Processing and characterization of polyethylene-based composites

Thermoplastic matrix polymer composites have gained commercial success in the semistructural and structural applications. Polyethylene (PE) is one of the most versatile and widely used thermoplastics in the world because of its excellent properties like toughness, near-zero moisture absorption, excellent chemical inertness, low coefficient of friction, ease of processing and unusual electrical properties. This review is designed for comprehensive source of PE-based polymer composites research, including structure and classification of PE manufacturing/processing techniques for PE composites, and it also described different characterization methods for PE composites. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) characterization methods were used to describe the thermal properties of PE composites. Morphological studies were explained by using scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) techniques. Rheological properties and dynamic mechanical analysis (DMA) are also discussed in this review. X-ray diffraction (XRD) characterization was described in this review to explain crystallinity in PE composites. Hence, this review offers a comprehensive discussion on processing and characterization of PE-based composites

Designing piezoelectric nanogenerator from PVDFHFP nanocomposite fibers containing cellulose nanocrystals and Fedoped ZnO

Self-powering devices harvest energy from the environment and perform based on a maintenance free approach. These materials are of utmost significance as they solve the problems associated with the energy crisis and management, to greater extends. Advances in material science and the design of various polymer nanocomposites developed many self-powering devices that are flexible, sensitive, less power consuming and of low cost. The semi-crystalline polymer, poly vinylidene fluoride (PVDF) and its co-polymers are notable for mechanical energy harvesting because of the typical crystalline phases in their structure. Various nanoparticles are added to such polymers to enhance their dielectric and piezoelectric properties as well. Since the alignment of crystalline phases improve the energy harvesting properties, techniques such as electrical poling are practiced to enhance their applicability. Among various alignment procedures, electrospinning stands as unique since the high voltage applied to the polymer solution generates nanofiber scaffolds in perfect alignments. The present work aims to develop electrospun composite fibers in nano-dimensions for designing self-powering nanogenerators. The co-polymer of PVDF, polyvinylidene fluoride hexa fluoropropylene (PVDF-HFP) was used as the base polymer and the iron-doped zinc oxide (Fe-ZnO) and cellulose nanocrystals (CNC) as the filler reinforcements. Fe-ZnO nanostructures were obtained by hydrothermal synthesis method from the ZnO precursor, while the CNC were synthesized following the acid hydrolysis of cellulose microfibers. The optimized concentration of 20 wt.% was used for obtaining the electrospun fibers of neat PVDF-HFP and various concentrations of nanoparticles were mixed with this base solution. Simple solvent mixing was employed using the acetone/DMF solvent mixture to prepare the composite solutions prior to electrospinning. The electrospinning conditions were also optimized by varying the applied voltage, tip to collector distance and speed of the rotating collector. Nice fibers were obtained at a voltage of 12-13 eV and rotating collector speed of 200 rpm. Composites of CNC with PVDF-HFP, Fe-ZnO with PVDF-HFP and the hybrid material of CNC/Fe-ZnO with PVDF-HFP were prepared and properties were investigated. All the fibers were tested for the morphology, structural, thermal and dielectric properties. The mechanical energy harvesting was performed using an assembled set up containing a frequency generator, shaker and data acquisition system. At 2 wt. % of the nanofillers, the PVDF-HFP/CNC generated about 2 V, the PVDF-HFP/Fe-ZnO generated about 4 V and the hybrid nanocomposite containing both nanoparticles generated about 6 V. The filler synergy plays a major role in regulating the material properties and here the combined effect of the piezoelectric performance of the cellulose nanocrystals and the modified ZnO nanoparticles enhanced the mechanical energy harvesting capability of the final nanocomposite. A nanogenerator is designed based on the developed polymer nanocomposite fibers and the piezoelectric performance on various conditions of stretching, pressing and twisting were also investigated. In all the cases the hybrid composite showed notable performance substantiating its application in designing self-powered nanogenerators. The dielectric properties of the hybrid material showed many fold increase in its dielectric constant, making it useful in electrical energy storage. In short, the designed device by electrospinning technique is highly useful in adding to the energy management and is environmentally safe and of good efficiency.qscienc

