Co-continuous Morphology Research Articles

Comparative Study on Experimental and Kerner Model Predictions of Viscoelastic Properties of Polyamide 6/ Polyvinyl Alcohol Blends

The Polyamide 6 (PA6) / Polyvinyl alcohol (PVOH) blends of different compositions (80/20, 60/40 and 50/50) were prepared by melt mixing in a Haake Rheomixer. The selected blend systems (80/20 and 60/40) were modified with dicumyl peroxide (DCP) and tertiary butyl cumyl peroxide (TBCP). The dynamic mechanical properties of blends were systematically investigated with special reference to the effect of blend ratio and effect of presence of peroxide over a temperature range -20°C to 110°C. The effect of change in the composition of the polymer blends on tan δ was studied to understand the damping characteristics. The mean field theory developed by Kerner has been used to estimate the dynamic properties and the estimated values are compared with the experimental values. The loss tangent curve of the blend exhibited single transition peak corresponding to the glass transition temperature (Tg) of Polyamide 6. Kerner model was found to satisfactorily predict the viscoelastic properties of the blends with polyamide content in the range 50 to 80 wt% assuming PA6 as matrix and for all compositions except 80/20 assuming PVOH as matrix. The Kerner model predictions for the selected blend systems with peroxides are not satisfactory and the co-continuous morphology of the peroxide treated blends were revealed by SEM observations.

Morphology and Mechanical Properties of Itaconic Anhydride Grafted Poly(lactic acid) and Thermoplastic Protein Blends

Abstract Blends between Novatein thermoplastic protein and polylactic acid (PLA) have been prepared by reactive extrusion using itaconic anhydride grafted PLA. At equal proportions of Novatein and PLA, the absence of a compatibilizer formed a dispersed phase morphology of Novatein in PLA and the incorporation of compatibilizer formed a co-continuous morphology. Incorporating PLA in Novatein can improve the tensile strength of Novatein by 42% and the impact strength by 36% at an equal proportion blend (50/50) in the presence of a compatibilizer. Thermal analysis revealed that 50/50 was the phase inversion point, above and below this composition the material behaved similarly. The effect of compatibilizer was evident in wide-angle X-ray scattering. In the absence of compatibilizer three phases were detected: crystalline Novatein, amorphous Novatein, and amorphous PLA phases. With compatibilizer, the blend was moving towards two phases: crystalline Novatein, and an amorphous blend of Novatein and PLA. Itaconic anhydride grafted PLA improved miscibility between Novatein and PLA, and its use can potentially lead to the production of Novatein/PLA foams.

Nanorods with Different Surface Properties in Directing the Compatibilization Behavior and the Morphological Transition of Immiscible Polymer Blends in Both Shear and Shear-Free Conditions

To explore the mechanism of how the nanorod surface properties regulate the compatibilization behavior and the morphology transition in demixing polymer blends, we perform dissipative particle dynamics simulations and study the impact of three typical nanorods on the phase separation kinetics and structure as well as their location and arrangement under both shear-free and shear conditions with the variation of nanorod–polymer affinity parameters. Depending on the dispersion and location of nanorods, blends in the quiescent case either undergo full phase separation and generate bulky two-phase morphology, or experience microphase separation and form BμE-like structure, or proceed viscoelastic phase separation and take the kinetically trapped cocontinuous network morphology, whereas shear flow can either accelerate domain coarsening or strongly impact the phase behavior through shear-induced bulk phase separation or shear-induced ordering transition. Particularly, the shear-induced lamellar phase in Janus ...

