Morphology and thermal stability of BR/clay composites prepared by a new method

A new potential preparation method named in situ organic modification was used to prepare intercalated polybutadiene rubber (BR)/clay/dimethyl dihydrogenated tallow ammonium chloride (DDAC) composites. That is, BR, pristine clay, and intercalatant DDAC were directly mixed in a Haake rheometer without pretreating the pristine clay with the intercalatant. The morphology of the BR/clay composites was investigated by means of X‐ray diffraction and scanning electron microscopy. The thermal stability of the BR/clay composites was analyzed by thermogravimetric analysis (TGA). The dispersion of clay particles in the BR/clay/DDAC composites is much better than that in the BR/pristine clay and similar to that in the BR/organoclay DK4 (modified with DDAC) composites. BR/clay/DDAC composites have much higher thermal stability than the gum BR, BR/pristine clay, and BR/DK4 composites. The clay/intercalatant ratio has little influence on the thermal stability of the BR/clay/DDAC composites, while clay content has a significant effect on their thermal stability. The enhanced thermal stability of the BR/clay/DDAC composites is related to the dispersion state of clay particles in BR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 905–913, 2006     

Envisioning the composition effect on structural,magnetic, thermal and optical properties of mesoporous MgFe2O4-GO nanocomposites

The effect of variation in composition on the structural, magnetic, optical and photo catalytic activity of magnesium ferrite (MgFe₂O₄) -graphene oxide (GO) nanocomposites was studied. Magnetic nanocomposites of GO and MgFe₂O₄ nanoparticles (NPs) with varying w/w ratio were synthesized by facile sonication method. X-Ray diffraction patterns confirmed the presence of spinel ferrite phase in the nanocomposites with the crystalline size 8–32 nm. Fourier transformation infrared (FT-IR) spectra of the nanocomposites displayed absorption bands corresponding to GO and MgFe₂O₄ NPs along with red shift of bands corresponding to C=O, C=C and O-H stretching. Thermo gravimetric analysis confirmed higher stability of nanocomposites over pristine GO. Saturation magnetization increased from 3.63 to 11.10 emu/g with the increase in content of MgFe₂O₄ NPs in the nanocomposites. Scanning electron microscopy analysis along with energy dispersive spectroscopy (SEM-EDX) confirmed the presence of MgFe₂O₄ NPs along with GO sheets. Immobilization of clusters of MgFe₂O₄ NPs onto GO sheets was evident from transmission electron micrographs (TEM) of all the nanocomposites. BET surface area of the nanocomposites ranged from 63.04 to 165.29 m²/g and was maximum when GO:MgFe₂O₄ w/w ratio was 1:0.5. It was markedly higher than pristine GO and MgFe₂O₄ NPs. Optical studies revealed lowering of the band gap in the nanocomposites upto 2.21 eV as compared to pristine MgFe₂O₄ NPs. Photoluminescence (PL) spectra of nanocomposites displayed quenching of PL intensity with increase of GO content. Band gap also displayed similar trend. The synthesized nanocomposites were used as photocatalysts for methylene blue dye degradation under visible light irradiation. The nanocomposite with GO to MgFe₂O₄ ratio 1:0.5 displayed best activity with complete degradation of dye in 30 min. The results confirmed that the composition of GO based magnetic nanocomposites can be tailored for efficient removal of contaminants.     

Effect of Al2O3 addition on thermo‐electrical properties of polymer composites: An experimental investigation

To develop a new class of composites with adequately high thermal conductivity and suitably controlled dielectric constant for electronic packages and printed circuit board applications, polymer composites are prepared with microsized Al₂O₃ particle as filler having an average particle size of 80–100 μm. Epoxy and polypropylene (PP) are chosen as matrix materials for this study. Fabrication of epoxy‐based composite is done by hand lay‐up technique and its counterpart PP‐based composite are fabricated by compression molding technique with filler content ranging from 2.5–25 vol%. Effects of filler loading on various thermal properties like effective thermal conductivity (k_eff), glass transition temperature (T_g), coefficient of thermal expansion (CTE) and electrical property like dielectric constant (ε_c) of composites are investigated experimentally. In addition, physical properties like density and void fraction of the composites along with there morphological features are also studied. The experimental findings obtained under controlled laboratory conditions are interpreted using appropriate theoretical models. Results show that with addition of 25 vol% of Al₂O₃, k_eff of epoxy and PP improve by 482% and 498% respectively, T_g of epoxy increases from 98°C to 116°C and that of PP increases from −14.9°C to 3.4°C. For maximum filler loading of 25 vol% the CTE decreases by 14.8% and 26.4% for epoxy and PP respectively whereas the dielectric constants of the composites get suitably controlled simultaneously. POLYM. COMPOS., 36:102–112, 2015. © 2014 Society of Plastics Engineers     

