Phase morphology control of immiscible polymer blends under vibration force field

The formulas of polymer melt velocity, shearing rate, and shearing stress under vibration force field are established through simplifying coaxial cylinder circular flow into plane motional flow. On the basis of the concept of energy ratio model, the rate of energy dissipation and the energy ratio about blending systems are expressed, and the affected factors on phase morphology are studied theoretically. The calculated and analytical results of dynamic flow field and energy ratio show that with the increasing of vibration strength, the fluctuating shearing force field exerted on polymer melt and the negative pressure diffusion behavior of instantaneous impulse strengthen. The energy consumption for phase inversion of immiscible polymer blends under vibration force field is less than that of steady state. The parameter controllability of vibration force field provides a more effective method for realizing phase inversion of immiscible polymer blends. The analysis of transmission electron microcopy micrographs of ethylene–propylene–diene terpolymer/polypropylene blends verifies that the energy ratio model and its phase morphology controlling theory have a good coincidence in comparison with experimental results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2299–2307, 2006     

Production of electrically conductive networks in immiscible polymer blends by chaotic mixing

A minor polymer was deformed into lamellar and fibrillar morphological forms in a chaotic mixer, which rendered the resultant immiscible blend electrically conductive along the flow direction. This was demonstrated using a blend consisting of 10 wt% polypropylene (PP), polyamide 6 (PA6), and 1 wt% conductive carbon black (CB) particles. It was found that PP‐phase containing CB particles deformed into lamellar and fibrillar morphological forms produced continuous networks in the flow direction, and provided conductivity by double percolation. Breakup of PP fibrils into droplets destroyed the continuous conductive networks, although conductivity was sustained purportedly due to migration of CB particles from the bulk to the surface of closely spaced PP droplets. This was augmented by the formation of much smaller PP droplets in the presence of CB particles. On continued mixing, the blend eventually turned into insulator as CB particles migrated from the polymer–polymer interfaces to PA6 phase. POLYM. ENG. SCI., 46:19–28, 2006. © 2005 Society of Plastics Engineers     

Shear-induced fractal morphology of immiscible reactive polymer blends

The origin of shear-induced morphology of two-component immiscible reactive polymer blends is studied by the example of grafting and crosslinking multilayer systems of statistic terpolymer of ethylene, butyl acrylate, and maleic anhydride and statistic copolymers including polyamide and acid groups terminated by acid and/or amine groups. It is found that in contrast to the non-reactive system, the reactive polymer blends display pronounced hydrodynamic instabilities followed by the formation of branched fingers. The observed morphologies are shown to evolve towards the fractal structures. Their fractal dimensions depend on the type of chemical interactions between the blend components resulting either in grafted or crosslinked interfaces. It is shown that the obtained morphologies resemble the Laplacian growth patterns. A simple model of the interface chemical modifications is discussed to explain a physical origin of the observed shear-induced finger instability.     

Compatibilization and morphology development of immiscible ternary polymer blends

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

Structure and improved properties of PPC/PBAT blends via controlling phase morphology based on melt viscosity

Poly(propylene carbonate) (PPC)/poly(butylenes adipate-co-terephthalate) (PBAT) blends with various composition ratios were prepared via melt mixing using a twin-screw extruder. The effect of melt viscosities of polymers on mechanical behavior, interfacial interaction, thermal properties, rheological responses, and phase morphology was investigated. Results showed that the phase morphology and properties of PPC/PBAT blends were affected by the composition of the blends and the melt viscosities of the two polymers. Results of tensile tests, FTIR, and dynamic rheological measurement of PBAT-rich blends exhibited a better mechanical properties, intermolecular interactions, and compatibility when compared with PPC-rich blends due to the differences of their melt viscosities. Incorporating of PBAT effectively improved the T_g of PPC and the thermal stability of the blends. The T_c of PPC/PBAT blends markedly increased from 37.5 to 66.8 °C with addition of only 10 wt% PPC, indicating an enhanced crystallization ability of PBAT. The improvement of T_c was helpful for blown film extrusion. SEM microphotographs showed that the size of the dispersed phase particles is much smaller and the distribution is more uniform for PBAT-rich blends, compared with that in PPC-rich blends. The processing stability of blown film extrusion was improved by blending PPC with PBAT. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48924.     

