Dispersed Blends Research Articles

MORPHOLOGICAL AND THERMAL PROPERTIES OF BIODEGRADABLE GRAFT COPOLYMER LLDPE-G-MA/GEL COMPOSITES

In this work, a biodegradable graft copolymer based on linear low density polyethylene grafted maleic anhydride and gelatin (LLDPE-g-MA/Gel) was formed by reactive mixing of functionalized polyethylene with gelatin to achieve finely dispersed blend morphology. Using a selection of components of the mixture, we’d studied its morphology and thermal properties. It was found that thermal stability (initial temperature) of the composition decreases as the amount of gelatin increases due to degradation of gelatin. In the temperature range of 400-500 ºC, the maximum rate of destruction of the graft copolymer increases significantly with higher gelatin content. Samples having identical composition were selected using a Brabender plastograph and a mechanical mixer; and when taken at different rates, the morphological structure of the samples was determined to depend on their mixing rate. The morphological structure was found to show that increased speed leads to effective reaction of two components and crushing of particles into smaller ones.

Investigation of structure, dielectric and thermal properties of hexagonal boron nitride dispersed polymer blends

In this work, an inorganic hexagonal boron nitride (h-BN) dispersed vinyl (PVDF) and acrylic (PMMA) polymer blends were synthesized and its structure–property relationships were investigated. The structural identification by X-ray diffraction pattern confirms the semi-crystalline property of the h-BN dispersed blends. The internal morphology and topography details of the blends were studied by transmission electron (TEM) and atomic force microscopy (AFM). The chemical functionality of the polymer blends are changing after the dispersion of h-BN as confirmed from the IR spectrum analysis. The molecular interaction between PVDF, PMMA and h-BN is highly enhanced for 2 wt% loadings of h-BN. The dielectric constant (e) as a function of frequency and temperature showed that there is a consistent increase in the value of e at low frequency and high temperature for increasing loadings of h-BN and also a relatively low dissipation factor (tan δ) was obtained. The thermal stability was analyzed by TGA which is showing the enhanced thermal stability of blends as the h-BN wt% increases. The major interest of this study is to improve the dielectric and thermal properties of polymer blends for efficient electronic device applications.

Pickering emulsion process assisted construction of regenerated chitin reinforced poly (lactic acid) blends

Regenerated chitin (RCh)/poly (lactic acid) (PLA) blends with enhanced properties were successfully prepared via the Pickering emulsion approach. An oil-in-water Pickering emulsion of PLA/dichloromethane (DCM) stabilized with RCh via an ultrasonic homogenizer was formed. A uniformly dispersed blends were obtained upon slow volatilization of DCM. The effects of RCh on physical/morphological, thermal, mechanical and rheology properties of the blends were studied. The introduction of RCh in PLA improved its crystallinity from 23.4% to over 38.0%. The blends displayed an improvement in storage modulus of 393% at 70 °C for 2 wt%RCh as compared with neat PLA. The RCh/PLA blends showed an enhancement in both tensile strength and elongation at break of 18% and 31% respectively at the loading of 1.5 wt%-RCh. Moreover, the complex viscosity of the blends was increased compared to neat PLA, and all the blends exhibited shear-thinning behaviour without any plateau region at low angular frequencies (ω < 10 rad/s). These results suggest that the low weight content RCh introduced to PLA matrix via this facile Pickering emulsion approach not only promotes nucleation in RCh/PLA blends but also acts as a promising reinforcing agent for PLA.

Carboxymethyl cassava starch/polyurethane dispersion blend as surface sizing agent

Surface sizing agent (SSA) is a material used to improve the surface quality of the paper. It is one of the compulsory components in the paper-related industries to impart surface smoothness, printability, water resistivity and brightness. An environmental friendly surface sizing agent based on carboxymethyl cassava starch/polyurethane dispersion (CCS/PUD) blend had been developed. A local cassava starch (CS) was modified with anionic reagent, sodium monochloroacetate (SMCA) via etherification, in a presence of sodium hydroxide (NaOH) to form sodium carboxymethyl cellulose (CCS). Later CCS was blended with 30 wt% polyurethane dispersion (PUD) to enhance its water resistivity. The CCS/PUD blend was applied onto the surface of a hand-made paper prior to being tested and characterised. Fourier transform infrared analysis had verified the successful of etherification process by showing peaks at 3,400 cm-1, 1,635 cm-1 and 1,440 cm-1, corresponding to carboxymethyl substituent. The highest degree of substitution (0.76) was obtained from the system that used 6 g SMCA at fixed 1 : 7 CS : Water ratio and 4 mL NaOH. Meanwhile, CCS/PUD-coated paper had improved water resistivity corresponded to higher water contact angle at 73°, in comparison with the CCS-coated paper (62°) and the uncoated paper (40°). This was supported with low surface energy showed by CCS/PUD-coated paper (33.9 mJ/m2).

