Dispersion,migration, and ‘network‐like’ structure formation of multiwall carbon nanotubes in co‐continuous,binary immiscible blends of polyamide 6 and acrylonitrile–butadiene–styrene copolymer during simultaneous melt‐mixing

Multiwall carbon nanotubes (MWNTs) were melt‐mixed in polyamide 6 (PA6) and acrylonitrile–butadiene–styrene (ABS) copolymer blends using a simultaneous mixing protocol in order to investigate the state of dispersion of MWNTs in PA6/ABS blends. The blend composition was varied from 40/60 (wt/wt) to 60/40 (wt/wt) in PA6/ABS blends, which showed ‘co‐continuous’ morphology in the presence of MWNTs. State of dispersion of MWNTs in these blends was assessed through bulk electrical conductivity measurements, morphological analysis, solution experiments, and UV‐vis spectroscopic analysis. MWNTs were subsequently modified with a novel organic modifier, sodium salt of 6‐aminohexanoic acid (Na‐AHA), to improve the state of dispersion of MWNTs. Blends with unmodified MWNTs exhibited the DC electrical conductivity in the range ～10^?11 to ～10^?5 S/cm, whereas blends with Na‐AHA‐modified MWNTs exhibited DC electrical conductivity in the range ～10^?7 to ～10^?5 S/cm. The reduction in MWNTs ‘agglomerate’ size (～73.7 μm for 40/60 blend with unmodified MWNTs to ～59.9 μm in the corresponding blend with Na‐AHA‐modified MWNTs) was observed through morphological analysis. The rheological studies showed increased complex viscosity and storage moduli in lower frequency region in case of blends with Na‐AHA‐modified MWNTs confirming a refined ‘network‐like’ structure of MWNTs. POLYM. ENG. SCI., 55:443–456, 2015. © 2014 Society of Plastics Engineers     

Blend composition dependence of the compatibilizing efficiency of graft copolymers for immiscible polymer blends

This work is concerned with the dependence of the compatibilizing efficiency of graft copolymers on the composition of immiscible polymer blends. A series of graft copolymers of polystyrene (PS) and polyamide 6 (PA6), denoted as PS‐g‐PA6, with different molecular structures were used as compatibilizers. The PS‐g‐PA6 was more efficient for the PS/PA6 (80/20) blend than for the PS/PA6 (20/80) one, indicating that a graft copolymer whose backbone and grafts match the matrix and the disperse phase polymers, respectively, has higher compatibilizing efficiency. This is in disagreement with the literature. Moreover, whatever the blend composition, for PS‐g‐PA6 graft copolymers with the same backbone and the same number of grafts per backbone, the longer the grafts, the higher their compatibilizing and stabilizing efficiency; for a given backbone/graft mass ratio, the longer the grafts and concomitantly the smaller the number of grafts per backbone, the higher the compatibilizing and stabilizing efficiency of the graft copolymer. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Preparation of polypropylene and polystyrene with NCO and NH2 functional groups and their applications in polypropylene/polystyrene blends

Isocyanate‐ and amine‐functionalized polypropylene (PP) and polystyrene (PS) were prepared through grafting and copolymerization method. These compounds are used as precursors for PP‐graft‐PS (PP‐g‐PS) copolymers and reacted at the matrix interface of PP/PS blends. Functionalized polymer structures were characterized by ¹H NMR and FTIR spectroscopy. The effects of the synthesized compatibilizer on the rheological and morphological behavior of PP/PS blends were investigated systematically. Results showed that the functional polymer was successfully synthesized, and the additional two different compatibilizer systems dramatically decreased the size of the dispersed phase domains in PP/PS blends. Compared with the uncompatibilized blends, compatibilized blends exhibited a slightly higher crystallization temperature because the melting points of the blend components were not evidently affected by the addition of compatibilizer, as revealed by differential scanning calorimetry. The compatibilizer effect on the PP/PS blends was reflected through rheological property and dynamic mechanical analysis. POLYM. ENG. SCI., 55:614–623, 2015. © 2014 Society of Plastics Engineers     

Compatibilization and morphology development of immiscible ternary polymer blends

