Friction on Ice

1988 ◽  
Vol 61 (1) ◽  
pp. 14-35 ◽  
Author(s):  
Asahiro Ahagon ◽  
Toshio Kobayashi ◽  
Makoto Mlsawa
Keyword(s):  
Melting Point ◽  
Energy Loss ◽  
Solubility Parameter ◽  
Low Temperatures ◽  
Fluid Layer ◽  
Frictional Resistance ◽  
High Viscosity ◽  
Polymer Chains ◽  
Solid Surfaces ◽  
Ice Surface

Abstract The friction on ice is strongly dependent on temperature. At sufficiently low temperatures, the frictional resistance on ice is high comparable to those on wet or even dry solid surfaces. As temperature rises and approaches the melting point of ice, however, friction rapidly decreases. Differing from the friction of a rubber on ordinary dry or wet solid surfaces the energy loss processes in the rubber do not seem to be the direct source of the frictional resistance on ice. Although frictional melting of ice could occur at high sliding speeds, an ice surface is inherently lubricated with a persistent mobile fluid layer at relatively high temperatures, near the melting point of ice. When a rubber slides on an ice surface, the fluid layer is sheared and undergoes drag flow. The energy loss process necessary for the frictional resistance takes place primarily in the fluid layer, and not in the rubber. The frictional resistance on ice is primarily determined by the viscosity and the thickness of the lubricating fluid layer. What is required of a rubber for better traction under such a condition is that the rubber surface follows the topography of the ice surface as closely as possible, so that more patches of ice surface can be sheared. Therefore, the rubber has to be sufficiently soft to show high friction on ice. Further improvement of the friction could be obtained by making it more resilient. Thus, a rubber with high friction on ice must be compounded so that the polymer chains maintain a high level of mobility at moderately low temperatures. This can be achieved by using polymers with low glass-transition-temperatures. An increased softener loading level helps to improve friction, but to a limited extent. In order to take maximum advantage of softeners, the choice of softener system is important. A relation common to all the mixed softener systems, except the ones containing high-viscosity softeners, was found to exist between the friction on ice and the solubility parameter of the softener mixture in the rubber. The friction on ice was maximized by selecting a softener system with a solubility parameter near that of the polymers in the rubber. The solubility parameter dependence of the friction was consistent with those of softness and resilience.

ELLIPSOMETRIC STUDY OF THE ICE SURFACE STRUCTURE JUST BELOW THE MELTING POINT

1987 ◽  
Vol 48 (C1) ◽  
pp. C1-495-C1-501 ◽  
Author(s):  
Y. FURUKAWA ◽  
M. YAMAMOTO ◽  
T. KURODA
Keyword(s):  
Melting Point ◽  
Surface Structure ◽  
Ice Surface ◽  
Ellipsometric Study

scholarly journals Static and Dynamic Behavior of Polymer/Graphite Oxide Nanocomposites before and after Thermal Reduction

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1008
Author(s):  
Kiriaki Chrissopoulou ◽  
Krystalenia Androulaki ◽  
Massimiliano Labardi ◽  
Spiros H. Anastasiadis
Keyword(s):  
Graphite Oxide ◽  
Thermal Reduction ◽  
Polymer Chains ◽  
Solid Surfaces ◽  
Relaxation Processes ◽  
Thermal Transitions ◽  
Reduced Graphite Oxide ◽  
Before And After ◽  
Similarities And Differences ◽  
Thermal Stability Of

Nanocomposites of hyperbranched polymers with graphitic materials are investigated with respect to their structure and thermal properties as well as the dynamics of the polymer probing the effect of the different intercalated or exfoliated structure. Three generations of hyperbranched polyester polyols are mixed with graphite oxide (GO) and the favorable interactions between the polymers and the solid surfaces lead to intercalated structure. The thermal transitions of the confined chains are suppressed, whereas their dynamics show similarities and differences with the dynamics of the neat polymers. The three relaxation processes observed for the neat polymers are observed in the nanohybrids as well, but with different temperature dependencies. Thermal reduction of the graphite oxide in the presence of the polymer to produce reduced graphite oxide (rGO) reveals an increase in the reduction temperature, which is accompanied by decreased thermal stability of the polymer. The de-oxygenation of the graphite oxide leads to the destruction of the intercalated structure and to the dispersion of the rGO layers within the polymeric matrix because of the modification of the interactions between the polymer chains and the surfaces. A significant increase in the conductivity of the resulting nanocomposites, in comparison to both the polymers and the intercalated nanohybrids, indicates the formation of a percolated rGO network.

scholarly journals Research on the Tunnel Excavated In Urumqi Glacier No. 1, Tianshan Glaciological Station, China

1987 ◽  
Vol 33 (113) ◽  
pp. 99-104 ◽  
Author(s):  
Huang Maohuan ◽  
Wang Zhongxiang
Keyword(s):  
Melting Point ◽  
Shear Strain ◽  
Maximum Shear Strain ◽  
Ice Surface ◽  
Basal Sliding ◽  
Glacier Ice ◽  
Glacier Motion

AbstractA tunnel was excavated in Urumqi Glacier No. 1, at the Tianshan Glaciological Station. Ice temperature, ice displacement, deformation, and basal sliding, etc. were observed at regular intervals. It is shown that the temperature near the glacier bed is close to the melting point and that the largest proportion of the overall glacier motion is within the lowermost ice layers. The glacier ice is in a state of compression. The maximum shear strain increases towards the entrance of the tunnel, corresponding to the change in slope of the ice surface, and also towards the bedrock.