Multifunctional e-spun colloidal nanofiber structures from various dispersed blends of PVA/ODA-MMT with PVP/ODA-MMT, poly(VP-alt-MA) and AgNPs incorporated polymer complexes as electro-active platforms

This work presented a new approach to fabricate polymer nanocomposites films with nanofiber structures from solution blends of poly(vinyl alcohol) + octadecyl amine-montmorillonite (ODA-MMT) (matrix) with poly(N-vinylpyrroli- done) + ODA-MMT (partner-1), poly(N-vinylpyrrolidone-alt-maleic anhydride) ((poly(VP-alt-MA)) + (ODA-MMT) (partner-2) and their silver (Ag)-carrying polymer complexes by electrospinning. Chemical and physical structures, surface morphologies, thermal behaviors, electrical conductivity and thermal resistance parameters of nanofiber structures were in- vestigated. Poly(VP-alt-MA) was used both as a crosslinker and a donor of the hydrophilic groups such as -COOH and -NH-C=O amide from pyrrolidone ring. Reactive poly(VP-alt-MA), in situ generated Ag nanoparticles (AgNPs) and orig- inal partner polymer had an significant effect on the morphology and diameter distribution of nanofibers. High and excel- lent conductive behaviors were observed for the homopolymer and copolymer of VP based fiber structures, respectively. Upon successive chemical cross-linking of the nanofiber structures by reactive partner copolymer, the conductivity of nanofiber films as electro-active platforms dramatically increased to 3.90·10 -2 S·cm -1 at room temperature. Comparative analysis results also indicated that electrical properties strongly depended on the loaded reactive organoclay and in situ gen- erated AgNPs.

Rheological study of copovidone and solid dispersion blend used for hot melt extrusion

ABSTRACTThe focus of this work is to generate rheological parameters using AR 2000EX rheometer for PVP VA64 and Compound A – PVP VA64 blend at different temperatures, which can then be subsequently used to identify hot melt extrusion process conditions. Addition of Compound A to the neat PVP VA64 shows a drop in storage modulus and loss modulus as compared to the neat PVP VA64. It appears that Compound A is acting as a plasticizer by increasing the separation of the polymer chains and thus results in reduction of viscosity of Compound A blends compared to polymer only samples. For both systems, based on low standard error of fit, Cross model was chosen as the best fit for the rheological data and temperature dependency of viscosity was assessed by Williams–Landel–Ferry (WLF) model. This approach can be applied to screen formulations with new chemical entities (NCEs) and generate rheological information with various extruding polymers at fixed/variable drug loading in polymer matrix to determine suitability for hot melt extrusion process and appropriate temperature for conducting hot melt extrusion. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43278.

Fabrication of Polysulfone/ZnO Membrane: Influence of ZnO Nanoparticles on Membrane Characteristics

ABSTRACTA mixed matrix membrane consisting of a polysulfone and nano‐ZnO particles has been fabricated by a combination of solution dispersion blending and phase‐inversion method. The study is focused on the influence of ZnO on membrane morphology, surface roughness, and hydrophilicity, which were investigated through the methods of scanning electron microscopy, atomic force microscopy, and contact angle meter, respectively. In addition, the changes in membrane characteristics with the addition nano‐ZnO particles were examined by pure water flux, water content and porosity, and salts rejection including NaCl and MgSO4. From the results, it was revealed that nano‐ZnO particles constructed a membrane having more hydrophilic, smooth, and tightly packed surface, which offered a high flux and an effective permeability barrier. Moreover, it was observed that nano‐ZnO particles produced spongy a membrane with uniform and well‐interconnecting pores. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2013, 32, 21369; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21369

Functionalized Graphene and Carbon Materials as Components of Styrene-Butadiene Rubber Nanocomposites Prepared by Aqueous Dispersion Blending

Emulsifier-free aqueous dispersions of functionalized graphene (FG) represent key intermediates for the production of rubber composites, enabling uniform dispersion of predominantly single FG sheets. In this comparative study on styrene-butadiene rubber (SBR) composites with conventional and novel carbon-based fillers the influence of filler type, content, and dispersion process is examined. For SBR/FG nanocomposites two aqueous dispersion blend strategies based on thermally and chemically reduced graphite oxide are explored. Electron microscopy and X-ray tomography confirm the highly effective FG dispersion in SBR leading to simultaneous improvement of mechanical properties, electrical conductivity, and gas barrier resistance.

