Immiscible Polymer Blends Research Articles

Structure and Properties of PVDF/PA6 Blends Compatibilized by Ionic Liquid-Grafted PA6.

Compatibilization of immiscible blends is critically important for developing high-performance polymer materials. In this work, an ionic liquid, 1-vinyl-3-butyl imidazole chloride, grafted polyamide 6 (PA6-g-IL(Cl)) with a quasi-block structure was used as a compatibilizer for an immiscible poly(vinylidene fluoride) (PVDF)/PA6 blend. The effects of two PA6-g-IL(Cl)s (E-2%-50K and E-8%-50K) on the morphology, crystallization behavior, mechanical properties, and surface resistance of the PVDF/PA6 blend were investigated systematically. It was found that the two types of PA6-g-IL(Cl)s had a favorable compatibilization effect on the PVDF/PA6 blend. Specifically, the morphology of the PVDF/PA6 = 60/40 blend transformed from a typical sea-island into a bicontinuous structure after incorporating E-8%-50K with a high degree of grafting (DG). In addition, the tensile strength of the PVDF/PA6/E-8%-50K blend reached 66 MPa, which is higher than that of PVDF, PA6 and the PVDF/PA6 blend. Moreover, the PVDF/PA6/E-8%-50K blend exhibited surface conductivity due to the conductive path offered by the bicontinuous structure and conductive ions offered by grafted IL(Cl). Differential scanning calorimetry (DSC) and wide-angle X-ray diffractometry (WAXD) results revealed that PA6-g-IL(Cl) exhibits different effects on the crystallization behavior of PVDF and PA6. The compatibilization mechanism was concluded to be based on the fact that the nongrafted PA6 blocks entangled with the PA6 chains, while the ionic liquid-grafted PA6 blocks interacted with the PVDF chains. This work offers a new strategy for the compatibilization of immiscible polymer blends.

Mechanical Upcycling Immiscible Polyethylene Terephthalate-Polypropylene Blends with Carbon Fiber Reinforcement.

Ineffective sorting of post-consumer plastics remains one of the major obstacles in the recycling of plastics. Consequently, these highly heterogeneous, mixed post-consumer plastics will end up in landfill or have to be incinerated as repurposing them directly would lead to a polymer blend with inferior quality for many end-uses. In this work, we demonstrate the use of carbon fibers (CFs) to practically upgrade the mechanical properties of mixed plastics, adding value to them. This will create a stronger demand for mixed plastics to be used in various engineering applications. Using polyethylene terephthalate (PET) and polypropylene (PP) as the model immiscible polymer blend, we showed that the incorporation of CFs increased the tensile, flexural, and single-edge notched fracture toughness of the resulting CF-reinforced PET/PP composite blends. Despite the high environmental burden associated with the production of CFs, cradle-to-grave life-cycle analysis showed that CF-reinforced PET/PP composites have a lower environmental impact than the life-cycle scenarios of “doing nothing” and repurposing immiscible PET/PP blends as it is without CF reinforcement. This can be attributed to the weight saving achieved, a direct result of their higher mechanical performance. Our work opens up opportunities for the use of mixed plastics in various higher value applications such that they can be diverted away from landfill or incineration, in line with the concept of circular economy.

Polymethyl Methacrylate/Polypropylene Blends Loaded with Graphene and Clay: Morphology, Mechanical Properties and Thermal Stability

In the research described here immiscible polymer blends based on amorphous poly(methyl methacrylate) (PMMA) and semi-crystalline polypropylene (PP) were produced via a melt-mixing method. The effects of the addition of graphene and clay nanoparticles on the compatibility and properties of the blends were investigated. Scanning electron microscopy results showed that the neat blends at all compositions were severely phase separated and a droplet-in-matrix morphology was attained. Introduction of graphene and clay caused the compatibility of the blends to be highly enhanced and, thus, a finer and more uniform morphology was obtained for the nanocomposites. Based on the morphology results, it was found that graphene had more affinity toward the PP phase and clay was more compatible with PMMA. This hypothesis was further proved via mechanical analysis and thermogravimetric analysis (TGA) results. The toughness of the neat blends was increased upon increasing the PP content; however, it was reduced for all the nanocomposites relative to the blend of the same polymer composition. The thermal stability of the blend at a composition of 70/30 PMMA/PP was improved via addition of clay and graphene. The first stage of degradation (PMMA) was shifted to higher temperatures once clay was added to the system while the second stage of degradation (PP) was impeded upon addition of graphene.

