea-island morphology, while upon compatibilization, the size and size distribution of the dispersed phase decreased significantly and the 3wt% PLA-g-MAH compatibilized blend exhibited the smallest phase size and the narrowest distribution of the dispersed particles. The interfacial tension between PLA and PETG was determined from the morphological characteristics and the viscoelastic response of PLA/PETG blends via using two emulsion models. A minimum for PLA/PETG blend containing 3wt% PLA-g-MAH was observed from both Palierne model and G–M model. The elongation-at-break increased by ∼320%, from 6.9% for PLA to 28.7% for the blend containing 3wt% PLA-g-MAH without significant loss in the tensile modulus and tensile strength.

Effect of OMMT on Morphology and Property of PTT/ASA Blends

Nanocomposites of poly(trimethylene-terephthalate)/poly(acrylonitrile-styrene-acrylate)/organic montmorillonite(PTT/ASA/OMMT) were prepared by means of melt-blending intercalation. The effect of OMMT contents on the phase morphology, crystallization behavior, rheological- and mechanicalproperties were investigated. The results show that the size of dispersed phases decreases with increasing OMMT content. The crystallization peak shifts to high temperature and melting peak moves to low temperature owing to the heterogeneous nucleation of OMMT. The exfoliated OMMT is located in the PTT matrix and at interface of PTT/ASA phases The rheological measurements show that the elastic modulus and complex viscosity increase with increasing OMMT content. The interfacial modulus and interfacial layer thickness predicted by Palierne and Gramspacher-Meissner models are enhanced by introduction of OMMT. The tensile strength and notched impact strength of blends increase with increasing OMMT content.

Morphology, mechanical, and rheological properties of poly(lactic acid)/ethylene acrylic acid copolymer blends processing via vane extruder

AbstractThis work aimed to study, for the first time, the melt blending of poly(lactic acid) (PLA) and ethylene acrylic acid (EAA) copolymer by a novel vane extruder to toughen PLA. The phase morphologies, mechanical, and rheological properties of the PLA/EAA blends of three weight ratios (90/10, 80/20, and 70/30) were investigated. The results showed that the addition of EAA improves the toughness of PLA at the expense of the tensile strength to a certain degree and leads the transition from brittle fracture of PLA into ductile fracture. The 80/20 (w/w) PLA/EAA blend presents the maximum elongation at break (13.93%) and impact strength (3.18 kJ/m2), which is 2.2 and 1.2 times as large as those of PLA, respectively. The 90/10 and 80/20 PLA/EAA blends exhibit droplet‐matrix morphologies with number average radii of 0.30–0.73 μm, whereas the 70/30 PLA/EAA blend presents an elongated co‐continuous structure with large radius (2.61 μm) of EAA phase and there exists PLA droplets in EAA phase. These three blends with different phase morphologies display different characteristic linear viscoelastic properties in the low frequency region, which were investigated in terms of their complex viscosity, storage modulus, loss tangent, and Cole‐Cole plots. Specially, the 80/20 PLA/EAA blend presents two circular arcs on its Cole‐Cole plot. So, the longest relaxation time of the 80/20 blend was obtained from its complex viscosity imaginary part plot, and the interfacial tension between PLA and EAA, which is 4.4 mN/m, was calculated using the Palierne model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40146.

Effects of emulsion parameters on relaxation behaviors for immiscible polymer blends

