Phase Inversion Region Research Articles

Natural Frequency Analysis of Horizontal Piping System Conveying Low Viscosity Oil–Gas–Water Slug Flow

The water cut (WC) has a significant effect on the flow parameters, such as liquid holdup, liquid phase velocity, and flow regimes of the low-viscosity oil–gas–water slug flow, and it can change the vibration characteristics of piping systems. To study the effect of water cut on the vibration characteristics of piping systems conveying such internal flow, a new dynamic model is developed. Galerkin’s method is used to discretize the equation and determine the natural frequencies by solving for the eigenvalues of the equation coefficient matrix. The results show that in the range of 10–90% WC, the natural frequency increases and then decreases, and the turning point occurs near the phase inversion region (WC = 40–60%). The main reason is the highly effective viscosity in the phase inversion region, which leads to an increase in the liquid holdup. The natural frequency increases and then decreases with superficial gas velocity, and the inflection point decreases with the increase in water cut in the oil-based flow regime and increases with the increase in water cut in the water-based flow regime. The critical gas velocity is lowest near the phase inversion region, but it should be noted that the presence of the critical gas velocity is related to the pipe length and superficial liquid velocity. The results of the study provide a reference for the design of safe pipeline operation.

Detecting Phase-Inversion Region of Surfactant-Stabilized Oil/Water Emulsions Using Differential Dielectric Sensors

Summary An experimental and theoretical investigation of surfactant-stabilized oil/water emulsion characteristics was carried out under water sweep (WS) and oil sweep (OS) conditions. Both hydrophilic and hydrophobic surfactants were used, with concentrations less than and more than the critical micelle concentration (CMC). Experimental data were acquired for detection of the phase-inversion region, which was measured simultaneously by several independent methods. These include a circular differential dielectric sensor (C-DDS), a rectangular differential dielectric sensor (R-DDS) (both sensors accurately detect the phase-inversion region), a pressure transducer, and a mass flowmeter. The addition of an emulsifier surfactant to an oil/water mixture generated a stable emulsion, which resulted in a phase-inversion delay. For water-continuous to oil-continuous flow, a hydrophilic surfactant was a better emulsifier, while for oil-continuous to water-continuous flow, a hydrophobic surfactant was a better emulsifier for creating more stable emulsions. The surfactant/oil/water emulsion resulted in an increase of the dispersed-phase volume fraction required for phase inversion, as compared to the case of oil/water dispersions without surfactant. For emulsions with surfactant concentrations above CMC, the presence of micelles contributed to further delay of the phase inversion, as compared to those with surfactant concentrations below CMC. The phase-inversion region exhibits a hysteresis between the OS and WS runs, below CMC and above CMC, which was due to the difference in droplet sizes caused by different breakup and coalescence processes for oil-continuous and water-continuous flow. This research shows that the DDS is an efficient instrumentation that can be used to detect the region where the emulsion phase inversion is expected to occur. Moreover, the experimental results and the pertinent analysis and discussion provide useful insights for a more informed design of surface facilities (including emulsion separators) in oil and gas production operations.

Stepwise behavior of surface properties caused by phase inversion in a polymer blend filled with dispersed iron

The surface properties, mechanical characteristics, and morphology of the PP/CPA-Fe composite based on a polymer blend of polypropylene (PP) and copolyamide (CPA) filled with dispersed iron (Fe) were studied. The effect of stepwise behavior of the surface energy and its dispersive and polar components was previously unknown and discovered for the first time when the composition of the polymer blend was varied in the entire composition range. The surface parameters were found by measuring the contact angle of the testing liquids (water and diiodomethane) and using Owens and Wendt’s approach. Stepwise behavior of the surface energy was caused by the morphology of the composite. The largest change in the surface parameters occurs in the phase inversion region, where the phases of PP and CPA-Fe are co-continuous. Below (for the structure of PP matrix with the inclusions of CPA-Fe) and above (for the structure of CPA-Fe matrix with the inclusions of PP) this interval, changes in the surface energy are minor. In the phase inversion region, the relative contributions of the polar and dispersive parts to the total surface energy were changed from 1 to 14% and from 99 to 86%, respectively that was caused by the interface interaction of the components of the blend. On the contrary, the values of elastic modulus (E) remain constant in the phase inversion region, while the largest changes occur below and above this region.