The Effect of Different Clay Dispersion Methods on the Properties of Polyurethane/Clay Nanocomposites

Polyurethane/clay (PU/clay) nanocomposites were synthesised using polymerisation and dispersion blending methods. The intercalation and exfoliation properties of the PU/clay nanocomposites were investigated by X-ray diffraction and transmission electron microscope. Clay intercalation of polymerised PU/nanocomposites was achieved and the interlayer spacing of clay was greatly enlarged from 17 Å to ~30 Å. Expansion in d-spacing was also observed for PU/clay nanocomposites prepared using dispersion methods. PU/clay nanocomposites prepared from dispersion of clay particles in the prepolymer matrix, followed by chain extension reaction, showed much high molecular weight and significant improvement in mechanical properties as compared with PU/clay nanocomposites produced using polymerisation or a simple high speed blending method in which clay was blended into the PU matrix. For PU/clay nanocomposites prepared using the blending method, high speed dispersion of 2 % clay in PU resulted in approximately a two-fold increase in the Young’s modulus. Further increase in the clay loading from 2 to 6 % made the corresponding nanocomposite polymer films more rigid and stiffer. This study shows that PU/clay nanocomposite properties are highly dependent on the preparation methods and provides useful guidelines for the future design and preparation of PU/clay nanocomposites.

Gelatin nanofibers fabricated by extruding immiscible polymer solution blend and their application in tissue engineering

A novel and simple approach for fabricating polymeric nanofibers has been established, and gelatin nanofibers have been successfully fabricated. Specifically, gelatin aqueous solution was evenly dispersed in ethyl acetate solution of cellulose acetate butyrate (CAB) to form an immiscible polymer solution blend, and then this well dispersed blend was extruded through a die extruder to composite coarse fibers through a dry-spinning process. Finally gelatin nanofibers were obtained in dispersion form in acetone after removal of the CAB matrix. Viscosity ratio of the solutions played an important role in dispersion of gelatin solution in CAB solution and formation of nanofibers during the extrusion. A viscosity ratio close to 1 can increase the shear deformation between the two phases and formation of nanofibers. FT-IR results showed that the approach was a physical process and no chemical derivation was involved. The gelatin nanofibers in a suspension can be easily applied in thin layers onto many surfaces. The nanofiber morphology was completely retained after coating, and the gelatin nanofiber coated surface was able to significantly increase the cell adhesion efficiency onto the surfaces, indicating that the application of gelatin nanofiber could improve surface properties and biocompatibility of medical devices and implants.

Effect of whey protein enzymatic hydrolysis on the rheological properties of acid-induced gels

A protein dispersion blend of β-lactoglobulin and α-lactalbumin was heat-denatured at pH 7.5, hydrolyzed by α-chymotrypsin and then acidified with glucono-δ-lactone to form gels at room temperature. Heat treatment induced the formation of whey protein polymers with high concentration of reactive thiol groups (∼37 μmol/g). The reactive thiol group concentration was reduced by half after 40 min enzymatic hydrolysis. It was further reduced after enzyme thermal deactivation. During acidification, the first sign of aggregation for hydrolyzed polymers occurred earlier than for non hydrolyzed polymers. Increasing the hydrolysis duration up to 30 min resulted in more turbid gels characterized by an open microstructure. Elastic and viscous moduli were both reduced, while the relaxation coefficient and the stress decay rate constants were increased by increasing the hydrolysis duration. After one week storage at 5 °C, the hardness of gels made from hydrolyzed polymers increased by more than 50%. The effect of polymer hydrolysis on acid-induced gelation is discussed in relation to the availability and reactivity of thiol groups during gel formation and storage.

Synthesis and characterization of intercalated ladder-like poly(vinylsilsesquioxanes)/organically modified montmorillonite nanocomposites

In this paper, ladder-like poly(vinylsilsesquioxanes) (LPVS)/organically modified montmorillonite (OMT) nanocomposites have been synthesized by ultrasonic dispersion and solution blending method. The structures of nanocomposites are characterized by small angle X-ray scattering (SAXS) and high-resolution transmission electronic microscopy (TEM). These results indicate that LPVS have already entered the galleries of OMT layers and intercalated LPVS/OMT nanocomposites have been formed. The effects of different reaction conditions, including solution concentration and the advantage of ultrasonic dispersion, are discussed. The intercalated nanocomposite is further treated at 250.0°C for 2 h in order to eliminate surfactant in OMT. On the basis of the SAXS and TGA results, it has been found that the treated product remains in its intercalated structure and presents better thermal stability, which provides potential usage in polymer composites. POLYM. COMPOS., 27: 660–664, 2006. © 2006 Society of Plastics Engineers

