Co-continuous Morphology Research Articles

Morphology Control and Stabilization in Immiscible Polypropylene and Polyamide 6 Blends with Organoclay

Abstract In the current study, 70/30 (w/w) polypropylene (PP)/polyamide 6 (PA6)/organoclay ternary blends were prepared by melt mixing in three different blending sequences, i. e., organoclay premixed with PA6 and then mixed with PP (S1 blending sequence), organoclay premixed with PP and then mixed with PA6 (S2 blending sequence), and organoclay, PA6 and PP mixed simultaneously (S3 blending sequence). The effects of organoclay on the phase morphologies, rheological properties and mechanical properties of the blends are examined to reveal the role of organoclay in these immiscible blends. First of all, the dispersion and distribution of organoclay is investigated using XRD and TEM techniques. The organoclay is exfoliated and distributed in the dispersed PA6 phase as well as at the interface between PA6 and PP. Interestingly, more organoclay sheets are observed at the interface when the S2 or S3 blending sequences are utilized. From the SEM images, it is clear that the domain size of the PA6 phase decreases remarkably after introducing organoclay into the PP/PA6 blends. Two different rheological protocols are applied to probe the effect of organoclay on the morphology of the blend by in-situ monitoring the morphological evolution. The rheological results reveal that the phase morphology of the PP/PA6 blends remains relatively stable during shear for a wide range of shear rates when 1.0 wt% organoclay has been added. For the blends with a relatively high clay loading (5.0 wt%), a characteristic and pronounced “plateau” is observed in the low frequency range of the G′-ω curves, which indicates the presence of a percolating network of clay nanosheets. From the mechanical measurements, we find that the tensile strength of the blends increases slightly first and then declines dramatically with increasing organoclay content. Moreover, the elongation at break drops sharply as the organoclay content increases. In summary, it is clear that the organoclay can effectively reduce the domain size of the dispersed PA6 phase and stabilize the phase morphology in shear flow. However, the mechanical properties of the blends are not really improved by clay addition, even though a cocontinuous morphology with a percolated clay network was generated.

Electromagnetic interference shielding materials derived from gelation of multiwall carbon nanotubes in polystyrene/poly(methyl methacrylate) blends.

Blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with different surface-functionalized multiwall carbon nanotubes (MWNTs) were prepared by solution blending to design materials with tunable EMI (electromagnetic interference) shielding. Different MWNTs like pristine, amine (∼NH2), and carboxyl acid (∼COOH) functionalized were incorporated in the polymer by solution blending. The specific interaction driven localization of MWNTs in the blend during annealing was monitored using contact mode AFM (atomic force microscopy) on thin films. Surface composition of the phase separated blends was further evaluated using X-ray photoelectron spectroscopy (XPS). The localization of MWNTs in a given phase in the bulk was further supported by selective dissolution experiments. Solution-casted PS/PMMA (50/50, wt/wt) blend exhibited a cocontinuous morphology on annealing for 30 min, whereas on longer annealing times it coarsened into matrix-droplet type of morphology. Interestingly, both pristine MWNTs and NH2-MWNTs resulted in interconnected structures of PMMA in PS matrix upon annealing, whereas COOH-MWNTs were localized in the PMMA droplets. Room-temperature electrical conductivity and electromagnetic shielding effectiveness (SE) were measured in a broad range of frequency. It was observed that both electrical conductivity and SE were strongly contingent on the type of surface functional groups on the MWNTs. The thermal conductivity of the blends was measured with laser flash technique at different temperatures. Interestingly, the SE for blends with pristine and NH2-MWNTs was >-24 dB at room temperature, which is commercially important, and with very marginal variation in thermal conductivity in the temperature range of 303-343 K. The gelation of MWNTs in the blends resulted in a higher SE than those obtained using the composites.

Bio‐plastics and elastomers from polylactic acid/thermoplastic polyurethane blends

ABSTRACTBlends of two biocompatible polymers: thermoplastic polyester‐urethane (TPU) and polylactic acid (PLA) were studied. The effect of the blending ratio on blend morphology and properties was examined by running a series of blends from 10 to 80 wt % of PLA. Increasing TPU concentration in the blends lowered the glass transition and melting point of PLA indicating that the components were compatible and partially miscible. The blends with 10–40 wt % PLA are hard, reinforced elastomers, while those with 60–80 wt % PLA are tough plastics. Cocontinuous morphology was suggested in samples with 40 and 50 wt % PLA. Inversion points between 30 and 40 wt % PLA (from globular phase is dispersed in the matrix to a cocontinuous morphology) and between 50 and 60 wt % PLA (a transition from cocontinuous to TPU dispersed in the PLA matrix) were observed. Elastomers with higher PLA content and intermediate morphology displayed a combination of high tensile strength, hardness, relatively high elongation and modulus. New materials have potential applications in the medical field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41104.

