Phase morphology development in PP/PA6 blends induced by a maleated thermoplastic elastomer

The effects of maleated thermoplastic elastomer (TPEg) on morphological development of polypropylene (PP)/polyamide 6 (PA6) blends with a fixed PA6 content (30 wt %) were investigated. For purpose of comparison, nonmaleated thermoplastic elastomer (TPE) was also added to the above binary blends. A comparative study of FTIR spectroscopy in above both ternary blends confirmed the formation of in situ graft copolymer in the PP/PA6/TPEg blend. Dynamic mechanical analysis (DMA) indicated that un‐like TPE, the incorporation of TPEg remarkably affected both intensity and position of loss peaks of blend components. Scanning electron microscopy (SEM) demonstrated that PP/PA6/TPE blends still exhibited poor interfacial adhesion between the dispersed phase and matrix. However, the use of TPEg induced a finer dispersion and promoted interfacial adhesion. Transmission electron microscopy (TEM) for PP/PA6/TPEg blends showed that a core‐shell structure consisting of PA6 particles encapsulated by an interlayer was formed in PP matrix. With the concentration of TPEg increasing, the dispersed core‐shell particles morphology was found to transform from discrete acorn‐type particles to agglomerate with increasing degree of encapsulation. The modified Harkin's equation was applied to illustrate the evolution of morphology with TPEg concentration. “Droplet‐sandwiched experiments” further confirmed the encapsulation morphology in PP/PA6/TPEg blends. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1050–1061, 2006     

Atomic force microscopy study on blend morphology and clay dispersion in polyamide‐6/polypropylene/organoclay systems

The phase structure and clay dispersion in polyamide‐6(PA6)/polypropylene(PP)/organoclay (70/30/4) systems with and without an additional 5 parts of maleated polypropylene (MAH‐g‐PP) as a compatibilizer were studied with atomic force microscopy (AFM). AFM scans were taken from the polished surface of specimens that were chemically and physically etched with formic acid and argon ion bombardment, respectively. The latter technique proved to be very sensitive to the blend morphology, as PP was far more resistant to ion bombardment than PA6. In the absence of the MAH‐g‐PP compatibilizer, the organoclay is located in the PA6 phase; this finding is in line with transmission electron microscopic results. Further, the PP is coarsely dispersed in PA6 and the adhesion between PA6 and PP is poor. The addition of MAH‐g‐PP resulted in a markedly finer PP dispersion and good interfacial bonding between PA6 and PP. In this blend, the organoclay was likely dispersed in the PA6‐grafted PP phase. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43:1198–1204, 2005     

Specific properties of in situ ruthenium‐catalyzed polyamide 12/polydimethylsiloxane compatibilized blend

The main objective of this work focused on the chemical modification of polyamide 12 (PA12) properties through the reaction with a hydride‐terminated polydimethylsiloxane (PDMS‐SiH). The investigated PA12/PDMS‐SiH blend was compatibilized by ruthenium derivative catalyzed hydrosilylation reaction in molten state. This original route enhanced interfacial adhesion and avoid PDMS‐SiH leaching phenomenon between the two immiscible phases. More specifically, the size of PDMS‐SiH domains in the blend decreased from around 4 μm to 800 nm and from 30 to 1 μm after compatibilization with 10 and 20 wt % PDMS‐SiH, respectively. For the best compatibilized PA12/PDMS‐SiH blend, the introduction of PDMS lowered the surface free energy and the PA12‐based blend turned from hydrophilic to hydrophobic behavior, as evidenced by the water contact angle measurements. Gas permeability and CO₂/H₂ and CO₂/He gas selectivity were also improved with the increase in PDMS content. Besides, the mechanical properties were enhanced with 13% increase in Young's modulus after in situ compatibilization with 15 wt % PDMS‐SiH. Thermal stability was also improved after compatibilization as the initial degradation temperature of reactive blends obviously increased compared with nonreactive ones. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 978–988     

Effect of dispersion and selective localization of carbon nanotubes on rheology and electrical conductivity of polyamide 6 (PA6), Polypropylene (PP), and PA6/PP nanocomposites