The effect of the embedded interface dynamics on mass transport in immiscible polymer blends

AbstractMass transport of solvents into immiscible blends may exhibit a non‐Fickian behavior due to the deformation of the embedded interface that couples with diffusion. We introduce an interface area covariant tensor N as a structural state variable and derive a set of thermodynamically‐consistent PDEs and ODEs transport equations for the bulk and time‐dependent boundaries. The proposed model, which is a reformulation of that derived by El Afif (2008) and El Afif et al. (2003), improves both mathematically and numerically the investigation of the diffusion‐interface coupling and provides reasonable predictions of the sorption‐permeation one dimensional treatment affording good agreement with experimental data. The tensor N englobes, into a single morphological quantity, all information regarding diffusion‐induced changes in the size and shape anisotropy of the interface area. Predicted results include concentration, components of N, residual stresses, mass‐uptake, and swelling. Scaling leads to three relevant dimensionless parameters: a mixing‐interface coupling constant and bulk and boundary diffusion Deborah numbers.

Interfacial Engineering with Rigid Nanoplatelets in Immiscible Polymer Blends: Interface Strengthening and Interfacial Curvature Controlling.

The interfacial nanoparticle compatibilization (INC) strategy has opened up a promising avenue toward simultaneous functionalization and interfacial engineering of immiscible polymer blends. While the INC mechanism has been well developed recently, few investigations have focused on rigid nanoplatelets because of the inherent steric hindrance of the surface-grafted polymer chains. Herein, surface-modified rigid nanoplatelets have been incorporated into an immiscible poly(l-lactide) (PLLA)/poly(butylene succinate) (PBSU) blend. It is demonstrated that the strong interfacial adhesion between PLLA and PBSU phases is promoted via molecular entanglements of the grafted chains on the surface of nanoplatelets with the individual components. A refined phase morphology with improved mechanical properties can be achieved with the addition of 5 wt % modified Gibbsite nanoplatelets. It was further found that the stiffness of nanoplatelets can change the geometry of the interface significantly. It is, therefore, indicated that the simultaneous interface strengthening and interfacial curvature controlling of rigid nanoplatelets originate from the selective swelling/collapse of the in situ-formed PLLA and PBSU grafts within the corresponding phase at the interface. Such a mechanism is confirmed by the Monte Carlo simulations. This work provides new opportunities for the fabrication of advanced polymer blend nanocomposites.

Measuring the Interfacial Thickness of Immiscible Polymer Blends by Nano-probing of Atomic Force Microscopy

Measuring the Interfacial Thickness of Immiscible Polymer Blends by Nano-probing of Atomic Force Microscopy

Toward high dielectric constant and low dielectric loss nanocomposite via kinetical migration

Controlling the selective localization of nanoparticles in an immiscible polymer blend is a promising concept for developing high-performance polymeric dielectrics. However, the mechanism of the dielectric regulation has not been lucidly studied. In this work, PLA/PVDF/CNTs nanocomposites with tunable dielectric properties were fabricated via tailoring the localizations of CNTs based on kinetic-based approach. The dielectric evolutions were attributed to the synergistic effects of the “sea-island” structure, and the number and average capacitance of the microcapacitors in PLA/PVDF/CNTs nanocomposites. Ultimately, we obtained the PLA/PVDF/CNTs nanocomposites with a high dielectric constant of 956.6@1 kHz, which was more than 100 times higher of the virgin PVDF, at a very-low dielectric loss of 0.17@1 kHz. Since the interface interaction was enhanced by locating CNTs at interface, the highest tensile strength of nanocomposites fabricated by two-step method reached 59.1 MPa at a mixing time of 12 min. This work not only reports a high-performance polymeric dielectric with a high dielectric constant and a low dielectric loss, but also intends to propose a general insight in the effect of kinetically regulated migration of conductive fillers on the as-prepared nanocomposites.