Irradiation processing of immiscible PP/EOC blend: Morphology control and processability modification

In this study, applying electron beam irradiation method at a relatively low-irradiation dose (20 kGy) under the air atmosphere to prepare injectable polypropylene (PP)/ethylene-octene copolymer (EOC) blends with fine morphology and appropriate performance was investigated. For this purpose, an extrusion PP grade with an EOC grade suitable to improve its impact resistance was melting blended. Gel content and rheological measurements revealed long-chain branching is predominant phenomenon occurring during the irradiation process of EOC. Blend irradiation resulted in changing its melt flow index proper for injection molding. A fine morphology obtained for the unirradiated blend was preserved for the irradiated blend. Moreover, irradiation thermally stabilized the blend morphology. Blends linear viscoelastic behavior discussed by proper rheological models revealed the existence of interfacial interactions and a reduction of the interfacial tension between irradiated blend phases. No significant effect of irradiation on the crystallization characteristics of EOC and the blend was observed. The satisfying impact resistance of the irradiated blend was near to that of the unirradiated blend, although its tensile mechanical properties were less.     

Morphology study of immiscible polymer blends in a vane extruder

This study reports the morphology development of polymer blends in a novel vane extruder in which polymer mainly suffers from elongational deformation field. Rapidly cooled samples of polypropylene/polystyrene (PP/PS) are collected in the vane extruder after stable extrusion. Furthermore, the shape and size of the dispersed phase from initial to final stages are analyzed. In addition, in order to compare the final size of the dispersed phase, different immiscible blends, including polypropylene/polyamide and PP/PS, are prepared by vane extruder and twin‐screw extruder, respectively. The results show that the dispersed phase is made to change rapidly from stretched striations to droplets under the strong elongational deformation field in the vane extruder. Furthermore, the droplet size of dispersed phase of blends prepared by vane extruder is much smaller than that prepared by twin‐screw extruder, indicating that the vane extruder is more efficient in mixing for immiscible polymer blends. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A preliminary investigation of conductive immiscible polymer blends as sensor materials

This paper discusses the feasibility of the application of conductive immiscible polymer blends as sensor materials for detection of organic liquid solvents. Immiscible polymer blends of polypropylene (PP), nylon 6 (Ny6) and carbon black (CB) have been used to produce a series of electrically conductive filaments by a capillary rheometer process. In these immiscible blends, PP serves as a semi‐crystalline matrix and Ny6 as the semi‐crystalline dispersed phase. The enhancement of conductivity in these blends is due to the attraction of CB to Ny6 and localization of CB particles at the PP/Ny6 interface, giving rise to conductive networks. The dc electrical resistivity of extruded filaments, produced at different shear levels, is found to be sensitive to various organic liquid solvents. The shear rate at which the filaments are produced has an important effect on the PP/Ny6/CB filament's sensitivity. The compositions studied were close to the double‐percolation structure believed to perform best as sensor materials. In addition, it seems that the PP/Ny6 interface plays a major role in the sensing process. Liquid contact/drying cycling of the filaments indicates stabilization of the sensitivity change making the sensing process reversible.     