We report a novel and effective strategy that compatibilizes three immiscible polymers, polyolefins, styrene polymers, and engineering plastics, achieved by using a polyolefin-based multi-phase compatibilizer. Compatibilizing effect and morphology development are investigated in a model ternary immiscible polymer blends consisting of polypropylene (PP)/polystyrene(PS)/polyamide(PA6) and a multi-phase compatibilizer (PP-g-(MAH-co-St) as prepared by maleic anhydride (MAH) and styrene (St) dual monomers melt grafting PP. Scanning electron microscopy (SEM) results indicate that, as a multi-phase compatibilizer, PP-g-(MAH-co-St) shows effective compatibilization in the PP/PS/PA6 blends. The particle size of both PS and PA6 is greatly decreased due to the addition of multi-phase compatibilizer, while the interfacial adhesion in immiscible pairs is increased. This good compatibilizing effect is promising for developing a new, technologically attractive method for achieving compatibilization of immiscible multi-component polymer blends as well as for recycling and reusing of such blends. For phase morphology development, the morphology of PP/PS/PA6 (70/15/15) uncompatibilized blend reveals that the blend is constituted from PP matrix in which are dispersed composite droplets of PA6 core encapsulated by PS phase. Whereas, the compatibilized blend shows the three components strongly interact with each other, i.e. multi-phase compatibilizer has good compatibilization between the various immiscible pairs. For the 40/30/30 blend, the morphology changed from a three-phase co-continuous morphology (uncompatibilized) to the dispersed droplets of PA6 and PS in the PP matrix (compatibilized).     

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     

Percolation phenomena in polymers containing dispersed iron

Metal‐polymer composites based on polyethylene (PE), polyoxymethylene (POM), polyamide (PA) and a PE/POM blend as matrix and dispersed iron (Fe) as filler have been prepared by extrusion of the appropriate mechanical mixtures, and their electrical conductivity, dielectric properties and thermal conductivity have been investigated. The filler spatial distribution is random in the PE‐Fe, POM‐Fe and PA‐Fe composites. In the PE/POM‐Fe composite the polymer matrix is two‐phase and the filler is contained only in the POM phase, resulting in an ordered distribution of dispersed Fe in the volume of polymer blend. The transition through the percolation threshold ?_c is accompanied by a sharp increase of the values of conductivity σ, dielectric constant ε′ and dielectric loss tangent tan δ. The critical indexes of the equations of the percolation theory are close to the theoretical ones in the PE‐Fe and POM‐Fe composites, whereas they take unusually high values in the PE/POMFe composite. Thus, t in the equation σ ～ (φ – φ_c)^t is 2.9–3.0 in the systems characterized by random distribution of dispersed filler and 8.0 in the PE/POM‐Fe system. The percolation threshold φ_c depends on the kind of polymer matrix, becoming 0.21, 0.24, 0.29 and 0.09 for the composites based on PE, POM, PA and PE/POM, respectively. Also the thermal parameters of the PE/POM‐Fe composite are different from those of all other composites. A model explaining the unusual electrical characteristics of the composite based on the polymer blend (PE/POM‐Fe) is proposed, in agreement with the results of optical microscopy.     

Evolution of phase morphology and ‘network‐like’ structure of multiwall carbon nanotubes in binary polymer blends during melt‐mixing

Polyamide6 (PA6)/acrylonitrile butadiene styrene copolymer (ABS) blends with unmodified multiwall carbon nanotubes (MWNTs) were prepared via melt‐blending in a conical twin‐screw micro‐compounder with varying melt‐mixing time. To improve the state of dispersion of MWNTs, non‐covalent organic modifiers for MWNTs have been utilized: sodium salt of 6‐amino hexanoic acid (Na‐AHA) and 1‐pyrene‐carboxaldehyde (PyCHO). PA6/ABS blends with MWNTs have shown a phase morphology transition from ‘matrix‐dispersed droplet’ type to ‘co‐continuous’ type as a function of melt‐mixing time with the exception of 40/60 PA6/ABS blend with PyCHO‐modified MWNTs. Non‐isothermal crystallization studies revealed the heterogeneous nucleating action of MWNTs through the presence of double crystallization exothermic peaks (at ～192^°C and >200^°C) while pure PA6 shows bulk crystallization peak at ～192°C. 40/60 and 60/40 (wt/wt) PA6/ABS blends with 5 wt% unmodified MWNTs exhibited electrical conductivity values of ～3.9 × 10^?11 S/cm and ～4.36 × 10^?6 S/cm, respectively. A significant enhancement in electrical conductivity was observed with Na‐AHA and PyCHO‐modified MWNTs (order of ～10^?6 and ～10^?4 S/cm, respectively). POLYM. ENG. SCI., 55:429–442, 2015. © 2014 Society of Plastics Engineers     