Improved thermal properties by controlling selective distribution of AlN and MWCNT in immiscible polycarbonate (PC)/Polyamide 66 (PA66) composites

A stable co-continuous morphology was achieved in immiscible polycarbonate (PC)/polyamide 66 (PA66) blend by controlling the selective distribution of multi-walled carbon nanotubes (MWCNT) and aluminum nitride (AlN) nanoparticles. SEM and TEM tests proved that hybrid fillers were both located in PA66 phase. Selective etching process was applied to confirm the gradual variation of morphologies. It indicated that the compatibilities between PC and PA66 were gradually enhanced since the phase size reduced significantly and the interface of two phases blurred after the fillers were incorporated. DMA confirmed that the glass transition temperature of PC and PA66 appeared a trend to merge, besides, the tensile properties were enhanced. TGA indicated that the in-situ generated PC-b-PA66 copolymer played an important role in the compatibilization effect. Besides, the raised interconnectivities were proved by theoretical models and the maximum thermal conductivity of 1.3 W/mK at hybrid fillers loading of 24.78 vol% was obtained.

Conducting polymer networks synthesized by photopolymerization-induced phase separation

Polymer mixtures composed of double networks of a polystyrene derivative (PSAF) and poly(methyl methacrylate) (PMMA) were alternatively synthesized by using ultraviolet (UV) and visible (Vis) light. The PSAF networks were generated by UV irradiation to photodimerize the anthracene (A) moieties labeled on the PSAF chains, whereas PMMA networks were produced by photopolymerization of methyl methacrylate (MMA) monomer and the cross-link reaction using ethylene glycol dimethacrylate (EGDMA) under Vis light irradiation. It was found that phase separation process of these networks can be independently induced and promptly controlled by using UV and Vis light. The characteristic length scale distribution of the resulting co-continuous morphology can be well regulated by the UV and Vis light intensity. In order to confirm and utilize the connectivity of the bicontinuous morphology observed by confocal microscopy, a very small amount, 0.1 wt%, of multi-walled carbon nanotubes (MWCNTs) was introduced into the mixture and the current–voltage (I–V) relationship was subsequently examined. Preliminary data show that MWCNTs are preferentially dispersed in the PSAF-rich continuous domains and the whole mixture became electrically conducting, confirming the connectivity of the observed bi-continuous morphology. The experimental data obtained in this study reveal a promising method to design various scaffolds for conducting soft matter taking advantages of photopolymerization-induced phase separation.

Double percolated MWCNTs loaded PC/SAN nanocomposites as an absorbing electromagnetic shield

This research reports on the preparation and characterization of absorbing electromagnetic (EM) nanocomposite shields based on polycarbonate (PC)/ polystyrene-co-acrylonitrile (SAN) 60/40 blend containing low contents of multi-walled carbon nanotubes (MWCNTs). The nanocomposites were prepared using a melt-compounding process at a temperature of 260 °C. The melt linear viscoelastic results together with scanning electron microscopy (SEM) micrographs implied a co-continuous type morphology, which remained unchanged by the addition of nanoparticles (NPs). The results of dynamic mechanical thermal analysis (DMTA) suggested a preferential localization of MWCNTs in the PC phase, evidenced by the transmission electron microscopy (TEM) micrograph. The direct current (DC) electrical conductivity results showed a low electrical double percolation threshold around 0.32 wt% of MWCNTs. A maximum DC electrical conductivity of 0.0834 S/cm was obtained for 1 wt% MWCNTs-filled nanocomposite. Applying EM theory based on the measured dielectric permittivity and magnetic permeability [over the X-band frequency (8.2–12.4 GHz)] suggested a maximum shielding efficiency of 25–29 dB for the 1 wt% MWCNTs-filled nanocomposite with a thickness of 10 mm. In addition, the contribution of the absorption mechanism below and above the electrical percolation threshold was studied. It was revealed that the shielding performance of the nanocomposites is mainly due to noticeable absorption of EM waves above the percolation threshold, which was attributed to the induced conductance loss as a result of the formation of conductive paths.