Mussel-mimicking sulfobetaine-based copolymer with metal tunable gelation, self-healing and antibacterial capability

In the present study, the sulfobetaine-based copolymer bearing a dopamine functionality showed gel formation adjusted by the application of metal salts for gelation and various values of pH. Normally, the liquid-like solution of the sulfobetaine-based copolymer and metal cross-linkers is transformed to a gel-like state upon increasing the pH values in the presence of Fe3+ and Ti3+. Metal-induced coordination is reversible by means of the application of EDTA as a chelating agent. In the case of Ag+ ions, the gel is formed through a redox process accompanied with the oxidative coupling of the dopamine moieties and Ag0 particle formation. Mussel-mimicking and metal-dependent viscoelastic properties were observed for Fe3+, Ti3+, and Ag+ cross-linking agents, with additionally enhanced self-healing behavior in comparison with the covalently cross-linked IO4 − analogues. Antibacterial properties can be achieved both in solution and on the surface using the proper concentration of Ag+ ions used for gelation; thus, a tunable amount of the Ag0 particles are formed in the hydrogel. The cytotoxicity was elucidated by the both MTT assay on the NIH/3T3 fibroblast cell line and direct contact method using human dermal fibroblast cell (F121) and shows the non-toxic character of the synthesized copolymer. © 2017 The AuthorsQatar University [QUUG-CAM-2017-1]; Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; Maersk Oil R&TC Qatar project; Qatar National Research Fund (Qatar Foundation) [9 - 219-2-105

Vibration sensing systems based on poly(Vinylidene fluoride) and microwave-assisted synthesized zno star-like particles with controllable structural and physical properties

This study deals with the effect of zinc oxide (ZnO) star-like filler addition to the poly(vinylidene fluoride) (PVDF) matrix, and its effect on the structural and physical properties and consequences to the vibration sensing performance. Microwave-assisted synthesis in open vessel setup was optimized for the preparation of the star-like shape of ZnO crystalline particles. The crystalline and star-like structure was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX). Furthermore, the PVDF-based composites were prepared using a spin-coating technique from solution. An investigation of the transformation of the α crystalline phase to the β crystalline phase of the neat PVDF matrix and with various filler concentrations was performed using Fourier-Transform infrared (FTIR) spectroscopy, which shows an enhanced β-phase from 44.1% to 66.4% for neat PVDF and PVDF with 10 wt.% of particles, respectively. Differential scanning calorimetry (DSC) measurements and investigation showed enhanced crystallinity and melting enthalpy of the composite systems in comparison to neat PVDF, since ZnO star-like particles act as nucleating agents. The impact of the filler content on the physical properties, such as thermal and dynamic mechanical properties, which are critical for the intended applications, were investigated as well, and showed that fabricated composites exhibit enhanced thermal stability. Because of its dynamic mechanical properties, the composites can still be utilized as flexible sensors. Finally, the vibration sensing capability was systematically investigated, and it was shown that the addition of ZnO star-like filler enhanced the value of the thickness mode d33 piezoelectric constant from 16.3 pC/N to 29.2 pC/N for neat PVDF and PVDF with 10 wt.% of ZnO star-like particles. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Qatar National Research Fund (a member of the Qatar Foundation) [NPRP-6-282-2-119]; Czech Science FoundationGrant Agency of the Czech Republic [19-17457S]; Ministry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2020/003

Influence of graphene oxide on mechanical, morphological, barrier, and electrical properties of polymer membranes