Regimes of microstructural evolution as observed from rheology and surface morphology of crosslinked poly(vinyl alcohol) and hyaluronic acid blends during gelation

ABSTRACTHyaluronic acid (HA)‐based materials are being investigated because of their role in biological fluids and tissues. Poly(vinyl alcohol) (PVA) when blended with HA at different compositions leads to superior mechanical properties compared to pure HA. The PVAHA blend hydrogels are potential candidates for pharmaceutical, biomedical, and cosmetic applications. It is essential to understand the structure, gelation time, and morphological properties of these hydrogels. In this work, a blend system of PVA crosslinked with glutaraldehyde in the presence of HA is studied. Semidilute solutions of PVA and HA are blended, followed by gelation due to crosslinking. The crosslinked gels as well as the gel cast membranes were examined. The effect of HA on the gelation process is investigated using rheological characterization. It is shown that kinetics of gelation is influenced by HA content, though storage modulus of the gels is influenced marginally. The structural features of PVAHA gels were also probed with scanning electron microscopy and dynamic light scattering. It is argued that there is a complex interplay between intra‐ and intermolecular crosslinking of PVA and PVA–HA interactions during the gel formation. Based on the insights obtained from various probing techniques for PVAHA gels with different HA content, three broad structural features were identified. It is shown that the hydrogel is semi‐interpenetrating network at lower HA content (<10% HA), cocontinuous morphology at moderate HA content and with domains at high HA content (>20% HA). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41081.

Hierarchically porous polymeric materials from ternary polymer blends

Hierarchically porous polymers with controllable pore size were generated through a novel polymer blending strategy in an A/B/C–B–C ternary blend system. Polylactide/high-density polyethylene/poly(styrene-ethylene/butylene-styrene) triblock copolymer (PLA/HDPE/SEBS) was used as a model system to demonstrate this technique. During melt blending, the SEBS was driven into the HDPE phase owing to the presence of the PE block in the copolymer. With proper volume fractions of PLA/HDPE/SEBS (e.g., 50/25/25), a bi-modal, dual co-continuous morphology was obtained and hierarchically porous polymeric materials were further generated by selectively removing the PLA and SEBS phases. Annealing and compositional variation were further employed to control the pore size and it is shown that the length scales of the two co-continuous morphologies can be controlled independently.

Effects of Carbon Nanotubes on the Morphology and Properties of Uncompatibilized and Maleic Anhydride-grafted Polypropylene-compatibilized Polyamide 6/Polypropylene Blends

The effects of carbon nanotubes (CNTs) on the morphology of uncompatibilized and maleic anhydride-grafted polypropylene (MAPP)-compatibilized polyamide 6 (PA6)/polypropylene (PP) (70/30 w/w) blends prepared using a torque rheometer were investigated. TEM observations showed that the CNTs were selectively located in the major PA6 phase and at the interface. Such localization of nanofillers in the literature usually leads to a refinement in a sea-island morphology. Unexpectedly, our results show that increasing amounts of CNTs in the samples prepared using a torque rheometer led to a transformation from typical sea-island morphology to co-continuous morphology for uncompatibilized PA6/PP blends and to partial fibrillization of the PP domains for MAPP-compatibilized PA6/PP blends. These unusual morphological changes are attributed to a retarded morphology evolution process caused by the CNTs. According to rheological measurements and theoretical analysis, this was achieved through the role of CNTs in enhancing the viscoelasticity of the PA6 phase and promoting interfacial slip. The electrical resistivites, crystallization, and melting behavior of all samples were also studied.