Effects of periodic and non‐periodic chaotic mixing on morphology development of immiscible polymer blends

The effects of periodic and non‐periodic chaotic mixing on the morphology development in the blending of polypropylene as dispersed phase and polyamide 6 as continuous phase in a 2D batch chaotic mixer were investigated with experimental and computational fluid dynamic (CFD) methods. The rotor motions were delivered in steady, periodic (sine waveform and square waveform), and non‐periodic (recursive protocol (RP) and restricted random sequence (RRS)) manners. The mixing efficiency was evaluated with flow number, Poincare map, morphology, droplet size and its distribution. Compared with the sine waveform, RP waveform could eliminate the island structures which existed in the flow domains and its corresponding spatial stretching distribution was more uniform. The recursively generated flow using RP lead to higher mixing efficiency and smaller droplet size with narrow distribution. However, the performance of RRS was ordinary even worse due to its random sequence.© 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Efficient polymer solar cells utilizing solution-processed interlayer based on different conjugated backbones

The poor energy conversion efficiency for those polymer solar cells (PSCs) creates an obstacle for their commercialization. Inspired by this issue, two cathode interlayers, PBTBTz-TMAI and PBTzPh-TMAI based on benzothiadiazole (BT) and benzotriazole (BTz)-conjugated or benzene (Ph) and BTz-conjugated alternating units (both exhibits the same tetravalent amine-end side chain), were synthesized via Suzuki coupling polymerization and trivalent amine-end ionization. When PBTBTz-TMAI and PBTzPh-TMAI were utilized as cathode interlayers in PSCs, the charge-carrier transfer from active layer to cathode electrode was significantly improved, accompanied by an optimized exciton dissociation efficiency, primarily attributed to the introduction of tetravalent amine groups. Consequently, the device with PBTBTz-TMAI exhibited power conversion efficiencies (PCEs) = 8.3 and 10.5% for the PTB7:PC₇₁BM-based and PBDB-T:ITIC-based PSCs, respectively. In parallel, devices with a PBTzPh-TMAI cathode interlayer (that were established on the active layers of PTB7:PC₇₁BM and PBDB-T:ITIC) obtained a remarkably superior optoelectric efficiency with PCEs = 8.5 and 10.8%. These findings offer an alternative tactic toward to high efficiency PSCs to meet the increasing energy crisis.     

High performance polylactic acid/thermoplastic polyurethane blends with in-situ fibrillated morphology

As an environment-friendly polyester, polylactic acid (PLA) shows great potential market value. While it still faces some obstacles in large-scale practical application due to its brittleness. In this work, a novel strategy to improve the toughness of polylactic acid is developed. By adjusting processing temperature during the melt-blending process, thermoplastic polyurethane/poly (D-lactic) acid/poly (L-lactic) acid (TPU/PDLA/PLLA) ternary blends with different morphology are obtained. The experimental results show that the TPU in ternary blends formed a fibrillated micro-morphology, and the interfacial compatibility between the components is improved when the processing temperature is adjusted to 200°C. Under the synergistic action of in-situ fibrillated TPU and stereocomplex (SC) crystals, the toughness of the ternary blends is improved significantly without sacrificing its own tensile strength. The maximum value of tensile strength, elongation at break, and fracture work of ternary blends are 61.9 MPa, 23.5%, and 1038.9 kJ/m³, respectively. In addition, the melt strength of ternary blends was significantly improved, which is a benefit to their processing application.     

Simple approach to fabricate MXene/cellulose paper for electromagnetic interference shielding applications

A simple approach was developed to fabricate high-performance MXene/cellulose (MC)-based electromagnetic interference (EMI) shielding papers. The oriented MXene sheets located on one side of cellulose filter paper construct a continuous conductive layer, endowing the MC paper with high electrical conductivity (240.1 S/m) and excellent EMI shielding effectiveness (29.3 dB for 0.192-mm thickness) at an MXene content of 0.72 vol%. Moreover, the EMI shielding effectiveness of four stacked MC papers reached 40.5 dB. This result means that 99.9911% of the microwave radiation is attenuated, and 0.0089% is transmitted, through the four-piece MXene/cellulose filter papers. Therefore, MC paper has promising properties for excellent EMI shielding materials in current electronic devices.     