Polypropylene‐dispersed domain as potential nucleating agent in PS and PMMA solid‐state foaming

The potential of using dispersive domains in a polymer blend as a bubble nucleating agent was investigated by exploiting its high dispersibility in a matrix polymer in the molten state and its immiscibility in the solid state. In this experiments, polypropylene (PP) was used as the nucleating agent in polystyrene (PS) and poly(methyl methacrylate) (PMMA) foams at the weight fraction of 10, 20, and 30 wt %. PP creates highly dispersed domains in PS and PMMA matrices during the extrusion processing. The high diffusivity of the physical foaming agent, i.e., CO₂ in PP, and the high interfacial tension of PP with PS and PMMA could be beneficial for providing preferential bubble nucleation sites. The experimental results of the pressure quench solid‐state foaming of PS/PP and PMMA/PP blends verified that the dispersed PP could successfully increase the cell density over 10⁶ cells/cm³ for PS/PP and 10⁷ cells/cm³ for PMMA/PP blend and reduce the cell size to 24 μm for PS/PP and 9 μm for PMMA/PP blends foams. The higher interfacial tension between PP and the matrix polymer created a unique cell morphology where dispersed PP particles were trapped inside cells in the foam. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Prediction of dispersed phase drop diameter in polymer blends: The effect of elasticity

This paper discusses the prediction of the dispersed phase drop diameter in polymer blends considering the viscoelastic properties of polymers. The prediction is based on a simple force proportionality. Polymers are viscoelastic, and thus the elasticity of the matrix and the elasticity of the dispersed phase affect the drop size. The forces that deform a polymer droplet in a polymer matrix are the shear forces, η_mγ, and the matrix first normal stress, T_11,m. This deformation is resisted by the interfacial forces, 2 Γ/D and the drop's first normal stress, T_11,d. As a first approximation, the forces were balanced to predict the particle size in polymer blends. The diameter of the dispersed phase was predicted reasonably well for several systems at different operating conditions. It was observed for some systems (PS/PP, PS/EPMA, PS/PA330) that, as the shear rate increased, the diameter of the dispersed phase initially decreased. At a critical shear rate, the diameter reached a minimum value, and beyond it, the diameter increased with shear. This critical value was found to be between 100 to 162.5 s⁻¹ for a PS/PP system. The force balance predicts this minimum drop diameter at a similar critical shear rate. The specific energy input (the amount of energy input into the blend) could not explain the phenomenon of a minimum drop diameter with increase in shear. This minimum is not observed for the high concentration systems, such as the 20% PP dispersed in PS, since the effects of coalescence become significant. In reactive blends, the predicted drop diameter was closer to the experimentally determined diameter, and there was less variation in diameter with changes in shear rate.     

Morphology evolution of immiscible polymer blends as directed by nanoparticle self-agglomeration

This work aims to clarify the effect of nanoparticle self-agglomeration structure on the morphology of polymer blends. The morphology development of polystyrene (PS)/polyamide (PA6) blends with titanium dioxide (TiO₂) nanoparticles preferentially localized in the PA6 domains was investigated by means of electron microscopy observation, viscoelastic analysis and selective extraction tests. It was shown that the preferential dispersion of TiO₂ leads to a significant reduction of the PA6 continuity in the PS/PA6 blend. The size of the PA6 domain increases gradually with further increasing the nanoparticle loading whereas the co-continuity of the PS/PA6/TiO₂ mixture is destroyed by isothermal post-treatments. These experimental results are completely different from those in carbon black, nanoclay or nano-silica-filled immiscible polymer blends. To elucidate the progression to the uneven morphology change, the dynamic process of microfibril break-up and droplet coalescence in the molten PS/PA6/TiO₂ mixture was traced in real-time through optical microscopy. It was confirmed that the self-agglomerating pattern of the nanoparticle in the polymer melts plays a key role in directing the morphology evolution of the immiscible polymer blend: unlike the self-agglomeration of carbon black to form three-dimensionally continuous network structure, the TiO₂ nanoparticles tend to form separate clusters in the PA6 phase. This prevents PA6 droplets from fusing together to form a continuous network during the coalescence and producing larger PA6 domains at higher TiO₂ loads.     

