PMMA assisted filler dispersion and morphology control in multifunctional PVDF based blend nanocomposites for absorption dominant EMI shielding and energy harvesting

Solution blended polyvinylidene fluoride (PVDF)‐20 wt% poly(vinyl acetate) (PVAc)‐natural graphite (NtGr) blend nanocomposites exhibit a very low electrical percolation threshold of less than 0.5 wt% NtGr due to the formation of graphite nanosheets. The electroactive gamma phase induced with and without NtGr in PVDF‐20 wt% PVAc blend film is confirmed by X‐ray diffraction, fourier transform infrared spectroscopy, and differential scanning calorimetry analyzes. The onset degradation temperature corresponding to PVDF in PVDF‐20 wt% PVAc blend nanocomposites is increased by 27°C when 1 wt% NtGr is incorporated into the blend, suggesting enhanced thermal stability of blend nanocomposites. Due to an increase in surface roughness of PVDF‐20 wt% PVAc‐3 wt% NtGr as evidence by field emission scanning electron microscopy analysis, the water contact angle increases to 141.6° from 83.44° for PVDF‐20 wt% PVAc blend. AC conductivity analysis suggests hopping conduction in PVDF‐20 wt% PVAc‐x wt% NtGr (x = 1, 3, 5) blend nanocomposites. The interjunction capacitance increases with graphite loading in the blend.

Poly(vinylidene fluoride) (PVDF) based conducting polymer composites with carbon nanomaterials can be used for mechanical energy harvesting through piezoelectric or triboelectric effect. This study aims to investigate the influence of PMMA molecular weight on the electrical, thermal, and wetting properties of PVDF/40 wt.% PMMA blend nanocomposites reinforced with expanded graphite (ExGr). The blend nanocomposites with 40 wt.% PMMA have been prepared by solution blending method by using two different molecular weights of PMMA whose melt flow indices are 2 g/10 min and 2.3 g/10 min. The coexistence of the electroactive gamma and non-polar alpha phases of PVDF in the blend nanocomposites has been confirmed by X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry analyses. While overall crystallinity (%) of low molecular weight PMMA employed blend nanocomposites is lower than that of high molecular weight PMMA blended nanocomposites, the electroactive gamma phase has been found to increase in the former blend nanocomposites. The dispersion of graphite nanosheets has been observed to be better in high molecular weight PMMA employed blend nanocomposites which results in higher electrical conductivity. Impedance analysis of PVDF-40 wt.% PMMA-2 wt.% ExGr blend nanocomposite with high molecular weight PMMA results in enhanced interjunction capacitance (74.5 pF) in comparison to low molecular weight PMMA mixed blend nanocomposites (68 pF). Water contact angle (WCA) increases with molecular weight of PMMA and ExGr loading level. Thermogravimetric analysis has shown that the char content (above 500°C) is slightly higher for the blend with low molecular weight PMMA than with high molecular weight PMMA.

ABSTRACTCarbon nanofiller reinforced polymeric materials offer the opportunity to obtain materials with desired properties. In the present study, effects of different loading of graphene oxide (GO) on the compatibility, thermomechanical, and morphological properties of incompatible polypropylene (PP)/polycarbonate (PC) polymer blends were investigated. The neat blend and blend nanocomposites were prepared by using a twin‐screw extruder under controlled shear pressure to explore the role of GO on thermomechanical properties of blends. Fourier transform infrared analysis showed the presence of GO in PC phase which was further confirmed by differential scanning calorimetry and morphological analysis. It was observed that up to loading of 0.5%, GO preferable dispersed in only PC phase and then dispersed in both PP and PC phase with further increase in GO loading due to increase in viscosity of PC phase. Field emission scanning electron microscopy investigation of PNCs showed the coalescence of PC phase with increase of GO loading. Tensile analysis confirmed that 1% of GO loading produced highest reinforcement in thermomechanical properties and further increase of GO loading deteriorate the mechanical properties. Dynamic mechanical analysis also showed high storage modulus for 1% loading. Thermal stability of 1% GO loaded nanocomposite was found to be higher than other blend nanocomposites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45062.

