Immiscible Polymer Research Articles

The effect of fibre sizing and compatibilizer of polypropylene/poly(butylene terephthalate) blends on the mechanical and interphase properties of basalt fibre reinforced composites

AbstractThe effect of basalt fibre sizing on the mechanical and interphase properties of fibre‐reinforced composites was studied. Two different chemical preparations of the fibre surface (PBT‐compliant and PP‐compliant) were used. The polymer matrix was prepared from polypropylene/poly(butylene terephthalate) (PP/PBT) immiscible polymer blend and the effect of different compatibilizers on the composite properties was evaluated. SEM hints at improved fibre adhesion to the polymer matrix when a PP‐compliant sizing is applied. SEM also reveals improved compatibilization effects when block copolymer instead of multiblock copolymer is used for the PP/PBT blend preparation. The pull‐out test was applied to quantitatively evaluate the interface adhesion between the fibres and matrices. It showed a high value of the interfacial shear strength between basalt fibres modified with PP‐compliant sizing and polymer blend compatibilized by block copolymer, thus confirming good adhesion. One possible explanation of such good mechanical properties can be related to the chemical interactions between functional groups, mainly maleic anhydride on basalt fibres and the polyolefin component (PP) of the polymer matrix. © 2017 Society of Chemical Industry

Capillary Force Lithography Pattern-Directed Self-Assembly (CFL-PDSA) of Phase-Separating Polymer Blend Thin Films.

We report capillary force lithography pattern-directed self-assembly (CFL-PDSA), a facile technique for patterning immiscible polymer blend films of polystyrene (PS)/poly(methyl methacrylate) (PMMA), resulting in a highly ordered phase-separated morphology. The pattern replication is achieved by capillary force lithography (CFL), by annealing the film beyond the glass transition temperature of both the constituent polymers, while confining it between a patterned cross-linked poly(dimethyl siloxane) (PDMS) stamp and the silicon substrate. As the pattern replication takes place because of rise of the polymer meniscus along the confining stamp walls, higher affinity of PMMA toward the oxide-coated silicon substrate and of PS toward cross-linked PDMS leads to well-controlled vertically patterned phase separation of the two constituent polymers during thermal annealing. Although a perfect negative replica of the stamp pattern is obtained in all cases, the phase-separated morphology of the films under pattern confinement is strongly influenced by the blend composition and annealing time. The phase-separated domains coarsen with time because of migration of the two components into specific areas, PS into an elevated mesa region and PMMA toward the substrate, because of preferential wetting. We show that a well-controlled, phase-separated morphology is achieved when the blend ratio matches the volume ratio of the elevated region to the base region in the patterned films. The proposed top-down imprint patterning of blends can be easily made roll-to-roll-compatible for industrial adoption.

Micromesh carbon nanosheet electrodes fabricated by phase-separation of immiscible polymer blends

We adopt micromesh structure in carbon nanosheets (M-CNS) fabricated by phase-separation of immiscible polyacrylonitrile/poly(methyl methacrylate) blend precursors to improve their properties as a transparent conductive electrode. The facile approach without any time-consuming patterning processes can improve trade-off between sheet resistance and optical transmittance of conventional CNS. The M-CNS exhibits improved sheet resistance of ∼50% without compromising optical transmittance, leading to a high power conversion efficiency of ∼2.07% for M-CNS electrode-based organic photovoltaics.

Fluctuation Effects on the Brush Structure of Mixed Brush Nanoparticles in Solution.

A potentially attractive way to control nanoparticle assembly is to graft one or more polymers on the nanoparticle, to control the nanoparticle-nanoparticle interactions. When two immiscible polymers are grafted on the nanoparticle, they can microphase separate to form domains at the nanoparticle surface. Here, we computationally investigate the phase behavior of such binary mixed brush nanoparticles in solution, across a large and experimentally relevant parameter space. Specifically, we calculate the mean-field phase diagram, assuming uniform grafting of the two polymers, as a function of the nanoparticle size relative to the length of the grafted chains, the grafting density, the enthalpic repulsion between the grafted chains, and the solvent quality. We find a variety of phases including a Janus phase and phases with varying numbers of striped domains. Using a nonuniform, random distribution of grafting sites on the nanoparticle instead of the uniform distribution leads to the development of defects in the mixed brush structures. Introducing fluctuations as well leads to increasingly defective structures for the striped phases. However, we find that the simple Janus phase is preserved in all calculations, even with the introduction of nonuniform grafting and fluctuations. We conclude that the formation of the Janus phase is more realistic experimentally than is the formation of defect-free multivalent mixed brush nanoparticles.