Review on morphology development of immiscible blends in confined shear flow

The bulk dynamics of immiscible polymer blends during flow is relatively well understood, especially when the system contains Newtonian components. Recently, a number of studies have focused on flow of immiscible blends in confined geometries. In that case, the morphology development is not only affected by the material characteristics and the type of flow, but also by the degree of confinement. Here, we present an overview on the morphology development in immiscible two-phase blends in confined shear flow. Firstly, we focus on the typical microstructures that are observed in confined dilute blends. Secondly, in order to understand those peculiar morphologies, the systematic studies on single droplets in confined shear flow are reviewed. In addition to the experimental work, theoretical, phenomenological, and numerical models that include the effects of confinement are discussed.     

Chemical sensing materials based on electrically‐conductive immiscible polymer blends

Two families of electrically‐conductive immiscible polymer blends were studied as liquid sensing materials for an homologous series of alcohols. The systems studied include: multiphase matrices [containing carbon black (CB)] consisting of either polypropylene or high‐impact polystyrene as the major phase and thermoplastic polyurethane as the minor dispersed phase; and polyaniline (PANI) dispersed within a polystyrene matrix. Extruded filaments, produced by a capillary rheometer at various shear‐rate levels were used in the sensing experiments. The electrical resistance of these filaments was selectively sensitive to the various alcohols. Moreover, the responses displayed by these filaments are reproducible and reversible. The sensing behaviour of these blends is determined by the nature of the blend components, the blend composition and the processing conditions. An attempt is made to identify the dominant mechanisms controlling the sensing process in CB‐containing immiscible polymer blends and PANI‐containing blends. In addition, the sensing performances of these blends are compared in the light of their sensing mechanisms. Copyright © 2005 Society of Chemical Industry     

Effect of ionic liquid segments of copolymer on compatibilization process and dielectric behavior of polylactide/polyvinylidene fluoride blends

Biodegradable polylactide (PLA) and polyvinylidene fluoride (PVDF) blends containing the copolymer of PEGMA and 1-vinyl-3-ethylimidazolium bromide (PMI) were prepared, and the effects of ionic liquid segments of PMI on the compatibility of PLA and PVDF were investigated by dielectric relaxation spectroscopy (DRS). PMI can obviously improve the compatibility of PLA and PVDF, compared with the copolymer of PEGMA and vinyl imidazole (PMV). DRS showed that the compatibility of PLA and PVDF was related to the relaxation behavior of the blends, which was identified with Maxwell-Wagner-Sillars (MWS) interfacial polarization. The ε' of PLA/PVDF/PMI blends was much higher than that of PLA/PVDF/PMV blends in the same temperature, resulting from the stimulation of MWS interfacial polarization by the ion mobility of PMI.     

Tuning gradient microstructures in immiscible polymer blends by viscosity ratio

Bioinspired gradient microstructures provide an attractive template for functional materials with tailored properties. In this study, filaments with gradient microstructures are developed by melt-spinning of immiscible polymer blends. The distribution of the gradient morphology is shown to be controlled by the viscosity ratio of polymers as well as the geometry of the capillary die. Distinct microstructure gradients with long thin fibrils near the surface region and short large droplets near the center region of the filament, as well as the inverse pattern, are formed in systems with different viscosity ratios. The shear flow field in the capillary can elucidate the formation mechanisms of gradient morphologies during processing. The results demonstrate how the features of a gradient microstructure can be tailored by the design of capillary geometry and processing conditions. The viscosity ratio is then introduced as an adjusting tool to control the gradient morphology in a given processing setup. In consequence, this study provides novel design routes for achieving gradient morphologies in immiscible polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48165.     

Phase morphology evolution and compatibilization of immiscible polyamide 6/polystyrene blends using nano‐montmorillonite