Polylactide (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blend nanocomposites including 3 wt% of cellulose nanocrystals (CNCs) were prepared by melt compounding method in a twin-screw extruder and an internal mixer. Blend nanocomposites were formulated by diluting three different masterbatches prepared by solution casting method that contained 7 wt% of CNC. These masterbatches were: (m1) PLA/PBAT/CNC masterbatch; (m2) PLA/CNC masterbatch; and (m3) PBAT/CNC masterbatch. These were to explore how different preparation methods affect the dispersion and localization of CNC and hence the properties of PLA/PBAT/CNC blend nanocomposites. Scanning electron microscopy (SEM) was used to study the structural changes of the blends. Rheological properties of PLA/PBAT blends and PLA/PBAT/CNC blend nanocomposites were also investigated. In the samples prepared by internal mixer, the rheological behavior of blend nanocomposite prepared through premixing of CNC particles with PLA showed a transition from liquid-like to a gel-like behavior. According to the rheological results and differential scanning calorimetry (DSC) analysis, it was found that the CNC overall enhanced the viscoelastic properties of blends and improved the PLA crystallization, respectively. Dynamic mechanical analysis (DMA) illustrated that the incorporation of CNC also enhanced the elastic modulus of PLA/PBAT blends specifically above the glass transition temperature of PLA. The expected improvements in mechanical properties did not occur due to the possible existence of residual solvent in the blends.

In this electronic era, there is a demand to switch from conventional polymers to conducting biopolymers. We developed conducting biopolymer nanocomposites of cashew gum (CG) and polypyrrole (PPy) with zinc oxide (ZnO) nanofillers [CG/PPy/ZnO] via in‐situ oxidative polymerization using a sustainable solvent. These nanocomposites were characterized using Fourier‐transform infrared spectroscopy (FTIR), UV–visible spectroscopy, field emission scanning electron microscope (FE‐SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The FTIR signal at 855 cm−1 confirms the successful inclusion of ZnO nanofillers into the biopolymer. UV–vis absorption of the blend nanocomposite increases with the nanoparticle doses. Among the various blend nanocomposites, the least bandgap energy was observed for 7 wt% ZnO loading. FE‐SEM revealed homogeneous dispersion of ZnO nanofillers in the CG/PPy blend at 7 wt% ZnO. TGA and DSC demonstrated that the CG/PPy/ZnO nanocomposites have better thermal stability and glass transition temperature than the pure polymer blend, indicating enhanced thermal properties. The CG/PPy/7 wt% ZnO showed the highest conductivity, 4.62 times greater than the pristine blend at 100 Hz. Dielectric constant, activation energy, AC conductivity and dielectric loss measurements demonstrated that the nanocomposites outperformed the pure polymer blend. Complex impedance analysis revealed increased impedance with rising temperature. Overall, CG/PPy/ZnO nanocomposites exhibit superior optical, morphological, thermal, electrical, and dielectric properties, making them promising for energy storage and optoelectronic applications.Highlights Ecofriendly synthesis of CG/PPy/ZnO nanocomposites Enhancement in optical, structural, and thermal properties of CG/PPy/ZnO Dielectric properties and temperature‐dependent AC conductivity are summarized. Blend nanocomposite shows higher AC conductivity and dielectric constant CG/PPy/ZnO nanocomposites are suitable for energy storage applications

This work presents the preparation of blended (HDPE/UHMWPE) nanocomposites with graphite nanosheets (GNS) by melt mixing (differing compositions) in an internal mixer. After graphite flake treatments to obtain GNS; HDPE/UHMWPE blends are produced using a Haake internal mixer with further compression molding. The blends were prepared as mixes of 0, 10, 20, and 30 wt% of UHMWPE in HDPE. The blend with the best mechanical and thermal properties is chosen to prepare the nanocomposites. The nanocomposites are produced from the 10 wt% UHMWPE in HDPE blend, with 0.5 and 1.0 wt% GNS using the same method as used for obtaining the blends. The functionalized graphite FTIR spectrum revealed functionalization with silane. However, after the ultrasonic bath these groups left the graphitic structure, and as shown by the diffractogram (XRD) and SEM images, good exfoliation continued. The nanocomposite blend with 10 wt% UHMWPE presented higher tensile strength values than pure UHMWPE, and the nanocomposite blend with the lower GNS percentage (0.5 wt%) presented the highest tensile strength. However the nanocomposite with 1.0 wt% GNS presented an increase in crystallization temperature.

Poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT) blend nanocomposites were prepared using melt blending technique followed by compression moulding. The blend nanocomposites were prepared with a variation of PBAT loading along with maleic anhydride and benzoyl peroxide ranging from 5 to 20 wt% along with two different commercially available nanoclays cloisite 93A and cloisite 30B (C30B) at 3 wt% loading. The maleic anhydride and benzoyl peroxide were used during the melt blending of the blend nanocomposites as a compatibilizer and as an accelerator respectively. Maleic anhydride used to enhance the compatibility of the PLA/PBAT blend and as well as the uniform adhesion of the nanoclays with them. The properties and characterizations of PLA matrix and the PLA/PBAT blend nanocomposites have been studied. The tensile strength, % elongation and impact strength increased with the preparation of PLA/PBAT blend nanocomposites as compared with PLA matrix. PLA/PBAT/C30B blend nanocomposites exhibited optimum tensile strength at 15 wt% of PBAT loading. Differential scanning calorimetry and thermogravimetric analysis also showed improved thermal properties as compared with virgin PLA. The wide angle X-ray diffraction studies indicated an increase in d-spacing in PLA/PBAT/C30B blend nanocomposite thus revealing intercalated morphology.

