Influence of bio‐resource‐derived graphene oxide on the mechanical and thermal properties of poly(vinyl alcohol) nanocomposites

Purpose of present study was to investigate the effect of different nanofillers doping on structural and thermal properties of poly(vinyl alcohol) (PVA)-based nanocomposite films. Herein, ZnO nanoparticles (NPs), CuO NPs, graphene oxide and reduced graphene oxide (RGO) nanosheets have been used as separate nanofillers in the formation of PVA nanocomposite films via solution casting approach. The prepared composite films were characterized using X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential scanning calorimetry and tensile strength testing. The results demonstrate the effect of various nanofillers on glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc), percentage crystallinity (%χc) and tensile strength of composite films. A doping with (0.02 wt%) RGO nanosheets caused significant influence on thermal properties and tensile strength of PVA composite films as compared to other test nanofillers. The doping with RGO nanosheets resulted in elevation of Tg (48.2 °C), Tm (218.3 °C), Tc (157.8 °C) and %χc (41.9%) as compared to that of pure PVA (Tg 38.4 °C, Tm 190.4 °C, Tc 115.1 °C and %χc 22.2%). Overall, the doping of PVA with graphene-based nanosheets exhibited better tensile strength and thermal stability of nanocomposite as compared with other tested nanofillers.

Effect of crosslinking on the mechanical and thermal properties of poly(vinyl alcohol)

The utilization of poly(amide-imide)/SiO2 nanocomposite as nanofiller for strengthening of mechanical and thermal properties of poly(vinyl alcohol) nanocomposite films

Graphene, which is a one atom thick layer of graphite, has been considerably studied in the past decade due to its extraordinary physical properties. The development of new routes of synthesis facilitates the use of graphene in polymer nanocomposite. The addition of very small amounts (<1%) of graphene in a polymer matrix does not only increase its thermal and mechanical properties, but it would also enhance permeability, by limiting the diffusion of water through the material. Graphene-polymer nanocomposite would be an interesting alternative to conventional polymer nanocomposite such as nanoclay-polymer nanocomposite. In this study, graphene oxide is synthesized from graphite flakes, following the Tour method, and modified with silane to improve its compatibility with the polymer. Polymer nanocomposite made from vinylester resin and 0.5 wt% graphene oxide is prepared as well as other types of typically used polymer nanocomposite such as graphite flake, silica fume or nanoclay based composite. Samples are soaked in a water bath to study the water absorption of these nanocomposites. Mechanical property measurements and thermal analyses are performed to evaluate the benefit of using graphene oxide. Results show a significant enhancement of the mechanical and thermal properties with a graphene oxide content ten times lower than the one needed with conventional nanoparticles. Moreover, unlike nanoclay-based polymer nanocomposite, graphene oxide does not increase water absorption at saturation.

Graphene, a single layer of graphite, has recently attracted a large amount of attention because of its extremely high electronic and thermal properties, as many nanoscale materials are based on individual graphene. Graphene oxide (GO), which is the intermediate during the chemical processing of graphene, consists of graphene functionalized with oxygen-containing functional groups that imparts the desirable solution-processability to the neat graphene. Herein, poly(vinyl alcohol) (PVA), a hydrophilic polymer, was selected as the matrix, and PVA/GO nanocomposites were prepared by a simple and environment friendly process using water as the proceeding medium. In the PVA matrix, GO was exfoliated and nanodispersed. We found that the nanocomposites constructed by the incorporation of GO up to 1% by weight possess remarkable properties, such as significantly high mechanical and thermal properties. These excellent reinforcement effects were achieved not only by the rigid structure and high aspect ratio of the exfoliated GO but also by the strong interaction between PVA and GO. Furthermore, owing to the sheet-like structure of GO, the barrier properties of the nanocomposites were found to be dramatically increased. The graphene oxide (GO)-reinforced poly(vinyl alcohol) (PVA) nanocomposites were prepared using a simple and environment friendly process using aqueous medium. GO was revealed to be nanodispersed in the PVA matrix. The Young’s modulus of the nanocomposites largely exceeded the predicted value with only a low content of GO. We also revealed the increase in the thermal resistance and the barrier properties. As a result, not only the excellent properties but also the advantageous effects derived from the sheet-like structure of GO were successfully imparted to the nanocomposites.