Partitioning of the components into two-demixed-macrophases from a solution blend emulating high impact polystyrene close to the phase inversion region

Blends of a butadiene rich-tapered diblock copolymer (DC) with polystyrene (PS) and/or polybutadiene (PB) in ethylbenzene (EB) were investigated to better understand the phenomena occurring during the synthesis of high impact polystyrene (HIPS). For the first time, the apparent partitioning of components between the demixed-phases of quaternary blends PS/PB/DC/EB was determined, involving variations of DC concentration, PS molar mass, simulated conversion of styrene and temperature. The new methodology combines FTIR, solvent extraction, TLC and mass balances and verifies important results by TEM and SEC. During demixing, a molecular fractionation occurs which depends on the DC composition distribution, the ratio between the molar masses of each of the copolymer blocks and the respective homopolymers and the viscosity ratio between the continuous and dispersed phases. The affinity between the low molar mass PS and the PS block in DC favors the stabilization of PS domains in the PB-rich phase.

Effect of Shear and Water Cut on Phase Inversion and Droplet Size Distribution in Oil–Water Flow

Oil–water dispersed flow occurs commonly in the petroleum industry during the production and transportation of crudes. Phase inversion occurs when the dispersed phase grows into the continuous phase and the continuous phase becomes the dispersed phase caused by changes in the composition, interfacial properties, and other factors. Production equipment, such as pumps and chokes, generates shear in oil–water mixture flow, which has a strong effect on phase inversion phenomena. The objective of this paper is to investigate the effects of shear intensity and water cut (WC) on the phase inversion region and also the droplet size distribution. A state-of-the-art closed-loop two phase (oil–water) flow facility including a multipass gear pump and a differential dielectric sensor (DDS) is used to identify the phase inversion region. Also, the facility utilizes an in-line droplet size analyzer (a high speed camera), to record real-time videos of oil–water emulsion to determine the droplet size distribution. The experimental data for phase inversion confirm that as shear intensity increases, the phase inversion occurs at relatively higher dispersed phase fractions. Also the data show that oil-in-water emulsion requires larger dispersed phase volumetric fraction for phase inversion as compared with that of water-in-oil emulsion under the same shear intensity conditions. Experiments for droplet size distribution confirm that larger droplets are obtained for the water continuous phase, and increasing the dispersed phase volume fraction leads to the creation of larger droplets.

Composition and compatibilization induced morphology alteration in PVDF/LLDPE blends: correlation between rheology and morphology

Correlation between the rheology and morphology of PVDF/LLDPE blends as well as the effect of LLDPE-g-MA compatibilizer on the microstructure and viscoelastic properties of these blends were studied in detail. Morphology development from matrix-dispersed to co-continuous and again to dispersed-matrix was well predicted using various linear viscoelastic analyses and confirmed via direct SEM experiments and continuity index analysis. Compatibilization induced alteration in the microstructure of the blends, particularly PVDF/PE 50/50 blend from co-continuous morphology to dispersed-matrix one, was also concluded from viscoelastic analysis and confirmed. It was shown that the feeding order had a distinct effect on morphology of the blends near the phase inversion composition. “Phase within a phase within a phase” morphology was observed near the phase inversion region, provided that the components are fed simultaneously. Different melting and crystallization temperature range of PVDF and PE phases was understood to be the main reason of this observation. It was also shown that compatibilization had higher impact on LLDPE-rich blends than PVDF-rich blends, while narrowed the co-continuity composition range.

Poly(ε-caprolactone) scaffolds of highly controlled porosity and interconnectivity derived from co-continuous polymer blends: model bead and cell infiltration behavior.