Effect of SEBS-g-MAH addition on the mechanical, rheological, and morphological properties of polycarbonate/acrylonitrile–butadiene–styrene blends

In this research, the effect of maleic anhydride–grafted styrene–ethylene/butylene–styrene (SEBS-g-MAH) compatibilizer on different properties of polycarbonate and poly(acrylonitrile–butadiene–styrene) (PC/ABS) blends was investigated. For this purpose, blends of PC and ABS at different ratios, without and with varying concentrations of compatibilizer, were prepared by melt compounding in a co-rotating twin-screw extruder followed by injection molding. The effectiveness of the compatibilizer was investigated by studying the microstructure and the mechanical, thermal, and rheological properties of the blends. It was found that the addition of the compatibilizer increases tensile strength, modulus, elongation at break, impact strength, complex viscosity, and thermal stability. This effect was noted at a loading of 1 wt% of compatibilizer, where enhanced interactions between the PC and ABS can be seen. Rheological methods, based on dynamic viscoelastic tests, allowed us to distinguish between emulsion-like and co-continuous morphologies and allowed an insight into the effect of the compatibilizer on the interfacial tension.

Novel Biodegradable Thermoplastic Elastomer Based on Poly(butylene succinate) and Epoxidized Natural Rubber Simple Blends

Novel biodegradable thermoplastic elastomer based on epoxidized natural rubber (ENR) and poly(butylene succinate) (PBS) blend was prepared by a simple blend technique. Influence of blend ratios of ENR and PBS on morphological, mechanical, thermal and biodegradable properties were investigated. In addition, chemical interaction between ENR and PBS molecules was evaluated by means of the rheological properties and infrared spectroscopy. Furthermore, the phase inversion behavior of ENR/PBS blend was predicted by different empirical and semi-empirical models including Utracki, Paul and Barlow, Steinmann and Gergen models. It was found that the co-continuous phase morphology was observed in the blend with ENR/PBS about 58/42 wt% which is in good agreement with the model of Steinmann. This correlates well to morphological and mechanical properties together with degree of crystallinity of PBS in the blends. In addition, the biodegradability was characterized by soil burial test after 1, 3 and 9 months and found that the biodegradable ENR/PBS blends with optimum mechanical and biodegradability were successfully prepared.

Effect of the viscosity ratio on the PLA/PA10.10 bioblends morphology and mechanical properties

PLA bio-blends with a predominantly biosourced PA10.10 in the composition range 10-50wt.% were prepared by melt blending in order to overcome the advanced brittleness of PLA. Due to the inherent immiscibility of the blends, 30 wt.% of PA was needed to achieve a brittle-to-ductile transition and a co-continuous morphology was predicted at 58 wt.% of PA. The initial enhancement of the PLA rheological behaviour through the environmentally friendly reactive extrusion process yielded a finer and more homogeneous microstructure and hence enhanced the mechanical properties of the bio-blends at much lower PA contents. The brittle-to-ductile transition could be achieved with only 10 wt.% and co-continuity was observed already at 44 wt.% of PA. Results indicate the significant potential of modifying PLA flow behaviour as a promising green manufacturing method toward expanding PLA-based bio-blends applications.

Effect of phase coarsening under melt annealing on the electrical performance of polymer composites with a double percolation structure.

The effect of phase coarsening on the evolution of the carbon black (CB) nanoparticle network under quiescent melt annealing and the electrical performance of polypropylene/polystyrene/carbon black (PP/PS/CB) composites with a double percolation structure was investigated. The results showed that when the CB content is low, the coarsening process of PP/PS/CB blends can be divided into two stages. In the first stage, the coarsening rate is fast before the formation of the CB nanoparticle network, and after annealing for a certain time, the evolution of the co-continuous morphology can drive the CB nanoparticles to self-assemble into a complete nanoparticle network. In the second stage, the coarsening rate is slow after the formation of the CB nanoparticle network. When the CB content is high, the CB nanoparticle network can be maintained throughout the whole annealing process, so that the conductivity and morphology of the PP/PS/CB composites are stable. Moreover, the electrical conductivity of the PP/PS/CB composites greatly increases after annealing for a certain time, and a percolation threshold as low as 0.07 vol% can be obtained. These results reveal the relationship between the evolution of the morphology and the conductivity in the conductive polymer composites with a double percolation structure, and provide a more in-depth and comprehensive understanding of the double percolation structure.