Electromagnetic interference (EMI),an unwanted phenomenon, oftenaffects the reliability of precise electronic circuitry. To preventthis, an effective shielding is prerequisite to protect the electronicdevices. In this study, an attempt was made to understand how processingof polymeric blend nanocomposites involving multiwalled carbon nanotubes(MWCNTs) affects the evolving interconnected network structure ofMWCNTs and eventually their EMI shielding properties. Thereby, theoverall blend morphology and especially the connectivity of the polycarbonate(PC) component, in which the MWCNTs tend to migrate, as well as theperfectness of their migration, and the state of nanotube dispersionare considered. For this purpose, blends of varying composition ofPC and poly(methyl methacrylate) were chosen as a model system asthey show a phase diagram with lower critical solution temperaturetype of characteristic. Such blends were processed in two differentways: solution mixing (from the homogeneous state) and melt mixing(in the biphasic state). In both the processes, MWCNTs (3 wt %) weremixed into the blends, and the evolved structures (after phase separationinduced by annealing in solution-mixed blends) and the quenched structures(as the blends exit the extruder) were systematically studied usingtransmission electron microscopy (TEM). Both the set of blends weresubjected to the same thermal history, however, under different conditionssuch as under quiescent conditions (in the case of solution mixing)and under shear (in the case of melt mixing). The electrical volumeconductivity and the evolved morphologies of these blend nanocompositeswere evaluated and correlated with the measured EMI shielding behavior.The results indicated that irrespective of the type of processing,the MWCNTs localized in the PC component; driven by thermodynamicfactors and depending on the blend composition, sea-island, cocontinuous,and phase-inverted structures evolved. Interestingly, the better interconnectednetwork structures of MWCNTs observed using TEM in the solution-mixedsamples together with larger nanotube lengths resulted in higher EMIshielding properties (−27 dB at 18 GHz) even if slightly higherelectrical volume conductivities were observed in melt-mixed samples.Moreover, the shielding was absorption-driven, facilitated by thedense network of MWCNTs in the PC component of the blends, at anygiven concentration of nanotubes. Taken together, this study highlightsthe effects of different blend nanocomposite preparation methods (solutionand melt) and the developed morphology and nanotube network structurein MWCNT filled blend nanocomposites on the EMI shielding behavior.

Biopolymer blend nanocomposite films composed of polyvinyl alcohol (PVA) and chitosan (CS) with varying quantities of hydroxyapatite (HA) nanoparticles were developed using a green solution casting method. The formation of blend nanocomposite was confirmed by Fourier‐transform infrared spectroscopy (FTIR), ultraviolet–visible (UV) spectrometer, field‐emission scanning electron microscopy (FE‐SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Mechanical parameters such as tensile strength, percentage elongation at break, hardness, dielectric constant, and temperature‐dependent alternating current (AC) conductivity were analyzed. The bonding between the nanoparticles and PVA/CS blend was verified by the shift in distinctive peaks of blend in the nanocomposites to a higher wavenumber in the FTIR spectra. The UV spectra demonstrated the difference in absorbance and transmittance of the PVA/CS blend with the reinforcement of HA nanofillers. The bandgaps of the nanocomposites marginally decreased with an increase in nanoparticle loading. The SEM and XRD patterns revealed the ordered arrangement of the blend matrix due to the presence of nanoparticles. The assessment of thermal characteristics obtained from DSC and TGA demonstrated a clear increase in phase transition temperature and thermal stability of nanocomposites. The electrical conductivity measurement indicated a rise in dielectric constant and AC conductivity of blend nanocomposites with the addition of nanoparticles. The temperature‐dependent AC conductivity showed a reduction in activation energy as temperature and nanoparticle loading increased. The tensile strength and surface hardness of the PVA/CS blend nanocomposite increased with the dosage of HA content in the blend matrix.Highlights A series of polyvinyl alcohol (PVA)/chitosan (CS)/hydroxyapatite (HA) nanocomposites were prepared by the green method Enhanced optical property, thermal stability, and glass transition temperature Possess excellent dielectric constant and alternating current conductivity The inclusion of HA increased the mechanical strength of the PVA/CS blend A potential blend nanocomposite for flexible optoelectronic and charge storage devices.