Porous structures destined for tissue engineering applications should ideally show controlled and narrow pore size distributions with fully interconnected pores. This study focuses on the development of novel poly(ε-caprolactone) (PCL) structures with fully connected pores of 84, 116, 141, and 162μm average diameter, from melt blending of PCL with poly(ethylene oxide) (PEO) at the co-continuous composition, followed by static annealing and selective extraction of PEO. Our results demonstrate a low onset concentration for PEO continuity and a broad region of phase inversion. A novel in vitro assay was used to compare scaffold infiltration by 10-μm diameter polystyrene beads intended to mimic trypsinized human bone marrow stromal cells (hBMSCs). Beads showed a linear increase in the extent of scaffold infiltration with increasing pore size, whereas BMSCs infiltrated 162 and 141μm pores, below which the cells aggregated and adhered near the seeding area with low infiltration into the porous device. While providing a baseline for non-aggregated systems, the beads closely mimic trypsinized cells at pore sizes equal to or larger than 141μm, where optimal retention and distribution of hBMSCs are detected. A cytotoxicity assay using L929 cells showed that these scaffolds were cytocompatible and no cell necrosis was detected. This study shows that a melt blending approach produces porous PCL scaffolds of highly controlled pore size, narrow size distribution and complete interconnectivity, while the bead model system reveals the baseline potential for a homogeneous, non-aggregated distribution of hBMSCs at all penetration depths.

Apparent Viscosity of Oil-Water (Coarse) Emulsion and Its Rheological Characterization During the Phase Inversion Region

A series of oil and water (coarse) emulsions has been systematically studied in order to obtain more knowledge about the flow characteristics. Experimental measurements were conducted using Rheo Stress 6000 from Therm O Haake. Several factors such as shear rate, oil volume fraction, temperature, emulsifying agent, and stirring time on the rheological characteristics of emulsions were investigated. The emulsions without emulsifying agent are discussed by Ostwald de Waele model, Casson model, and Bingham model, respectively, according to different oil volume fractions. Sixteen models of the apparent viscosity were evaluated to predict these emulsions. The results show that existing models of the apparent viscosity exhibit large deviations from the experimental data over the range of low and middle oil volume fractions (ϵo < 0.5) due to the droplets fast flocculation, and but can give a good prediction at high oil volume fractions (ϵo > 0.6). Furthermore, emulsifying agent and shear rate have few influences on the phase inversion point and the maximum value of the apparent viscosity appears around ϵo = 0.6. At the phase inversion point, the viscoelastic behavior of the emulsions were also analyzed by shear stress sweeps and frequency sweeps, respectively. These findings are helpful to improve the pipeline transportation of an immiscible oil and water two-phase dispersed flow.

Oil–gas–water three-phase upward flow through a vertical pipe: Influence of gas injection on the pressure gradient

An experimental study of three-phase flow in a vertical pipe with 50mm diameter has been carried out. The experiments were conducted under the input superficial phase velocity: water from 0 to 0.885m/s, oil from 0 to 0.90m/s and gas from 0 to 0.85m/s. In order to investigate the influence of gas injection on an oil–water two-phase flow, the average in situ phase fraction and pressure gradient were measured. The results showed that gas injection had little impact on the phase invasion and the phase inversion was still taking place at the same oil volume fraction. The average in situ gas fraction reached to its lowest value around the phase inversion point. In comparison to oil–water flow, the presence of gas decreased considerably the gravity pressure gradient and the total pressure gradient was reduced. However, when the input oil fraction was close to the phase inversion point, the contribution of frictional and gravity terms to the total pressure gradient became more equal, hence the total pressure gradient in three-phase flow could be higher than that in oil–water flow around the phase inversion region. In addition, several methods based on an oil–water flow as a single phase flow were evaluated to predict the pressure gradient of three-phase vertical bubbly flow. A good agreement was obtained between theory and data in this work and those in the literature.

Effect of crosslinking on morphology and phase inversion of EPDM/PP blends

This study investigates the effect of cross-linking on morphology and phase inversion of EPDM/PP blends. Several EPDM/PP blends without and with cross-linking agent were prepared in a Haake batch mixer under constant conditions. The morphology was studied by electronic microscopy (SEM and TEM), and cross-linking was followed by EPDM gel content and swelling. The results showed that the position of the phase inversion region is essentially governed by composition, being independent of the viscosity ratio of the EPDM/PP blend. The TPVs’ morphology of the EPDM/PP blend, with 70 and 50wt% of PP, consists of EPDM cross-linked particles dispersed in the PP matrix. For EPDM-rich composition (30wt% of PP), the TPVs’ morphology appears to be co-continuous. Even though dynamic vulcanisation of the rubber phase always improves the dispersion of the EPDM phase, complete phase inversion (from fully dispersed PP in the EPDM matrix to EPDM fully dispersed in the PP matrix) was achieved only with low viscosity EPDM.The results suggest that phase inversion driven by cross-linking can occur at viscosity ratios lower than those estimated for the respective EPDM/PP blends at phase inversion.