The “Solidification” of Grain Boundaries with Increasing Temperature

1994 ◽  
Vol 357 ◽  
Author(s):  
Witold Lojkowski ◽  
Bogdan Palosz
Keyword(s):  
Solid State ◽  
Melting Point ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Temperatures ◽  
Low Temperatures ◽  
Melting Behavior ◽  
Wetting Transitions ◽  
Increasing Temperature ◽  
Segregation Of Impurities

AbstractThe aim of the paper is to explain the recently observed de-wetting grain boundary transition with increasing temperature. On the example of a bicrystal from the Fe-6at.%Si alloy, it was found recently that as temperature is increased, the following GB transitions take place: “solid” (or regular) GB-→“premelted” GB →“solid” GB. At the same time the wetting/de-wetting transitions have taken place. Another example of such GB behavior was discovered during sintering of alumina. The inverse melting behavior is explained as follows: low melting point impurities cause GB premelting at low temperatures, However de-segregation of impurities at high temperatures causes return of the GB structure to its regular “solid” state.

Effect of Storage and Temperature on Flexibility of Natural and Synthetic Rubbers

1948 ◽  
Vol 21 (4) ◽  
pp. 864-876
Author(s):  
John B. Gregory ◽  
Irving Pockel ◽  
John F. Stiff
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Strain Curve ◽  
Polymer Chains ◽  
Stress Strain Curve ◽  
Low Temperature Storage ◽  
Synthetic Rubber ◽  
Loading And Unloading ◽  
Temperature Storage ◽  
Natural And Synthetic

Abstract A new method for measuring the flexibility of rubber has been described. The method consists essentially in determining the stress-strain curve obtained by loading and unloading a loop formed from a one-inch by six-inch strip cut from a test slab. A coefficient of flexibility independent of the thickness of the sample and, in addition, information on per cent resilience were obtained. By the use of the method described, the behavior of various natural and synthetic rubber gas mask facepiece compounds was studied during one month to three months' exposure at various temperatures down to −20° F. Progressive stiffening probably due to crystallization was found for natural rubber, GR-I, and GR-M compounds at low temperatures. No tendency to crystallize was noted for the GR-S compound. Of the crystallizable polymers GR-I was the most resistant, and GR-M the least resistant to stiffening during low temperature storage. It is of course evident that different polymers have inherently different degrees of resistance to low temperatures. Disregarding these inherent differences the work reported indicates that the resistance of elastomer compounds to stiffening during prolonged low temperature storage is favored by the following: 1. Use of interpolymers made from monomer mixtures having a relatively large proportion of each component, thus obtaining mutual intereference with crystallization. 2. Use of a “tight” cure which probably so impedes the movement of the polymer chains as to make crystallization difficult.

scholarly journals Complex Temperature and Concentration Dependent Self-Assembly of Poly(2-oxazoline) Block Copolymers

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1495 ◽  
Author(s):  
Loan Trinh Che ◽  
Marianne Hiorth ◽  
Richard Hoogenboom ◽  
Anna-Lena Kjøniksen
Keyword(s):  
High Temperatures ◽  
Self Assembly ◽  
Low Temperatures ◽  
Polymer Concentration ◽  
Random Copolymer ◽  
Polymer Chains ◽  
Relaxation Modes ◽  
Self Association ◽  
Copolymer Structure ◽  
Complex Temperature

The effect of polymer concentration on the temperature-induced self-association of a block copolymer comprising a poly(2-ethyl-2-oxazoline) block and a random copolymer block consisting of 2-ethyl-2-oxazoline and 2-n-propyl-2-oxazoline (PEtO80-block-P(EtOxx-stat-PropO40-x) with x = 0, 4, or 8 were investigated by dynamic light scattering (DLS) and transmittance measurements (turbidimetry). The polymers reveal a complex aggregation behavior with up to three relaxation modes in the DLS data and with a transmittance that first goes through a minimum before it declines at high temperatures. At low temperatures, unassociated polymer chains were found to co-exist with larger aggregates. As the temperature is increased, enhanced association and contraction of the aggregates results in a drop of the transmittance values. The aggregates fragment into smaller micellar-like clusters when the temperature is raised further, causing the samples to become optically clear again. At high temperatures, the polymers aggregate into large compact clusters, and the samples become turbid. Interestingly, very large aggregates were observed at low temperatures when the polymer concentrations were low. The formation of these aggregates was also promoted by a more hydrophilic copolymer structure. The formation of large aggregates with an open structure at conditions where the solvent conditions are improved is probably caused by depletion flocculation of the smaller aggregates.

