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Production of Starch Films Using Propolis Nanoparticles as Novel Bioplasticizer
Get PDFBecause starch is a biodegradable polymer with low cost and wide availability it is an attractive material for producing edible films for fruits. Films produced with pure starch have the disadvantage of being fragile. To overcome this issue, propolis nanoparticles were used as a novel plasticizer. Mechanical, thermal and morphological properties of the films containing 0.5, 1 and 3 wt.% propolis nanoparticles were evaluated. The best performance was obtained using 0.5 wt.% propolis, increasing the Young’s modulus and decreasing the glass transition temperature (Tg), showing their plasticizing effect. The results of scanning electron microscopy (SEM) and atomic force microscopy (AFM) images showed a homogenous material with a low quantity of cracks and higher roughness than the pristine starch film. A more hydrophobic material was obtained due to the resin and wax compounds present in the propolis nanoparticles. This study shows the novel use of propolis as plasticizer for starch films
Thermal-Mechanical Characterization of Polyurethane Rigid Foams: Effect of Modifying Bio-Polyol Content in Isocyanate Prepolymers
Get PDFNowadays, green polyurethane (PU) foams are mostly synthesized by replacing an amount of petrochemical polyol with biobased polyol. Here we report five different families of isocyanate prepolymer formulations that were prepared with biobased sources and the correlation between the structure of chains and the properties of the produced PU foam. Foam behavior in tension, torsion, compression, shape memory tests and physical properties were studied by dynamic mechanical thermal analysis (DMTA); interactions in the polymer chains were analyzed by Fourier transform infrared spectroscopy (FTIR); and thermal analysis was performed by thermogravimetry (TGA) and differential scanning calorimetry (DSC). The results showed that high content of biobased macrotriol in the prepolymer formulation implies a softer final material than commercial polyester polyol foams due to the branched biobased molecules that do not allow enough packaging of the polymer matrix. Moreover, mechanical and thermal properties of the final PU foam are affected by the length, functionality and polarity of the biobased molecules used in the isocyanate prepolymer synthesis
Design and Characterization of Biocomposites from Poly(lactic acid) (PLA) and Buriti Petiole (Mauritia flexuosa)
Get PDFBuriti or miriti (Mauritia flexuosa) is a palm tree found in the Brazilian cerrado. Herein buriti petiole, part of the trunk that supports the leaves, was ground and used without any treatment as low density load to prepare poly(lactic acid) biocomposites. X-ray microtomography of buriti petiole showed its porous structure, with a wide pore size distribution determined with the aid of SEM. The obtained biocomposites with 1, 5 and 10 wt% of buriti petiole particles were investigated by their sessile drop contact angle, FTIR, TGA and tensile test. The tensile properties indicated poor adhesion between phases, which is crucial to optimize the biocomposite’s performance. Further studies with fiber treatment are being planned
Synthesis and Characterization of Nanocrystalline Cellulose Derived from Pineapple Peel Residues
Get PDFPineapple peel biomass was used as raw material for nanocellulose extraction. The raw material is a residue from the Costa Rican fruit industry. The nanocellulose was obtained by a two-step hydrolysis process. Firstly, the cellulose was hydrolyzed with HCl to obtain microcrystalline cellulose. In the second step, the hydrolysis was carried out using H2SO4 to obtain smaller fragments and decrease the lignin content. A timedependent study was carried out to determine the particle size decrease depending on the contact time with the H2SO4. The chemical, thermal and morphological properties were analyzed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), zeta potential, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The nanofiber-like cellulose was obtained after 60 minutes of exposure to 65 wt% H2SO4
Physico-Chemical and Morphological Characterization of Cellulosic Samples Obtained from Sisal Fibers
Get PDFIn this work, the main chemical reactions conditions of a succession of specific chemical treatments used for the isolation of nanocellulose from sisal fibers were evaluated. The novelty of this work is the study done to analyze the effect of different reaction conditions (time or concentration) in fiber structure and composition as well as in the characteristics of obtained cellulosic samples. In order to achieve this goal different physicochemical, thermal and morphological characterization techniques were used after each chemical treatment and the most suitable reaction conditions were selected for the subsequent treatment. Moreover, the thermal stability evolution of cellulose nanocrystals during the dialysis process was evaluated
Preparation and Characterization of the Nanocomposites from Chemically Modified Nanocellulose and Poly(lactic acid)