The effect of aluminium nitrate hydrate (Al(NO3)3·9H2O) on the crystalline, thermal and mechanical properties of PVA was studied in this paper. The interaction between Al(NO3)3·9H2O and PVA was investigated by Fourier transform infrared (FT-IR) spectroscopy. The influence of Al(NO3)3·9H2O on the crystalline, thermal, and mechanical properties of PVA was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing, respectively. The results indicated that Al(NO3)3·9H2O could form interaction with the hydroxyl group on PVA chain. The XRD studies revealed that the crystallites of PVA were destroyed by Al(NO3)3·9H2O. DSC studies showed that Al(NO3)3·9H2O could increase the flexibility of PVA chains and decrease the Tg of PVA. Tensile testing showed that after the addition of Al(NO3)3·9H2O the tensile strength of PVA film decreased and elongation at break increased. All these results show that Al(NO3)3·9H2O has a high plasticizing efficiency for PVA. However, Al(NO3)3·9H2O is a Lewis acid and the acidic property of Al(NO3)3·9H2O would cause the significant decrease of the thermal stability of PVA.

Poly(lactic acid) (PLA)/poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) blends are typically phase‐separated, and there is limited research on using graphene oxide (GO) as their matrix filler. PLA/PHBV/GO composites using 1, 3, or 5 wt% GO were prepared by melt mixing, after which their morphology and thermal properties were determined. All the components were hydrophilic (Contact angles less than 90°), and the wetting coefficient value of 3.52 suggested that GO would be dispersed in PLA during surface energy evaluations (SEES). Scanning electron microscopy (SEM) showed that PLA/PHBV blends are immiscible and phase‐separated; however, adding GO brought partial miscibility. Differential scanning calorimetry (DSC) showed that GO plasticized the polymers at lower contents (1 wt%) and inhibited their crystallization at higher contents (3 and 5 wt%). Fourier‐transform infrared spectroscopy (FTIR) measurements showed that a chemical interaction exists between GO and the polymers, and X‐ray diffraction (XRD) results confirmed that GO inhibited crystallization in the polymers at high contents. Adding GO to the polymers generally improved the thermal stability of PLA, verifying the affinity thereof during thermogravimetric (TGA) analyses. Merging of the thermal degradation steps implied that GO induced partial miscibility on polymers. Concurrently, the polymers thermally masked the GO to prolong its lifespan. Composites with 1 wt% GO were the optimal and ideal materials. Highlights Melt mixed PLA/PHBV blends and their composites with GO as a filler. GO brought partial miscibility to the blends and favored the PLA phase. 1 wt% GO contents provide optimal thermal and morphological properties. 3 and 5 wt% GO contents form chemical bonds with the polymers. Initial GO loadings increase the crystallinity of the polymers.

This study aimed to find the characteristics of mechanical, morphological, and thermal properties of poly(vinyl alcohol) (PVA)/ bentonite nanocomposites. The method used in making nanocomposites is a sol-gel method. The natural bentonite (size of 35.26 nm) obtained from North Sumatra, Indonesia, was added to the solution of poly(vinyl alcohol) with the quantity varied, namely 0, 2, 4, 6, 8 wt %. The nanocomposites yielded were then characterized by using tensile test, scanning electron microscopy, and differential scanning calorimetry. The results showed that the maximum weight of added bentonite, which improved the mechanical properties and produced a more homogenous surface, was 6 wt %, whereas the variation of 2, 4, and 8 wt % of bentonite resulted in a decreased elasticity modulus. However, thermal properties are preferable to improve in the 0 wt % of bentonite.

ABSTRACTCellulose fiber-reinforced composite has received great attention due to the high strength, stiffness, biodegradability, and renewability of the excellent natural biomaterials. Cellulose nanofibers for the development of organic–inorganic hybrid composite is relatively new filed of research. Cellulose macro and nanofibers can be used as reinforcement in the hybrid composite because of improved mechanical, thermal, optical, electrical, morphological, and biological properties. The hybrid nanocomposites were synthesized by an in situ sol–gel process in the presence of coupling agent. The sol–gel process has definitely proven its potential by providing the synthesis of various functional organic–inorganic hybrid nanocomposites through an in situ sol–gel process. The hybrid nanocomposites have been prompted by the ability to control the morphology of final materials. The photoluminescence spectral studies indicate that the emission shifts toward higher wavelength (326–532 nm) accompanied by a reduction in impurity centers with increasing concentration of poly(vinyl alcohol)–TiO2 and hybrid nanocomposite. The final nanostructured TiO2 hybrid nanocomposites with particle size ranging from 0.32 to 20 nm were characterized by Field -emission transmission electron microscopy (FE-TEM) analysis. Furthermore, cellulose–poly(vinyl alcohol)–nano-TiO2 hybrid composite was characterized by Fourier transform infrared, X-ray diffraction, UV, Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), FE-SEM–EDX, Field-emission scanning electron microscopy (FE-SEM), and FE-TEM analysis. The different analysis results of the hybrid composite indicate the optical transparency, optical properties, Tg, crystallinity, thermal stability, and controlled morphology of hybrid nanocrystalline composites. Finally, the cellulose–poly(vinyl alcohol)—nano-TiO2 hybrid nanocomposites were tested against pathogens such as Gram-positive Bacteria Bacillus cereus and Gram-negative Escherichia coli for antimicrobial activity. These results show that the hybrid composite exhibited excellent antimicrobial properties against pathogens.