scholarly journals Phase behavior of light gas mixtures at high pressures

1971 ◽  
Vol 40 ◽  
pp. 363-370 ◽  
Author(s):  
William B. Streett
Keyword(s):  
Phase Behavior ◽  
Structural Model ◽  
High Pressures ◽  
Fluid Layer ◽  
Gas Mixtures ◽  
Solid Surfaces ◽  
Coexisting Phases ◽  
New Hypothesis ◽  
Very High ◽  
Equal Density

If solid surfaces exist beneath the visible clouds of the major planets, they may be expected to exist at depths and pressures at which the component gas mixtures solidify under their own weight. The elucidation of phase behavior in mixtures of light gases at very high pressures is therefore essential to the solution of the problem of deep atmosphere structures in these planets. Available experimental evidence suggests several possible extrapolations of the H2-He phase diagram to high pressures. These have been used to develop a structural model for a H2-He atmosphere. In this model, gravitational separation of coexisting phases results in a layered structure, and it is shown that masses of H2-rich solid can exist in dynamic and thermodynamic equilibrium with a fluid layer of equal density but higher He content. This model forms the basis of a new hypothesis for Jupiter's Red Spot.

scholarly journals Radiation Damage in Ice at Low Temperatures Studied by Proton Channelling

1978 ◽  
Vol 21 (85) ◽  
pp. 247-258 ◽  
Author(s):  
I. Golecki ◽  
C. Jaccard
Keyword(s):  
Energy Loss ◽  
Radiation Damage ◽  
Low Temperatures ◽  
Activation Enthalpy ◽  
Rutherford Backscattering ◽  
Electronic Excitations ◽  
Arrhenius Law ◽  
Random Direction ◽  
Higher Temperature ◽  
Minimum Yield

Abstract 100 keV protons with fluxes between 3 × 1015 and 3 × 1016 m-2 s-1 and in doses up to 4 × 1020 m-2 have been used in ice between - 191°C and -87°C to create damage and to analyse it. The Rutherford backscattering minimum yield along the c-axis (about 0.05 in good monocrystals) increases up to unity with the dose, according to a function which can be scaled by a critical dose depending mainly on temperature (Arrhenius law with activation enthalpy of 0.17 ± 0.04 eV above -185°C). Higher flux produces more damage above -180°C, but less below. A beam in a random direction is more efficient below - 180°C, but less at higher temperature than an aligned beam. Beam-induced reordering is observed at definite temperatures and doses. The damage is shown to be due to energy loss by electronic excitations, which decay and produce disordered molecule clusters, mainly by incoherent aggregation of vacancies and interstitials.

scholarly journals The rigidity of solid unimolecular films

1927 ◽  
Vol 114 (769) ◽  
pp. 690-697 ◽  
Keyword(s):  
Melting Point ◽  
Stearic Acid ◽  
Low Temperatures ◽  
Solid Acid ◽  
Benzene Solution ◽  
Static Method ◽  
Langmuir Trough ◽  
Solid Film ◽  
Small Torque

On evaporation at low temperatures of a benzene solution of palmitic or stearic acid on the surface of water an apparently solid film is left. The experiments of I. Langmuir and N. K. Adam have shown that these films are unimolecular in character, and inasmuch that they possess a fairly well defined melting point, although this varies with the acidity of the underlying solution, we may regard these films as unimolecular sheets of orientated solid acid. Anyone who examines these films even superficially cannot fail to notice their exceptional strength, all the more extraordinary when we consider their extreme thinness. Whilst the compressibility of such films, a property which can be readily determined by examination of the slope of the force area curve obtained with the well-known Langmuir trough apparatus, does not present any unusual features, being of the order anticipated for a hydrocarbon, yet we may expect that the coefficient of rigidity will be unexpectedly high. It seemed a matter of some importance to attempt to measure the rigidity of such films, by applying a suitable torque and determining the displacements effected, a method suggested to us by Prof. G. I. Taylor. In our preliminary experiments we endeavoured to employ a simple static method of placing a disc at the centre of a large circular film and applying torsion by means of a torsion head and wire on the disc to which a mirror is attached. We have to express our thanks to Prof. G. I. Taylor for the loan of an excellent and finely-calibrated head for this purpose. After numerous attempts with various modifications of the method we were reluctantly compelled to abandon it. The results were invariably the same; on applying a small torque to the disc no motion was visible on the image of the mirror attached to the disc. If the torque be increased the film is ruptured and the disc breaks loose and slips, generally forcing itself entirely from attachment to the film. Even with discs coated with wax or corrugated and milled on the circular edge no better results were obtained. Evidently the grip on the disc being only of one molecule thick is not sufficient to hold the slightest movement on the part of the shearing disc.

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