Nanocomposites of organic nano‐montmorillonite (nano‐OMMT)‐filled immiscible polyamide 6 (PA6)/polystyrene (PS) blends were prepared by three different processing methods. Masterbatch M1 of OMMT/PA6 and masterbatch M2 of OMMT/PS were prepared as separate masterbatchs by melt mixing with PA6 or PS, and then either mixed together or each mixed individually with appropriate amounts of PS or PA6, respectively. The effects of nano‐OMMT content and processing method on the structure, phase morphology, and mechanical properties of the PA6/PS/OMMT nanocomposites were investigated by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and mechanical properties tests. The results showed that the nano‐OMMT by M1 and M2 masterbatches dispersed primarily as exfoliated platelets in the PA6 matrix in the final composites regardless of the method of preparation. A drastic decrease of dispersed PS phase size and a very homogeneous size distribution were observed with the addition of nano‐OMMT. The PA6/PS/OMMT nanocomposites prepared from the M2 displayed the smallest dispersed PS phase size and best distribution of OMMT. The improvement of the mechanical properties of the PA6/PS/OMMT nanocomposites was attributed to the enhanced compatibilization of the immiscible PA6/PS blends by using nano‐OMMT. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Preparation of polyurethane foam fine polishing wheel for stainless steel surface

Comparing with dry polishing, the wet-polishing of the stainless steel surface can significantly reduce dust, noise and other pollution, and improve the polished quality. Thus, it is important to develop new polishing tools. In this work, the effects of the foaming agent and diluents on the mechanical properties of the polyurethane foam (PUF) system were investigated, and then the effect of the filler of graphite on the structure and mechanical properties of PUF was studied. Furthermore, the PUF fine polishing wheel with aluminum oxide was prepared. Results show that the bi-component diluents combined cyclohexane and dimethylformamide significantly affects the porosity and hardness of the PUF matrix. The filler of graphite can decrease the mechanical properties of the polyurethane matrix and increase the porosity of PUF, consequently, improve the self-sharpening of the PUF polishing wheel. The PUF fine polishing wheel with aluminum oxide shows fine polishing performance.     

High thermal conductivity of liquid crystalline monomer-poly (vinyl alcohol) dispersion films containing microscopic-ordered structure

The thermal conductivity of bulk polymers is usually very low, which is due to the amorphous domains where chains are randomly entangled, improving the degree of the chain alignment and forming a continuous thermal conduction network are expected to enhance the thermal conductivity. A series of liquid crystalline monomer-poly (vinyl alcohol) dispersion (MDLC) films with high thermal conductivity containing microscopic-ordered structure were prepared by introducing a highly ordered liquid crystalline monomer (LCM) exhibiting Smectic phase. The thermal conductivity of MDLC films was strongly related to the amount of LCM, which firstly increased and then decreased with the increase of LCM content. The thermal conductivity of MDLC film reached up to 1.20 W m⁻¹ K⁻¹ when the content of LCM was 15 wt% and rapidly decreased to 0.85 W m⁻¹ K⁻¹ as the content of LCM further increased to 25 wt%. LCM with low content (1–15 wt%) showed good fluidity, dispersity and interfacial compatibility in PVA molecular chains, which further increases the regularity of molecular chains alignment.     

Properties of tire tread compounds based on functionalized styrene butadiene rubber and functionalized natural rubber

Tire tread compounds based on various rubber types, that is, solution styrene-butadiene rubber (SSBR), functionalized (propylamine and dimethoxysilane) solution styrene-butadiene rubber (F-SSBR), natural rubber (NR), chloroacetate-modified natural rubber (CNR), and their blends, were prepared and used as raw rubbers. Properties of tire tread compounds and tire performance were then investigated. Due to the presence of chloroacetate group on its mainchains, CNR demonstrates increases in glass transition temperature and rubber-filler interaction compared to NR leading to a significant improvement in tire performance, particularly wet grip (WG; ~88%), fuel-saving efficiency (FSE; ~15%), and abrasion resistance (~11%). Similarly, F-SSBR shows a greater tire performance than SSBR (~20, ~13, and ~7% improvements in WG, FSE, and abrasion resistance, respectively). Among the rubber blends, F-SSBR/CNR gives the highest tire performance, followed by F-SSBR/NR, SSBR/CNR, and SSBR/NR, respectively. The results suggest the significant enhancement in properties of tire tread compounds by the presence of active functional groups in NR and SSBR molecules. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48696.