ABSTRACTThe relaxation behaviors of the binary immiscible blends reflected on the plots of the storage modulus and the imaginary part of complex viscosity were investigated using the Maxwell and the Palierne models. It was revealed that the peaks in the high‐ and low‐frequency regions on the complex viscosity imaginary part plot are owing to the relaxations of the blend and deformed dispersed droplets, respectively. Based on these two models, six emulsion parameters (interfacial tension, relaxation times and viscosities of two components, and dispersed phase volume fraction) were investigated in terms of their effects on the shape features of the plots of the imaginary part of complex viscosity and the Cole–Cole. The results showed that the viscosities of two components and dispersed phase volume fraction play key roles in the radii of the two circular arcs on the Cole–Cole plot. Furthermore, the two circular arcs are well separated in the case of lower interfacial tensions and dispersed phase viscosities, shorter matrix relaxation times, and higher matrix viscosities and dispersed phase volume fractions. The total relaxation time of the deformed dispersed droplets increases with increasing the viscosities of two components, especially with decreasing the interfacial tension. Three types of polymer blends were prepared and their dynamic frequency sweep testing results demonstrated the effectiveness of the corresponding predicted results. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39690.

An Investigation on Polypropylene/Nylon 66/TiO<sub>2</sub> Blend Nanocomposites: Rheological Models

Nanocomposites based on polypropylene (PP), polyamide 66 (nylon 66) and PP/nylon 66 immiscible blends containing 5wt% TiO2nanoparticles were prepared via melt compounding. The influences of TiO2on the rheology of nanocomposites and blend nanocomposites were investigated. Scanning electron microscopy results revealed the size of inclusion phase was smaller in PP/PA 66/TiO275/25/5 comparing to the PP/PA 66/TiO225/75/5. A co-continuos phase was observed at 50/50 composition. Melt dynamic rheology showed that the moduli of the PP increased with incorporation of TiO2nanoparticles at the moderate frequencies, while this effect was reverse in PA 66 nanocomposite. Several rheological and rheo-morphological models were used for prediction of rheological parameters. The well-known models for rheology of suspensions proposed by Einstein, Roscope and Eilers-van Dijck were successful for prediction of viscosity of PA nanocomposite. Palierne model was fitted to the experimental values especially for the: PP/PA 66/ TiO225/75/5 blend nanocomposite.

Dispersive mixing efficiency of an elongational flow mixer on PP/EPDM blends: Morphological analysis and correlation with viscoelastic properties

Polypropylene and ethylene-propylene-diene terpolymer (PP/EPDM) blends were melt compounded in a new mixing device, designed in our laboratory under the trademark of RMX®, which predominantly generates elongational flows. Dispersion of the EPDM minor phase in PP was carried out in both RMX® and in an internal mixer (Haake Rheomix 600) at equivalent specific mixing energies and the resultant morphologies obtained by SEM were analyzed and compared. A better dispersive mixing efficiency of the RMX® mixer, i.e., lower Dn and Dv of the dispersed EPDM phase was observed. The impact of elongational flow was more pronounced for blends having a high viscosity ratio p, indicating an enhanced droplet break-up mechanism, which was attributed to the combination of high shear rates inside the mixing element and important elongational flows in the convergent/divergent zones. The morphology of the blends was correlated with their linear viscoelastic properties by using the Palierne model. Very good agreement was found for the PP/EPDM 80/20 blends but for higher EPDM content, the Palierne model failed to describe the rheological behavior, which was attributed to percolation of the minor phase with increasing the concentration. Higher elasticity at low frequencies was observed for blends processed in the RMX®, which was attributed to a higher generated interfacial area. POLYM. ENG. SCI., 54:1444–1457, 2014. © 2013 Society of Plastics Engineers

Glass Transition Distribution in Miscible Polymer Blends: From Calorimetry to Rheology

At their glass transition, simple liquids and polymers exhibit a broad spectrum of relaxation—with a width of more than 4 decades in time. Blends of miscible polymers exhibit an even broader relaxation spectrum. Here, we assume that a blend can be considered as an ensemble of domains of various local glass transition temperatures. Using calorimetric data, with or without aging, we probe the distribution of glass transition temperature (Tg) of miscible polymer blends of polybutadiene (PB) and styrene butadiene rubber (SBR). Using the self-consistent averaging method inspired by the Olroyd–Palierne model, we predict quantitatively, with no adjustable parameter, the viscoelastic spectrum of our blends from the Tg distribution obtained by calorimetry. This quantitative prediction confirms thus the assumption that mechanically a blend can be considered as an ensemble of domains, each of which have a different glass transition temperature.