Evaluation of the phase stability,and mechanical and thermal properties of Ba(Sr1/3Ta2/3)O3 as a potential ceramic material for thermal barrier coatings

Ba(Sr_1/3Ta_2/3)O₃ (BST) ceramic was synthesized by a solid-state reaction method. The phase stability, microstructural evolution, and mechanical and thermal properties of the BST ceramic were investigated and characterized to evaluate the potential application of BST as a top coating material for thermal barrier coatings (TBCs). The results show that BST can maintain a stable hexagonal perovskite structure up to 1600 °C. Anisotropic growth of the grains above 1400 °C was observed. Its low elastic modulus and high fracture toughness suggest a high damage tolerance for the BST ceramic. In addition, the moderate coefficient of thermal expansion and superior heat insulation capability of the BST ceramic provide this ceramic the potential to serve as a top coating material of TBCs at higher temperature.     

Dynamic mechanical,rheological, and thermal properties of intercalated polystyrene/organomontmorillonite nanocomposites: Effect of clay modification on the mechanical and morphological behaviors

Polystyrene (PS)/organomontmorillonite nanocomposites were prepared by melt processing with a twin‐screw extruder. Sodium montmorillonite was organically modified with stearyl trimethyl ammonium chloride to evaluate the effect of clay modification on the performance of the nanocomposites. A comparative account of nanocomposites prepared with the commercial clay Cloisite 20A (C20A) is presented. X‐ray diffraction studies indicated that the clay layers were completely dispersed, and a delaminated structure was formed in the case of C20A/PS and organomontmorillonite/PS nanocomposites. The dispersion characteristics of the clays within the matrix polymer were further investigated through transmission electron microscopy analysis. Mechanical tests revealed increases in the tensile, flexural, and impact strengths of 83, 55, and 74%, respectively, for C20A/PS nanocomposites at a 5% clay loading. The viscoelastic response of the nanocomposites, studied with dynamic mechanical analysis, also showed a substantial increase in the storage modulus of the nanocomposites with the incorporation of organically modified nanoclays. Furthermore, the melt‐state rheology of the organically modified nanocomposites displayed three distinct regions—glassy, plateau, and terminal—from the high‐frequency region to the low‐frequency region, with a considerable increase in the storage modulus in the glassy and terminal regions. Differential scanning calorimetry and thermogravimetric analysis were also used to evaluate the effect of the addition of nanoclays on the glass‐transition temperature and thermal stability of the PS matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Optimization of material formulation and processing parameters in relation to mechanical properties of bioepoxy/clay nanocomposites using Taguchi design of experiments

This article aims to study the effects of material formulation and processing parameters on mechanical properties of bioepoxy/clay nanocomposites based on epoxidized soybean oil (ESO) via Taguchi design of experiments (DoEs). A mixed‐level DoE with an L₁₆ orthogonal array was constructed to achieve maximum levels of tensile strength, tensile modulus, and impact strength for corresponding bionanocomposites. Pareto analysis of variance (ANOVA) was used to identify significant factors and preferred formulations in the manufacture of bioepoxy/clay nanocomposites. The ESO content was found to have the most significant effect with regards to bionanocomposite mechanical properties with contribution percentages of 66.63, 72.96, and 40.14% for their tensile strength, tensile modulus, and impact strength, respectively. With regards to material processing parameters, mechanical mixing speed was identified as a critical factor to achieve optimal tensile and impact properties. Nonetheless, the results also indicated clay content to be a significant factor for tensile strength, whereas curing agent type was vital for the improvement of tensile modulus and impact strength. Clay type and sonication time were also found to be significant factors for impact strength. In contrast to this, manufacturing parameters such as mechanical mixing temperature, mixing time, and sonication frequency were considered to be non‐significant factors due to their low cumulative contribution percentages of <10%. Finally, experimental confirmation tests based on the preferred combination of factors demonstrated good agreement with statistically predicted results. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45769.     

