Dynamic Compression Modulus of Expanded Polystyrene Foams.

Abstract We investigated the effect of gelation solvent, monomer type, and monomer concentration on the physical properties of freeze-dried poly(urethane)-poly(isocyanurate) (PUR-PIR) aerogels, with particular emphasis on their thermal conductivity. It was found that the gelation solvent considerably affects aerogel morphology and physical properties. Aerogels with the lowest thermal conductivity were obtained using a mixture of tetrahydrofuran (THF) and acetonitrile, in a 50% volume ratio. The influence on thermal conductivity of polyol and isocyanate structure and of their concentration was also investigated. Rigid precursors, phloroglucinol (POL), and an aromatic polyisocyanate based on toluene diisocyanate (Desmodur RC) yielded the lowest thermal conductivity. Our results were compared with recent work reporting on parameters that could be used as predictors of thermal conductivity and other physical properties of organic aerogels. None of these parameters were found to be satisfactory predictors of aerogel properties. For example, no systematic correlation between solvent solubility parameters and aerogel properties was observed. We also examined the role of the K-index. This index, defined as the ratio between porosity and contact angle, was shown recently to be a good predictor of the properties of polyurea aerogels. While the thermal conductivity scaled with the K-index, the scaling was different for each of the isocyanate monomers considered in our experiments. Thermal conductivity, instead, scaled well with the product of density and shrinkage of aerogels, independent of monomer type. The reasons of this dependence on shrinkage and density are discussed, and the use of these parameters to guide experimentation on other systems is discussed. Physical properties such as static and dynamic compression modulus and thermal stability of the most promising formulations were also examined.

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Dynamic Compression Modulus of Close-Celled Polyethylene Foams.

KOBUNSHI RONBUNSHU ◽

10.1295/koron.58.56 ◽

2001 ◽

Vol 58 (1) ◽

pp. 56-58

Author(s):

Hiromasa ADACHI ◽

Teruo HASEGAWA

Keyword(s):

Dynamic Compression ◽

Compression Modulus

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Experimental Study on the Dynamic Modulus and Damping Ratio of Compacted Loess under Circular Dynamic Stress Paths

Advances in Civil Engineering ◽

10.1155/2021/9574548 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Liguo Yang ◽

Shengjun Shao ◽

Zhi Wang

Keyword(s):

Principal Stress ◽

Dynamic Stress ◽

Dynamic Compression ◽

Damping Ratio ◽

Stress Path ◽

Compression Modulus ◽

Dry Density ◽

Dynamic Shear Modulus ◽

Dynamic Shear ◽

Compacted Loess

Dynamic loads such as earthquakes and traffic will simultaneously generate vertical dynamic stress and horizontal shear stress in the foundation soil. When the vertical dynamic stress amplitude is twice the horizontal shear dynamic stress amplitude, and the phase difference between them is 90°, a circular dynamic stress path is formed in the τ z θ d ∼ σ zd − σ θ d / 2 stress coordinate system. To simulate the stress state of soil in the area of the circular dynamic stress path caused by bidirectional dynamic stress coupling, a series of tests of compacted loess under the action of a circular dynamic stress path were carried out using a hollow cylindrical torsion shear apparatus. The effects of the mean principal stress, dry density, and deviatoric stress ratio (the ratio of deviator stress to average principal stress) on the dynamic modulus and damping ratio of compacted loess were mainly studied. The test results show that, under the action of the circular dynamic stress path, the larger the mean principal stress is, the larger the dynamic compression modulus and dynamic shear modulus are. The dynamic compression modulus increases obviously with increasing dry density, but the dynamic shear modulus increases only slightly. When the deviator stress ratio increases from 0 to 0.4, the dynamic compression modulus and dynamic shear modulus increase to a certain extent. In addition, the greater the dry density and deviatoric stress ratio are, the greater the initial dynamic compression modulus and initial dynamic shear modulus of the compacted loess. The dynamic compression damping ratio of compacted loess increases with increasing mean principal stress, but the dynamic shear damping ratio decreases with increasing mean principal stress. Dry density basically has no effect on the dynamic compression damping ratio and dynamic shear damping ratio of compacted loess. When the dynamic strain exceeds 1%, the greater the deviatoric stress ratio is, the smaller the dynamic compression damping ratio and the dynamic shear damping ratio are. The research results can provide reference for the study of dynamic modulus and damping ratio of loess under special stress paths.