Metallized Organoclays as New Intermediates for Aqueous Nanohybrid Dispersions, Nanohybrid Catalysts and Antimicrobial Polymer Hybrid Nanocomposites

AbstractSummary: The chemical metallization of aqueous bentonite dispersions afforded stable aqueous hybrid nanoparticle dispersions containing simultaneously dispersed sodium bentonite nanoplatelets together with bentonite supported silver, palladium, or copper nanoparticles with average metal nanoparticle diameters varying between 14 and 40 nm. Such aqueous bentonite/metal hybrid nanoparticle dispersions were blended with cationic PMMA latex to produce PMMA hybrid nanocomposites containing exfoliated polymer‐grafted organoclay together with bentonite supported metal nanoparticles. This dispersion blend formation was investigated with respect to the role of nanostructure formation and mechanical properties. Palladium/bentonite hybrid dispersions were used as catalysts for hydrogenation reactions and the electroless plating of copper. In contrast to the conventional organoclay nanocomposites, the PMMA hybrid nanocomposites, containing simultaneously dispersed organoclay nanoplatelets together with organoclay supported silver nanoparticles, exhibited high antimicrobial activity against the ubiquitous bacterium Staphylococcus aureus, even at low silver content.Preparation of a polymer hybrid nanocomposite.magnified imagePreparation of a polymer hybrid nanocomposite.

On metallic characteristics in some conducting polymers

Polyaniline (PANI) exhibits a dc conductivity σ ≈ 10 −1 S/cm when it is doped with poly(styrenesulfonic acid) (PSSA) such that the number of sulfonate groups per two-ring PANI unit ( y) is 2. On increasing the dopant amount to y = 12, σ drops to 10 −5 S/cm. The EPR-derived magnetic susceptibility of these two conducting polymers gives nearly the same density of states at the Fermi level N( E F) ≈ 0.65 ± 0.05 states/eV 2-rings. The corresponding electronic specific heat coefficient as calculated from this N( E F) value does not appear to be inconsistent with the results from low temperature calorimetric measurements. Similarly, with y′ defined as the number of sulfonate groups per three-ring PEDOT unit, PSSA-doping of poly(ethylenedioxythiophene) (PEDOT) yields different σ ≈ 10 −1 and 10 −5 S/cm at y′ = 5.7 and 45.9, respectively, but the same N( E F) ≈ 0.55 ± 0.05 states/eV 3-rings. These observations suggest that the additional dopants, which help with dispersion in processing conducting polymers, do not alter the metallic domains but are located in the disordered regions surrounding them. The N( E F) values also remain practically the same between p-toluenesulfonic acid (PTSA) doped PANI and its dispersed blend in poly(methylmethacrylate) (PMMA), as well as for PEDOT–PTSA before and after its being subjected to an additional dispersion step.

Effect of β-irradiation on mechanical properties of metallocene elastomers/PA6 blends

Binary blends of metallocene polymers with polyamide-6 as dispersed phase and ternary blends with a metallocene-grafted rubber as compatibilizer were prepared and treated by electron beam radiation. Thermal stability and mechanical properties were studied, showing that thermosetting rubbers and thermoplastic elastomers with excellent mechanical properties and thermal stability may be obtained by β-irradiation. The irradiated ternary blends displayed high break elongation values, similar to other thermoplastic rubbers based on EPDM or EPR materials. On the other hand, the Shore D hardness, tensile strength, high-temperature behavior, compression set and reprocessing ability were found to be clearly dependent on the metallocene polymer used as bulk phase and the irradiation dose employed.

Structural changes during cryogenic mechanical milling of iPP/sPS blends

Recent investigations on Cryogenic Mechanical Milling (CMM) of thermoplastic polymers indicated that macromolecules undergo chain scission leading to the formation of free macro-radicals, crosslinking or amorphization. This makes CMM a promising strategy for the design of highly dispersed blends of thermodynamically immiscible polymers in order to obtain new materials with desirable properties. In this study, CMM is applied on immiscible syndiotactic polystyrene (sPS)/isotactic polypropylene (iPP) blends and compared to conventional melt blending. The resultant blends are characterized by their microstructure in particular their thermal properties. The domain size of iPP in the CMM blends was found to be markedly reduced compared to conventional melt blended samples, although the samples were recrystallized from the molten state.