Synthesis,structure, and thermal properties of new polypropylene nanocomposites prepared by using MgCl2‐mica/TiCl4 based catalyst

Preparation of polypropylene/mica nanocomposites via in situ polymerization is investigated. The nanocomposites were successfully synthesized using a Ziegler‐Natta catalyst based on MgCl₂/modified mica/TiCl₄. Muscovite mica was organically modified with quaternary ammonium salt, and with triethylaluminum. The treatment with triethylaluminum increased the disorder in the stacking of clay layers, producing a more active catalyst for propylene polymerization, although the mica containing catalysts had lower activity than the standard one prepared without clay. The nanostructure of the composites was characterized by X‐ray diffraction. The results showed that part of the mica layers were exfoliated in the polymer matrix, although tactoids were still present. Small‐angle X‐ray scattering analysis was used to determine how mica and its concentration influence the size of the polymer nanocrystals. Differential scanning calorimetry was used to investigate both melting and crystallization temperatures, as well as the crystallinity of the nanocomposite samples. Thermogravimetric analysis showed that polypropylene/mica nanocomposites presented much higher thermal stability than the polypropylene without mica, which means that mica had a barrier effect against heat. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45587.     

An experimental and theoretical investigation of the compressive properties of multi-walled carbon nanotube/poly(methyl methacrylate) nanocomposite foams

Polymer nanocomposite foams are promising low density substitutes for nanocomposites. Carbon nanotube/polymer nanocomposite foams possess high strength, low density, and can be made conductive. Good control of foam properties is of great importance in the application of such materials. In the current study, multi-walled carbon nanotubes (MWNTs) with controlled aspect ratio were used to alter the foam morphology in MWNT/poly(methyl methacrylate) (PMMA) nanocomposite foams produced by a supercritical carbon dioxide (CO₂) foaming process. It was found that with the addition of one weight percent of MWNTs, the Young’s modulus of polymer foams increased by as much as 82%, and the collapse strength increased by as much as 104%. The influence of MWNT aspect ratio on the compressive properties of nanocomposite foams was investigated. The addition of MWNTs influenced the foam properties in two ways: improving the compressive properties of the solid matrix, and reducing the bubble size of the nanocomposite foams. A modified constitutive model for predicting the compressive properties of high density closed-cell polymer foams was developed. The influence of the bubble size on the mechanical properties of polymer foams was discussed based on the new model.     

Characterization of polypropylene/polystyrene boehmite alumina nanocomposites: Impact of filler surface modification on the mechanical,thermal, and rheological properties

The influences of surface treatment and the concentration of boehmite alumina (BA) particles on polypropylene and polystyrene (PS) (80/20) blends produced via melt compounding were examined. The results show that p‐toluene sulfonic acid‐treated BA particles yielded the highest stiffness improvement (27.5%), followed by untreated particles (25.7%), and dodecylbenzene sulfonic acid‐treated BA particles (8.5%). Transmission electron microscopy revealed that p‐toluene sulfonic acid‐treated BA particle agglomerates were dispersed in the PS phase, whereas untreated particles formed agglomerations at the interfaces. Dodecylbenzene sulfonic acid‐treated particles were poorly dispersed in both matrices. Differential scanning calorimetry showed that both untreated and p‐toluene sulfonic acid‐treated BA particles acted as nucleating agents in the blend because of the shifting of crystallization peaks to higher temperatures by 12 and 8 °C, respectively. A significant increase in decomposition temperatures occurred upon 7 wt % loading of all types of BA particles into the blend. Heat deflection temperature measurements showed that all types of BA particles improved the thermal properties of the blend. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46376.     