Morphology Development via Static Crosslinking of (Polylactic Acid/Acrylic Rubber) as an Immiscible Polymer Blend

AbstractThe interrelation between crosslinking and morphology is investigated for an immiscible blend of polylactic acid (PLA) and acrylic rubber (ACM). The blends are prepared by solution mixing and static crosslinking is used to avoid the simultaneous effect of the flow field that occurs in dynamic vulcanization. It is carried out at different temperatures, times, and curing agent contents. Scanning force microscopy (SFM) and polarized optical microscopy are used to determine the morphology of the blends. The chemical interactions and viscoelastic properties of the blends after crosslinking are also studied using infrared spectroscopy and rheological tests, respectively. Before crosslinking, SFM shows matrix‐droplet morphology for the samples that it is retained after that for the blend with 30 wt% ACM; however, it is changed to cocontinuous one in the blend with 50 wt% ACM. Partially, grafting of PLA on the crosslinked ACM is confirmed by Fourier transform infrared spectroscopy. The rheological results show that the incorporation of ACM to the PLA slows down the chain relaxation and vulcanization intensifies this effect. A model is proposed to explain the morphology evolution during static crosslinking of an immiscible blend.

In-situ compatibilization of an immiscible liquid hydroxyl-terminated polymer pair by rate controlled reactions with a diisocyanate

Low molecular weight Hydroxyl-Terminated-Polybutadiene (HTPB) and Glycidyl Azide Polymer (GAP) are completely immiscible. These pre-polymers were compatibilized by allowing the slow reacting GAP hydroxyls to react first with toluenediisocyanate (TDI) and only then adding HTPB with relatively fast reacting hydroxyls. The two stage procedure yielded a macroscopically homogenous rubber. The rubber is composed of cross-linked HTPB continuum scattered with 1–10 μm non-bonded GAP droplets. The droplet material was identified using Infra-Red (IR), Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC) analyses before and after extraction of the rubber. Dynamic Mechanical Analysis (DMA) was used for assessing the effect equivalent ratio ([NCO]/[OH]), composition (%GAP in the rubber) and reaction time (GAP/TDI 1st stage) have on the rubber properties. We have concluded that the large difference in the condensation rate of GAP hydroxyls versus HTPB hydroxyls with TDI (kHTPB/kGAP = 3.7@65 °C) is responsible for in situ formation of surface active species as GAP-b-(HTPB)n or GAP-g-(HTPB)n n ≥ 1, which enables compatibilization of the immiscible polymers. The formation of the postulated species is also supported by GPC analysis. This simple two step procedure eliminated the need to prepare a pre-made co-polymer or introduce appropriate functional groups on one or both component to achieve surface reaction and compatibilization.

Carbon nanotubes toughened immiscible polymer blends

Abstract The incorporation of CNTs into the immiscible blends are increasingly attractive because of high performance, its wide application and great prospects for development in the future. The objective of this review focuses on CNTs toughened immiscible polymer blends based on the selective localization of CNTs in the immiscible blends. Firstly, the thermodynamic and kinetic factors that determines the localization of CNTs are introduced. The former is relative to the wetting coefficient that can be applied to evaluate the favorable polymer component for CNTs; and the latter relates to the migration of CNTs in polymer blends. Combined with the morphology evolution accompanying with the incorporation of CNTs, the selective localization of CNTs can be distributed in dispersed phase, continuous phase or at the interface, exhibiting different unique properties. Among these properties, CNTs toughened the immiscible polymer blends can be found in these two cases: CNTs disperse in one phase (droplets or continuous) or CNTs disperse at the interface. With the presence of CNTs in immiscible blend, the toughening mechanisms involve: 1) the formation of percolative CNTs network; 2) formation of “cross-linked”-like structure; 3) morphology evolution; 4) compatibilization of immiscible blends; 5) nanobridge effect of CNTs at the interface. This review details recent works for the above mentioned selective localization of CNTs in immiscible blend and corresponding the toughening mechanisms of CNTs for immiscible blends, which is proposed to provide a guidance for the polymer toughening.