Nanocomposites were prepared by adding 1–3 vol % multiwalled carbon nanotubes (MWCNTs) to polyamide 6 (PA6), polypropylene (PP), and their co‐continuous blends of 60/40 and 50/50 volume compositions. Because of the good interaction and interfacial adhesion to the PA6, nanotubes were disentangled and distributed evenly through nanocomposites containing PA6. In contrast, lack of active interactions between the matrix and the CNTs resulted in poor tube dispersion in PP. These observations were then verified by studying the rheology and electrical conductivity of their respective nanocomposites. Absence of percolated CNT clusters and possible wrapping of the tubes by PA6 resulted in low electrical conductivity of PA6/CNT nanocomposites. On the other hand, despite the weak dispersion of the tubes, electrical conductivities of PP/CNT nanocomposites were much higher than all other counterparts. This could be the result of good three‐dimensional distribution of the agglomerated bundles and secondary aggregation of tubes in PP. Adding CNTs to blends of PA6/PP (60/40 and 50/50) resulted in almost full localization of carbon nanotubes in PA6, leading to their higher effective concentration. At the same CNT loadings, the blend nanocomposites had three to seven orders of magnitude higher electrical conductivity than pure PA6. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 368–378     

Morphology development of immiscible polymer blends during melt blending: Effects of interfacial agents on the liquid-solid interfacial heat transfer

This article reports on a new phenomenon: The presence of a compatibilizer accelerates the melting/plastification of an immiscible polymer blend during melt blending. The increase in the rate of melting as a result of the addition of a compatibilizer is believed to be one of the important factors responsible for the fact that the morphology of compatibilized blends develops much faster than that of their uncompatibilized counterparts. To substantiate the above statement, blends based on polypropylene (PP) and polyamide 6 (PA6) were used as model systems. The compatibilizer was a graft copolymer (PP-g-PA6) with PP as the backbone and PA6 as grafts. Its presence in a PP/PA6 blend accelerated the rate of melting of the PA6. This effect was observed only when the compatibilizer itself was molten and migrated to the interfacial layer between the PA6 and PP phases. It is likely that the presence of the compatibilizer increased the chain entanglements at the PP and PA6 interface and consequently reduced the thermal resistance of the interfacial layer. Detailed mechanisms are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3368–3384, 1999     

Polymer blends of polyamide-6 (PA6) and poly(phenylene ether) (PPE) compatibilized by a multifunctional epoxy coupler

A tetrafunctional epoxy monomer, N,N,N′-N′-tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM), has demonstrated to be a highly efficient reactive compatibilizer in compatibilizing the immiscible and incompatible polymer blends of polyamide-6 (PA6) and poly(2,6-dimethyl-1,4-phenylene ether) (PPE). This epoxy coupler can react with both PA6 and PPE to form various PA6-co-TGDDM-co-PPE mixed copolymers. These interfacially formed PA6-co-TGDDM-co-PPE copolymers tend to anchor along the interface to reduce the interfacial tension and result in finer phase domains and enhanced interfacial adhesion. A simple one-step melt blending has demonstrated to be more efficient in producing a better compatibilized PA6/PPE blend than a two-step sequential blending. The mechanical property improvement of the compatibilized blend over the uncompatibilized counterpart is very drastic, by considering the addition of a very small amount, a few fractions of 1%, of this epoxy coupling agent. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1805–1819, 1998     

In situ compatibilization of PET/PS blends through carbamate‐functionalized reactive copolymers

To investigate the effect of reactive compatibilization in the immiscible poly(ethylene terephthalate) (PET)/polystyrene (PS) blend, poly(styrene‐co‐methacryloyl carbamate) (PSM) was synthesized as a reactive compatibilizer. The interfacial reaction of the carbamate group in PSM with OH/COOH in PET was confirmed by atomic force microscopy. The interfacial roughness developed rapidly with an increase in the methacryloyl carbamate (MAC) content and then leveled off above the optimum content (3.8 wt %). These results were well‐reflected in the interfacial adhesion, morphology, and mechanical properties of the PET/PS blends, showing a maximum value at the optimum MAC content. The existence of a maximum value is believed to stem from a reciprocal relationship between the sufficient formation of in situ copolymer and the fast diffusion rate of reactive polymers at the interface. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1396–1404, 2000     