Swelling and tribological properties of melt-mixed fluoroelastomer/nitrile rubber blends under crude oil

The melt-mixed fluoroelastomer (FKM)/ nitrile rubber (NBR) blends of (90/10, 80/20, 70/30, 60/40 and 50/50) ratios with same hardness were prepared, and their swelling and tribological properties under crude oil were investigated for the purpose of developing high performance cost-effective elastomers meeting requirement of oil extraction progressive cavity pump stator. Differential scanning calorimetry confirmed compatible blend system for all blends. Field emission scanning electron microscopy (FE-SEM) showed co-continuous morphology of 200–400 nm phase size for all blends, expect FKM/NBR (90/10) which exhibited partially continuous phase morphology of 100–250 nm phase size. The results of swelling and linear wear tests under crude oil indicated that swelling percentage, coefficient of friction and specific wear rate of FKM/NBR blends were much better than NBR, with FKM/NBR (90/10 and 80/20) showing swelling percentage and specific wear rate very close to FKM. Attenuated total reflectance-Fourier transform infrared spectroscopy disclosed that fracture of macromolecular chains was the main mechanochemical effect of unswollen and swollen worn surfaces, in addition to oxygenated degradation detected with increasing NBR ratio in the blends. The fracture of macromolecular chains resulted in slight fatigue wear mechanism, which was also confirmed by FE-SEM of the worn surfaces.

Multiple-shape memory behavior of nanocomposite based on polymethylmethacrylate/poly (lactic acid)/graphene nanoplatelets (PMMA/PLA/GNP)

In this study, nanocomposite samples based on polymethylmethacrylate/poly (lactic acid)/graphene nanoplatelets (PMMA/PLA/GNP) were prepared via melt mixing method and thermal multiple shape memory was induced. Dynamic mechanical thermal analysis results showed that two polymers are miscible in the selected blend ratio (70/30, 50/50, 30/70 w/w; PLA/PMMA) and was not affected by the presence of GNP (1 and 2 phr). The dispersion and distribution status of GNP were observed by scanning electron microscopy (SEM). The co-continuous morphology was dominant in all samples due to complete miscibility of two phases. Multi-shape memory was induced using a tensile test machine equipped with the hot oven at 65 and 100 °C. The results revealed that shape recovery was affected by the presence of GNP at high temperature(for example increasing from 93.34% in neat PLA/PMMA(50/50 w/w) to 96.67% in the sample containing 1 phr of GNP) while there was no considerable effect at low temperature. At high temperature, amorphous phases of two polymers are extended and un-melted chains of PMMA can be as hard segment and leads to good recovery. Due to nucleation and reinforcement effects of GNP, the higher degree of crystallization of PLA and higher storage modulus were obtained and caused to the enhancement of the shape fixity values at the presence of GNP.

Effect of polyamide 6 on the morphology and electrical conductivity of carbon black-filled polypropylene composites.

Carbon black (CB)-filled polypropylene (PP) with surface resistivity between 106 and 109 Ω sq−1 is the ideal antistatic plastic material in the electronics and electric industry. However, a large amount of CB may have an adverse effect on the mechanical properties and processing performance of the material, thus an improved ternary system is developed. Blends of CB-filled PP and polyamide 6 (PA6) have been prepared by melt blending in order to obtain electrically conductive polymer composites with a low electrical percolation threshold based on the concept of double percolation. The morphological developments of these composites were studied by scanning electron microscopy. The results showed that CB particles were selectively dispersed in PA6 phases due to the good interaction and interfacial adhesion between CB and PA6. At the same CB loadings, the surface resistivity of PP/PA6/CB composite was smaller than that of PP/CB composite system, which indicated the better conductivity in the former composite. The increasing amount of PA6 in the composites changed the morphology from a typical sea–island morphology to a co-continuous morphology. What is more, with 8 wt% of CB and PP/PA6 phase ratio of 70/30 in which the PP and PA6 phases formed a co-continuous structure, the electrical conductivity of the composite peaked at 2.01 × 105 Ω sq−1.

