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Synthesis, Structure and Properties of Poly(ester-Urethane- Urea)s Synthesized Using Biobased Diamine
Get PDFModern polymer science and technology is focused on the development of partial or fully green polymers. This focus is related to green chemistry trends, which propose using natural and renewable resources as monomers in the synthesis of polymers. In this study, biobased diamine was used as a chain extender of ester-urethane prepolymer. Obtained poly(ester-urethane-urea) contains 16 wt% of biobased diamine. There is mention of an amine curing agent that is an amine derivative of dimerized fatty acids (obtained from vegetable oils). Application of two chain extenders, i.e., 1,4-butanediol and biobased diamine (applied separately or in mixture), with different molecular weights and chemical structures, resulted in obtaining materials with diversifi ed properties. The chemical structure (by FTIR method), mechanical properties (tensile properties, hardness and elasticity), and thermomechanical properties (by DMTA method) were determined for the synthesized poly(ester-urethane-urea)s
Polyols Based on Poly(ethylene terephthalate) and Tall Oil: Perspectives for Synthesis and Production of Rigid Polyurethane Foams
Get PDFThis study presents the synthesis of novel polyols made from tall oil (TO) and poly(ethylene terephthalate) (PET) with different TO/PET molar ratios. Rigid polyurethane foams based on these synthesized polyols were obtained and characterized to evaluate polyols’ suitability for the development of light materials with insulating properties. The effect of TO/PET molar ratios on the physical, morphological and mechanical properties of the obtained foams, as well as their thermal insulation characteristics, were evaluated. Increasing amounts of PET in polyurethane foams resulted in higher compression strength and closed cell content, while water absorption was not affected. Results indicated that certain TO/PET polyols can be successfully used for preparing rigid polyurethane foams
Dispersion of Axisymmetric Longitudinal Waves in A Bi-Material Compound Solid Cylinder Made of Viscoelastic Materials
Get PDFThe paper studies the dispersion of axisymmetric longitudinal waves in the bi-material compound circular cylinder made of linear viscoelastic materials. The investigations are carried out within the scope of the piecewise homogeneous body model by utilizing the exact equations of linear viscoelasto-dynamics. The corresponding dispersion equation is derived for an arbitrary type of hereditary operator and the algorithm is developed for its numerical solution. Concrete numerical results are obtained for the case where the relations of the constituents of the cylinder are described through fractional exponential operators. The influence of the viscosity of the materials of the compound cylinder on the wave dispersion is studied through the rheological parameters which indicate the characteristic creep time and long-term values of the elastic constants of these materials. Dispersion curves are presented for certain selected dispersive and non-dispersive attenuation cases under various values of the problem parameters and the influence of the aforementioned rheological parameters on these curves is discussed. As a result of the numerical investigations, in particular, it is established that in the case where the rheological parameters of the components of the compound cylinder are the same, the viscosity of the layers' materials causes the axisymmetric wave propagation velocity to decrease
A Model to Describe the Fracture of Porous Polygranular Graphite Subject to Neutron Damage and Radiolytic Oxidation
Get PDFTwo linked models have been developed to explore the relationship between the amount of porosity arising in service from both radiolytic oxidation and fast neutron damage that influences both the strength and the force-displacement (load-displacement) behaviour and crack propagation in pile grade A graphite used as a nuclear reactor moderator material. Firstly models of the microstructure of the porous graphite for both unirradiated and irradiated graphite are created. These form the input for the second stage, simulating fracture in lattice-type finite element models, which predicts force (load)-displacement and crack propagation paths. Microstructures comprising aligned filler particles, typical of needle coke, in a porous matrix have been explored. The purpose was to isolate the contributions of filler particles and porosity to fracture strength and crack paths and consider their implications for the overall failure of reactor core graphite
Thermal Behavior of a U-shaped Channel Subject to a Convective Air Jet and Immersed in an Isothermal Medium
Get PDFA numerical study of mixed convection from a U-shaped channel is carried out. The flow is considered two dimensionnel. The inlet opening is adjusted in the right vertical part of the channel, while the outlet one is placed on the left vertical part. Navier–Stokes equations are solved using a control volume method and the SIMPLEC algorithm is considered for the treatment of pressure–velocity coupling. Special emphasis is given to detail the effect of the Reynolds and Rayleigh numbers on the heat transfer generated by mixed convection. The results are given for the parameters of control as, Rayleigh number (5.103≤Ra≤107), Prandtl number (Pr = 0.72), the hight of the vertical walls (h=5) and Reynolds number (100≤Re≤700). The results show that the flow structure and the heat transfer depend significantly on the inlet opening boundary conditions. Two principal kinds of the problem solution have emerged. Significant correlations are proposed related to the Nusselt number variation with Re or with Ra
Solution of Liouville's Equation for Uncertainty Characterization of the Main Problem in Satellite Theory