Melt Spinning of Flexible and Conductive Immiscible Thermoplastic/Elastomer Monofilament for Water Detection.

In many textile fields, such as industrial structures or clothes, one way to detect a specific liquid leak is the electrical conductivity variation of a yarn. This yarn can be developed using melt spun of Conductive Polymer Composites (CPCs), which blend insulating polymer and electrically conductive fillers. This study examines the influence of the proportions of an immiscible thermoplastic/elastomer blend for its implementation and its water detection. The thermoplastic polymer used for the detection property is the polyamide 6.6 (PA6.6) filled with enough carbon nanotubes (CNT) to exceed the percolation threshold. However, the addition of fillers decreases the polymer fluidity, resulting in the difficulty to implement the CPC. Using an immiscible polymers blend with an elastomer, which is a propylene-based elastomer (PBE) permits to increase this fluidity and to create a flexible conductive monofilament. After characterizations (morphology, rheological and mechanical) of this blend (PA6.6CNT/PBE) in different proportions, two principles of water detection are established and carried out with the monofilaments: the principle of absorption and the short circuit. It is found that the morphology of the immiscible polymer blend had a significant role in the water detection.

Janus Nanoshards Prepared Based on High Internal Phase Emulsion Templates for Compatibilizing Immiscible Polymer Blends

Janus Nanoshards Prepared Based on High Internal Phase Emulsion Templates for Compatibilizing Immiscible Polymer Blends

The Effects of Copolymer Compatibilizers on the Phase Structure Evolution in Polymer Blends-A Review.

This paper summarizes the results of studies describing the effect of block and graft copolymers on the phase structure formation and evolution in immiscible polymer blends. The main phenomenological rules for prediction of the copolymer compatibilization efficiency are briefly described and compared with selected experimental data. The results of the theories of equilibrium distribution of a copolymer between the blend interface and the bulk phases and its effect on the blend interfacial tension are summarized. The theories of the compatibilizer effect on the droplet breakup in flow are analyzed. The mechanisms of the copolymer effect on the coalescence of droplets in flow are compared and their effect on the droplet size is shown. The problems of reliable description of the effect of a copolymer on the coalescence in quiescent state are presented. Obstacles to derivation of a realistic theory of the copolymer effect on the competition between the droplet breakup and coalescence are discussed. Selected experimental data are compared with the theoretical results.

Multiscale Modeling and Simulation of Polymer Blends in Injection Molding: A Review.

Modeling and simulation of the morphology evolution of immiscible polymer blends during injection molding is crucial for predicting and tailoring the products’ performance. This paper reviews the state-of-the-art progress in the multiscale modeling and simulation of injection molding of polymer blends. Technological development of the injection molding simulation on a macroscale was surveyed in detail. The aspects of various models for morphology evolution on a mesoscale during injection molding were discussed. The current scale-bridging strategies between macroscopic mold-filling flow and mesoscopic morphology evolution, as well as the pros and cons of the solutions, were analyzed and compared. Finally, a comprehensive summary of the above models is presented, along with the outlook for future research in this field.

Porous Fibers Templated by Melt Blowing Cocontinuous Immiscible Polymer Blends.

We report a scalable melt blowing method for producing porous nonwoven fibers from model cocontinuous polystyrene/high-density polyethylene polymer blends. While conventional melt compounding of cocontinuous blends typically produces domain sizes ∼1-10 μm, melt blowing these blends into fibers reduces those dimensions up to 35-fold and generates an interpenetrating domain structure. Inclusion of ≤1 wt % of a block copolymer compatibilizer in these blends crucially enables access to smaller domain sizes in the fibers by minimizing thermodynamically-driven blend coarsening inherent to cocontinuous blends. Selective solvent extraction of the sacrificial polymer phase yielded a network of porous channels within the fibers. Fiber surfaces also exhibited pores that percolate into the fiber interior, signifying the continuous and interconnected nature of the final structure. Pore sizes as small as ∼100 nm were obtained, suggesting potential applications of these porous nonwovens that rely on their high surface areas, including various filtration modules.

