Melt Electrospinning Designs for Nanofiber Fabrication for Different Applications

Nanofibers have been attracting growing attention owing to their outstanding physicochemical and structural properties as well as diverse and intriguing applications. Electrospinning has been known as a simple, flexible, and multipurpose technique for the fabrication of submicro scale fibers. Throughout the last two decades, numerous investigations have focused on the employment of electrospinning techniques to improve the characteristics of fabricated fibers. This review highlights the state of the art of melt electrospinning and clarifies the major categories based on multitemperature control, gas assist, laser melt, coaxial, and needleless designs. In addition, we represent the effect of melt electrospinning process parameters on the properties of produced fibers. Finally, this review summarizes the challenges and obstacles connected to the melt electrospinning technique.Scopu

Thermal properties of TiO 2 NP/CNT/LDPE hybrid nanocomposite films

This work aims to investigate the effect of hybrid filler concentration on the thermal stability of low-density polyethylene (LDPE) matrices. LDPE-based composite films were synthesized by melt mixing, followed by compression molding, to study the influence of titanium oxide nanoparticles (TONPs) and/or multi-walled carbon nanotubes (CNTs) on the thermal properties of LDPE matrices. Fourier transform infrared (FTIR) spectroscopy confirmed the slight increase in the band intensities after TONP addition and a remarkable surge after the incorporation of CNTs. The value of crystallization temperature (T c ) was not modified after incorporating TONPs, while an enhancement was observed after adding the hybrid fillers. The melting temperature (T m ) was not changed after introducing the CNTs and CNT/TONP hybrid fillers. The percentage crystallinity (X c %) was increased by 4% and 6%, after incorporating 1 wt % and 3 wt % CNTs, respectively. The TONP incorporation did not modify the X c %. Moreover, thermal gravimetric analysis (TGA) thermograms confirmed the increased thermal stability after introducing CNTs and hybrid fillers compared to TONP incorporation. � 2018 by the authors.Acknowledgments: This work was made possible by NPRP grant # (NPRP5-039-2-014) from the Qatar National Research Fund (a member of Qatar Foundation). The findings herein reflect the work, and are solely the responsibility of the authors. The publication of this article was funded by the Qatar National Library.Scopu

Role of TiO2 and carbon nanotubes on polyethylene, and effect of accelerated weathering on photo oxidation and mechanical properties

In this work, LLDPE-based composite films were prepared by melt mixing followed by compression molding to investigate the role of titanium oxide nanoparticles (TONPs) and/or multiwalled carbon nanotubes (CNTs) on the accelerated weathering samples (maximum of 39 days). Accelerating weathering caused the emerging of oxidation peaks in the FT-IR spectra for LLDPE and LLDPE/TONPs. These peaks were not pronounced in the LLDPE/CNTs samples. The same prevention of oxidation peaks were noticed for the hybrid additives samples. Tensile properties decreased by exposing the composite samples to accelerating weathering. TONPs increased the tensile strength of the samples by 11.5% but deterioration of this property is the same as the pristine sample after accelerated weathering for 39 days. Addition of CNTs had negligible effect on the tensile strength but it kept the same approximate value of the original before the accelerated weathering (e.g., 23.2 MPa for 1 wt% of CNTs). CNTs also protected the samples even with the presence of TONPs because of the absorbance and antioxidants effects. The addition of CNTs into LLDPE network have not only retarded decomposition of LLDPE but also decreased catalytic activity of TONPs to activate degradation due to accelerated weathering. J. VINYL ADDIT. TECHNOL., 25:19-25, 2019.This article was made possible by NPRP Grant 5-0-39-2-0-14 from the Qatar National Research Fund (A member of Qatar Foundation).Scopu

Mechanical properties of gamma irradiated TiO2NPs/MWCNTs/LDPE hybrid nanocomposites

This work investigates the impact of ϒ-irradiation on the mechanical properties of titanium oxide nanoparticles (TiO2NPs)/multi-walled carbon nanotubes (MWCNTs) hybrid low-density polyethylene (LDPE) nanocomposites. Hybrid LDPE nanocomposite films prepared using melt mixing technique were exposed to different doses of ϒ-radiation, ranging from 5 to 50 kGy. The tensile strength was diminished after TiO2NP or MWCNT addition, then increased with a further increase in the carbon nanotube (CNT) content. This behavior can be ascribed to stress transfer between the filler and the LDPE network. Besides, the tensile strength was enhanced after exposure to a dosage of 5 and 25 kGy of ϒ-radiation, then followed by a decline when exposed to 50 kGy, especially in the case of hybrid films due to the degradation and cross-linking of LDPE chains caused by ϒ-radiation. Because of the absorbance and antioxidant effects of CNTs, the CNT addition retarded the degradation of LDPE networks and decreased the catalytic activity of TiO2NPs to activate degradation upon radiation exposure. Therefore, the tensile strength was retained after exposure to a dose of 50 kGy of ϒ-radiation, especially in case of less TiO2NPs and more CNTs filled hybrid films. Furthermore, the % of the total elongation at break is decreased after incorporating MWCNTs. The % of the total elongation at break after exposure to a dosage of 25 kGy was reduced as a result of chain scissions and molecular weight decrease. Young’s modulus of the irradiated composites was lower than without irradiation. This effect was more significant for neat LDPE and TiO2NPs filled LDPE films, whereas MWCNTs had some stability effects on the nanocomposites.This work was made possible by NPRP Grant 5-0-39-2-0-14 from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Recent overviews in functional polymer composites for biomedical applications