We present a novel approach to the fabrication of advanced polymeric nanocomposites from poly(vinyl alcohol) (PVA) by incorporation of PVA-grafted graphene oxide. In this work, we have synthesized PVA-grafted graphene oxide (PVA-g-GO) for the strong interfacial adhesion of graphene oxide (GO) to the PVA matrix. It was found that the mechanical properties of PVA were greatly improved by incorporating PVA-g-GO. For example, the tensile strength and Young's modulus of the PVA nanocomposite films containing 1 wt % net GO in the PVA-g-GO significantly increased by 88 and 150%, respectively, as compared to unfilled PVA. The elongation at break was also increased by 22%, whereas the GO/PVA nanocomposite containing 1 wt % pristine GO was decreased by 15%. Therefore, the presence of the PVA-g-GO in the PVA matrix could make the PVA not only stronger but also tougher. The strong interfacial adhesion between PVA-g-GO and the PVA matrix was attributed to the good compatibility between PVA-g-GO and the matrix PVA as well as the hydrogen-bonding between them.

Towards the dehydration of ethanol using pervaporation cross-linked poly(vinyl alcohol)/graphene oxide membranes

Calcium nitrate (Ca(NO3)2) was used as the plasticizer to improve the properties of Poly(vinyl alcohol) (PVA). The interaction between Ca(NO3)2 and PVA was investigated by Fourier transform infrared (FTIR) spectroscopy. The influence of Ca(NO3)2 on the crystalline, thermal, and mechanical properties of PVA was studied by X‐Ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile testing, respectively. FTIR studies showed that Ca(NO3)2 could strongly interact with PVA molecule and reduce the intensity of the hydrogen bonding between PVA molecules. The crystallization of PVA was interrupted and the degree of crystallinity of PVA decreased due to the strong interaction between Ca(NO3)2 and PVA. DSC studies showed that the glass transition temperature of PVA decreased with the addition of Ca(NO3)2. However, the thermal stability of PVA decreased with the addition of Ca(NO3)2. The mechanical properties of PVA was improved with the addition of Ca(NO3)2, PVA film became soft and ductile, with lower tensile strength and higher elongation at break compared with original PVA. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Layer‐structured poly(vinyl alcohol)/graphene oxide nanocomposites in the form of films are prepared by simple solution processing. The structure and properties of these nanocomposites are studied using X‐ray diffractions, scanning electron microscopy, Fourier‐transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The results indicate that graphene oxide is dispersed on a molecular scale and aligned in the poly(vinyl alcohol) matrix, and there exists strong interfacial interactions between both components, which are responsible for the significant improvement in the thermal and mechanical properties of the nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Preparation and characterization of reinforced poly(vinyl alcohol) films by a nanostructured, chiral, L-leucine based poly(amide-imide)/ZrO2 nanocomposite through a green method

Carbon nanomaterials are well-known for their unique physical properties. They have attracted interest as reinforcing fillers because of their superb mechanical properties. We report the excellent reinforcement properties of polymer nanocomposites by the incorporation of nanodiamond (ND). ND has been expected to offer polymer nanocomposites optimal properties because of its smooth surface and excellent optical, mechanical, and thermal properties, which can approach the values of single diamond crystal. We prepared advanced nanocomposites membranes based on poly(vinyl alcohol) (PVA) and ND in a single step using the solution casting method from aqueous medium and achieved the high dispersibility of ND in the PVA matrices. The thermal, mechanical and rheological properties of the membranes were investigated by means of thermogravimetry (TGA), dynamic mechanical analysis (DMA) and Ares G2 rheometer. The resulting nanocomposites had excellent properties derived both from ND and PVA. Thermal and mechanical properties increased dramatically with increasing ND content, indicating a strong interaction between ND and PVA. We anticipate that ND will be able to compete as a nano filler against conventional carbon-based nano fillers for polymer composites, and it is possible their reinforcement properties will be extended in the future.