Formation of co‐continuous PLLA/PC blends with significantly improved physical properties by reactive comb polymers

ABSTRACTA kind of reactive comb (RC) polymer, which is constituted by poly(methyl methacrylate) backbone and side chains and a few epoxide groups that distribute randomly along the backbone, has been applied as compatibilizers for the thermodynamically immiscible poly(l‐lactide) (PLLA)/polycarbonate (PC) blend (50/50, wt/wt). Phase morphology and physical properties of the compatibilized PLLA/PC blends are characterized by scanning electron microscopy, transmission electron microscopy, and tensile tests. It has been found that the morphologies of the PLLA/PC blends are significantly ameliorated with the addition of RC polymers. A type of PLLA/PC blend with stable co‐continuous morphology has been achieved by the incorporation of more than 3 wt % of RC polymers. The mechanical tests showed that the co‐continuous PLLA/PC blends have an excellent stiffness‐toughness balance with high modulus and significantly improved ductility. Especially, the elongation at break of the PLLA/PC blend compatibilized by 10 wt % of RC polymers is 10 times higher than that of neat PLLA, in which the blend exhibits a cocontinuous lamellar microstructure. Furthermore, the PLLA/PC blends with cocontinuous morphology exhibit dramatically improved thermal stability as compared to neat PLLA when the temperature is over the Tg of the PLLA phase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46047.

Electron-induced reactive processing of polyamide 6/polypropylene blends: Morphology and properties

Electron-induced reactive processing (EIReP) recently has appeared as an advanced processing technology to modify several polymer compounds at melt state by its spatial and temporal precise energy input. In the present work, an attempt was made to prepare a compatible blend from polar polyamide 6 (PA6) and non-polar polypropylene (PP) using EIReP without any chemical crosslinking and chemical additives. EIReP modified blends were prepared at different doses (5, 10 and 20 kGy) and dose per revolutions (3, 6 and 12 kGy/rev) while keeping constant the values of mass ratio (PA6/PP 50/50 w/w), electron energy (1.5 MeV), rotor speed (60 rpm) and temperature (230 °C). EIReP process parameters-morphology-property relationship of this blend was studied. Interestingly, co-continuous morphology of the blend was converted to droplet-matrix morphology after EIReP whether PA6 was continuous phase. Influence of dose and dose per revolution on the DMT modulus (Derjaguin-Muller-Toporov) at different phases of the blends was also measured and analyzed using advanced PeakForce Quantitative Nanomechanical Mapping atomic force microscopy (PF QNM AFM) technique. Improved nano- and macroscopic properties of EIReP modified blends were originated from the properties of the continuous matrix phase, electron-induced branching and also from the reduction of domain size of PP phase with increased dose.

Manipulating morphology in thermoplastic protein/polyester blends for improved impact strength

AbstractNovatein thermoplastic protein was blended with 10 wt% poly(butylene adipate‐co‐terephthalate) (PBAT) compatibilized with Joncryl ADR‐4368 and 2‐methylimidazole (2MI). Morphology was tailored for favorable impact strength through changing viscosity ratio (λ) and interfacial tension (γ12). For uncompatibilized blends, λ decreased and γ12 increased with increasing Novatein water content, whereas compatibilizers caused a decrease in both λ and γ12. PBAT continuity was high when uncompatibilized, but dispersion improved with decreasing λ and increasing γ12. The dispersed domain size decreased in all compatibilized blends; PBAT continuity was lowest in samples with the smallest λ. Compatibilized blends had higher impact strength than Novatein and uncompatibilized blends through improved interfacial adhesion, smaller domain size, and increased dispersion. By altering λ and γ12, and with appropriate chemical interaction, a morphology can be created for improved impact strength. Increasing PBAT content showed further increases in impact strength; however, a cocontinuous morphology formed, demonstrating that composition can override the effect of λ and γ12.