Blends of epoxy resins and polyphenylene oxide as processing aids and toughening agents 2: Curing kinetics, rheology, structure and properties

The curing behaviour, chemorheology, morphology and dynamic mechanical properties of epoxy − polyphenylene oxide (PPO) blends were investigated over a wide range of compositions. Two bisphenol A based di-epoxides − pure and oligomeric DGEBA − were used and their cure with primary, tertiary and quaternary amines was studied. 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) showed high levels of cure and gave the highest exotherm peak temperature, and so was chosen for blending studies. Similarly pure DGEBA was selected for blending due to its slower reaction rate because of the absence of accelerating hydroxyl groups. For the PPO:DGEBA340/MCDEA system, the reaction rate was reduced with increasing PPO content due to a dilution effect but the heat of reaction were not significantly affected. The rheological behaviour during cure indicated that phase separation occurred prior to gelation, followed by vitrification. The times for phase separation, gelation and vitrification increased with higher PPO levels due to a reduction in the rate of polymerization. Dynamic mechanical thermal analysis of PPO:DGEBA340/MCDEA clearly showed two glass transitions due to the presence of phase separated regions where the lower Tg corresponded to an epoxy-rich phase and the higher Tg represented the PPO-rich phase. SEM observations of the cured PPO:DGEBA340/MCDEA blends revealed PPO particles in an epoxy matrix for blends with 10 wt% PPO, co-continuous morphology for the blend with 30 wt% PPO and epoxy-rich particles dispersed in a PPO-rich matrix for 40wt% and more PPO.

Surface roughening of PET films through blend phase coarsening.

In this study, a novel method to increase the surface roughness of polyethylene terephthalate (PET) films is proposed. The mechanism of phase coarsening at the surface in extruded thin films of PET blended with low concentrations of polystyrene (PS) was investigated. A small amount of poly(hyroxyl ether) of bisphenol A (phenoxy resin, PKHH) was found to significantly increase the surface roughness due to its effect on the PS-PET interfacial tension. X-ray photoelectron spectroscopy (XPS) results indicated that in the presence of PKHH, PS droplets migrated spontaneously towards the surface of the polymer film. An increased local concentration of PS near the surface took the form of encapsulated droplets. Above the flow temperature of the blend, the local concentration of PS eventually reached a level where a co-continuous morphology occurred, resulting in the instabilities on the surface of the film. The adhesion properties of films with various roughnesses were determined using a pull-off test and found to be significantly increased, which suggested that co-continuous morphology and the coarsening process increased the adhesive properties of the film.

Physical Properties, Compatibility and Morphology of Hydrogenated Nitrile Rubber/Fluoroether Rubber Blends

The physical properties, compatibility, and morphology of blends of hydrogenated nitrile rubber (HNBR) with fluoroether rubber were investigated with reference to the blends ratio. The results show that the blends have excellent physical properties. Minimum torque (ML), maximum torque (MH), optimum curing time (t90), compression set, volume and mass change in fluid, and specific gravity are linear with the content of HNBR. On the other hand, MH-ML, hardness and 100% modulus show synergistic effect when the blend ratio is 50/50, indicating that there is some special morphology or interaction between the two polymers. There are two glass transition (Tg) peaks in Tanδ-T, Loss modulus (E")-T and Differential Scanning Caloricity (DSC) curves of the 50/50 blend and the Cole-Cole curve of the 50/50 blend shows two modified semicircles, suggesting the absence of segmental miscibility of the blends. The thermal gravimetric analysis (TGA) curves demonstrate that the 50/50 blend is thermo-stable to the highest temperature which may be due to the interaction between the two materials. Scanning electron microscope (SEM) was used to investigate the morphology of the blends. The micrographs of 75/25 and 25/75 HNBR/fluoroether rubber blends have phase separated structures with the Sea-Island morphology. For the 50/50 blend, the SEM micrographs show a co-continuous morphology, which is suggested to be the reason for the synergistic effects of MH-ML, hardness, and the 100% modulus at the given ratio. In conclusion, the physical properties, DSC, TGA, dynamical mechanical thermal analysis, and SEM micrographs agree in suggesting that the HNBR and fluoroether rubber are not thermodynamically miscible but mechanically compatible.