Comparative study of interphase viscoelastic properties in polyethylene/polyamide blends compatibilized with clay nanoparticles or with a graft copolymer

The linear viscoelastic properties of immiscible polyethylene/polyamide blends filled with clay nanoparticles or compatibilized by a copolymer, exhibiting identical nodular morphologies, have been studied. The apparent compatibilizing effect of clay nanoparticles, exclusively located at the interface, was evidenced and compared to the more classical organic compatibilization due to the formation of a macromolecular interphase. The results show that there are some analogies between the two types of compatibilization, but mainly highlight significant differences in rheological properties of the two types of interphase involved in the compatibilization mechanisms. The major differences in interphase viscoelastic properties were evidenced not only directly from the experimental data but also indirectly by using the Palierne's model for different clay or compatibilizer contents.

Influence of Multiwall Carbon Nanotubes Trapped at the Interface of an Immiscible Polymer Blend on Interfacial Tension

AbstractThe influence on interfacial energy of multiwall unfunctionalized carbon nanotubes (CNTs) trapped at the interface of an immiscible blend of polyamide 12 (PA12) and acrylate‐ethylene (EA) copolymer is investigated with the help of the Palierne model combined with transmission electron microscopy (TEM) observations. It is found that the interfacial energy is unaffected by the interfacially trapped CNTs. The reduced droplet size observed in the presence of CNTs can neither be ascribed to a classical compatibilizer effect due to lower interfacial energy leading to enhanced breakup during processing, nor to the minute changes of the continuous phase viscosity induced by the CNTs. Another explanation based on steric hindrance is proposed. A network CNT layer that acts as a rigid shell is formed, which prevents coalescence of colliding droplets.

Relaxation of loose agglomerates of magnesium hydroxide in a polymer melt

The study of agglomerates of magnesium hydroxide badly dispersed in an olefinic polymer by means of oscillatory shear flow in the melt indicates that the agglomerates behave as a distinct phase. Optical and rheo-optical measurements carried out on these agglomerates also show that they are wetted by the melt and that they can be easily deformed under shear. However, the relaxation of shape in oscillatory shear is also the trace of the existence of an effective interfacial tension between the agglomerates containing high amounts of filler and the polymer matrix. The analogy with the behavior of polymer blends and the modeling by the Palierne model enables the calculation of such an interfacial tension. The surface free energy of magnesium hydroxide that can be calculated from this result by a simple mixing law is 95 mN m−1. This value is compared with data from the literature on brucite and similar minerals.

Reactive extrusion of polypropylene/polystyrene blends with supercritical carbon dioxide

A reactive extrusion process for immiscible polypropylene/polystyrene (PP/PS) blends with peroxides and multifunctional agents in the presence of supercritical carbon dioxide (scCO2) was studied. The PP/PS blends were investigated by rheological measurement, scanning electron microscopy, thermal analyzer, and mechanical testers. The results show that the complex viscosity and the storage modulus of the blends increase with the addition of peroxides and multifunctional agents, which might represent the formation of copolymer during melt processing. From the morphology analysis of the blends, the size of the dispersed PS domain decreases significantly. Moreover, the analysis of the blends also reveals that the use of supercritical carbon dioxide leads to an increase of complex viscosity and a decrease of domain size. It was believed that the use of scCO2 improved the compatibility of the blends. The interfacial tensions of the PP/PS blends were predicted theoretically from the rheological data using the Choi and Schowalter model and the Palierne model. The values of the interfacial tension decreased as the compatibility of PP/PS blends was improved. From the results above, we strongly suggest that the use of supercritical carbon dioxide-assisted reactive extrusion is an effective way to improve the compatibility of the PP/PS blends.