Interpenetrating polymer network (IPN) as tool for tuning electromechanical properties of electrochemical actuator operating in open-air

Electrochemical actuators operating in open-air are trilayer electrochemical devices based on an ionically conducting membrane sandwiched between two electrodes of electronic conducting polymers (ECP). Tuning functional properties of the actuator, i.e. the output force, is demonstrated via the modification of the ECP’s surrounding macromolecular architecture. Theoretical models have suggested that the output force of trilayer actuators is related to the Young’s modulus of the electrodes. As a consequence, we designed Interpenetrating Polymer Network (IPN) membranes combining three different polymer networks with a co-continuous morphology to act as a host matrix for ECP electrodes. Each of these polymer networks is chosen for a specific role: (i) poly(ethylene oxide) network providing ionic transport medium within the ECP electrodes, (ii) Nitrile Butadiene Rubber providing endurance, flexibility and robustness to the final device and (iii) polystyrene to increase the Young’s modulus of the ECP electrodes. The synthesized IPNs have been thoroughly characterized. The performances of resulting actuators have been assessed. The output force is almost doubled due to the stiffening effect of the polystyrene phase, as predicted by the beam theory.

Multiwalled carbon nanotube promotes crystallisation while preserving co-continuous phase morphology of polycarbonate/polypropylene blend

The influence of multiwalled carbon nanotubes (MWCNTs) on phase morphology, lamellar structure, thermal stability, melting behaviour and isothermal crystallisation kinetics of polycarbonate/polypropylene (PC/PP) blend nanocomposites has been investigated. Both neat blends and PC/PP (60/40)/MWCNT nanocomposites were prepared by melt mixing method. Morphological analyses were performed by high-resolution X-ray micro-computed tomography and scanning electron microscopy. The co-continuous morphology of the blend was retained irrespective of MWCNT loading. In addition, a substantial refinement in the co-continuous structure was observed. Wide angle and small angle X-ray scattering studies were used to analyse the structural properties of the blend nanocomposites. The addition of MWCNT increases the long period of polypropylene. The influence of addition of MWCNT on the crystallisation temperature and equilibrium melting temperature (Tm°) of polypropylene was followed. The MWCNTs promote crystallisation rate of polypropylene in the blend nanocomposites.

Tailoring co-continuous like morphology in blends with highly asymmetric composition by MWCNTs: Towards biodegradable high-performance electrical conductive poly(l-lactide)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blends

The performance of polymer blends greatly depends on the phase morphologies and the incorporation of nanofillers provides a low-cost but efficient strategy to tailor the morphology and performance of immiscible polymer blends. In this work, we obtained co-continuous like morphology in poly(l-lactide) (PLLA)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) blend with highly asymmetric composition (80/20, wt/wt) through the self-networking behavior of multi-walled carbon nanotubes (MWCNTs). It was found that the electrical conductivity and the ductility of PLLA/P(3HB-co-4HB)/MWCNTs composites were enhanced at the same time compared with PLLA/MWCNTs composites. The percolation threshold of the prepared PLLA/P(3HB-co-4HB)/MWCNTs composites was 0.58 wt%, 36% lower than that of PLLA/MWCNTs composites and the highest value of elongation at break for PLLA/P(3HB-co-4HB)/MWCNTs composites was 226.4% when the content of MWCNTs was 1 wt%. The results indicate that MWCNTs can contribute to the formation of co-continuous like structure and our work provides a new way to prepare biodegradable high-performance conductive polymer composites with excellent conductivity and mechanical properties.

Physical blends of PLA with high vinyl acetate containing EVA and their rheological, thermo-mechanical and morphological responses

Rheological, morphological and thermo-mechanical responses of poly(lactic acid) (PLA)/ethylene-co-vinyl-acetate copolymer (EVA) blends at EVA volume fractions varying in the range of 0–0.35 were evaluated. The micro-structural analysis demonstrated dispersive mixing at low content and co-continuous morphology at 30 wt % of EVA in PLA. Dynamic rheology demonstrated enhanced storage modulus and complex viscosity (η*) with increase in frequency of the blends indicated strong phase interaction. Cole-Cole and Han plots indicated partial miscibility and incompatibility between the polymer matrix and the dispersed phase. Dynamic mechanical analysis (DMA) revealed slight increase in damping parameters which indicated interaction or reinforcement in the blends. Additionally, the thermogravimetric analysis (TGA) of the blends showed two step degradation and enhanced thermal stability.