Polystyrene and polyester polyurethane elastomer blends compatibilized by SMA

Blends of polystyrene (PS) with polyester polyurethane elastomer (PU‐es) were compatibilized by addition of poly(styrene‐co‐maleic anhydride) (SMA) containing 7 wt % of maleic anhydride. Binary nonreactive (PS/PU‐es) blends, binary reactive (SMA/PU‐es) blends, and ternary reactive blends (PS/SMA/PU‐es) were prepared with 10 and 20 wt % of PU‐es. The maleic anhydride content in the ternary reactive blends was varied through addition of different SMA amounts from 0.5 to 5 wt %. Polyurethane in the blends was crosslinked by using dicumyl peroxide or sulfur to improve its mechanical properties. The experimental processing conditions, such as temperature and rotor speed in an internal mixer, were analyzed before blend preparation by processing the individual polymers, PS and SMA, and the PS/PU‐es nonreactive blend (90/10), to prevent the degradation of the polymer during melt mixing and to assure macroscopic homogeneity. The torque behavior during the mixture indicated a grafting copolymerization, which was responsible for the significant drop of the PU‐es domain size in the glassy matrix, as observed by scanning electronic microscopy (SEM). The miscibility of the glassy matrix, which was shown to be dependent on the composition and the phase behavior of ternary blends, became very complex as the SMA concentration increased, as concluded from dynamical–mechanical analysis. Blends containing 20 wt % of PU‐es presented an increase up to a factor of 2 in the deflection at break in relation to PS. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2297–2304, 2004     

Polymer blends of poly(trimethylene terephthalate) and polystyrene compatibilized by styrene‐glycidyl methacrylate copolymers

The compatibilizing effects of styrene‐glycidyl methacrylate (SG) copolymers with various glycidyl methyacrylate (GMA) contents on immiscible blends of poly(trimethylene terephthalate) (PTT) and polystyrene (PS) were investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and ¹³C‐solid‐state nuclear magnetic resonance (NMR) spectroscopy. The epoxy functional groups in the SG copolymer were able to react with the PTT end groups (? COOH or ? OH) to form SG‐g‐PTT copolymers during melt processing. These in situ–formed graft copolymers tended to reside along the interface to reduce the interfacial tension and to increase the interfacial adhesion. The compatibilized PTT/PS blend possessed a smaller phase domain, higher viscosity, and better tensile properties than did the corresponding uncompatibilized blend. For all compositions, about 5% GMA in SG copolymer was found to be the optimum content to produce the best compatibilization of the blend. This study demonstrated that SG copolymers can be used efficiently in compatibilizing polymer blends of PTT and PS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2247–2252, 2003     

CO2 foaming of poly(ethylene glycol)/polystyrene blends: Relationship of the blend morphology,CO2 mass transfer,and cellular structure

When polymer blends are foamed by physical foaming agents, such as CO₂ or N₂, not only the morphology and viscosity of the blend polymers but also the solubility and diffusivity of the physical foaming agents in the polymers determine the cellular structure: closed cell or open cell and monomodal or bimodal. The foam of poly(ethylene glycol) (PEG)/polystyrene (PS) blends shows a unique bimodal (large and small) cellular structure, in which the large‐size cells embrace a PEG particle. Depending on the foaming condition, the average size of the large cells ranges from 40 to 500 μm, whereas that of small cells becomes less than 20 μm, which is smaller than that of neat PS foams. The formation mechanism of the cellular structure has been investigated from the viewpoint of the morphology and viscosity of the blend polymer and the mass‐transfer rate of the physical foaming agent in each polymer phase. The solubility and diffusivity of CO₂, which determine the mass‐transfer rate of CO₂ from the matrix to the bubbles, were measured by a gravimetric measurement, that is, a magnetic suspension balance. The solubility and diffusivity of CO₂ in PS differed from those in PEG: the diffusion coefficient of CO₂ in PEG at 110°C was 3.36 × 10^?9 m²/s, and that in PS was 2.38 × 10^?10 m²/s. Henry's constant in PEG was 5600 cm³ (STP)/(kg MPa) at 110°C, and that in PS was 3100 cm³ (STP)/(kg MPa). These differences in the transport properties, morphology of the blend, and CO₂‐induced viscosity depression are the control factors for creating the unique cellular structure in PEG/PS blends. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1899–1906, 2005     

Effect of in situ synthesized macroactivator on morphology of PA6/PS blends via successive polymerization

In situ polymerization and in situ compatibilization was adopted for preparation of ternary PA6/PS‐g‐PA6/PS blends by means of successive polymerization of styrene, with TMI and ε‐caprolactam, via free radical copolymerization and anionic ring‐opening polymerization, respectively. Copolymer poly(St‐g‐TMI), the chain of which bears isocyanate (? NCO), acts as a macroactivator to initiate PA6 chain growth from the PS chain and graft copolymer of PS‐g‐PA6 and pure PA6 form, simultaneously. The effect of the macroactivator poly(St‐g‐TMI) on the phase morphology was investigated in detail, using scanning electron microscopy. In case of blends with higher content of PS‐g‐PA6 copolymer, copolymer nanoparticles coexisting with the PS formed the matrix, in which PA6 microspheres were dispersed evenly as minor phase. The content of the compositions (homopolystyrene, homopolyamide 6, and PS‐g‐PA6) of the blends were determined by selective solvent extraction technique. The mechanical properties of PA6/PS‐g‐PA6/PS blends were better than that of PA6/PS blends. Especially for the blends T10 with lower PS‐g‐PA6 copolymer content, both the flexural strength and flexural modulus showed significantly improving because of the improved interfacial adhesion between PS and PA6. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of EPDM‐g‐MAH on the morphology and properties of PA6/EPDM/HDPE ternary blends

The formation of core‐shell morphology within the dispersed phase was studied for composite droplet polymer‐blend systems comprising a polyamide‐6 matrix, ethylene‐propylene‐diene terpolymer (EPDM) shell and high density polyethylene (HDPE) core. In this article, the effect of EPDM with different molecular weights on the morphology and properties of the blends were studied. To improve the compatibility of the ternary blends, EPDM was modified by grafting with maleic anhydride (EPDM‐g‐MAH). It was found that core‐shell morphology with EPDM‐g‐MAH as shell and HDPE as core and separated dispersion morphology of EPDM‐g‐MAH and HDPE phase were obtained separately in PA6 matrix with different molecular weights of EPDM‐g‐MAH in the blends. DSC measurement indicated that there may be some co‐crystals in the blends due to the formation of core‐shell structure. Mechanical tests showed that PA6/EPDM‐g‐MAH/HDPE ternary blends with the core‐shell morphology exhibited a remarkable rise in the elongation at break. With more perfect core‐shell composite droplets and co‐crystals, the impact strength of the ternary blends could be greatly increased to 51.38 kJ m^?2, almost 10 times higher than that of pure PA6 (5.50 kJ m^?2). POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Investigation on particular phase morphology of immiscible polyamide 12 and polystyrene blends prepared via anionic ring‐opening polymerization