Reinforcement of solid‐melt interfaces for semicrystalline polymers in a sequential two‐staged injection molding process

The solid‐melt interfaces between polyethylene (PE) and polyamide 6 (PA6) reinforced by in situ reactive compatibilization in a sequential two‐staged injection molding process has been studied in this work. The effects of the maleic anhydride grafted PE content and processing parameters, such as injection pressure, injection speed, melt temperature, and mold temperature, on the interfacial adhesion were investigated experimentally. The results of the interfacial adhesion characterized by lap shear measurement showed that the interfacial temperature and heat transfer between PE and PA6 interfaces play a very significant role in the bonding process. The fracture surfaces of the specimens prepared at different calculated interfacial temperature were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), which suggested that the fracture failure changes from adhesive to cohesive failure with increasing interfacial temperature. The contribution of crystalline parts of the in situ formed copolymers to the enhancement in interfacial adhesion also was determined by DSC analysis. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1112–1124, 2009     

Macromorphology of polypropylene homopolymer tacticity mixtures

The macromorphology of isotactic/atactic (iPP/aPP) and isotactic/syndiotactic (iPP/sPP) polypropylene mixtures is examined by optical microscopy. The spherulitic macrostructure of equimolecular weight [weight‐average molecular weight (M_w) = 200k] iPP/aPP blends is volume‐filling to very high aPP concentrations when the crystallization temperature is 130 °C. Similar spherulitic macrostructures (spherulite size and volume‐filling nature) are observed for iPP homopolymer and a 50/50 iPP/aPP blend at low crystallization temperatures (115–135 °C). At higher crystallization temperatures (140–145 °C), a equimolecular weight (M_w = 200k) 50/50 iPP/aPP blend exhibits nodular texture that blurs the spherulitic boundaries. Double temperature jump experiments show that the nodular texture is due to melt phase separation that develops prior to crystallization. The upper critical solution temperature (UCST) of a 50/50 iPP/aPP blend (M_w = 200k) lies below 155 °C, and the blend is miscible at conventional melt processing temperatures. The UCST behavior is controlled by the blend molecular weight and aPP microstructure. aPP microstructures containing increased isospecific sequencing (although still noncrystalline) exhibit a reduced tendency for phase separation in 50/50 mixtures (M_w = 200k) and the absence of nodular texture at low undercoolings (140–145 °C). Equimolecular weight (M_w = 200k) 50/50 iPP/sPP mixtures exhibit phase‐separated texture at all crystallization temperatures. The size scale of the phase‐separated texture decreases with decreasing crystallization temperature because of a competition between crystallization and phase separation from a melt initially well mixed from the initial solution blending process. Extended melt annealing experiments show that the 50/50 iPP/sPP mixture (M_w = 200k) is immiscible in the melt at conventional melt processing temperatures. The iPP/sPP pair shows a much stronger tendency for phase separation than the iPP/aPP polymer pair. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1947–1964, 2000     

Impact‐specific essential work of fracture of maleic anhydride‐compatibilized polypropylene/elastomer blends and their composites