This paper expresses a short review of research on the effects of graphene oxide (GO) as a nanocomposite element on polymer morphology and resulting property modifications including mechanical, barrier, and electrical conductivity. The effects on mechanical enhancement related to stress measurements in particular are a focus of this review. To first order, varying levels of aggregation of GO in different polymer matrices as a result of their weak inter-particle attractive interactions mainly affect the nanocomposite mechanical properties. The near surface dispersion of GO in polymer/GO nanocomposites can be investigated by studying the surface morphology of these nanocomposites using scanning probe microscopy such as atomic force microscope (AFM) and scanning electron microscope (SEM). In the bulk, GO dispersion can be studied by wide-angle X-ray scattering (WAXD) by analyzing the diffraction peaks corresponding to the undispersed GO fraction in the polymer matrix. In terms of an application, we review how the hydrophilicity of graphene oxide and its hydrogen bonding potential can enhance water flux of these nanocomposite materials in membrane applications. Likewise, the electrical conductivity of polymer films and bulk polymers can be advantageously enhanced via the percolative dispersion of GO nanoparticles, but this typically requires some additional chemical treatment of the GO nanoparticles to transform it to reduced GO. 2015 Production and hosting by Elsevier B.V.The authors acknowledge the support of the ACS-#52997-ND7 Petroleum Research Foundation. The authors extend their sincere appreciations to the Deanship of Scientific Research at King Saud University for its funding this Prolific Research group (PRG-1436-14) for this graphene oxide based membranes review study.Scopu

Mechanical Properties of Gamma Irradiated TiO\u3csub\u3e2\u3c/sub\u3eNPs/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

Thermal Properties of TiO₂NP/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 (Tc) was not modified after incorporating TONPs, while an enhancement was observed after adding the hybrid fillers. The melting temperature (Tm) was not changed after introducing the CNTs and CNT/TONP hybrid fillers. The percentage crystallinity (Xc %) was increased by 4% and 6%, after incorporating 1 wt % and 3 wt % CNTs, respectively. The TONP incorporation did not modify the Xc %. Moreover, thermal gravimetric analysis (TGA) thermograms confirmed the increased thermal stability after introducing CNTs and hybrid fillers compared to TONP incorporation

Core-Shell Nanofibers of Polyvinylidene Fluoride-based Nanocomposites as Piezoelectric Nanogenerators

Flexible piezoelectric nanogenerators (PENG) are widely applied to harvest sustainable energy from multiple energy sources. The rational and simple design of PENG have great potential in soft electronics. Here we design a highly flexible PENG using the polyvinylidene fluoride (PVDF) and its copolymer, polyvinylidene hexafluoropropylene (PVDF-HFP) with two nanoarchitectures of semiconducting metal oxides, TiO2 and ZnO. The nanotubes of TiO2 and nanoflowers of ZnO are embedded in these different polymeric media by solvent mixing, and new fiber mats are generated by coaxial electrospinning technique. This process aligns the dipoles of polymers and nanomaterials, which is normally a pre-requisite for higher piezo potential. With excellent mechanical strength and flexibility, the tailored lightweight fiber mats are capable of producing good output voltage (a maximum of 14 V) during different mechanical vibrations at various frequencies and in response to human motions. The hybrid nanocomposite PENG is durable and inexpensive and has possible applications in wearable electronics

Polymer-metal oxide composite nanofibers

Extensive studies have been conducted on different kinds of polymers, their composites, and multifunctionalities, depending on their structural features. Metal oxides and their polymer nanocomposites offer technological characteristics due to mechanical, electrical, and electronic properties. Nanofibers have considerable morphological significance, owing to their structural identity and behavior. Polymer composite nanofibers can be rodlike, porous, hollow, or core-shell, depending on the fabrication techniques that are used. Recently, electrospinning has been emerged as an important tool to fabricate microfibrous or nanofibrous membranes of polymers, biopolymers, and their composites. However, this procedure can be challenging, owing to the related cost and required external conditions, such as solvents and heat. Composite nanofibers can find applications in membrane, biomedical and pharmaceutical, food packaging, and environmental applications. This chapter discusses selected composite nanofibers and their characteristics, taking into account the electroactivity, elastomeric nature, and biofriendliness of the polymers.Scopu