Composite materials are considered as an essential part of our daily life due to their outstanding properties and diverse applications. Polymer composites are a widespread class of composites, characterized by low cost, facile processing methods, and varied applications ranging from daily-use issues to highly complicated electronics and advanced medical combinations. In this review, we focus on the most important fabrication techniques for bioapplied polymer composites such as electrospinning, melt-extrusion, solution mixing, and latex technology, as well as in situ methods. Additionally, significant and recent advances in biomedical applications are spotlighted, such as tissue engineering (including bone, blood vessels, oral tissues, and skin), dental resin-based composites, and wound dressing. ? 2018 by the authors

Experimental and theoretical studies on the mechanical and structural changes imposed by the variation of clay loading on poly(vinyl alcohol)/cloisite 93A nanocomposites

Polymer nanocomposites (PNC) structures are promising materials due to their novel properties. However, many of their characteristic physical, mechanical, and chemical behavior have not been quantified. Depending on the interface interactions between polymeric chains and clay sheets, various classes of polymer/clay nanocomposite exist: Intercalated, flocculated and exfoliated nanocomposites. In this work, we present an experimental study of poly(vinyl alcohol) (PVA)-cloisite 93A followed by a classical molecular dynamic (MD) simulations. The structural properties of the system were studied using X-ray diffraction (XRD), nanoscanning electron microscopy (NSEM). Both revealed intercalation between PVA chains and cloisite 93A nanoclay. Another evidence of the intercalation between PVA and cloisite 93A nanoclay was realized from the differential scanning calorimetry (DSC) which confirmed as surge in crystallinity upon intercalation. A main focus for the intercalated structure was to investigate the impact of nanofillers content on the mechanical performance. Intercalation significantly influenced both Young's modulus and the % of elongation of PVA/cloisite 93A blends. Young's modulus and tensile stress were raised with the content of the filler content up to 3 wt%. For higher content, opposite observations are addressed owing to the formation of aggregates of nanofillers and as consequence construction of microvoids. From the MD simulations, the intercalation has been shown by the increase of the d-spacing with the clay loading. By calculating the density profile, it has been demonstrated that in case of low clay loading, the cloisite 93A has its nitrogen groups on the clay surface and the long tails form layers. For the high loading of clay, nitrogen and carbon groups are together on the surface. Young modulus calculated theoretically follows the same experimental trend where an increase of the values has been observed with a clay loading up to 3 wt%, followed by a decrease of the values for higher clay loading. J. VINYL ADDIT. TECHNOL., 25:172181, 2019.This paper was made possible by an NPRP 09-260-1-048 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. We are also grateful to University College London for using their high performance computing facilities.Scopu

Comparison of the effect of carbon, halloysite and titania nanotubes on the mechanical and thermal properties of LDPE based nanocomposite films

In this study, titania nanotubes (TNTs) were prepared by hydrothermal method with the aim to compare the properties of these one-dimensional tubular nanostructures' reinforced nanocomposites with the carbon and halloysite nanotubes' (CNTs and HNTs, respectively) reinforced nanocomposites. Low density polyethylene (LDPE) was used as the matrix material. The prepared nanocomposites were characterized and compared by means of their morphological, mechanical and thermal properties. SEM results showed enhanced interfacial interaction and better dispersion of TNTs and HNTs into LDPE with the incorporation of a MAPE compatibilizer, however, these interactions seem to be absent between CNTs and LDPE, and the CNTs remained agglomerated. Contact angle measurements revealed that CNT filled nanocomposites are more hydrophilic than HNT composites, and less than TNT composites. CNTs provided better tensile strength and Young's modulus than HNT and TNT nanocomposites, a 42% increase in tensile strength and Young's modulus is achieved compared to LDPE. Tear strength improvement was noticed in the TNT composites with a value of 35.4 N�mm? 1, compared to CNT composites with a value of 25.5 N�mm? 1�s? 1. All the prepared nanocomposites are more thermally stable than neat LDPE and the best improvement in thermal stability was observed for CNT reinforced nanocomposites. CNTs depicted the best improvement in tensile and thermal properties and the MAPE compatibilizer effectiveness regarding morphological, mechanical and thermal properties was only observed for TNT and HNT systems. 2017 Elsevier B.V.This work was made possible by NPRP grant # ( NPRP5-039-2-014 ) from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Degradation of Diallyl Phthalate (DAP) by fenton oxidation: Mechanistic and kinetic studies