In this article, the particular phase morphology of immiscible polyamide 12/polystyrene (PA12/PS) blends prepared via in situ anionic ring‐opening polymerization of laurolactam (LL) in the presence of polystyrene (PS) was investigated. Scanning electron microscopy (SEM) and Fourier Transform infrared Spectroscopy (FTIR) were used to analyze the morphology of the blends. The results show that the PS is dispersed as small droplets in the continuous matrix of PA12 when PS content is 5 wt%. However, when the PS content is higher than 10 wt%, two particular phase morphologies appeared. Firstly, dispersed PS‐rich particles with the spherical inclusions of PA12 can be found when PS content is between 10 and 15 wt%. Then the phase inversion occurred (the phase morphology of the PA12/PS blends changed from the PS dispersed/PA12 matrix to PA12 dispersed/PS matrix system) when PS content is 20 wt% or higher, which is unusual for polymer blends prepared via conventional methods such as mixing, hydrolytic polycondensation and so on. The formation of this particular phase morphology development was simply elucidated via a phase inversion mechanism. Furthermore, the stability of the phase morphology of the PA12/PS blends after annealing at 230°C was also investigated via SEM. POLYM. ENG. SCI., 52:1831–1838, 2012. © 2012 Society of Plastics Engineers     

Electrical,spectroscopic, and thermal properties of blends formed by PEDOT,PVC, and PEO

This study describes the preparation of blends between an amorphous polymer (PVC) and a crystalline polymer (PEO), with a third polymeric part that presents electronic conduction capacity (PEDOT‐PSS). Binary (PEO/PVC, PEO/PEDOT‐PSS, PVC/PEDOT‐PSS) and ternary (PVC/PEO/PEDOT‐PSS) blends were prepared by changing the concentrations of the constituents and were analyzed by electronic conductivity, Raman spatial resolution, infrared spectroscopies, and thermogravimetric analysis. The Raman and FTIR analyses showed the incorporation of PEDOT‐PSS within the blends. The higher conductivity presented by the ternary blend was 8.6 × 10^?6 Scm^?1, composed of 24% of PVC, 16% of PEO, and 60% of PEDOT‐PSS. For binary blends the conductivity was proportional to the PEDOT‐PSS content. The thermal stability could be observed through the TG curves of the blends that presented an increase of 19 K in the weight loss temperature at the 10% level when compared to the pure components. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1710–1715, 2005     

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     

Preparation of well‐controlled porous carbon nanofiber materials by varying the compatibility of polymer blends

The relationships between the compatibility in binary polymer blends and the pore sizes of carbon nanofibers (CNFs) prepared from the blends were investigated. Compatibility was determined by the difference between the solubility parameters of each polymer in the polymer blends. Porous CNFs were prepared by an electrospinning and carbonization process using binary polymer blends, consisting of polyacrylonitrile (PAN) as the carbonizing polymer and poly(acrylic acid) (PAA), poly(ethylene glycol), poly(methyl methacrylate) or polystyrene (PS) as the pyrolyzing polymer. The pore size of the CNFs increased with increasing difference in solubility parameter. The CNFs prepared using the PAN/PAA blend, which had the smallest solubility parameter difference, exhibited a pore size of 1.66 nm compared to 18.24 nm for the CNFs prepared using the PAN/PS blend. The prepared CNF webs with controlled meso‐sized pores showed a stable cycle performance in cyclic voltammetry measurements and improved impedance characteristics. This method focusing on the compatibility in polymer blends was simple to apply and effective for controlling the pore sizes and surface area of CNFs for application as electrode materials in energy storage systems. © 2013 Society of Chemical Industry     

Improved thermal conductivity of ceramic filler‐filled polyamide composites by using PA6/PA66 1:1 blend as matrix

Polyamide‐type composites with improved thermal conductivity are prepared by using polyamide 6(PA6)/polyamide 6,6 (PA66) 1:1 blend as the matrix and aluminum nitride (AlN) as the filler through melt compounding. Field emission scanning electron microscopy coupled with energy dispersive spectrometry (EDS) mapping of Al is used to investigate distribution of AlN. Differential scanning calorimeter is used to investigate the crystallization behavior of the composites. The thermal conductivity of PA6/PA66/AlN composite with 50 wt % AlN is 1.5 W m^?1 K^?1, 88% enhancement compared to those of single polymer based PA6/AlN or PA66/AlN composites. The reason for the improved thermal conductivity is the increased effective volume concentration of AlN in one (probably PA66) phase. The experimental data are fitted into Bruggeman and Agari–Uno model. Composites with similar thermal conductivity are also prepared using silicon carbide as the filler instead of AlN, showing that using PA6/PA66 1:1 blend as the matrix is a universal method to prepare thermally conductive composites with less filler loading. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45371.