Charpy drop‐weight‐impact and essential work of fracture (EWF) characteristics of maleic anhydride (MA)‐compatibilized styrene–ethylene butylene–styrene (SEBS)/polypropylene (PP) blends and their composites reinforced with short glass fibers (SGFs) were investigated. MA was grafted to either SEBS copolymer (SEBS‐g‐MA) or PP (PP‐g‐MA). The mPP blend was prepared by the compounding of 95% PP and 5% PP‐g‐MA. Drop‐weight‐impact results revealed that the mPP specimen had an extremely low impact strength. The incorporation of SEBS or SEBS‐g‐MA elastomers into mPP improved its impact strength dramatically. Similarly, the addition of SEBS was beneficial for enhancing the impact strength of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids. A scanning electron microscopy examination of the fractured surfaces of impact specimens revealed that the glass‐fiber surfaces of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids were sheathed completely with deformed matrix material. This was due to strong interfacial bonding between the phase components of the hybrids associated with the MA addition. Impact EWF tests were carried out on single‐edge‐notched‐bending specimens at 3 m s^?1. The results showed that pure PP, mPP, and the composites only exhibited specific essential work. The nonessential work was absent in these specimens under a high‐impact‐rate loading condition. The addition of SEBS or SEBS‐g‐MA elastomer to mPP increased both the specific essential and nonessential work of fracture. This implied that elastomer particles contributed to the dissipation of energy at the fracture surface and in the outer plastic zone at a high impact speed of 3 m s^?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1881–1892, 2002     

Structural and morphological studies on the deformation behavior of polypropylene/multi‐walled carbon nanotubes nanocomposites prepared through ultrasound‐assisted melt extrusion process

Structural and morphological behavior under stress–strain of polypropylene/multi‐walled carbon nanotubes (PP/MWCNTs) nanocomposites prepared through ultrasound‐assisted melt extrusion process was studied by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, small angle X‐ray scattering (SAXS), and wide angle X‐ray scattering (WAXS). A high ductile behavior was observed in the PP/MWCNT nanocomposites with low concentration of MWCNTs. This was related to an energy‐dissipating mechanism, achieved by the formation of an ordered PP‐CNTs interphase zone and crystal oriented structure in the undeformed samples. Different strain‐induced‐phase transformations were observed by ex situ SAXS/WAXS, characterizing the different stages of structure development during the deformation of PP and PP/MWCNTs nanocomposites. The high concentration of CNTs reduced the strain behavior of PP due to the agglomeration of nanoparticles. A structural pathway relating the deformation‐induced phase transitions and the dissipation energy mechanism in the PP/MWCNTs nanocomposites at low concentration of nanoparticles was proposed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 475–491     

Measuring the Interfacial Thickness of Immiscible Polymer Blends by Nano-probing of Atomic Force Microscopy

Immiscible polymer blends are an important family of polymer materials. The interfacial thickness between different phases is a very important parameter that dictates, to a great extent, the morphology and properties of such a blend. This work explores and optimizes an up-to-date atomic force microscopy (AFM) of type NanoIR2? system in order to quantitatively measure the interfacial thickness of immiscible polymer blends. This system is equipped with two nano-probes capable of detecting the response of a material to an infrared pulse called AFM-infrared spectroscopy mode (AFM-IR) or conducting resonance called AFM-Lorentz Contact Resonance mode (AFM-LCR), respectively. Its potential for quantitatively measuring the interfacial thickness of immiscible polymer blends is evaluated using blends composed of polyamide 6 (PA6) and polyolefin elastomer (POE) in the presence or absence of a POE containing maleic anhydride (POE-g-MAH) as a compatibilizer. Surface roughness affects adversely the signal intensity and consequently an accurate measurement of the interfacial thickness. Optimum sample surface preparation procedures are proposed.

     

Foaming behavior of polypropylene/polystyrene blends enhanced by improved interfacial compatibility

A series of polypropylene (PP)/polystyrene (PS) blends were prepared by solvent blending with PS‐grafted PP copolymers (PP‐g‐PS) having different PS graft chain length as compatibilizers. The interfacial compatibility was significantly improved with increasing PS graft chain length until the interface was saturated at PS graft chain length being 3.29 × 10³ g/mol. The blends were foamed by using pressure‐quenching process and supercritical CO₂ as the blowing agent. The cell preferentially formed at compatibilized interface because of low energy barrier for nucleation. Combining with the increased interfacial area, the compatibilized interface lead to the foams with increased cell density compared to the uncompatibilized one. The increase in interfacial compatibility also decreased the escape of gas, held more gas for cell growth, and facilitated the increase in expansion ratio of PP/PS blend foams. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1641–1651, 2008     