Study of non-Newtonian polymer blends using large amplitude oscillatory shearing flow

Large amplitude oscillatory shear (LAOS) was performed on non-Newtonian minor phase in Newtonian matrix phase polymer blends as a first step toward understating more complex immiscible polymer blends under high deformation condition. The blend consists polybutadiene (PBD) as the droplet phase and polydimethylsiloxane (PDMS) as the matrix phase. The PBD droplet phase was an elastic “Boger” fluid prepared by dissolving a high-molecular-weight PBD into a low-molecular-weight Newtonian PBD. Different percentages of the high-molecular-weight PBD were used to prepare different types of Boger fluids that resulted in blends with different viscosity ratios from lower than unity, to unity and higher than unity. Furthermore, the LAOS results of the blends were analyzed by using the Fourier Transform (FT) technique. From a theoretical point of view, the constrained volume model (CV-model) for Newtonian components is adapted to the case of a Newtonian matrix phase and non-Newtonian Boger fluid droplet phase by taking into account stresses that arise in the Boger fluids. The adapted model and the Newtonian CV-model were compared to the experimental results of FT-LAOS for checking the predictability of the model against the rheological properties. The adapted model shows some reasonable qualitative and quantitative agreements at high strain amplitude values.

Investigations of the 80/20 (wt/wt) PA6/ABS blends system in presence of SMA co-polymers as Reactive Compatibilizer and Encapsulated Multiwall Carbon Nanotubes (MWNTs)

Introduction: The modification of a polymeric material with tailored properties was carried out either by blending with another polymer or by using suitable filler or by taking the advantages of both. The immiscible polymer blends were generally forming coarse and unstable phase morphology, which hamper mechanical properties of the materials. Therefore, it was essential to control and stabilize a desired type of morphology in order to generate polymeric materials with favourable properties through controlling composition, processing conditions, viscosity of the materials and can be compatibilized by using either reactive compatibilizer or filler or combination of both to reduce the interfacial tension. Methods: Keeping these aspects in mind, a novel strategy was introduced during melt-mixing of 80/20 (wt/wt) polyamide6 (PA6) and acrylonitrile-butadiene-styrene (ABS). Styrene maleic anhydride (SMA) co-polymer having 8, 14 and 50 wt% of maleic anhydride (MA) content was utilized as reactive compatibilizers for 80/20 (wt/wt) PA6/ABS blends system. Multiwall carbon nanotubes (MWNTs) were considered as a filler material to improve the stiffness and strength of the blends composites. To overcome the van der Waals’ forces of the MWNTs and achieve the uniform dispersion of the MWNTs in the blends phosphonium based modifier, namely octadecyl triphenyl phosphonium bromide (OTPB) was studied with Raman spectroscopy and transmission electron microscopic analysis (TEM). To restrict the MWNTs in one of the phase and/or at the interfaces and taking the advantages of the compatibilizer and filler, the MWNTs were encapsulated by the SMA (8, 14, 50) co-polymer. A simple solution method was adopted for the preparation of the SMA (8, 14, 50) encapsulated MWNTs. Results & Discussions: A detail morphological analysis was carried out in context to the migration of the MWNT along with a decrease in dispersed droplet size of ABS phase with varying interfacial energy differences between the matrix and the dispersed phase. The morphological observations were further substantiated by FTIR spectroscopy and DSC non-isothermal crystallization studies. To understand the morphological changes (refinement) in 80/20 (wt/wt) PA6/ABS binary blends in presence of SMA encapsulated MWNTs in context to melt-viscosity factor and thermodynamic aspect during melt-mixing. These observations were supported by the torque rheometry, FTIR analysis and TEM images. Conclusions: Dynamic mechanical thermal analysis (DMTA) concluded that all combinations enhances the storage modulus with decrease in Tg compared to the 80/20 (wt/wt) PA6/ABS blends. However, SMA encapsulated MWNTs enhances highest storage modulus, may be due to the better interfacial adhesion between filler and polymers. Hence, a novel compatibilization strategy was developed and evaluated for 80/20 (wt/wt) PA6/ABS blends using a hybrid compatibilizer involving MWNT. Keywords: PA6/ABS blends, Reactive and hybrid compatibilizers, Multi-wall carbon Nanotubes, Encapsulation Acknowledgment: Professor Arup Ranjan Bhattacharyya, MEMS and SAIF Indian Institute of Technology Bombay (IITB), Mumbai. References B.F. Jogi, M. Sawant, M. Kulkarni and P.K. Brahmankar, Dispersion and Performance Properties of Carbon Nanotubes (CNTs) Based Polymer Composites: A Review. Journal of Encapsulation and Adsorption Science, Scientific Research Publishing, 2012;(2):69–78. doi: 10.4236/jeas.2012.24010. G.S. Lohar, P.B. Tambe, B.F. Jogi, Influence of dual compatibilizer and carbon black on mechanical and thermal properties of PP/ABS blends and their composites. Composite Interfaces, Taylor and Francis, 2020;(12)1101–1136. https://doi.org/10.1080/09276440.2020.1726137. R.M. Dhajekar, B. F. Jogi and S.R. Nirantar, Preparation and Characterization of PAEK based Polymer Nanocomposites in the Presence of MMT Clay as Nanofiller to Study Tensile and Impact Properties. Materials Today: Proceedings, 2018;(5),6848–6854.