Get PDFCellulose nanocrystals (CNCs) are renewable and sustainable filler for polymeric nanocomposites. However, their high hydrophilicity limits their use with hydrophobic polymer for composite materials. In this study, freeze-dried CNCs were modified by transesterification with canola oil fatty acid methyl ester to reduce the hydrophilicity. The transesterified CNCs (CNCFE) were compounded with PLA into nanocomposites. CNCFE with long-chain hydrocarbons plays a role as plasticizer. Increasing CNCFE loadings resulted in clear plasticizing effects. Lower Tg and Tm were achieved for CNCFE-based nanocomposites. Plasticizing nanocomposite melt with CNCFE can mitigate the degradation of CNCs during thermal processing. The elongation at break of nanocomposites containing 5% CNCFE was increased. Dynamic rheological study showed the highest elastic and viscous moduli (G′ and G″) and complex viscosity (G*) of nanocomposites with addition of 2% CNCFE. By tailoring the loadings of the transesterified CNCs, tunable structure and properties of nanocomposites can be obtained
TRISim: A Triage Simulation System to Exploit and Assess Triage Operations for Hospital Managers - Development, Validation and Experiment
Get PDFTriage is a method for determining the priority of patients’ treatment to improve survival rates. Different triage methods are used in hospitals, and they are applied after performing an evaluation based on standard methods such as the Japan Triage Acuity Scale (JTAS) or Emergency Severity Index (ESI). It is important to consider the characteristics of all the hospitals when assigning triage methods and emergency levels to them; the hospital managers make these decisions. We propose a multi-agent simulation method to support the hospital managers in employing the triage protocols according to their environment. We developed a prototype simulation system called TRISim to explore and assess the triage operations. In this paper, we provide an overview of TRISim and present our experimental results to validate the system
Dynamic Analysis of Non-Symmetric Functionally Graded (FG) Cylindrical Structure under Shock Loading by Radial Shape Function Using Meshless Local Petrov-Galerkin (MLPG) Method with Nonlinear Grading Patterns
Get PDFIn this paper, dynamic behavior of non-symmetric Functionally Graded (FG) cylindrical structure under shock loading is carried out. Dynamic equations in the polar coordinates are drawn out using Meshless Local Petrov-Galerkin (MLPG) method. Nonlinear volume fractions are used for radial direction to simulate the mechanical properties of Functionally Graded Material (FGM). To solve dynamic equations of non-symmetric FG cylindrical structure in the time domain, the MLPG method are combined with the Laplace transform method. For computing the inverse Laplace transform in the present paper, the Talbot algorithm for the numerical inversion is used. To verify the obtained results by the MLPG method, these results are compared with the analytical solution and the Finite Element Method (FEM). The obtained results through the MLPG method show a good agreement in comparison to other results and the MLPG method has high accuracy for dynamic analysis of non-symmetric FG cylindrical structure. The capability of the present method to dynamic analysis of non-symmetric FG cylindrical structure is demonstrated by dynamic analysis of the cylinder with different volume fraction exponents under harmonic and rectangular shock loading. The present method shows high accuracy, efficiency and capability to dynamic analysis of non-symmetric FG cylindrical structure with nonlinear grading patterns, which furnishes a ground for a more flexible design
Form Finding and Collapse Analysis of Cable Nets Under Dynamic Loads Based on Finite Particle Method
No full textThis paper presents form finding and collapse analysis of cable net structure under strong wind using the finite particle method (FPM). As a kind of particle method, the theoretical fundamentals of the FPM are given. Methods to handle geometric and material nonlinearities of cable element are proposed. The fracture criterion and model for cable element are built to simulate the failure of cable nets. The form-finding and load analysis of two cable nets are then performed in order to initialize the successive of nonlinear analysis. The failure progress of cable nets under dynamic loads is simulated, and the dynamic responses of the typical fracture element are given in details. Analyses of the energy variations during the collapse process also show the failure mechanisms of cable nets, which is useful for the structure collapse resistance design. The numerical applications highlight the capability of the proposed procedure to solve complicate collapse problems with the FPM
Structural Design and Numerical Analysis of a Novel Biodegradable Zinc Alloy Stent
No full textBiodegradable zinc alloy stents are a prospective solution for complications caused by the incompatibility between artery and permanent stents. However, insufficient scaffolding has limited the clinical application of biodegradable zinc alloy stents. Therefore, in this study, a new stent concept was designed to improve the scaffolding. The mechanical performances of the new and a traditional design stent were investigated and compared using finite element analysis (FEA). The new and traditional design stent were expanded to the intended radial displacement of 0.24 mm under the expansion pressure of 0.58 MPa and 0.45 MPa, respectively. Then, a pressure load of 0.35 MPa was exerted on the outer surfaces of the two stents to compress them. The results showed that the radial recoiling ratio were 45.3% and 83.3% for the new and the traditional stent, respectively. The simulations demonstrate that the biodegradable zinc alloy stent offers enhanced support because of the new structural design. This study implies that biodegradable zinc alloy stent can be a new competitive intervention device for the future clinical cardiovascular application