Compatibility effect on the thermal degradation behaviour of polypropylene blends with polyamide 6, ethylene propylene diene copolymer and polyurethane

The morphology and thermal behaviour of polypropylene/polyamide 6 (PP/PA6), polypropylene/copolymer ethylene propylene diene (PP/PEBAX) and polypropylene/rigid polyurethane (PP/PUR) blends compatibilised with polypropylene-graft-maleic anhydride (PP-g-MA) were studied using scanning electron microscopy and thermogravimetric analyses. The study focuses on the influence of different blends obtained by mixing a thermoplastic, thermoplastic elastomer or thermoset with PP, compatibilised with PP-g-MA. The compatibilising effect of PP-g-MA in an immiscible PP/PA6 blend induces a homogeneous dispersion due to interfacial adhesion. For the PP/PEBAX and PP/PUR binary blends studied slight changes in the morphology were observed with a continuous phase but the PEBAX or PUR domains remained in the PP matrix. The deconvolution of the TGA curve permitted an evaluation of the decomposition stage of the undiluted and blend systems. Thermal stability is slightly influenced by the position of the maximum decomposition rate temperature of the first derivative thermogravimetric curve (DTG). However, the DTG curve profile remains consistent. The activation energy of undiluted PP was in the range of 162–169 kJ mol⁻¹ determined by the Ozawa method. The stabilized activation energy value for all blends studied above a 0.4 weight-loss fraction is discussed.     

Interplay between solid state microstructure and photophysics for poly(9,9‐dioctylfluorene) within oriented polyethylene hosts

We present a study of isotropic and uniaxially oriented binary blend films comprising ≤1 wt % of the conjugated polymer poly(9,9‐dioctylfluorene) (PFO) dispersed in both ultra‐high molecular weight (UHMW) and linear‐low‐density (LLD) polyethylene (PE). Polarized absorption, fluorescence and Raman spectroscopy, scanning electron microscopy, and X‐ray diffraction are used to characterize the samples before and after tensile deformation. Results show that blend films can be prepared with PFO chains adopting a combination of several distinct molecular conformations, namely glassy, crystalline, and the so‐called β‐phase, which directly influences the resulting optical properties. Both PFO concentration and drawing temperature strongly affect the alignment of PFO chains during the tensile drawing of the blend films. In both PE hosts, crystallization of PFO takes place during drawing; the resulting ordered chains show optimal optical anisotropy. Our results clarify the PFO microstructure in oriented blends with PE and the processing conditions required for achieving the maximal optical anisotropy. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 22–38     

Reactive blending of PE‐GMA/PA6 effect of composition and processing conditions

Blends of ethylene‐glycidyl methacrylate copolymer (PE‐GMA) and polyamide 6 (PA6) were prepared in a corotating twin screw extruder. Two processing temperatures were used in order to disperse PA6 in two forms: at high temperature in the molten state in molted PE‐GMA Matrix (emulsion type mixture) and at lower temperature as fillers in molted PEGMA matrix (suspension type mixture). Processed blends were analyzed by scanning electron microscopy and dynamic mechanical experiments to probe the reactivity in the extruder and the compatibilization phenomena. The dependence of the morphology and the rheological properties of PE‐GMA/PA6 blends on blend composition and screw rotational speed was also investigated and is discussed in the paper. The results show that dispersion of the two polymers in the molten state leads to a higher level of interfacial reaction. They also show that whatever the screw rotational speed and the temperature of extrusion are, the rate of interfacial reaction in PE‐GMA/PA6 blends is higher for 50/50 PE‐GMA/PA blends than for 70/30 PE‐GMA/PA blends. Copyright © 2015 John Wiley & Sons, Ltd.     

