Poly(ethylene‐graft‐ethylene oxide) (PE‐PEO) and poly(ethylene‐co‐acrylic acid) (PEAA) as compatibilizers in blends of LDPE and polyamide‐6

In a blend of two immiscible polymers a controlled morphology can be obtained by adding a block or graft copolymer as compatibilizer. In the present work blends of low‐density polyethylene (PE) and polyamide‐6 (PA‐6) were prepared by melt mixing the polymers in a co‐rotating, intermeshing twin‐screw extruder. Poly(ethylene‐graft‐polyethylene oxide) (PE‐PEO), synthesized from poly(ethylene‐co‐acrylic acid) (PEAA) (backbone) and poly(ethylene oxide) monomethyl ether (MPEO) (grafts), was added as compatibilizer. As a comparison, the unmodified backbone polymer, PEAA, was used. The morphology of the blends was studied by scanning electron microscopy (SEM). Melting and crystallization behavior of the blends was investigated by differential scanning calorimetry (DSC) and mechanical properties by tensile testing. The compatibilizing mechanisms were different for the two copolymers, and generated two different blend morphologies. Addition of PE‐PEO gave a material with small, well‐dispersed PA‐spheres having good adhesion to the PE matrix, whereas PEAA generated a morphology characterized by small PA‐spheres agglomerated to larger structures. Both compatibilized PE/PA blends had much improved mechanical properties compared with the uncompatibilized blend, with elongation at break (ε_b) increasing up to 200%. Addition of compatibilizer to the PE/PA blends stabilized the morphology towards coalescence and significantly reduced the size of the dispersed phase domains, from an average diameter of 20 μm in the unmodified PE/PA blend to approximately 1 μm in the compatibilized blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2416–2424, 2000     

同向双螺杆熔体输送段捏合盘错列角对不相容体系共混物相态结构的影响

对啮合同向双螺杆挤出机,将捏合盘置于熔体输送段,通过改变捏合盘错列角,研究双螺杆挤出过程熔体输送段捏合盘错列角对不相容体系共混物相态结构的影响。应用差示扫描量热仪对两相共混体系HDPE/PS的热性能进行了实验研究,结果表明:螺杆构型对共混物的相容性影响不大。同时采用扫描电子显微镜考察了HDPE/PS共混物在熔体输送段末端位置和机头末端所取试样的相态结构,研究表明:置于熔体输送段捏合盘元件错列角对共混物分散相的相畴尺寸有一定影响。     

Phase morphology development and melt rheological behavior in nylon 6/polystyrene blends

Phase morphology development in immiscible blends of polystyrene (PS)/nylon 6 was investigated. The blends were prepared by melt blending in a twin‐screw extruder. The influence of the blend ratio, rotation speed of the rotors, and time of mixing on the phase morphology of the blends was carefully analyzed. The morphology of the samples was examined under a scanning electron microscope (SEM) and the SEM micrographs were quantitatively analyzed for domain‐size measurements. From the morphology studies, it is evident that the minor component, whether PS or nylon, forms the dispersed phase, whereas the major component forms the continuous phase. The 50/50 PS/nylon blend exhibits cocontinuous morphology. The continuity of the dispersed phase was estimated quantitatively based on the preferential solvent‐extraction technique, which suggested that both phases are almost continuous at a 50/50 blend composition. The effect of the rotor speed on the blend morphology was investigated. It was observed that the most significant breakdown occurred at an increasing rotor speed from 9 to 20 rpm and, thereafter, the domain size remained almost the same even when the rotor speed was increased. The studies on the influence of the mixing time on the blend morphology indicated that the major breakdown of the dispersed phase occurred at the early stages of mixing. The melt rheological behavior of the blend system was studied using a capillary rheometer. The effect of the blend ratio and the shear stress on the melt viscosity of the system was investigated. Melt viscosity decreased with increase in the shear stress, indicating pseudoplastic behavior. With increase of the weight fraction of PS, the melt viscosity of the system decreased. The negative deviation of the measured viscosity from the additivity rule indicated the immiscibility of the blends. The domain size versus the viscosity ratio showed a minimum value when the viscosities of the two phases were matched, in agreement with Wu's prediction. The morphology of the extrudates was analyzed by SEM. From these observations, it was noted that as the shear rate increased the particle size decreased considerably. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3537–3555, 2002     

Morphology and properties of nylon 6 and high density polyethylene blends in presence of nanoclay and PE‐g‐MA

In this study, we report the synergistic effect of nanoclay and maleic anhydride grafted polyethylene (PE‐g‐MA) on the morphology and properties of (80/20 w/w) nylon 6/high density polyethylene (HDPE) blend. Polymer blend nanocomposites containing nanoclay with and without compatibilizer (PE‐g‐MA) were prepared by melt mixing, and their morphologies and structures were examined with scanning electron microscopy (SEM) and wide angle X‐ray diffractometer (WAXD) study. The size of phase‐separated domains decreased considerably with increasing content of nanoclay and PE‐g‐MA. WAXD study and transmission electron microscopy (TEM) revealed the presence of exfoliated clay platelets in nylon 6 matrix, as well as, at the interface of the (80/20 w/w) nylon 6/HDPE blend–clay nanocomposites. Addition of PE‐g‐MA in the blend–clay nanocomposites enhanced the exfoliation of clays in nylon 6 matrix and especially at the interface. Thus, exfoliated clay platelets in nylon 6 matrix effectively restricted the coalescence of dispersed HDPE domains while PE‐g‐MA improved the adhesion between the phases at the interface. The use of compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Binary blends of metallocene polyethylene with conventional polyolefins: Rheological and morphological properties

The rheology and morphology of four sets of binary blends of polyethylene synthesized with metallocene catalysis (metallocene polyethylene: MCPE) with polyolefins prepared using Ziegler‐Natta catalysts have been investigated. The blend systems are MCPE with high density polyethylene (MCPE‐HDPE), polypropylene (MCPE‐PP), poly(propylene‐co‐ethylene) (MCPE‐CoPP), and poly(propylene‐co‐ethylene‐co‐1‐butylene) (MCPE‐TerPP). Cole‐Cole plots [storage melt viscosity (η′) versus loss melt viscosity (η″)], plots of the dynamic storage modulus (G′) versus the dynamic loss modulus (G″), and plots of the log melt viscosity (η*, η′, and η″) versus blend compositions were constructed. The morphology of the blends after microtoming and etching was studied. The phase morphology of MCPE‐HDPE appeared homogeneous, whereas the other three blends were heterogeneous. Rheological and morphological investigations indicated that the MCPE‐HDPE blend was miscible, but the other three blends were immiscible in the melt as well as in the solid state. These observations can be rationalized in terms of the similarity of the chemical structures of the polyolefins.     

Cocontinuous phase morphology of asymmetric compositions of polypropylene/high‐density polyethylene blend by the addition of clay

A novel method of developing cocontinuous morphology in 75/25 and 80/20 w/w polypropylene/high density polyethylene (PP/HDPE) blends in the presence of small amount (0.5 phr) of organoclay has been reported. SEM study indicated a reduction in average domain sizes (D) of disperse HDPE when PP, HDPE, and the organoclay were melt‐blended simultaneously at 200°C. However, when the two‐sequential heating protocol was employed, (that is, the organoclay was first intercalated by HDPE chains at 150°C, followed by melt blending of PP at 200°C), very interestingly a cocontinuous morphology was found even for very asymmetric blend compositions. WAXD study revealed the intercalation of both PP and HDPE chains inside the clay galleries, when PP/HDPE and clay were melt‐mixed together at 200°C. However, when the two‐sequential heating protocol was used the organoclay platelets were selectively intercalated by the HDPE chains. Addition of SEPS in the blend decreased the D of HDPE domains in both the blending methods. Thus, the observed cocontinuous morphology in asymmetric composition of PP/HDPE blend in presence of clay is because of the barrier effect of the clay platelets in the HDPE phase that restrict the phase inversion into the domain/matrix morphology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphology and mechanical property changes in compatibilized high density polyethylene/polyamide 6 nanocomposites induced by carbon nanotubes

Addition of carbon nanotubes to immiscible polymer blends with co‐continuous morphology features to improve the electrical conductivity has attracted much attention in recent years; however, less attention has been paid to the effect of carbon nanotubes on the morphology and corresponding physical properties of immiscible polymer blends with typical sea‐island morphology. In this work, therefore, functionalized multiwalled carbon nanotubes (FMWCNTs) were introduced into an immiscible high density polyethylene/polyamide 6 (HDPE/PA6) blend which was compatibilized by maleic anhydride grafted HDPE (HDPE‐MA). The distribution of FMWCNTs and the phase morphologies of the nanocomposites were characterized using scanning electron microscopy and transmission electron microscopy. The crystallization and melting behaviors of the components were analyzed by differential scanning calorimetry, which is thought to be favorable for an understanding of the distribution of FMWCNTs. It is interesting to observe that the morphology of PA6 particles is very dependent on the method of preparation of the nanocomposites. Correspondingly, FMWCNTs exhibit an apparent reinforcement effect and/or an excellent toughening effect for the compatibilized HDPE/PA6 blend, depending upon their distribution state and the variation of PA6 morphology. This work proves that FMWCNTs have a potential application in further improving the mechanical properties of compatibilized immiscible polymer blends. Copyright © 2012 Society of Chemical Industry     

Crystallization kinetics and tensile modulus of blends of metallocene short‐chain branched polyethylene with conventional polyolefins

In this study, blends of metallocene short‐chain branched polyethylene (SCBPE) with low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polystyrene (PS), ethylene–propylene–diene monomer (EPDM), and isotactic polypropylene (iPP) were prepared in weight proportions of 80 and 20, respectively. The crystallization behaviors of these blends were studied with polarized light microscopy (PLM) and differential scanning calorimetry. PLM showed that SCBPE/LDPE, SCBPE/HDPE, and SCBPE/EPDM formed band spherulites whose band widths and sizes were both smaller than that of pure SCBPE. No spherulites were observed, but tiny crystallites were observed in the completely immiscible SCBPE/PS, and the crystallites in SCBPE/iPP became smaller; only irregular spherulites were seen. The crystallization kinetics and mechanical properties of SCBPE were greatly affected by the second polyolefin but in different way, depending on the phase behavior and the moduli of the second components. SCBPE may be phase‐miscible in the melt with LDPE, HDPE, and EPDM but phase‐separated during crystallization. A big change in the crystal morphology and crystallization kinetics existed in the SCBPE/iPP blend. The mechanical properties of the blends were also researched with dynamic mechanical analysis (DMA). DMA results showed that the tensile modulus of the blends had nothing to do with the phase behavior but only depended on the modulus of the second component. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1816–1823;2005     

Effect of the high‐density polyethylene melt index on the microcellular foaming of high‐density polyethylene/polypropylene blends

The effect of high‐density polyethylene (HDPE)/polypropylene (PP) blending on the crystallinity as a function of the HDPE melt index was studied. The melting temperature and total amount of crystallinity in the HDPE/PP blends were lower than those of the pure polymers, regardless of the blend composition and melt index. The effects of the melt index, blending, and foaming conditions (foaming temperature and foaming time) on the void fractions of HDPEs of various melt indices and HDPE/PP blends were also investigated. The void fraction was strongly dependent on the foaming time, foaming temperature, and blend composition as well as the melt index of HDPE. The void fraction of the foamed 30:70 HDPE/PP blend was always higher than that of the foamed 50:50 HDPE/PP blend, regardless of the melt index. The microcellular structure could be greatly improved with a suitable ratio of HDPE to PP and with foaming above the melting temperature for long enough; however, using high‐melt‐index HDPE in the HDPE/PP blends had a deleterious effect on both the void fraction and cell morphology of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 364–371, 2004     

Effect of core‐shell morphology evolution on the rheology,crystallization, and mechanical properties of PA6/EPDM‐g‐MA/HDPE ternary blend

In this article, polyamide 6 (PA6), maleic anhydride grafted ethylene‐propylene‐diene monomer (EPDM‐g‐MA), high‐density polyethylene (HDPE) were simultaneously added into an internal mixer to melt‐mixing for different periods. The relationship between morphology and rheological behaviors, crystallization, mechanical properties of PA6/EPDM‐g‐MA/HDPE blends were studied. The phase morphology observation revealed that PA6/EPDM‐g‐MA/HDPE (70/15/15 wt %) blend is constituted from PA6 matrix in which is dispersed core‐shell droplets of HDPE core encapsulated by EPDM‐g‐MA phase and indicated that the mixing time played a crucial role on the evolution of the core‐shell morphology. Rheological measurement manifested that the complex viscosity and storage modulus of ternary blends were notable higher than the pure polymer blends and binary blends which ascribed different phase morphology. Moreover, the maximum notched impact strength of PA6/EPDM‐g‐MA/HDPE blend was 80.7 KJ/m² and this value was 10–11 times higher than that of pure PA6. Particularly, differential scanning calorimetry results indicated that the bulk crystallization temperature of HDPE (114.6°C) was partly weakened and a new crystallization peak appeared at a lower temperature of around 102.2°C as a result of co‐crystal of HDPE and EPDM‐g‐MA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

An effective method of processing immiscible polymer blends into strong fiber

A unique methodology employing a “nearly co‐continuous morphology” for processing immiscible polymers into strong fiber is presented, and an immiscible polypropylene/polystyrene (PP/PS) blend is used as a model system to demonstrate the effectiveness of this methodology. The “nearly co‐continuous morphology” is easier to obtain than the fully co‐continuous structure, and yet, it provides an engineering solution to the production of strong fiber from an immiscible polymer blend. In addition, a process different from traditional melt spinning is used to prepare fiber with good mechanical properties. Traditional melt spinning involves large jet stretch and therefore introduces large interfacial orientation but little molecular orientation in polymer blends. To address this issue, the PP/PS blend is spun with nearly zero jet stretch and after solidification undergoes hot drawing at temperature close to the glass transition temperature of PS. This process sequence imparts a large degree of molecular orientation to the PP phase and produces a strong fiber. The proposed methodology can be extended to other blend systems and provides a potential route for directly recycling commingled polymer waste without preseparation or compatibilization. POLYM. ENG. SCI., 59:2052–2061, 2019. © 2019 Society of Plastics Engineers     

Viscoelastic properties of reactive and non‐reactive blends of ethylene‐methyl acrylate copolymers with styrene‐maleic anhydride copolymer

The effects of compatibilizing reactions on the viscoelastic properties and morphology of ethylene‐methyl acrylate copolymers were studied. Potentially reactive blends of styrene‐maleic anhydride copolymer (SMAH) and a terpolymer of ethylene/methyl acrylate/glycidyl methacrylate (E‐MA‐GMA) were compared with a non‐reactive blend of SMAH and an ethylene/methyl acrylate (E‐MA) copolymer with similar rheological properties. Melt mixing was carried out in a batch mixer and in a co‐rotating twin screw extruder. The morphology of the reactive blends showed smaller domain sizes than the non‐reactive blends, and the viscoelastic properties of the blends were very different. The storage and loss moduli and the complex viscosity of the reactive blends were greater than those of non‐reactive blends. The reactive blends had a higher zero shear viscosity, plateau modulus and mean relaxation time than their non‐reactive counterparts, indicating a higher degree of melt elasticity. The melt elasticity was maximum at 25% functionalized ethylene‐methyl acrylate concentration.     

Effect of nanoclay on the morphology and properties of poly(methyl methacrylate)/high‐density polyethylene blends

The effect of nanoclay on the morphology and properties of poly(methyl methacrylate) (PMMA)/high‐density polyethylene (HDPE) blends was studied. A scanning electron microscopy study of the PMMA/HDPE (70/30 w/w) blends with nanoclay indicated a reduction in the average domain sizes of the dispersed HDPE phase and, hence, a better extent of mixing compared to that of the blends without any nanoclay. An X‐ray diffraction study and transmission electron microscopy revealed the localization of intercalated nanoclay in the PMMA matrix of the PMMA/HDPE (70/30 w/w) blend. However, the same effect of clay was not observed in the PMMA/HDPE (30/70 w/w) blend when HDPE became the matrix. In the PMMA/HDPE (30/70 w/w) blend, the addition of nanoclay increased the domain size of the dispersed PMMA domains by preferential location of the clays inside the PMMA domains. The addition of polyethylene‐grafted maleic anhydride in both compositions of the PMMA/HDPE blend effectively reduced the domain size of the disperse phases in the blend. However, the presence of clay increased the tensile strength and storage modulus of the PMMA/HDPE blends in both blend compositions. Thus, in the PMMA/HDPE blend, the clay platelets acted as a effective compatibilizer as long as they were dispersed mainly in the matrix phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication of nanostructured polycarbonate/poly(methyl methacrylate) blends with improved optical and mechanical properties by high‐shear processing