Localization of Poly(glycidyl methacrylate) Grafted on Reduced Graphene Oxide in Poly(lactic acid)/Poly(trimethylene terephthalate) Blends for Composites with Enhanced Electrical and Thermal Conductivities

Interfacial localization of conductive fillers in a cocontinuous immiscible polymer blend is an efficient way of improving the electrical and thermal conductivities of the composite. Conductive path formation at the interface of a cocontinuous structure is expected to provide high conductivity by a smaller amount of the filler, which can be used for applications as conductive materials. In this study, biobased poly(lactic acid) (PLA) was blended with poly(trimethylene terephthalate) (PTT) to make the cocontinuous immiscible polymer blend. Poly(glycidyl methacrylate) (PGMA) was grafted on reduced graphene oxide (rGO) to make a PGMA-grafted rGO (rGO-PGMA). The epoxy group of GMA on rGO-PGMA reacted with the end groups of both PLA and PTT and localized at the interface between PLA and PTT by a two-step blending procedure to form the conductive path between PLA and PTT. From transmission electron microscopy observation, it was found that rGO-PGMA localized between the interface of PLA and PTT. Both electrical and thermal conductivities of the composite were improved, which was confirmed by the electrical volume resistivity and thermal diffusivity measurements, compared with neat polymers and other blends.

Evolution of the electrical resistivity at rest and during oscillatory shearing of co‐continuous morphology (PP/PMMA)/MWCNT systems

AbstractIn this work, a modified parallel‐disks configuration on a strain‐controlled ARES rheometer (TA Instrument) was used to study the evolution of the electrical resistivity at rest and during oscillatory shearing of a co‐continuous immiscible polymer blend morphology based on polypropylene and /polymethyl(methacrylate) (PP/PMMA) in which various amounts (0–3 wt%) of multiwall carbon nanotubes (MWCNT) were added. The co‐continuity of both PP and PMMA phases allowed the buildup of a conductive network due to the preferential localization of the conductive MWCNT at the interface between PP and PMMA. Under a stepwise increase of the oscillatory strain amplitude below a critical value (γc = 6.3%), a significant decrease in the electrical resistivity was observed for MWCNT concentrations above the percolation threshold (0.3 wt%) due to the conductive paths induced by both thermal (Brownian) motion and oscillatory shearing. However, for deformation amplitudes higher than γc, the resistivity increased due to the destruction of the MWCNT paths induced by the large deformation imposed on the PP/PMMA interface. These observations were also confirmed by the evolution of the storage modulus (G′) which remained constant for γc < 6.3% (linear viscoelastic regime), while the values decreased above γc due to the destruction of the system's morphology.