Predicting phase inversion based on the rheological behavior in Polyamide 6/Polyethylene blends

Models have been proposed to describe the rheology of immiscible polymer blends in relation to their morphologies, either for dilute droplet emulsions or for concentrated blends with complex interfaces. The morphologies obtained in reactively compatibilized blends are the result of a complex interplay between instabilities due to chemical reaction at interfaces and drop breakup and coalescence processes. We have studied reactively compatibilized Polyamide6/High Density Polyethylene (PA6/HDPE) blends with widely different viscosity ratios, obtained by changing the length of PA chains. The composition at phase inversion is shifted to high concentration of the most viscous component, as may be expected from simple rheological considerations. The relationships between the morphologies and the rheological behavior are discussed. The objective of this work is to relate the rheological behavior to the morphologies. Specifically, we show that phase inversion can be reasonably predicted, based on the rheological behavior of blends in the linear regime. This result could be of significant benefit for applications, since rheological studies are often easier to perform in the applicative context than electron microscopy observations, which are needed to characterize the morphologies at sub-micrometric scales.

Elongational Effect on Immiscible Polymer Blends via Novel Vane Plasticating Extruder

The vane plasticating extruder (VPE) is a novel polymer processing equipment which is based upon elongational rheology. According to the basic structural analysis and movement interpretation, generation mechanism of elongational flow field was derived. Elongational effects during the controlled recovery of immiscible polymer blends, containing polystyrene (PS) matrix and linear low density polyethylene (LLDPE) as dispersed phase, were studied. The morphological results revealed the elongational effect of vane extruder. LLDPE morphology evolution was precisely predicted by a mathematical model. Elongational ratio and elongational strain via VPE were calculated separately, both of which established that the VPE does imposed elongational force field on polymer blends. DOI: http://dx.doi.org/10.5755/j01.mech.23.6.19855

Nanoscale PtO2 Catalysts-Loaded SnO2 Multichannel Nanofibers toward Highly Sensitive Acetone Sensor.

PtO2 nanocatalysts-loaded SnO2 multichannel nanofibers (PtO2-SnO2 MCNFs) were synthesized by single-spinneret electrospinning combined with apoferritin and two immiscible polymers, i.e., poly(vinylpyrrolidone) and polyacrylonitrile. The apoferritin, which can encapsulate nanoparticles within a small inner cavity (8 nm), was used as a catalyst loading template for an effective functionalization of the PtO2 catalysts. Taking advantage of the multichannel structure with a high porosity, effective activation of catalysts on both interior and exterior site of MCNFs was realized. As a result, under high humidity condition (95% RH), PtO2-SnO2 MCNFs exhibited a remarkably high acetone response (Rair/Rgas = 194.15) toward 5 ppm acetone gases, superior selectivity to acetone molecules among various interfering gas species, and excellent stability during 30 cycles of response and recovery toward 1 ppm acetone gases. In this work, we first demonstrate the high suitability of multichannel semiconducting metal oxides structure functionalized by apoferritin-encapsulated catalytic nanoparticles as highly sensitive and selective gas-sensing layer.

Rheology of Nanosilica-Compatibilized Immiscible Polymer Blends: Formation of a “Heterogeneous Network” Facilitated by Interfacially Anchored Hybrid Nanosilica

Exclusive localization of nanofillers at the interface of immiscible polymer blend has been confirmed to be effective in improving compatibility and facilitating the formation of nanofiller-network with very low percolation threshold, while the rheology of such nanofiller compatibilized blends has seldom been investigated. Herein, we present a systematic rheological study on nanosilica-compatibilized PVDF/PLLA (poly(vinylidene fluoride)/poly(l-lactide)) blends. The linear viscoelastic properties of the systems are evaluated using small amplitude oscillatory shear (SAOS). It is found that the interfacial jammed Janus grafted silica (JGS) located at the interface increases dynamic moduli at low frequency even with very low filler loadings. The nonterminal effects become more pronounced with increasing JGS loadings. Weighted relaxation spectra inferred from SAOS reveals that the shape relaxation of PVDF-droplets is strongly influenced by addition of JGS. The solid-like behavior of JGS-filled blends has been ...

Control of the dispersed-to-continuous transition in polymer blends by viscoelastic asymmetry

Controlling the dispersed-to-continuous transition (DCT) in immiscible polymer blends is still a challenging task due to multiple parameters dependency of DCT in the mixing process. In this study, the DCT of different polymer blends was investigated through controlling the viscoelastic asymmetry of polymers. The results demonstrate that the DCT is well correlated with the deformation of the dispersed domains and the ability to raise the aspect ratio of the dispersed domains. Both the viscosity ratio and the elasticity ratio are important to determine the aspect ratio of the dispersed domains. A diagram was suggested to control the DCT concentration by viscoelastic asymmetry, i.e., viscosity ratio and elasticity ratio. It is proved that DCT concentration as low as about 10% can be achieved for Polycarbonate/Poly (lactic acid) (PC/PLA) blends at the suitable viscoelastic asymmetry.