Free Standing Hierarchically-Structured Electrodes for Energy Storage Devices

Fabrication of novel three-dimensional material architectures is essential for successful development of energy storage devices that allow high rate operation along with sufficient energy capacity. We will present our work on development of nanofiber-based hierarchically structured materials for applications in electric double layer capacitors and lithium-based batteries using a simple and scalable electrospinning methodology. As a first step, a comprehensive study on fabrication and structure-control of porous carbon nanofibers exhibiting specific surface areas of >1500 m2/g and multi-levels of pore sizes in the range of micro (<2 nm), meso (<50 nm) and macropores (>50 nm) was conducted. In particular, blends of polyacrylontritrle (PAN) and a sacrificial polymer in dimethyl formamide (DMF) were electrospun into non-woven nanofiber mats with diameters in the range of 200-300 nm. Fast evaporation of solvent (~200 nl/s) and high elongational flow rate (~105 s-1) during electrospinning allowed us to prevent phase separation and develop a co-continuous morphology of PAN and the sacrificial polymer in the nanofibers. Electrospun nanofiber mats were subjected to stabilization and carbonization processes to obtain porous carbon nanofibers (CNFs) as PAN converted to carbon and the sacrificial polymer decomposed out to create intra-fiber pores (Figure 1). These materials exhibit specific surface area of up to 1600 m2/g without any activation process. We exhibit the tunability of the pore sizes within CNFs by varying material composition. These materials were tested as free-standing electrodes (without any binder) for electric double-layer supercapacitors. Our study shows that they exhibit a large specific capacitance (210 F/g and 80 F/cm3), possibly due to the presence of a large fraction of meso-pores (2-4 nm) and macropores (>50 nm) compared to state-of-the-art activated carbons (pores <2 nm), which leads to an increase in the accessible carbon surface, thereby improving specific capacitance. These electrodes exhibit near-ideal rectangular CV curve even at a high scan rate of 2V/s (Figure 2). This again is attributed to the relatively larger pore size in these materials compared to most activated carbons, which allows faster ion transport and charge/discharge. Note that activated carbons often deviate from ideal behavior even at a scan rate of 100 mV/s scan rate.These materials retain 75% performance at a large current density of 20 A g1indicating excellent power handling capability. Preliminary data on use of these hierarchically structured materials for high energy density lithium-based batteries – Lithium-sulfur and Lithium-air, will be presented.

Enhancement in crystallization kinetics of the bacterially synthesized poly(β-hydroxybutyrate) by poly(butylene succinate)

Poly(β-hydroxybutyrate), PHB, is a bio-based and biodegradable material. However processing and application of the PHB are disturbed by its low crystallization rate. In this manuscript the crystallization behavior of the PHB was improved via incorporation of another biodegradable polymer, i.e. poly(butylene succinate), PBS. The two polymers show phase separation in the blends. PBS varies from a dispersed phase to a continuous phase with increasing its content from 20 to 70 wt% and a co-continuous morphology is observed at PBS 50 wt%. Although the spherulitic radial growth rate of the PHB is retarded to a certain extent by the PBS, the non-isothermal crystallization temperature is increased by around 30 °C while the half-life crystallization time is reduced significantly, indicating an increased overall crystallization rate of the PHB. The increased crystallization rate of PHB is attributed to a modified multi-nucleation mechanism, i.e. homogeneous nucleation, heterogeneous nucleation and self-enhanced nucleation.

Fabrication of Small Pore-Size Nickel Foams Using Electroless Plating of Solid-State Foamed Immiscible Polymer Blends

A novel fabrication process of small pore-size nickel foams has been developed using electroless plating of solid-state foamed immiscible polymer blends. Ethylene acrylic acid (EAA) and polystyrene (PS) were melt-blended with extrusion to obtain a dual phase cocontinuous morphology. Gas saturation and foaming studies were performed to determine appropriate process conditions for foaming of the two-phase material. Open-celled polymer templates were obtained by extracting the PS phase with dichloromethane (DCM). The templates were subsequently used for nickel foam plating in ethanol-based electroless plating solutions. Nickel foams with pore sizes on the level of tens of micrometers and porosity above 90% were fabricated. It was found that gas concentration and foaming temperature were major process variables significantly affecting the foam porosity. Foaming allowed faster PS extraction and higher porosity of the nickel plating templates. Because of the small pore size, ethanol-based solutions need to be used to ensure the infiltration of plating solutions. The developed process is a bulk method and can be used for large-scale fabrication of small pore-size nickel foams with high porosity.