Solid‐State Structure and Mechanical Properties of Blends of an Amorphous Polyamide and a Poly(amino‐ether) Resin

AbstractSummary: Finely dispersed blends of an amorphous polyamide (AP) and a poly(amino‐ether) (PAE) resin were obtained by direct injection moulding. The blend components reacted slightly, mainly in PAE‐rich compositions, as seen by torque increases and FT‐IR. Both negative volumes of mixing and preferential orientation were observed in blends with very high AP contents, leading to synergisms in both the modulus of elasticity and the yield stress. In PAE‐rich blends, the effects of these two structural characteristics were negative, but the higher presence of reacted products also led to an overall synergistic modulus of elasticity. With the exception of blends very rich in PAE, in which the more extensive reactions led to brittle materials, the reactions compatibilized the blends due to the presence of small amounts of reacted copolymers, probably at the interface.Cryogenically fractured surface of the skin of the AP/PAE 80/20 w/w blend.imageCryogenically fractured surface of the skin of the AP/PAE 80/20 w/w blend.

Rheo‐optical determination of the interfacial tension in a dispersed blend

AbstractIn this work, we present two novel methods to determine the interfacial tension of a disperse polymer blend through rheo‐optical measurements of flow‐induced single drop distortions. A counter‐rotating shearing device with transparent plates is used to measure drop distortions. The cell geometry allows for a top view of the deforming drop, i.e., along the velocity gradient direction. Such a view is the only possible option for all currently available commercial rheo‐optical instruments. Two different quantities are monitored, namely, the drop axis along the vorticity direction, and the rotation period of the drop surface. We use drops of a polyacrilamide aqueous solution (a shear thinning liquid) immersed in a polyisobutene matrix. Experimental results are interpreted in terms of theories for Newtonian liquids, where the relevant parameter is the Capillary number. If an appropriate viscosity ratio is chosen, that accounts for the shear thinning behaviour of the drop phase, good agreement is found between measurements and theoretical predictions. As a result, a robust estimate of the blend interfacial tension, that makes use only of the information acquired from top view experiments, is obtained.

Cryogenic mechanical alloying as an alternative strategy for the recycling of tires

Cryogenic mechanical alloying (CMA) is investigated as a viable strategy by which to produce highly dispersed blends composed of thermoplastics and tire, thereby providing a potentially new route by which to recycle discarded tires. Morphological characterization of these blends by near-edge X-ray absorption fine structure (NEXAFS) microscopy demonstrates that, upon CMA, ground tire is highly dispersed within poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET) matrices at sub-micron size scales. Incorpo-ration of polyisoprene (PI) homopolymer into the blends to improve dispersion efficacy is also examined. Neither PI nor the tire is found to interact chemically with PMMA or PET under the milling conditions employed here.

Experimental investigation of the morphology development of polyblends in corotating twin-screw extruders

Compounding extruders are still designed based on experience and time-consuming experimental examinations. This work investigates the morphology development of incompatible polyblends along a mixing zone at the end of a corotating twin-screw extruder. During the process, the samples are taken from the running extruder using special barrel plates. These samples are subsequently examined by means of scanning electron microscopy (SEM). This method allows sampling in less than 1 min and thus extremely fast and almost unaffected. The experimental investigation of the morphology development improves the knowledge about the factors essentially influencing the blending process. It also allows the verification as well as improvement of theoretical models. Polyblends of polypropylene (PP) and polyamide (PA) with 7.5, 15, and 30 wt % PA were examined. As well as the relevance of the mass percentage of the dispersed phase, the influence of the screw geometry, the screw speed, the melt temperature, the melt throughput, and the pressure profile was investigated. Apart from the melt throughput, all varied factors show an influence on the resulting blend morphology that may not be neglected. However, the changes of the mean particle sizes in the observed mixing zones are only gradual (mean particle size ≈ 1–4 μm), which can be attributed to the extremely fine blend morphology already existing during or after the melting. That means that the application of “classic melting zones” generally already produces finely dispersed blend morphologies, thus proving the essential importance of the melting zones regarding the development of the blend morphology. Consequently, the mean particle sizes, calculated by means of quantitative image analyses of SEM micrographs in the mixing zones following the homogenizing section only slightly depend on the compounding conditions (screw speed, melt throughput, screw geometry, melt temperature, and pressure profile). However, the direct visual analysis of the SEM images, especially in the first parts of the mixing zones, shows the simultaneous existence of large PA6 particles in the PP matrix. In addition, a downstream unification of the particle size distribution can be observed. Especially the number and size of the coarser particles decreases in the mixing zones. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 708–721, 2000