The synthesis of highly flexible conductive rubber blend nanocomposites using a conductive polymer with metal oxide is a new and promising approach. In this work, the effect of titanium dioxide (TiO2) on the performance of chlorinated natural rubber/polyindole (Cl‐NR/PIN) blend nanocomposites was systematically studied. Fourier‐transform infrared spectra revealed the successful incorporation of nanoparticles in the blend system. UV analysis assessed the increased absorption spectra of the nanocomposite compared to the pure blend. The X‐ray diffraction confirms the presence of TiO2 nanostructure in the blend. The high resolution transmission electron microscope results exhibited the uniform dispersion of TiO2 in the blend. Differential scanning calorimetry and thermogravimetric analysis show the increased glass transition temperature and thermal stability of the blend nanocomposite with an increase in TiO2 concentration. The linear low‐frequency AC conductivity demonstrated the occurrence of electrode polarization and the exponential increase in AC conductivity after a threshold frequency illustrated the semiconducting behavior of the composites. The maximum dielectric constant and AC conductivity were measured for the composite with 5 wt% filler loading, as the threshold level for the maximum interfacial contact. The hopping conduction, activation energy, improved conductivity and dielectric properties suggest that these blend nanocomposite films are promising candidates for the development of flexible energy storage devices.

Graphene provides thermal and electrical conductivity to polymer composites, which significantly improves the properties of heat dissipation and electromagnetic interference (EMI) shielding. However, due to the low concentration and stability of graphene dispersion, its industrial application is greatly hindered. In this work, graphite nanosheet (GNS) paste was successfully fabricated from the expanded graphite through wet ball‐milling technology in a one pot process. The ultrahigh GNS concentration is up to 59.4 mg mL−1, and exhibits high stability for 6 months. Furthermore, the average thickness of GNS is less than 10 layers. The GNS paste could mix uniformly with polymer dispersion to obtain large‐area and flexible films by the doctor‐blading process. The composites containing 80 wt% GNS exhibit layered structure, leading to high thermal conductivities with an in‐plane value of 71.18 W m−1 K, far surpassing the pristine polymer material (0.19 W m−1 K), and reveal an efficient total electromagnetic shielding (SEtot≈ 45 dB in the range of 8.2 to 12.4 GHz). This work provides a direct route to prepare composites with high thermal conductivity and EMI shielding from ultrahigh concentration GNS paste.

Influence of graphene oxide and reduced graphene oxide on TiO2-reinforced flexible poly(vinyl alcohol) films for electromagnetic interference shielding

Electrically conducting biopolymer blend nanocomposites based on different contents of boehmite (BHM) reinforced cashew gum (CG) /polypyrrole (PPy) blend is synthesized by an in situ polymerization technique using water as a green solvent. The resulting bio-blend nanocomposites underwent comprehensive analysis concerning their structural, morphology, thermal, and electrical properties, such as dielectric constant, dielectric loss, electric modulus, and AC conductivity. The Fourier transform infrared spectroscopy (FTIR) spectra revealed the presence of metal oxide stretching in the blended nanocomposite at 512 cm −1 . Field emission scanning electron microscopy (FE-SEM) confirmed the attachment and uniform dispersion of BHM within the CG/PPy blend at 7 wt% loading, and beyond this loading, the nanoparticles get agglomerated in the biopolymer blend. The glass transition temperature and thermal stability of all the blended nanocomposites are higher than that of the pure CG/PPy blend and these thermal properties increase with the loading of nanoparticles. Conductivity experiments demonstrated that as the nanofiller content increases up to 7 wt%, there is a concurrent rise observed in AC conductivity, dielectric loss, and dielectric constant. There is a substantial difference of 1.21 Scm −1 between the maximum and minimum AC electrical conductivity, at 10 2 Hz. However, a decrease in electrical properties is observed at the highest loadings of BHM due to the agglomeration of nanoparticles in the polymer blend matrix. The lowest activation energy value (0.049 × 10 −4 eV) is also exhibited by 7 wt% BHM nanocomposites. Furthermore, the electrical properties of both CG/PPy and CG/PPy/BHM nanocomposites exhibited a temperature-dependent behavior, progressively increasing until reaching maximum values. This study suggests that such bio-based polymer dielectrics could be promising materials for various applications, offering enhanced thermal and electrical properties through careful control of nanofiller content and dispersion.

In-situ polymerized boehmite/ cashew gum/ polyvinyl alcohol/ polypyrrole blend nanocomposites with tunable structural, electrical, and mechanical properties for enhanced energy storage applications

Green blend nanocomposites developed from waste sericin, polyvinyl alcohol and boehmite for flexible electronic devices