Overmolded polylactide/jute-mat eco-composites: A new method to enhance the properties of natural fiber biodegradable composites

Environmentally friendly, biodegradable composites were prepared via overmolding of poly(lactic acid) (PLA) onto PLA/jute-mat, named as “ecosheets,” reinforced continuous fiber composite sheets. Film stacking procedure was used to prepare ecosheets via using a hot-press. The fiber orientation was changed as −45°/+45° and 0°/0°. −45°/+45° orientation exhibited higher properties as compared to 0°/0° for ecosheets; therefore, this construction was used to produce overmolded composites (OMCs). The mechanical tests showed that flexural modulus and strength of OMCs were improved in comparison to neat PLA. The dynamic mechanical analysis exhibited that the thermomechanical resistance of PLA was enhanced for OMCs. Scanning electron microscopy investigation showed that the jute/PLA interphase needs to be improved to further increase the properties. It was concluded that one of the biggest advantages of this novel technique was the increase of mechanical properties of PLA without altering the density. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48692.     

Impact of titanium and silica/titanium fumed oxide nanofillers on the elastic properties and thermal decomposition of a polyester resin

The impact of nanoparticles of titanium (rutile) and silica–titanium fumed oxide (STO) on both the acoustic properties and thermal decomposition of a styrene‐crosslinked unsaturated polyester resin were studied with the methods of ultrasonic probing and thermal decomposition mass spectrometry at filler loadings ranging from 0.5 to 5.0%. It was shown that the elastic modulus, Poisson's ratio, and thermal resistivity in the titanium‐filled nanocomposites increased at small loadings of about 0.5%, whereas in the STO‐filled nanoparticles, the decreases in the parameters at loadings of up to 1.5% was replaced by some increases at higher loadings of up to 5.0%. Distinctions in the concentration dependences of the elastic parameters and the thermal decomposition intensity for both fillers could be explained by the features of the polymer–particle interactions because of the differences in both the number of active sites located on the particle's surface and the polymer structure within interface regions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42010.     

Morphology and thermal properties in the binary blends of poly(propylene-co-ethylene) copolymer and isotactic polypropylene with polyethylene

The morphology and thermal properties of isothermal crystallized binary blends of poly(propylene-co-ethylene) copolymer (PP-co-PE) and isotactic polypropylene (iPP) with low molecular weight polyethylene (PE) were studied with differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). In PP-co-PE/PE binary blends, however, the connected PE acted as a phase separating agent to promote phase separation for PP-co-PE/PE binary blends during crystallization. Therefore, the thermal properties of PP-co-PE/PE presented double melting peaks of PE and a single melting temperature of PP during melting trace; on the other hand, at cooling trace, the connected PE promoted crystallization rate because of enhanced segmental mobility of PP-co-PE during crystallization. At isothermal crystallization temperature between the melting points of iPP and PE, the binary blend was a crystalline/amorphous system resulting in persistent remarkable molten PE separated domains in the broken iPP spherulite. And then, when temperature was quenched to room temperature, the melted PE separated domains were crystallized that presented a crystalline/crystalline system and formed the intra-spherulite segregation morphology: these PE separated domains/droplet crystals contained mixed diluent PE with connected PE components. On the other hand, in the iPP/PE binary blends, the thermal properties showed only single melting peaks for both PE and iPP. Moreover, the glass transition temperature of iPP shifted to lower temperature with increasing PE content, implying that the diluent PE molecules were miscible with iPP to form two interfibrillar segregation morphologies: iPP-rich and PE-rich spherulites. In this work, therefore, we considered that the connected PE in PP-co-PE functioned as an effective phase separating agent for PP and diluent PE may be due to the miscibility between connected PE and diluent PE larger than that between PP and dispersed PE.     

Study of polypropylene/montmorillonite nanocomposites prepared by solid‐state shear compounding (S3C) using pan‐mill equipment: the morphology of montmorillonite and thermal properties of the nanocomposites

In this paper, polypropylene (PP)/organophilic montmorillonite (OMMT) nanocomposites were successfully prepared without any compatibilizers by solid‐state shear compounding (S³C) using pan‐mill equipment. X‐ray diffraction (XRD) patterns show that the OMMT characteristic (001) peak at 2θ equal to 4.59 degrees disappeared for the milled OMMT and corresponding composites. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) photographs show that the thickness of pan‐milled OMMT decreased from ca 100–200 nm to ca 30–50 nm, and OMMT was partly exfoliated in the PP matrix because the pan‐type mill can exert fairly strong squeezing force in the normal direction and shearing force in both radial and tangential directions on milled materials. PP/OMMT nanocomposites at low OMMT loading have higher melting point, crystallization temperature, thermal degradation temperature and heat distortion temperature than those of neat PP. Moreover, addition of OMMT accelerates crystallization of PP significantly. S³C is a novel approach to prepare polymer/layered silicate nanocomposites with high performances at low filler loading. Copyright © 2004 Society of Chemical Industry     