In this work, the degradation and mineralization of Diallyl Phthalate (DAP) in water by Fenton oxidation was investigated. The effects of different experimental parameters including the initial pH, the hydrogen peroxide (H2O2) dose, the catalyst (Fe2+) dose, the iron source, and the DAP concentration on the rate and the yield of DAP degradation by Fenton oxidation were evaluated. DAP and its intermediates were quantified by high performance liquid chromatography (HPLC) analysis and the measurement of total organic carbon (TOC) during Fenton oxidation. The results obtained confirmed that hydroxyl radicals (HO?) generated from Fenton's reaction were capable of completely eliminating DAP from water. Fenton oxidation of 100 mg/L DAP aqueous solution at pH = 3.2 required 1000 mg/L H2O2 and 50 mg/L Fe2+. Under these conditions, more than TOC removal exceeded 95% after 300 min Fenton oxidation. The competition kinetics method was used to determine an absolute rate constant of 7.26.109 M-1 s-1 for the reaction between DAP and HO? radicals. HPLC analysis showed that phthalic acid, 1,2-dihydroxybenzene, 1,2,4-trihydroxybenzene, maleic acid, formic acid and oxalic acid were the main intermediates formed during DAP degradation. Accordingly, a simple DAP degradation mechanism by the Fenton reaction was proposed. These promising results proved the potential of Fenton oxidation as a cost-effective method for the decontamination of wastewaters containing phthalates. ? 2018 by the authors.Acknowledgments: The publication of this article was funded by the Qatar National Library.Scopu

Graphene a promising electrode material for supercapacitors?

The global demand for high performance and environmentally friendly energy storage systems leads to intensive research on new and advanced electrode materials that are able to satisfy the fast-growing global market in various applications. The 2D graphene material is one of the most promising candidates for next-generation energy storage applications, particularly supercapacitor devices due to its exceptional intrinsic properties such as highest theoretical specific surface area (2600?m2/g), high electrical charges mobility (230?000?cm2/V?s), thermal conductivity (3000?W/mK), and highest strength (130?GPa). This comprehensive review summarizes the most recent progress made on the graphene material in its different structural forms of foams (3D), thin films (2D), nano-fibers (1D), and nano-dotes (0D) for supercapacitor electrodes. It initiates with a brief historical introduction on graphene discovery and its current production techniques that retain its intrinsic properties ranging from mechanical exfoliation of graphene in high quality to its epitaxial growth by chemical vapor deposition on metal substrates and its derivation by chemical reduction of graphene oxide. In addition to highlighting its main characterization techniques such as Raman spectroscopy, atomic force microscopy, and transmission electron microscopy, as well as, its critical properties including electrical, optical, mechanical, and thermal properties. Its potential applications are also illustrated with emphasizing on its usage as an electrode material in supercapacitors. Finally, its main challenges and future prospects are considerably pointed out.Scopu

Synthesis and characterization of poly(vinyl alcohol): Cloisite 20A nanocomposites

Polymeric nanocomposite materials are very important materials because of their promised applications. However, many of their fundamental physical, mechanical, and chemical behaviors have not been quantified. Depending on the interface forces between polymer and clay, different configurations of polymer-clay nanocomposites exist: intercalated, flocculated, and exfoliated nanocomposites. In this paper, a study on the first two configurations is presented. Poly(vinyl alcohol) (PVA)-Cloisite 20A was chosen for the intercalated system and PVA-Cloisite 10A was chosen for the flocculated one. In both cases, the phyllosilicate clays used were organically modified by tallow-triethanol-ammonium ion. The morphology of the two systems was investigated by using X-ray diffraction and nanoscanning electron microscopy. Although both confirmed the intercalation between PVA and 20A nanoclay, they confirmed the nonintercalation between PVA and 10A nanoclay. Another confirmation of the intercalation phenomena in PVA and 20A nanoclay was obtained from differential scanning calorimetry, which showed an increase in crystallinity upon intercalation. A main focus for the intercalated system was to study the effect of the nanoparticle's loading on the mechanical properties. Intercalation markedly affected both Young's modulus and the extent of elongation of the PVA-Cloisite 20A nanocomposite. Young's modulus and tensile stress increased with the loading of the clay up to 2 wt%. For higher loading, opposite results were reported due to the agglomeration of nanoparticles and as a consequence of the formation of microvoids. J. VINYL ADDIT. TECHNOL., 23:181-187, 2017.This paper was made possible by a NPRP Grant 09–260‐1–048 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu