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Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/ Purifi ed Cellulose Fiber Composites by Melt Blending: Characterization and Degradation in Composting Conditions
Get PDFNovel biodegradable composites based on poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) and different contents of purifi ed alpha-cellulose fi bers (3, 10, 25 and 45%) were prepared by melt blending and characterized. The composites were characterized by scanning electron microscopy (SEM), wide-angle X-ray scattering (WAXS) experiments, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanic analysis (DMA) and Shore D hardness measurements. Disintegrability under composting conditions was studied according to the ISO 20200 standard. Morphological results showed that high dispersion of the fi bers was achieved during mixing. Good adhesion on the fi ber-matrix interface was also detected by SEM. The addition of low and medium cellulose contents did not result in lower thermal resistance with respect to the neat PHBV. A reinforcing effect of the cellulose fi bers was detected in all samples, this effect being more pronounced at high temperatures. The composting results show that the addition of the fi bers did not affect the disintegrability of the PHBV, and thus compostable “green” low-cost PHBV/cellulose composites can be obtained
Modulation of Acid Hydrolysis Reaction Time for the Extraction of Cellulose Nanocrystals from Posidonia oceanica Leaves
Get PDFIn this research, the revalorization of Posidonia oceanica leaf sea waste was studied and the acid hydrolysis processing times were modulated in order to optimize the extraction of cellulose nanocrystals (CNCs). The obtained CNCs were deeply investigated. A two-step treatment was applied to extract cellulose nanocrystals from Posidonia oceanica leaves. First, a chemical treatment leads to the removal of lignin and production of holocellulose, while the second chemical process of acid hydrolysis allows the obtainment of cellulose nanocrystals in aqueous suspension. The unbleached and bleached leaves and cellulose nanocrystals were characterized by using thermogravimetric analysis, infrared spectroscopy and morphological investigation; the birefringence properties were also studied in order to determine the efficiency of the acid hydrolysis treatment. Cellulose nanocrystals were successfully obtained from Posidonia oceanica leaves and they showed a monocrystalline rod-shaped acicular structure with a 5–10 nm diameter and 200–450 nm length. KEYWORDS: Marine waste revalorizatio
Nanocellulose-Enabled Electronics, Energy Harvesting Devices, Smart Materials and Sensors: A Review
Get PDFCellulose nanomaterials have a number of interesting and unique properties that make them well-suited for use in electronics applications such as energy harvesting devices, actuators and sensors. Cellulose nanofibrils and nanocrystals have good mechanical properties, high transparency, and low coefficient of thermal expansion, among other properties that facilitate both active and inactive roles in electronics and related devices. For example, these nanomaterials have been demonstrated to operate as substrates for flexible electronics and displays, to improve the efficiency of photovoltaics, to work as a component of magnetostrictive composites and to act as a suitable lithium ion battery separator membrane. A discussion and overview of additional potential applications and of previously published research using cellulose nanomaterials for these advanced applications is provided in this article. The concept of using cellulose nanofibrils in stimuli-responsive materials is illustrated with highlights of preliminary results from magnetostrictive nanocellulose membranes actuated using magnetic fields
A Piecewise Linear Isotropic-Kinematic Hardening Model with Semi-Implicit Rules for Cyclic Loading and Its Parameter Identification
Get PDFA simple constitutive model, called semi-implicit model, for cyclic loading is proposed for steel materials used for structures such as building frames in civil engineering. The constitutive model is implemented in the E-Simulator, which is a software package for large-scale seismic response analysis. The constitutive relation is defined in an algorithmic manner based on the piecewise linear combined isotropic-kinematic hardening. Different rules are used for the first and subsequent loading states to incorporate characteristics such as yield plateau and Bauschinger effect of rolled mild steel materials. An optimization method is also presented for parameter identification from the results of cyclic and monotonic loading tests. Therefore, the proposed model is readily applicable to practical elastoplastic analysis of building frames. Accuracy of the model is demonstrated in an example of a cantilever subjected to various types of cyclic loading
The Numerical Accuracy Analysis of Asymptotic Homogenization Method and Multiscale Finite Element Method for Periodic Composite Materials
Get PDFIn this paper, we discuss the numerical accuracy of asymptotic homogenization method (AHM) and multiscale finite element method (MsFEM) for periodic composite materials. Through numerical calculation of the model problems for four kinds of typical periodic composite materials, the main factors to determine the accuracy of first-order AHM and second-order AHM are found, and the physical interpretation of these factors is given. Furthermore, the way to recover multiscale solutions of first-order AHM and MsFEM is theoretically analyzed, and it is found that first-order AHM and MsFEM provide similar multiscale solutions under some assumptions. Finally, numerical experiments verify that MsFEM is essentially a first-order multiscale method for periodic composite materials
A Finite Element Procedure for Analysis of Chemo-Mechanical Coupling Behavior of Hydrogels
Get PDFChemo-mechanical coupling behavior of materials is a transformation process between mechanical and chemical energy. In this paper, based on the coupled chemo-mechanical constitutive equations and governing equations during isothermal process, the equivalent integral forms of chemo-mechanical coupling governing equations and corresponding finite element procedure are obtained by using Hamilton's principle. An isoparametric plane element for chemo-mechanical coupling is associated into ABAQUS finite element package through user element subroutine UEL. The numerical examples exhibit that the ionic concentration variation can cause mechanical deformation and mechanical action can produce redistribution of ionic concentration for hydrogels. It is proved that the present developed chemo-mechanical coupling finite element procedure can be utilized to model the coupling behavior of hydrogels effectively
Automated Synthesis of Wideband Bandpass Filters Based on Slow-wave EBG Structures
Get PDFThis paper is focused on the automated synthesis of wideband bandpass filters operating at microwave frequencies and based on electromagnetic bandgap (EBG) structures. The classical counterpart of such filter consists of a combination of transmission line sections and shunt-connected grounded stubs placed at equidistant positions. By replacing the transmission line sections with capacitively-loaded lines (a kind of EBG-based lines) exhibiting the same phase shift at the lower cutoff frequency and the same characteristic (actually Bloch) impedance, filter size is reduced and the spurious pass bands can be efficiently suppressed. In practice, the loading capacitances are implemented by means of patches, in order to achieve a fully planar filter implementation. The presence of the patches reduces the effective phase velocity of the capacitively-loaded lines, thus providing a slow-wave effect useful for filter miniaturization. Moreover, due to periodicity, such EBG-based lines exhibit wide stop bands, which are used for spurious suppression. Even though such EBG-based filters were previously reported by some of the authors, a systematic synthesis method was not applied for filter design. In this paper, the main aim is to demonstrate the potential of aggressive space mapping (ASM) for that purpose, and it will be shown that such filters can be automatically synthesized
Polymers from Biobased-Monomers: Macroporous Itaconic Xerogels Prepared in Deep Eutectic Solvents
Get PDFNew methods of preparation of crosslinked polymers from itaconic acid as a renewable monomer have been explored. Synthesis of hydrogels and xerogels from the acid in deep eutectic solvents (DESs) are described and some basic properties of the materials are reported. Most importantly, a surfactant-free method of creation of macroporous poly(itaconic-co-bisacrylamide) by phase separation polymerization in binary mixture of the DES and poly(ethylene glycol) is demonstrated
Valorization of Agricultural Wastes for the Production of Protein-Based Biopolymers
Get PDFIn this study we provide an overview of the latest developments on the extraction, production, modification and applications of fruit residues and by-products in the formation of protein-based biopolymers, in particular for the formulation of edible films. Our aim was mainly to demonstrate the highly transdisciplinary character of these topics by giving an overview of the main developments and research topics in the chemistry and engineering aspects of protein-based biopolymers. These innovative raw materials have been evaluated for the production of biomaterials to be used in some key sectors, such as food packaging
Fracture Characterization of High-Density Polyethylene Materials Using the Energetic Criterias
No full textImpact behavior of polymers has received considerable attention in recent years, and much work based on fracture mechanic approaches has been carried out. In this paper, fracture behavior in large deformation of a high density polyethylene (HDPE) materials was investigated through experimental impact testing on single edge notched specimen (SENB) and by using theoretical and analytical fracture criteria concepts. Moreover, a review of the main fracture criteria is given in order to characterize the toughness of this polymer in the both cases (static and dynamic). The fractured specimens obtained from the Charpy impact test were characterized with respect to their fracture surfaces. Characteristic zones of the fracture surface can be assigned to different stages and mechanisms of the fracture process. Finally, for a better understanding of fracture and damage mechanisms and to provide the best estimation of fracture toughness in impact, an experimental approach based on microscopic observations (SEM) was used