Halloysite Nanotubes and Silane-Treated Alumina Trihydrate Hybrid Flame Retardant System for High-Performance Cable Insulation

The effect of the presence of halloysite nanotubes (HNTs) and silane-treated alumina trihydrate (ATH-sil) nanofillers on the mechanical, thermal, and flame retardancy properties of ethylene-vinyl acetate (EVA) copolymer/low-density polyethylene (LDPE) blends was investigated. Different weight percentages of HNT and ATH-sil nanoparticles, as well as the hybrid system of those nanofillers, were melt mixed with the polymer blend (reference sample) using a twin-screw extruder. The morphology of the nanoparticles and polymer compositions was studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The mechanical properties, hardness, water absorption, and melt flow index (MFI) of the compositions were assessed. The tensile strength increases as a function of the amount of HNT nanofiller; however, the elongation at break decreases. In the case of the hybrid system of nanofillers, the compositions showed superior mechanical properties. The thermal properties of the reference sample and those of the corresponding sample with nanofiller blends were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Two peaks were observed in the melting and crystallization temperatures. This shows that the EVA/LDPE is an immiscible polymer blend. The thermal stability of the blends was improved by the presence of HNTs and ATH-sil nanoparticles. Thermal degradation temperatures were shifted to higher values by the presence of hybrid nanofillers. Finally, the flammability of the compositions was assessed. Flammability as reflected by the limiting oxygen index (OI) was increased by the presence of HNT and ATH-sil nanofiller and a hybrid system of the nanoparticles.

Ultra-Low Percolation Threshold Induced by Thermal Treatments in Co-Continuous Blend-Based PP/PS/MWCNTs Nanocomposites.

The effect of the crystallization of polypropylene (PP) forming an immiscible polymer blend with polystyrene (PS) containing conductive multi-wall carbon nanotubes (MWCNTs) on its electrical conductivity and electrical percolation threshold (PT) was investigated in this work. PP/PS/MWCNTs composites with a co-continuous morphology and a concentration of MWCNTs ranging from 0 to 2 wt.% were obtained. The PT was greatly reduced by a two-step approach. First, a 50% reduction in the PT was achieved by using the effect of double percolation in the blend system compared to PP/MWCNTs. Second, with the additional thermal treatments, referred to as slow-cooling treatment (with the cooling rate 0.5 °C/min), and isothermal treatment (at 135 °C for 15 min), ultra-low PT values were achieved for the PP/PS/MWCNTs system. A 0.06 wt.% of MWCNTs was attained upon the use of the slow-cooling treatment and 0.08 wt.% of MWCNTs upon the isothermal treatment. This reduction is attributed to PP crystals’ volume exclusion, with no alteration in the blend morphology.

Effect of the selective localization of carbon nanotubes and phase domain in immiscible blends on tunable microwave dielectric properties

In recent years, the immiscible polymer blend system has attracted much attention as the matrix of nanocomposites. Herein, from the perspective of dynamics, the control of the carbon nanotubes (CNTs) migration aided with the interface of polystyrene (PS) and poly (methyl methacrylate) (PMMA) blends was achieved through a facile melt mixing method. Thus, we revealed a comprehensive relationship between several typical CNTs migrating scenarios and the microwave dielectric properties of their nanocomposites. Based on the unique morphologies and phase domain structures of the immiscible matrix, we further investigated the multiple microwave dielectric relaxation processes and shed new light on the relation between relaxation peak position and the phase domain size distribution. Moreover, by integrating the CNTs interface localization control with the matrix co-continuous structure construction, we found that the interface promotes double percolation effect to achieve conductive percolation at low CNTs loading (~1.06 vol%). Overall, the present study provides a unique nanocomposite material design symphonizing both functional fillers dispersion and location as well as the matrix architecture optimization for microwave applications.

Shear Flow and Relaxation Behaviors of Entangled Viscoelastic Nanorod-Stabilized Immiscible Polymer Blends

To blend and process different high molar mass polymers into multiphase materials, predicting/controlling their morphology and rheological behavior is paramount. Herein, a segmental repulsive poten...