Migration of nanosilica particles in polymer blends

Hydrophilic pyrogenic silica melt mixed in immiscible polypropylene/poly (ethylene‐co‐vinyl acetate) (PP/EVA) blend was found to migrate from the PP matrix to the EVA dispersed domains and remained confined inside them. Surprisingly, it was shown than silica was also able to migrate from a dispersed PP phase to an EVA matrix but this transfer was slower and not complete. The same silica with a hydrophobic surface treatment moved and accumulated to the blend interface and in PP. The mechanisms from which this migration proceeds are discussed. Whereas self diffusion of the particles was shown to have almost no effect, shear induced movements and collisions with dispersed drops is believed to be the most efficient mechanism. The possible trapping of silica aggregates during droplet–droplet coalescence was impossible to observe but is thought to be a possible additional mechanism. No quantification on the relative importance of the latter phenomenon can be drawn at the moment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1976–1983, 2008     

Reactive compatibilization of polyamide‐6 (PA 6)/polybutylene terephthalate (PBT) blends by a multifunctional epoxy resin

A multifunctional epoxy resin has been demonstrated to be an efficient reactive compatibilizer for the incompatible and immiscible blends of polyamide‐6 (PA 6) and polybutylene terephthalate (PBT). The torque measurements give indirect evidence that the reaction between PA and PBT with epoxy has an opportunity to produce an in situ formed copolymer, which can be as an effective compatibilizer to reduce and suppress the size of the disperse phase, and to greatly enhance mechanical properties of PA/PBT blends. The mechanical property improvement is more pronounced in the PA‐rich blends than that in the PBT‐rich blends. The fracture behavior of the blend with less than 0.3 phr compatibilizer is governed by a particle pullout mechanism, whereas shear yielding is dominant in the fracture behavior of the blend with more than 0.3 phr compatibilizer. As the melt and crystallization temperatures of the base polymers are so close, either PA or PBT can be regarded as a mutual nucleating agent to enhance the crystallization on the other component. The presence of compatibilizer and in situ formed copolymer in the compatibilized blends tends to interfere with the crystallization of the base polymers in various blends. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 23–33, 2000     

Structure–property relationships in polyamide 6/multi‐walled carbon nanotubes nanocomposites

Polyamide 6 (PA6)/multi‐walled carbon nanotubes (MWCNT) nanocomposites were produced by diluting a masterbach containing 20 wt % nanotubes using melt mixing. The influence of the addition of well dispersed MWCNT (as indicated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM)) on the thermal transitions, and crystallization behavior of the PA6 matrix is investigated. Differential scanning calorimetry (DSC) results show a reduction in heat capacity jump at the glass transition which is interpreted by an immobilized interfacial layer near the nanotubes. Furthermore, both DSC and X‐ray diffraction (XRD) measurements indicate that nanotubes favor the formation of the α crystalline form of PA6. These findings are correlated with the observed improvement of the storage modulus as revealed by dynamic mechanical thermal analysis (DMTA). Additionally, a new crystallization peak appears when MWCNT are added, and is attributed to the formation of a different morphology of the same type crystallite around the nanotubes walls (trans‐crystallinity). Finally, water sorption measurements show an increase of water content, normalized to the amorphous polymer fraction, in the nanocomposites. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 764–774, 2009     

Compatabilization of polystyrene/polypropylene blends by styrene–butadiene block copolymers with differing polystyrene block lengths

Compatibilization of polystyrene/polypropylene (PS/PP) blends, by use of a series of butadiene–styrene block copolymers was studied by means of small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM). The compatibilizers used differ in molar mass and the number of blocks. It was shown that the ability of a block copolymer (BC) to participate in the formation of an interfacial layer (and hence in compatibilization) is closely associated with the molar mass of styrene blocks. If the styrene blocks are long enough to form entanglements with the styrene homopolymer in the melt, then the BC is trapped inside this phase of the PS/PP blends, and its migration to the PS/PP interface is difficult. In this case, the BC does not participate in the formation of the interfacial layer nor, consequently, in the compatibilization process. On the other hand, the BC's with the molar mass of the PS blocks below the critical value are proved to be localized at the PS/PP interface. This preferable entrapping of some styrene–butadiene BC's in the PS phase of the PS/PP blend is, of course, connected to the differing miscibility of the BC blocks with corresponding components of this blend. Although the styrene block is chemically identical to the styrene homopolymer in the blend, the butadiene block is similar to the PP phase. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1647–1656, 1999