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Evaluation of Dynamic Compression Modulus of Micro-Cell Polyurethane Foams by Dynamic Viscoelastic Measurements

KOBUNSHI RONBUNSHU ◽

10.1295/koron.63.273 ◽

2006 ◽

Vol 63 (4) ◽

pp. 273-276

Author(s):

Hiromasa ADACHI

Keyword(s):

Dynamic Compression ◽

Compression Modulus ◽

Polyurethane Foams

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Controlled production of alginate nanocomposites with incorporated silver nanoparticles aimed for biomedical applications

Journal of the Serbian Chemical Society ◽

10.2298/jsc121108148s ◽

2012 ◽

Vol 77 (12) ◽

pp. 1709-1722 ◽

Cited By ~ 16

Author(s):

Jasmina Stojkovska ◽

Jovana Zvicer ◽

Zeljka Jovanovic ◽

Vesna Miskovic-Stankovic ◽

Bojana Obradovic

Keyword(s):

Silver Nanoparticles ◽

Electrostatic Potential ◽

Biomedical Applications ◽

Dynamic Compression ◽

Compression Modulus ◽

Biomechanical Properties ◽

The Other ◽

Unconfined Compression ◽

Alginate Hydrogel ◽

Other Hand

Production of nanocomposite alginate microbeads with electrochemically synthesized silver nanoparticles (AgNPs) based on electrostatic extrusion technique was investigated with respect to potentials for utilization in pharmaceutical and biomedical applications. It was shown that electrochemical synthesis of AgNPs results in reduction of practically all Ag+ ions present in the initial solution yielding stable Ag/alginate colloid solutions that were demonstrated to be suitable for sterilization, manipulation, and electrostatic extrusion with retention of AgNPs. Presence of AgNPs in alginate colloid solutions had negligible effects on the size of the produced Ag/alginate microbeads, which was chiefly determined by the applied electrostatic potential during the extrusion. On the other hand, incorporation of AgNPs within the alginate hydrogel induced slight changes in biomechanical properties determined in a biomimetic bioreactor, so that packed beds of nanocomposite Ag/alginate microbeads exhibited slightly higher dynamic compression modulus as compared to that of control alginate microbeads (154 ? 4 and 141 ? 2 kPa, respectively). On the other hand, equilibrium unconfined compression modulus was significantly lower for nanocomposite microbeads as compared to that of controls (34 ? 2 and 47 ? 0.5 kPa, respectively).

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Dynamic Study of Reinforcement

Rubber Chemistry and Technology ◽

10.5254/1.3543109 ◽

1951 ◽

Vol 24 (4) ◽

pp. 787-809

Author(s):

J. R. S. Waring

Keyword(s):

Electrical Conductivity ◽

Carbon Black ◽

Natural Rubber ◽

Dynamic Modulus ◽

Dynamic Compression ◽

Compression Modulus ◽

Dynamic Study ◽

General Level ◽

Temperature Range ◽

Effects Of Temperature

Abstract The measurements were undertaken to obtain a better understanding of the mechanism of the reinforcement of rubber by carbon black. Results are given for the dynamic compression modulus and its temperature and amplitude coefficients, in the temperature range 30° to 70° C and at amplitudes of vibration around 0.0036 cm., for natural rubber, Neoprene Type GN, GR-S, and Perbunan. Data are also given on the effect of vibration and temperature on electrical conductivity. The results are discussed in relation to the general level of reinforcement. Evidence is given for the rupture of more than one type of cohesive bond in repeated cycles of vibration. A tentative system of analysis is proposed. The different effects of temperature and continuous vibration on dynamic modulus are attributed to a thixotropic breakdown in the case of vibration. The significance of such a “structure” dynamically hard at small amplitudes of vibration, is related to abrasion of tires in service.

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