Styrene–butadiene–styrene copolymer compatibilized carbon black/polypropylene/polystyrene composites with tunable morphology, electrical conduction and rheological stabilities

We report a facile kinetic strategy in combination with styrene-butadiene-styrene (SBS) copolymer compatibilizers for preparing carbon black (CB) filled immiscible polypropylene (PP)/polystyrene (PS) (1/1) blends with finely tuned morphologies and show the important role of location and migration of CB nanoparticles in determining the electrical conductivity and rheological behaviour of the composites. A novel method of mixing a SBS/CB (5/3) masterbatch with the polymers allowed producing composites with CB aggregates dispersed partially in the unfavorable PP phase and partially in the PP side of the interface to exhibit diverse phase connectivity and electrical conductivity depending on the compounding sequences. A cocontinuous morphology with CB enrichment along the interface was formed in the composite prepared by mixing the SBS/CB masterbatch with the premixed PP/PS blend, giving rise to a highest electrical conductivity and dynamic moduli at low frequencies. On the other hand, mixing the masterbatch with one and then with another polymer yielded droplet (PS)-in-matrix (filled PP) composites. The composites underwent phase coalescence and CB redistribution accompanied by marked dynamic electrical conduction and modulus percolations as a function of time during thermal annealing at 180 °C. The composites with the initial droplet-in-matrix morphology progressed anomalously into the cocontinuous morphology, reflecting a common mechanism being fairly nonspecific for understanding the processing of filled multicomponent composites with tailored performances of general concern.

Amphiphilic poly(acrylonitrile)-co-poly(2-dimethylamino)ethyl methacrylate conetwork-based anion exchange membrane for water desalination

We report the preparation of a novel cross-linked anion exchange membrane (AEM) from poly(acrylonitrile)-co-poly(2-dimethylamino)ethyl methacrylate (PAN-co-PDMA) copolymer by quaternizing the DMA moieties followed by cross-linking of –CN groups. This process avoids the use of the carcinogenic reagent, chloromethyl ether (CME) which is widely employed for the chloromethylation reaction in the preparation of AEMs. Key parameters were evaluated via electrodialysis (ED) during water purification and revealed that a copolymer containing 28 wt% PDMA possesses all the required properties of a high performance AEM, such as, reasonable water uptake (21%), good ion-exchange capacity (IEC = 1.30 m eq g−1), high ionic conductivity (Km = 2.22 mS cm−1), a high transport number (t− = 0.88) and good mechanical properties (9.2 MPa of tensile stress at break and 2.4 Kg cm−2 of burst strength in the water wet state). The AEM was directly tested in an ED unit in the recirculation mode by varying the concentration of the NaCl feed and the applied potential, showing a current efficiency as high as 80%. Such combination of physical and electrochemical properties of the membrane is attributed to its co-continuous morphology and its low degree of phase separation as confirmed by swelling, differential scanning calorimetry, the homogeneous distribution of oppositely charged dye and by the transparency of the membrane in both the dry and swelled states.

Suppression of phase coarsening in immiscible, co-continuous polymer blends under high temperature quiescent annealing

The properties of polymer blends greatly depend on the morphologies formed during processing, and the thermodynamic non-equilibrium nature of most polymer blends makes it important to maintain the morphology stability to ensure the performance stability of structural materials. Herein, the phase coarsening of co-continuous, immiscible polyamide 6 (PA6)-acrylonitrile-butadiene-styrene (ABS) blends in the melt state was studied and the effect of introduction of nano-silica particles on the stability of the phase morphology was examined. It was found that the PA6-ABS (50/50 w) blend maintained the co-continuous morphology but coarsened severely upon annealing at 230 °C. The coarsening process could be divided into two stages: a fast coarsening process at the initial stage of annealing and a second coarsening process with a relatively slow coarsening rate later. The reduction of the coarsening rate can be explained from the reduction of the global curvature of the interface. With the introduction of nano-silica, the composites also showed two stages of coarsening. However, the coarsening rate was significantly decreased and the phase morphology was stabilized. Rheological measurements indicated that a particle network structure was formed when the concentration of nano-silica particles was beyond 2 wt%. The particle network inhibited the movement of molecular chains and thus suppressed the coarsening process.

Influence of morphology on PTC effect for poly (ethylene-co-butyl acrylate)/nylon6 blends with multiwall carbon nanotubes dispersed at interface and in matrix