The structure and properties of polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends fabricated using a high‐shear extruder at different shear rates were investigated. It was found that the morphologies of the blends were greatly dependent on the shear rate exerted during melt processing. High‐shear processing leads to a nanostructured PC/PMMA blend, in which PMMA domains with a size of less than 50 nm are homogeneously dispersed in the PC matrix. The prepared nanostructured blends exhibit not only excellent optical properties with a transmittance of more than 90% in the visible region but also a higher modulus than pure PC. In contrast, the PMMA domain size ranges from submicron to micrometer for the same blends processed at a low‐shear rate. These blends are opaque and display much lower elongation at break compared with the blends processed at a high‐shear rate. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Improvement of melt spinning properties and conductivity of immiscible polypropylene/polystyrene blends containing carbon black by addition of styrene‐ethylene‐butene‐styrene block copolymer

Conducting polymeric materials prepared from immiscible blends, such as polypropylene (PP)/polystyrene (PS), together with carbon black (CB), are known to have a relatively high electrical conductivity, because of a selective distribution of CB (double percolation). Melt spinning of immiscible blends containing CB has, however, not been extensively reported on previously. An immiscible 1:1 blend of PP and PS to which 4 wt% CB was added exhibited a very low melt draw‐down ratio at rupture compared wit PP with the same content of CB. By adding 5 wt% SEBS (styrene‐ethylene‐butene‐styrene block copolymer), the ultimate melt draw‐down ratio increased about 10 times, which made the material more suitable for melt spinning. As‐extruded samples of the immiscible blends (with CB) did not have higher electrical conductivities than PP/CB. A heat treatment increased the conductivity of immiscible PP/PS/CB composites, and longer treatment times and higher temperatures promoted the conductivity. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effect of confinement on glass dynamics and free volume in immiscible polystyrene/high‐density polyethylene blends

The effect of confinement on glass dynamics combined with the corresponding free volume changes of amorphous polystyrene (PS) in blends with semi‐crystalline high‐density polyethylene (HDPE) have been investigated using thermal analyses and positron annihilation lifetime spectroscopy (PALS). Two different glass transition temperatures (T_g) were observed in a PS/HDPE blend due to the dissimilarity in the chemical structure, consistent with an immiscible blend. However, T_g of PS in the incompatible PS/HDPE blend showed an upward trend with increasing PS content resulting from the confinement effect, while T_g of the semi‐crystalline HDPE component became lower than that of neat HDPE. Moreover, the elevation of T_g of PS was enhanced with a decrease of free volume radius by comparing annealed and unannealed PS/HDPE blends. Positron results showed that the free volume radius clearly decreased with annealing for all compositions, although the free volume hole size agreed well with linear additivity, indicating that there was only a weak interaction between the two components. Combining PALS with thermal analysis results, the confinement effect on the glass dynamics and free volume of PS phase in PS/HDPE blends could be attributed to the shrinkage of HDPE during crystallization when HDPE acted as the continuous phase. © 2015 Society of Chemical Industry     

Comparison of olefin copolymers as compatibilizers for polypropylene and high‐density polyethylene

Some polyolefin elastomers were compared as compatibilizers for blends of polypropylene (PP) with 30 wt % high‐density polyethylene (HDPE). The compatibilizers included a multiblock ethylene–octene copolymer (OBC), two statistical ethylene–octene copolymers (EO), two propylene–ethylene copolymers (P/E), and a styrenic block copolymer (SBC). Examination of the blend morphology by AFM showed that the compatibilizer was preferentially located at the interface between the PP matrix and the dispersed HDPE particles. The brittle‐to‐ductile (BD) transition was determined from the temperature dependence of the blend toughness, which was taken as the area under the stress–strain curve. All the compatibilized blends had lower BD temperature than PP. However, the blend compatibilized with OBC had the best combination of low BD temperature and high toughness. Examination of the deformed blends by scanning electron microscopy revealed that in the best blends, the compatibilizer provided sufficient interfacial adhesion so that the HDPE domains were able to yield and draw along with the PP matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Morphology and properties of nylon6 and high density polyethylene blends in absence and presence of nanoclay