Absorption of CO&lt;sub&gt;2&lt;/sub&gt; into Alkane/Water Emulsions in a Stirred Tank

Absorption of pure carbon dioxide into aqueous emulsions of three different n-alkanes (n-heptane, n-dodecane and n-hexadecane) has been studied at 0 to 100% oil volume fraction in a stirred tank at a high stirring speed (1000 min−1). Phase inversion (o/w to w/o) occurs for n-dodecane and n-hexadecane at 60–65% oil volume fraction; for n-heptane, there is no clear inversion point. The volumetric mass transfer coefficient kLa was evaluated from the pressure decrease during saturation under isochoric and isothermal (298.2 K) conditions. The o/w emulsions of both n-dodecane and n-hexadecane show the same trends: kLa first increases to a maximum at 2% oil fraction, then decreases towards the phase inversion region. The maximum might indicate an additional transport mechanism; the decrease at higher oil fractions is expected based on the increase in emulsion viscosity. Differently, the o/w emulsions of n-heptane always show higher kLa values compared to pure water. The increase in kLa (by +280% at 25% n-heptane) might be explained by a bubble covering mechanism enabled by the high spreading coefficient. In w/o emulsions of n-hexadecane, from 100% oil to the phase inversion region, kLa monotonously decreases with increasing fraction of the dispersed water phase as expected due to the viscosity effect. Surprisingly, for both n-heptane and n-dodecane, kLa does not decrease, but rather increases substantially. At the phase inversion region, the relative kLa increase compared to pure oil is by +107% for n-dodecane, and even +143% for n-heptane.

Applications of instrumented indentation testing for the characterization of polypropylene materials

In this study, instrumented indentation testing, or so-called depth-sensing indentation testing, was used to characterize polypropylene (PP) materials. The influence of molecular weight and cooling rate on the hardness was investigated showing that low cooling rates and relatively low molecular weight lead to higher hardness values. In random copolymers of propene with butene and hexene, the correlation between hardness and degree of crystallinity is linear and the conversion to the amorphous state could be detected. Blends of PP with ethylene–propylene elastomer show a strong negative deviation of indentation modulus from linear rule of mixture. This behaviour can be described by Kerner’s model in the case of particulate arrangement and by Davies’ model in the phase inversion region. The addition of high-density polyethylene to PP results in a synergistic behaviour of modulus which can be attributed to nucleation effects. Furthermore, the application of indentation testing to detect physical ageing of a surface of an injection-moulded specimen and heterogeneity of weld lines was shown. Orientations in a biaxially oriented film could be detected using Knoop indenter.

Evolution of properties in ABS/PA6 blends compatibilized by fixed weight ratio SAGMA copolymer

Blends of acrylonitrile-butadiene-styrene (ABS) and Nylon 6 (PA6) incorporating styrene-acrylonitrile-glycidyl methacrylate (SAGMA) copolymer as compatibilizer have been studied across five different compositions by varying the PA6 ratio from 15 wt% to 55 wt%. The evolution of morphology from discrete dispersed PA6 particles to phase inversion to co-continuous phases effected due to the compatibilizer have been studied vis-a-vis preliminary melt flow analysis, viscoelastic behavior, physico-mechanical and thermal properties of the blends. Single point viscosity measurements during melt flow analyses are indicative of a significant increase in viscosity upon initial incorporation of PA6 followed by narrow increases with content. It is observed that while there are gradual positive modifications in physico-mechanical properties with increasing PA6 content, the most significant improvements are observed for room temperature izod impact strength and break elongation effected in the region of phase inversion on to the formation of a co-continuous phase. The low temperature impact strength at −40 °C essentially remains comparable to that of control ABS. DMTA analysis evidences partial dissolution of the blend components by the shifts of the damping peaks (Tg) of PB rich phase, SAN and PA6. Broadening of the damping peak of PB rich phase of ABS is attributed to increasing interfacial region due to PA6-g-SAGMA molecular layer at the interface. Thermal stability of the blends were not significantly affected in comparison to control ABS and PA6.