Reactive compatibilization of poly(lactic acid)/polystyrene blends and its application to preparation of hierarchically porous poly(lactic acid)

In this work hierarchically porous poly(lactic acid) (PLA) with bimodal pore size distribution was derived from reactively compatibilized ternary immiscible polymer blends. We first demonstrated the generation of submicron pores from cocontinuous PLA/oxazoline functional polystyrene (PS-OX) blends. The oxazoline groups in PS-OX reacted with the carboxylic acid end groups of PLA and formed graft copolymer at the interface, which significantly reduced the domain size. Hierarchically structured “tri-continuous” morphology was further obtained in a ternary PLA/PS-OX/linear low density polyethylene (LLDPE) blend. Porous PLA was made by selectively removing the PS-OX and LLDPE phases. Static annealing was used to control the pore size. The pores formed by PS-OX (∼0.5–2 μm) were one order of magnitude smaller than the pores formed by LLDPE (∼5–20 μm). The underlying thermodynamic mechanism for formation of hierarchical morphology in PLA/PS-OX/LLDPE blend was studied, and it was found that PLA/PS/PE ternary blends demonstrated complete wetting behavior with PS located at PLA/PE interface. Our results show that compatibilization with graft/block copolymer is a versatile way to achieve hierarchical microstructures in multiphase polymer blends.

Synthesis and characterization of poly(styrene sulfonic acid-co-1-vinylimidazole-co-styrene) and its blends with poly(vinyl chloride) as proton conducting membranes

The development of proton conducting membranes based on poly(styrene sulfonic acid-co-1-vinylimidazole-co-styrene) (PSSA-co-PVIm-co-PS)/poly(vinyl chloride) (PVC) blends is firstly reported. PSSA-co-PVIm-co-PS with three different terpolymer compositions were synthesized via conventional free radical polymerization by varying styrene feed. Successful syntheses were confirmed by 1H-nuclear magnetic resonance spectroscopy (1H-NMR), elemental analysis, and Fourier transform infrared spectroscopy (FTIR). Hydrolytically stable PSSA-co-PVIm-co-PS/PVC blend membranes were prepared via solution-cast method. Scanning electron microscopy (SEM) images along with two glass transition temperatures observed from differential scanning calorimetry (DSC) suggested immiscible polymer blends. Water uptake and ion exchange capacity (IEC) were found to decrease with increasing PS content in terpolymer. All blend membranes had high thermal decomposition onsets of 230 °C. The blends demonstrated high storage moduli at room temperature and high oxidative stability. Proton conductivity at 25 °C of membranes equilibrated with water vapor was found to depend on PS content, and a maximum conductivity of 7.8 × 10−5 S/cm was achieved from 1:1:4/PVC blend membrane. For dry membranes, the effect of PS amount on proton conduction was not clearly observed at elevated temperatures (100–120 °C).

Effect of Solvent Volatility on Diameter Selection of Bicomponent Nanofibers Produced by Gas Jet Fiber Process Test

Abstract This paper addresses the role of solvent volatility on diameter selection of bicomponent polymer nanofibers produced via gas jet fibers (GJF) process whereby an axisymmetric turbulent gas jet is used for liquid jet initiation, liquid jet stretching, and solvent evaporation. Several morphological forms, such as interpenetrating network (IPN), bi-lobal, and core-shell are obtained by spinning homogeneous solutions of two immiscible polymers in two mutually miscible solvents. The diameter selection of fibers of the same morphology, e. g., bi-lobal, is achieved by spinning polymer solutions of two sets of solvents of different volatility. The results show that fiber diameter is strongly dependent on the value of vapor pressure of the solvents while the morphology is strongly dependent on the vapor pressure difference of the two respective solvents. The diameter selection by GJF process is most prominent for IPN nanofibers, moderately prominent for core-shell fibers, and almost indifferent for bi-lobal nanofibers. The relative rates of solvent evaporation are useful in interpreting the experimental trend.

Study on the Compatibilizing Effect of Janus Particles on Liquid Isoprene Rubber/Epoxy Resin Composite Materials

Janus hybrid particles (MPS-SiO2@PDVB-DM, JPs) were successively fabricated by grafting dodecyl mercaptan (DM) onto polydivinylbenzene (PDVB) lobe and 3-(trimethoxysilyl)propyl methacrylate (MPS) chains onto SiO2 lobe in the case of SiO2@PDVB Janus particles as the template. Moreover, MPS-SiO2@PDVB-DM Janus particles were used as the compatibilizer of immiscible polymer blends of liquid isoprene rubber (LIR) and epoxy resin (ER). The modified Janus particles were embedded in the interface of LIR and ER, which could improve the compatibility of LIR and ER, mitigating the macrophase separation in the blends. Besides, the compatibilizing effect of MPS-SiO2@PDVB-DM depends not only on the Janus molecular structure but also on the blending process and the curing agent of ER.