Interfacial Properties, Viscoelasticity, and Thermal Behaviors of Poly(butylene succinate)/Polylactide Blend

Biodegradable poly(butylene succinate)/polylactide (PBS/PLA) blends with various blending ratios were prepared by melt mixing for morphological and rheological studies. Dynamic rheological measurements were performed on the blend systems and the viscoelastic responses were analyzed with several emulsion models. The results show that the PBS/PLA is an immiscible blend system with very narrow cocontinuous region and high percolation threshold. The phase inversion point could be precisely predicted by the small-amplitude oscillatory shear (SAOS) response. The Palierne model gave a better description of the viscoelastic response of PBS/PLA blends than that of the Gramespacher and Meissner (G-M) model. In addition, the interfacial tension between the two polymers was measured by several techniques, such as surface property characterizations, deformed drop retraction, and rheological approaches. The differences observed by these various methodologies were then further explored. Moreover, the melting and crystallization behaviors of the blends were also studied in order to reach a deeper insight into the relations between the phase behavior and the macroscopic thermal properties of the PBS/PLA blends.

The influence of epoxy resin on the morphological and rheological properties of PET/PA66 blend

Interfacial reactions have dominant effects on the morphological and rheological properties of compatibilized polymer blends. This work aims to investigate the effect of epoxy resin, as a coupling agent, on the interface properties and subsequent influences on the morphological and rheological properties of polyethylene terephthalate/polyamide66 (PET/PA66) blend. PET/PA66 70/30 blends with different amount of bisphenol A epoxy resin (0, 1, 3, and 5 wt.%) were prepared. SEM micrographs show reduction in droplet size with increasing epoxy resin concentration, confirming the reactive compatibilizing effect of the epoxy resin. Reactions at the interface of the PET-EP-PA66 blend are confirmed by FTIR spectra. Shear viscosity results demonstrates that adding epoxy resin could suppress the interfacial slip at the blend interphase. Obtained results from storage modulus (G′) curves show the presence of one plateau for the blends at low frequency region; nevertheless, relaxation spectra indicate the presence of two more relaxation mechanisms than precursors which are related to the shape relaxation of droplets and the interface relaxation. The presence of the interface relaxation time in the blend without epoxy resin can prove the presence of reactions between two condensation polymers; however, adding the epoxy resin results in reducing both relaxation time and interfacial tension and increasing interfacial shear modulus. These observations indicate that the epoxy resin has been successful to boost the reactions at the interface between two polymers. Fitting the obtained experimental data using Palierne model indicates that the general Palierne model could describe rheological properties of the blends very well.

Morphology and melt rheology of biodegradable poly(lactic acid)/poly(butylene succinate adipate) blends: effect of blend compositions

Effect of the blend ratios on the morphology and melt rheology of poly(lactic acid) (PLA)/poly(butylene succinate adipate) (PBSA) blends were investigated using scanning electron microscope, strain-controlled rheometer, and capillary rheometer techniques. The morphological analysis shows that the average radius of the dispersed droplets of PBSA particles increases with change in the blend composition, and a co-continuous structure was generated when PBSA content reached 40%. For the linear viscoelasticity, the increase in the storage modulus at low-frequency region was more distinct in PLA/PBSA blends than in their pure components. A second plateau is clearly observed when the PBSA content was 20% or higher. Weight relaxation spectra showed that there was a longer relaxation time for blend system. These relaxation times were considered to be the shape relaxation periods of the droplets, which increase with change in the blend composition. The interfacial tensions of the PLA/PBSA blends at different compositions were between 5.3 and 6.1 mN/m, calculated from the weighted relaxation spectra and slightly higher than those obtained from Palierne model. These values are relatively high, indicating the poor miscibility of the two polymers. Both pure PLA and PBSA follow the Cox–Merz rule, in good manner. Though, the rule does not satisfy with the PLA/PBSA blends. In addition, PLA/PBSA blends show more non-Newtonian tendencies than their pure components.