Prediction of Frictional Pressure Gradient in Horizontal Oil/Water Dispersion Flow

SummaryA novel model has been developed for the prediction of frictional pressure gradient in unstable turbulent oil/water dispersion flow in horizontal pipes. This model uses the friction-factor approach, based on the law of the wall, to predict the pressure gradient. Modification of both the von Karman coefficient κ' and the parameter B' have been carried out in the law of the wall to include the effect of the dispersed phase—namely, the dispersed-phase volume fraction and the characteristic-droplet-size diameters. The developed model applies to both dilute and dense flows, covering the entire range of water cuts. Model predictions have been compared with a comprehensive experimental database collected from literature, resulting in an absolute average error of 9.6%. Also, the comparisons demonstrate that the developed model properly represents the physical phenomena exhibited in unstable turbulent oil/water dispersions. These include drag reduction, increase in frictional pressure gradient with increasing dispersed-phase volume fraction, and the peak in the frictional pressure gradient at the oil/water phase-inversion region.

Phase Morphology and Miscibility of iPP/PcBR Blends

Isotactic polypropylene/poly(cis-butadiene) rubber (iPP/PcBR) blends were prepared by melt mixing. Phase morphology of the blends was investigated by scanning electronic microscopy (SEM). It was found that the dispersed phase spread in continuous phase in a form of spherical particles. The size of the dispersed phase increased as its content increased. The phase-inversion region was the composition of 50/50 and 40/60 vol% in the blends. In the phase-inversion region, a double continuous phase was formed. The glass transition temperatures (T g ) of iPP, PcBR and blends were analyzed by dynamic mechanical analysis (DMA). The blend compositions exhibited two distinct glass transition temperatures corresponding to the iPP-rich and PcBR-rich phases, respectively. The approach of these two peaks with increasing PcBR content indicated partial miscibility between the iPP and PcBR, which was verified by the equilibrium melting point depression of blends.

THE EFFECT OF BLENDING SEQUENCE ON PHASE MORPHOLOGY OF NYLON 6/ABS/SMA BLENDS

The preparation process-dependent phase morphology of blends composed of nylon 6 and acrylonitrile-butadiene-styrene (ABS) over a composition range of 30-70 wt% using a styrene-maleic anhydride (SMA) copolymer as the compatibilizing agent with a constant content (5phr) was investigated. The results of the scanning electron microscope (SEM) observation revealed that compared with the binary blends of nylon 6 and ABS, the existence of SMA caused a composition shift of phase inversion to a higher weight fraction of nylon 6 when ABS was blended with the preblended nylon 6/SMA blend, while the co-continuous structures could be observed over a considerably narrower composition range when nylon 6 was blended with the pre-blended ABS/SMA blend. An examination through dynamic mechanical analysis (DMA) tests confirmed the results obtained with SEM. It is found that near the phase inversion region a remarkable change in the dynamic storage modulus (G′) and the loss tangent (tanδ) appears. Moreover, the influence of blending sequence on the size of dispersed particles has been probed for uncompatibilized and compatibilized blends of nylon 6 and ABS over a wide range of compositions below or beyond the phase inversion points. For the blends of ABS dispersed in a nylon 6 matrix, little discernible effects of blending sequence on particle size could be observed. Furthermore, there exists a significant difference in morphologies of the blends prepared by nylon 6 particles dispersing in a ABS matrix in cases of different blending sequences used. Some possible factors responsible for the above asymmetric behaviors have been proposed.