Multiwall carbon nanotubes (MWCNTs) filled poly (ethylene-co-butyl acrylate)/nylon6 (EBA/PA6) blends were prepared by melt-mixing method. MWCNTs were localized in PA6 phase and the percolation threshold was 6 wt%. A weak PTC (positive temperature coefficient) effect was observed. The method that EBA-g-MAH was first reacted with MWCNTs, and then blended with EBA/PA6 was employed to prepare EBA/PA6/EBA-g-MAH/MWCNTs composites. TEM results showed that MWCNTs were localized both at the interface and in PA6 phase, resulting in the sharp decrease of the percolation threshold. Influence of morphology on the PTC effect of EBA/PA6/EBA-g-MAH/MWCNTs composites was studied. In composites with dispersed PA6 phase, the conductive pathways were fabricated by the contact of dispersed PA6 phase and MWCNTs in PA6 phase. The melt of polyethylene segment crystals in EBA and PA6 phase interrupted the contact of dispersed phases and conductive network formed by MWCNTs in PA6 phase, resulting in the double PTC effect. For composites with dispersed EBA phase, although the conductive pathways were similar with the composites with dispersed PA6 phase, the single PTC effect was observed. And the PTC effect was attributed to the melt of PA6 phase. The conductive pathways of composites with co-continuous morphology were fabricated by MWCNTs at the interface and in continuous PA6 phase. Two strong and a weak PTC effect were observed. PTC effects appeared at the melting temperature of PA6 crystals, polyethylene segment crystals and viscous flow temperature of butyl acrylate units in EBA.

Morphologies in Polyamide 6/High Density Polyethylene blends with high amounts of reactive compatibilizer

The morphologies (dispersed, stretched dispersed, fibrillar and co-continuous) obtained in twin screw extruders in reactively compatibilized PA6/HDPE/Maleic Anhydride-grafted-HDPE blends have been studied over a broad range of compositions, specifically with high amounts of compatibilizer, by Scanning Electron Microscopy (SEM) after selective phase dissolution. The conversion ratio of the compatibilization reaction is estimated to be very high (of order 80%) in co-continuous morphologies. The morphologies exhibit two characteristic sizes: subdispersions of a few tens of nm coexist with larger (micrometric) scale morphologies. Large scale morphology regions have been identified in ternary compositions diagrams. The location of the co-continuity region agree with theoretical models based on rheological properties. The observed large scale morphologies, however, are not compatible with the high fraction of copolymer formed in the system after reactive extrusion. This implies that most of the copolymers are under the form of nanometric subdispersions within large size domains.

Epoxy/Polycaprolactone Systems with Triple-Shape Memory Effect: Electrospun Nanoweb with and without Graphene Versus Co-Continuous Morphology.

Triple-shape memory epoxy (EP)/polycaprolactone (PCL) systems (PCL content: 23 wt %) with different structures (PCL nanoweb embedded in EP matrix and EP/PCL with co-continuous phase structure) were produced. To set the two temporary shapes, the glass transition temperature (Tg) of the EP and the melting temperature (Tm) of PCL served during the shape memory cycle. An attempt was made to reinforce the PCL nanoweb by graphene nanoplatelets prior to infiltrating the nanoweb with EP through vacuum assisted resin transfer molding. Morphology was analyzed by scanning electron microscopy and Raman spectrometry. Triple-shape memory characteristics were determined by dynamic mechanical analysis in tension mode. Graphene was supposed to act also as spacer between the nanofibers, improving the quality of impregnation with EP. The EP phase related shape memory properties were similar for all systems, while those belonging to PCL phase depended on the structure. Shape fixity of PCL was better without than with graphene reinforcement. The best shape memory performance was shown by the EP/PCL with co-continuous structure. Based on Raman spectrometry results, the characteristic dimension of the related co-continuous network was below 900 nm.

Effect of morphology on the interfacial slip of immiscible polypropylene/polystyrene blends

The interfacial slip of the immiscible isotactic polypropylene/polystyrene (PS) blends with different morphologies was studied. The morphologies were obtained by choosing different PS contents (7, 21, and 55 vol%) and different processing methods (multilayered co-extrusion and conventional blending). The interfacial slip was obviously found in the multilayered morphology and the co-continuous morphology, but did not occur in the sea-island morphology. Besides, it was observed that the slip velocity of the multilayered system was higher than that of the conventional blends with co-continuous morphology and could be promoted with the increase of layer numbers. However, the interfacial slip in the multilayered system would be suppressed by the layer deformation and breaking during the test, when the thickness of layers was thin enough. The effect of composition on the interfacial slip velocity was also discussed in the multilayered composites.

High impact toughness of polyamide 6/poly (vinylidene fluoride) blends induced by an ionic liquid

Abstract This study reports the high impact toughness of polyamide 6 (PA6)/poly (vinylidene fluoride) (PVDF) blends achieved via adding an ionic liquid. The presence of the ionic liquid in the blends promotes the transformation of sea-island structure into co-continuous morphology, which to a large extent accounts for the improvement in toughness. In addition, it is believed that the enhanced mobility of the PA6 matrix by the ionic liquid also contributes to the high impact toughness.