The morphology and properties of nylon6/HDPE blends without and with nanoclay has been reported. Scanning electron microscopy study of the (70/30 w/w) nylon6/HDPE blends with small amount (0.1 phr) of nanoclay indicated a reduction in the average domain sizes (D) of dispersed HDPE phase and hence better extent of mixing compared to the blend without any nanoclay. X‐ray diffraction study and transmission electron microscopy revealed that nanoclay layers were mostly located in nylon6 matrix of the (70/30 w/w) nylon6/HDPE blend. However, the same effect of nanoclay on the morphology was not observed in (30/70 w/w) nylon6/HDPE blend where HDPE became the matrix. In (30/70 w/w) nylon6/HDPE blend, addition of nanoclay increased the D of dispersed nylon6 domains by preferential location of the clays in side the nylon6 domains. Thus, the clay platelets in the matrix phase acted as barrier that restricted the coalescence of dispersed domains during melt‐mixing. Addition of PE‐g‐MA in both the compositions of nylon6/HDPE blend effectively reduced the D of dispersed phases. Storage modulus and thermal stability of the blend were improved in presence of small amount of clay, whereas addition of PE‐g‐MA lowered the mechanical and thermal properties of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Co‐crystallization in ternary polyethylene blends: tie crystal formation and mechanical properties improvement

Understanding the co‐crystallization behavior of ternary polyethylene (PE) blends is a challenging task. Herein, in addition to co‐crystallization behavior, the rheological and mechanical properties of melt compounded high density polyethylene (HDPE)/low density polyethylene (LDPE)/Zeigler ? Natta linear low density polyethylene (ZN‐LLDPE) blends have been studied in detail. The HDPE content of the blends was kept constant at 40 wt% and the LDPE/ZN‐LLDPE ratio was varied from 0.5 to 2. Rheological measurements confirmed the melt miscibility of the entire blends. Study of the crystalline structure of the blends using DSC, wide angle X‐ray scattering, small angle X‐ray scattering and field emission SEM techniques revealed the formation of two distinct co‐crystals in the blends. Fine LDPE/ZN‐LLDPE co‐crystals, named tie crystals, dispersed within the amorphous gallery between the coarse HDPE/ZN‐LLDPE co‐crystals were characterized for the first time in this study. It is shown that the tie crystals strengthen the amorphous gallery and play a major role in the mechanical performance of the blend.© 2016 Society of Chemical Industry     

Solid‐state modification of isotactic polypropylene (iPP) via grafting of styrene. II. Morphology and melt processing

Grafting of vinyl monomers onto isotactic polypropylene (iPP) in the solid state represents a convenient route to chemically modify iPP and, consequently, its properties. Solid‐state modification can be carried out on iPP powder directly from the polymerization reactor. The modified powder is then processed in the melt, usually with the addition of fillers and/or additives, to obtain the final product. In this work we have studied the effect of melt processing on the morphology of solid‐state polymerized PP/polystyrene (PS) blends, i.e., of a iPP powder previously modified in the solid‐state with styrene (St) and optionally in the presence of divinylbenzene (DVB). A series of samples containing different amounts of PS and displaying different grafting efficiencies were investigated before and after processing in the melt. Transmission electron microscopy, scanning electron microscopy, and solid‐state NMR were used to investigate the morphology on different length scales. It was shown that PS coalescence during processing can be hindered, thereby stabilizing the initially polymerized iPP/PS blends morphology. Indeed, reducing the PS amount in the blend or increasing the grafting efficiency resulted in less coalescence of the PS domains. Crosslinking of the PS phase during the solid‐state polymerization resulted also in a very fine but heterogeneous morphology. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 575–583, 2005