The linear viscoelastic behaviors of Nylon1212 blends toughened with elastomer

The linear viscoelastic behaviors of nylon1212 blends toughened with (styrene-[ethylene-(ethylene-propylene)]-styrene block copolymer) (SEEPS) elastomer were carried out. The results show that dynamic storage modulus (G′) curves of the blends are located between those of virgin nylon and SEEPS within the frequency (ω) tested, and the G′ of blends increases with increasing of the SEEPS content. Moreover, the predictive results of Palierne emulsion model show that it is unsuitable for describing the viscoelastic behaviors of the double phase systems toughened with elastomer, especially for the system with high content of elastomer. The positive deviation in the plots of G′ vs. blend composition demonstrates that the blends are immiscible. From the point of phase transition, the phase inversion region for these blends was predicted to be in the range of 30–50 wt % of SEEPS, which agrees with the morphology analysis of nylon1212/SEEPS blends. In addition, “Cole–Cole” plots of modulus at different temperatures show that the microstructures of blends are unstable in the phase transition region. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blends

AbstractUncrosslinked and chemically crosslinked binary blends of low‐ and high‐density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt‐mixing process using 0–3 wt % tert‐butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation‐at‐break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co‐continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261–3270, 2007

Conjugated effects of the compatibilization and the dynamic vulcanization on the phase inversion behavior in poly(butylene terephthalate)/epoxide-containing rubber reactive polymer blends

The conjugated effects of both reactive compatibilization and dynamic vulcanization on the phase inversion behavior of poly(butylene terephthalate) (PBT)/epoxide-containing rubber blends have been studied in detail. Pure ethylene–methyl acrylate random copolymer (E-MA) and ethylene–methyl acrylate–glycidyl methacrylate random terpolymer (E–MA–GMA) were used as non reactive or reactive rubber phase, respectively. Location of the phase inversion region was studied using several techniques, including transmission electron microscopy (TEM) and dynamical mechanical thermal analysis (DMTA). To evaluate the relative influence of the blend compatibilization and the dynamic vulcanization on the phase inversion behavior, the relative kinetics of the two reactions were modified using different PBT and E–MA–GMA grades. The obtained results show unambiguously that the position and the width of the phase inversion region is essentially governed by the kinetic of the dynamic vulcanization process. The effect of the blend compatibilization remains quite limited even in the case of fast interfacial reaction. The crosslinking of the rubber phase induces an important shift of the phase inversion composition to higher rubber content. For blends containing low molecular weight PBT, up to 60 wt% of rubber can be homogeneously dispersed in the PBT matrix at long mixing time. In this case, development of high performance PBT based thermoplastic vulcanisates can be envisioned.

Melt rheology and morphology of uncompatibilized and in situ compatibilized nylon‐6/ethylene propylene rubber blends

AbstractMelt rheology and morphology of nylon‐6/ethylene propylene rubber (EPR) blends were studied as a function of composition, temperature, and compatibilizer loading. Uncompatibilized blends with higher nylon‐6 content (N90 and N95) and rubber content (N5 and N10) had viscosities approximately intermediate between those of the component polymers. A very clear negative deviation was observed in the viscosity–composition curve over the entire shear rate range studied for blends having composition N30, N50, and N70. This was associated with the interlayer slip resulting from the high‐level incompatibility between the component polymers. The lack of compatibility was confirmed by fracture surface morphology, given that the dispersed domains showed no sign of adhesion to the matrix. The phase morphology studies indicated that EPR was dispersed as spherical inclusions in the nylon matrix up to 30 wt % of its concentration. A cocontinuous morphology was observed between 30 and 50 wt % nylon and a phase inversion beyond 70 wt % nylon. Various models based on viscosity ratios were used to predict the region of phase inversion. Experiments were also carried out on in situ compatibilization using maleic anhydride–modified EPR (EPR‐g‐MA). In this reactive compatibilization strategy, the maleic anhydride groups of modified EPR reacted with the amino end groups of nylon. This reaction produced a graft copolymer at the blend interface, which in fact acted as the compatibilizer. The viscosity of the blend was found to increase when a few percent of modified EPR was added; at higher concentrations the viscosity leveled off, indicating a high level of interaction at the interface. Morphological investigations indicated that the size of the dispersed phase initially decreased when a few percent of the graft copolymer was added followed by a clear leveling off at higher concentration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 252–264, 2004