Get PDFThis paper presents a closed form solution to Liouville's equation governing the evolution of the probability density function associated with the motion of a body in a central force field and subject to J2. It is shown that the application of transformation of variables formula for mapping uncertainties is equivalent to the method of characteristics for computing the time evolution of the probability density function that forms the solution of the Liouville's partial differential equation. The insights derived from the nature of the solution to Liouville's equation are used to reduce the dimensionality of uncertainties in orbital element space. It is demonstrated that the uncertainty propagation is fastest in the semi-major axis and the mean anomaly phase sub-space. The results obtained for uncertainty propagation for the two body problem are applied to investigate the uncertainty propagation in the presence of the J2 perturbation using a combination of osculating and mean element perturbation theory. Analytical orbital uncertainty propagation calculations are validated using Monte-Carlo results for several representative orbits
Analysis of Metamaterial Cloaks Using Circular Split Ring Resonator Structures
Get PDFA novel microwave cloak using circular split ring resonator (SRR) based metamaterial structure has been proposed in this paper. The cloak which operates at a frequency of 10.6 GHz is composed of cylindrical dielectric sheets printed with circular split ring resonators of spatially varying and anisotropic material properties. The article also focuses on the phenomenon of resonant splitting in circular SRR microwave cloak. A detailed analysis of various linear metamaterial arrays and their response has also been elucidated
Development of a Device in Detection of Glaucoma for Rural Eye Care Using Additive Manufacturing and TRIZ
Get PDFPurpose: The main purpose of this study is to develop a device for the indicative measurement of intraocular pressure (IOP) of eyeball, a key cause for glaucoma. In early diagnosis and treatment of glaucoma accurate measurement of IOP is important. The methods and devices which are available for the measurement of IOP have their own limitations which cause discomfort to the patients during measurement and needs anesthesia. There is a dare need of a device for the measurement of intraocular pressure by making the contact of plunger with closed eyelid eliminating the need of anesthesia and expert ophthalmologist. Method: Additive manufacturing (AM) is an era of technical development and innovation. Developing a device for detecting glaucoma by using AM and TRIZ ‘The theory of inventive problem solving’ (A Collaborative approach) can overcome the disadvantages that classic tonometer have. The field of Ophthalmology will be experiencing a paradigm shift towards the use of collaborative approach of TRIZ with AM. The developed new device was tested on 40 patient’s eye at Government Hospital Bhandara, (M. S.), India. The results of new device were cross verified by expert clinicians using calibrated Schiotz’s tonometer and digital palpation technique. Result: The developed new device was tested on patient’s eye through eyelid and results were compared with calibrated Schiotz’s tonometer. The results from the new device were found in good agreement with results from Schiotz’s tonometer with the average error of 0.033 ± 0.18 (mean ± SD) mm of Hg and mean relative error was -0.0018 ±0.0096 (mean ± SD). Conclusion: There is a substantial need for early detection and diagnosis of glaucoma in rural and remote areas (worldwide). A new device for detection of glaucoma using AM and TRIZ was introduced in this paper and measurements by the new device were by currently well accepted Schiotz’s tonometer. The new device will help the medical practitioners in rural and remote areas for early detection of glaucoma
Editorial
Get PDFa special issue containing 12 papers is presented here.The Guest Editors of this special issue are grateful to Alessandro Gandini, co-editor in-chief of the Journal of Renewable Materials, Linda Mohr, the Journal Editors’ assistant, as well as to the entire journal team for their valuable contributions that made this excellent work possible. Last but not least, our sincere appreciation to the contributing authors for the work performed and to all the reviewers involved, for their critical and con-structive comments on the submitted manuscripts.A special acknowledgement to Martin Scrivener for his constant follow-up and support.We look forward for other special issues of the Workshop on Green Chemistry and Nanotechnologies in Polymer Chemistry
Superhydrophobic and Oleophobic UV-Curable Surface Engineering of Cellulose-Based Substrates
Get PDFCellulose-based materials are one of the most widely used materials provided by nature to mankind. In particular, cotton fi bers have been used for millennia to produce clothing items. This wide usage stems from the inherent properties of cotton fabrics such as hydrophilicity and permeability to water vapor. However, increasingly sophisticated uses for cotton-based clothing (e.g., technical textiles) demand specifi c properties such as hydrophobicity and oleophobicity for repellent functions. The current surface treatments used to attain these functionalities are based on thermally initiated polymerization reactions, using water-based formulations. Thus, the current technologies are energy- and water-intensive. The advantages of using alternative polymerization routes based on actinic radiation are thus clear and include lower energy consumptions, increased processing speeds and smaller plant space. However, example current drawbacks include issues related to the loss of substrate fl exibility, breathability and hand. In order to overcome these issues, a durable surface treatment has been developed based on UV-curable polymeric materials that provide superhydrophobic and oleophobic properties to cotton substrates, maintaining intrinsic useful properties of cotton fabrics such as pleasant hand. In this article are reported the innovative surface treatment formulations and procedures developed