Effect of a chain extender on the properties of poly(lactic acid)/zinc oxide/copper chlorophyll acid antibacterial nanocomposites

Poly(lactic acid) (PLA)/nano zinc oxide/copper chlorophyll acid (CCA) antibacterial nanocomposites with excellent mechanical properties were prepared in the presence of a chain extender named tolylene diisocyanate (TDI). The effect of the chain extender on the PLA long chain was confirmed by the increased molecular weight shown in the mass flow rate and gel permeation chromatography. Escherichia coli were adopted to examine the antibacterial ability of the blends. The effect of CCA is also discussed with regard to the enhancement of the antibacterial effect of zinc oxide (ZnO) over E. coli. Scanning electron microscopy and transmission electron microscopy were used to view the agglomeration and dispersion of ZnO in the PLA matrix. Differential scanning calorimetry and thermogravimetric analysis revealed a relatively stable thermal performance of the nanocomposites with and without TDI. A sharp increase in the mechanical properties was also observed after the addition of the chain extender under different processing conditions. Additionally, we found that the nanocomposites with the incorporation of TDI and the masterbatches in batches effectively improved the mechanical properties of PLA/ZnO/CCA without a sacrifice of the antibacterial effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41561.     

An investigation of intercalation-induced stresses generated during lithium transport through sol-gel derived LixMn2O4 film electrode using a laser beam deflection method

The stress changes Δσ generated during lithium transport through the sol-gel derived Li_xMn₂O₄ film electrodes annealed at 773 and 873 K were quantitatively determined as a function of the lithium stoichiometry x using a laser beam deflection method (LBDM). Δσ generated during a real potential step between an initial electrode potential and a final applied potential was uniquely specified by the Δσ versus x curve. The Li_xMn₂O₄ film annealed at 773 K for 24 h (low temperature (LT)-Li_xMn₂O₄) showed larger capacity than the Li_xMn₂O₄ film annealed at 873 K for 6 h (high temperature (HT)-Li_xMn₂O₄) and this result is ascribed to the fact that the smaller the grain size is, the more increases the electrochemically active area of the film electrode. From the analysis of the normalised Δσ transient measured simultaneously along with the cyclic voltammogram in the potential range of 2.5-3.4 VLi/Li⁺, it is found that normalised Δσ generated in the LT-Li_xMn₂O₄ was smaller than that in the HT-Li_xMn₂O₄ during the lithium intercalation/de-intercalation around 3.0 VLi/Li⁺ region. This result gives an experimental evidence for the fact that the Jahn-Teller distortion is suppressed by the increase in the average oxidation state of manganese with decreasing in annealing temperature.     

An investigation of intercalation-induced stresses generated during lithium transport through Li1 − δCoO2 film electrode using a laser beam deflection method

The stress change, Δσ, generated during lithium transport through the rf sputter-deposited Li_{1 − δ}CoO₂ film was exactly determined as a function of the lithium stoichiometry, (1 − δ), using a laser beam deflection method (LBDM) combined with cyclic voltammetry, galvanostatic intermittent titration technique and potentiostatic current transient technique. Tensile and compressive stresses were generated during the lithium intercalation and deintercalation, respectively. Δσ varied remarkably with (1 − δ) in the single-α-phase region as well as in the two-phase region, but it remained almost constant in the single-β-phase region. Δσ generated during a real potential step between an initial electrode potential and a final applied potential was uniquely specified by (1 − δ). The value of Δσ coincided well with that value derived from the Δσ versus (1 − δ) curve (stress transient) measured simultaneously along with the galvanostatic intermittent titration discharge curve. From the comparison between the values of Δσ measured experimentally and calculated theoretically, it was suggested that Δσ in the single-α-phase region and the two-phase region originate from the molar volume change of the α-phase and from the lattice parameter mismatch between the α-phase and β-phase, respectively.