Design of thermochromic polymer blends containing low‐mass compounds

ABSTRACTWe investigated the light transmittance of an immiscible polymer blend comprising a copolymer of ethylene and vinyl acetate (EVA) and a terpolymer of vinyl butyral, vinyl alcohol, and vinyl acetate (PVB). Both EVA and PVB are used in the interlayers of laminated glass. We found that the transparency of the blend depends on the ambient temperature. This can be attributed to the difference in the temperature dependence of the refractive index between EVA and PVB. The blend has good transparency at room temperature because the difference between the refractive indices of its components is minimal. At high or low temperatures, however, the blend becomes opaque owing to light scattering. The addition of a plasticizer favorably affects the temperature range over which the blend exhibits high transparency, because the refractive index and its temperature dependence are affected by the plasticizer. We also evaluated the interphase transfer of a plasticizer between EVA and PVB at various temperatures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45927.

Immiscible polymer blends compatibilized with reactive hybrid nanoparticles: Morphologies and properties

Hybrid nanoparticles (NPs) having both reactive epoxide groups (from polyhedral oligomeric-silsesquioxane (POSS) grafts) and long poly(methyl methacrylate) (PMMA) chains, POSS(epoxy)x-g-PMMAy, were synthesized and used as reactive compatibilizers for immiscible polyvinylidene fluoride/poly(l-lactide) (PVDF/PLLA) (50/50) blends. It was anticipated that the NPs would react with the PLLA during melt mixing and would be located solely at the PLLA/PVDF interface because the PMMA side chains and the in-situ grafted PLLA chains would entangle with the PVDF and PLLA phases, respectively. However, effective compatibilization was only achieved by first blending the NPs with the PLLA followed by melt mixing with the PVDF. Elemental mapping images indicated that the NPs had a greater affinity for PVDF than for PLLA and were encapsulated in PVDF during one-step melt mixing or initial mixing with PVDF. The affinity of the compatibilizer with the blend components is therefore critically important for the effective compatibilization of immiscible polymer blends.

Polypropylene/polyamide blend featuring mechanical interlocking via controlled interfacial diffusion and recrystallization

The prevalent way to enhance interface interaction of immiscible polymer blend is adding some low molecular weight compatibilizers with “soft” nature, unfortunately throwing negative effects on the final mechanical strength. Here, an interfacial interlocking design strategy for immiscible polypropylene (PP)/polyamide (PA) blend is proposed. The formation process involves aryl amide-based compounds firstly were selectively enriched in PA phase, followed by controlled release and recrystallization at the subsequent annealing process, into fiber-like crystals at the interface. Accordingly, the blend featuring mechanical interlocking was successfully prepared, where the interfacial grown fibers functioned as interlocks to integrate the two immiscible components via large interfacial friction. Furthermore, the density and dimension of the interfacial fibers were tailored by adjusting the annealing temperatures. Specially, at the elevated temperature, the large and dense fibers were generated at the interface to offer stronger interfacial friction, which in turn strengthened the interfacial interaction. The interfacial topological regulation can effectively solve the interfacial problems and also can extend broadly to the other immiscible bi-phase systems.

Biodegradable compatibilized polymer blends for packaging applications: A literature review

ABSTRACTThe majority of materials used for short‐term and disposable packaging application are non‐biodegradable which are not satisfying the demands in environmental safety and sustainability. Biodegradable polymers are an alternative for these non‐biodegradable materials. The biodegradable polymeric materials can degrade in a reasonable time period without causing environmental problems. However, biodegradable polymers possess some limitations such as comparatively high cost, insufficient mechanical performances, and inferior thermal stability to extend their widespread application in packaging industry. To overcome these limitations, one of the most commonly used strategies is melt blending of dissimilar biodegradable polymers. Unfortunately, most of the biodegradable polymer blends exhibit insufficient performance because they are thermodynamically immiscible as well as exhibit poor compatibility between the blended components. It has been established that the compatibilization is a well‐known strategy to improve the performances of the immiscible biodegradable polymer blends by enhancing the adhesion between the phases. As a result, recent studies focus on various compatibilizers to enhance the performances of the resulting biodegradable polymer blends. This review summarizes the recent developments on a variety of biodegradable polymer blends compatibilized by melt processing with a main focus of ex situ and in situ compatibilization strategies. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45726.