Search results for " foam"
showing 10 items of 59 documents
Applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon
2023
Hybrid aspens have long attracted scientific interest, but the research on their use as feedstocks for chemical applications are still very limited. The bark biomass of the poplar species contains many valuable extractives that can be utilized as value-added products. This paper examines the applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon. To explore this, the study considers 1) the basic chemical composition of the bark in terms of added value potential, 2) the basic chemical composition of the bark extract and the effect of its pretreatment on the extract composition, 3) the production of rigi…
Forming of aluminum foam sandwich panels: Numerical simulations and experimental tests
2006
Abstract The forming of the completed aluminium foam sandwich (AFS) panels would determine an improvement in the manufacturing of parts and panels. In this paper the authors have investigated the formability of AFS through experiments and numerical simulations. As far as the former are concerned, commercially prepared panels have been considered and bending and stamping processes have been taken into account. In addition, FEM analyses have been developed, utilizing a porous material model following the evolution of the material density throughout the forming processes.
Identification and Evaluation of Hazardous Pyrolysates in Bio-Based Rigid Polyurethane-Polyisocyanurate Foam Smoke
2021
In this study, rigid polyurethane (PU) and polyisocyanurate (PIR) foam samples made from renewable material (tall oil fatty acid) based polyols were analyzed by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) to obtain information about the full relative smoke content, with a focus on substance identification by their functional groups and hazardousness. The relative content of gaseous products produced during the thermal degradation was evaluated between the two samples, differenced by their assigned isocyanate (NCO) index value—150 and 300. The main thermal degradation components of the rigid PU-PIR foam were found to originate from the decomposition of isocyanate, primarily for…
The Quantum Scalar Field in Spherically Symmetric Loop Quantum Gravity
2013
We consider the quantization of a spherically symmetric gravitational system coupled to a massless scalar field within the loop quantum gravity framework. Our results rely on the uniform discretizations method developed during the last years. We minimize the associated discrete “master constraint” using a trial state whose gravitational part is peaked around the classical Schwarzschild solution.
Testing Soil Encasing Materials for Measuring Hydraulic Conductivity of a Sandy-Loam Soil by the Cube Methods
2008
The Cube Method (CM) and the Modified Cube Method (MCM) were developed for measuring vertical (K v ) and horizontal (K h ) saturated hydraulic conductivity of a single soil sample. By these methods, a cube of soil is carved out in situ and a suitable material is applied to enclose the cube in a tightly fitting casing before moving the sample to the laboratory. Problems may be associated with the use of gypsum, originally used to encase soil. The suitability of molten wax and expandable polyurethane foam to encase a soil cube was tested for a sandy-loam soil. Wax-treated samples yielded lower conductivity results than untreated samples by a maximum factor of 3.7. The observed discrepancies w…
Investigation on the behaviour of fully thermoplastic composite sandwich beams under concentrated loads
2009
The recent development of new low cost manufacturing processes adopting thermoplastic matrices in the production of structural long fibre reinforced laminates is fostering an increasing interest towards this class of materials. The automotive sector in particular is attracted by the high energy absorbing, damage tolerance performances and manufacturing and recycling potentials of structural thermoplastic composites. In this study a number of fully thermoplastic sandwich beams have been manufactured in order to investigate flexural and shear rigidity performances as well as the indentation behavior under static concentrated loads.
Reinforcement Efficiency of Cellulose Microfibers for the Tensile Stiffness and Strength of Rigid Low-Density Polyurethane Foams
2020
Rigid low-density closed-cell polyurethane (PU) foams are widely used in both thermal insulation and structural applications. The sustainability of PU foam production can be increased by using bio-based components and fillers that ensure both enhanced mechanical properties and higher renewable material content. Such bio-based foams were produced using polyols derived from rapeseed oil and microcrystalline cellulose (MCC) fibers as filler. The effect of MCC fiber loading of up to 10 wt % on the morphology, tensile stiffness, and strength of foams has been evaluated. For estimation of the mechanical reinforcement efficiency of foams, a model allowing for the partial alignment of filler fibers…
The quantum, the geon, and the crystal
2015
Effective geometries arising from a hypothetical discrete structure of space-time can play an important role in the understanding of the gravitational physics beyond General Relativity. To discuss this question, we make use of lessons from crystalline systems within solid state physics, where the presence of defects in the discrete microstructure of the crystal determine the kind of effective geometry needed to properly describe the system in the macroscopic continuum limit. In this work we study metric-affine theories with non-metricity and torsion, which are the gravitational analog of crystalline structures with point defects and dislocations. We consider a crystal-motivated gravitationa…
Electromagnetic shielding efficiency in Ka-band: carbon foam versus epoxy/carbon nanotube composites
2012
The wide application of microwaves stimulates searching for new materials with high electrical conductivity and electromagnetic (EM) interference shielding effectiveness (SE). We conducted a comparative study of EM SE in K a -band demonstrated by ultra-light micro-structural porous carbon solids (carbon foams) of different bulk densities, 0.042 to 0.150 g/cm 3 , and conventional flexible epoxy resin filled with carbon nanotubes (CNTs) in small concentrations, 1.5 wt.%. Microwave probing of carbon foams showed that the transmission through a 2 mm-thick layer strongly decreases with decreasing the pore size up to the level of 0.6%, due to a rise of reflectance ability. At the same time, 1 mm…
The role of EPS in fouling and foaming phenomena occurring in an UCT-MBR pilot plant
2012
The aim of this study is to detect a possible relationship between EPS and fouling and EPS and foaming in a University Cape Town (UCT) membrane bioreactor (MBR) pilot plant. The UCT-MBR pilot plant was fed with 40 L/h of real wastewater and monitored for 165 days. Specifically physical/chemical features of influent, permeate and mixed liquor in different sections were analyzed. The fouling phenomenon was studied monitoring the hydraulic resistances of the membrane. The extracellular polymeric substances (EPSs) concentration inside the aerobic tank were also measured. The foaming phenomenon was monitored by performing the Foam Power and Scum Index testes. Results have shown a high correlatio…