Inhibition of Crystallization of Rubber by High Pressure

1939 ◽  
Vol 12 (3) ◽  
pp. 496-497 ◽  
Author(s):  
R. B. Dow
Keyword(s):  
High Pressure ◽  
Pressure Measurement ◽  
Atmospheric Pressure ◽  
Isopropyl Alcohol ◽  
Amorphous State ◽  
Time Curve ◽  
Temperature Range ◽  
The Press ◽  
Pressure Changes ◽  
Manganin Gauge

Abstract Bekkedahl has shown that crude rubber at atmospheric pressure freezes in the temperature range from −40° to + 10°C. and melts in the temperature range from 6° to 16° C. The transition is from amorphous rubber to crystalline rubber which is the stable modification between −72° and 6° C. His measurements of the freezing at 0° C. showed that about 280 hours were necessary for completion of the transition, the volume decreasing by 2.2 per cent in such a manner that the volume-time curve was S-shaped. This communication reports the inhibition of crystallization at high pressure. Crude smoked sheets were packed tightly in a pressure chamber and isopropyl alcohol was used to transmit the pressure. The chamber was kept at 0° C. in a well-circulated ice bath. A pressure of 8000 kg. per sq. cm. was applied, and its constancy observed over a period of 14 days. The sensitivity of the manganin gauge used for pressure measurement was such that changes of 5 kg. per sq. cm. were detectable. Outside of slight erratic pressure changes caused by change of temperature around part of the press that was not kept at 0°, “no change of pressure due to crystallization was detected during the 14 days.” Examination of the rubber immediately after pressure was released showed that it was still in the amorphous state.

scholarly journals Polymer matrix ferroelectric composites under pressure: Negative electric capacitance and glassy dynamics

2019 ◽  
Vol 42 (9) ◽  
Author(s):  
Szymon Starzonek ◽  
Aleksandra Drozd-Rzoska ◽  
Sylwester J. Rzoska ◽  
Kena Zhang ◽  
Emilia Pawlikowska ◽  
...  
Keyword(s):  
High Pressure ◽  
Relaxation Time ◽  
Barium Strontium Titanate ◽  
Atmospheric Pressure ◽  
Polyvinylidene Difluoride ◽  
Broadband Dielectric Spectroscopy ◽  
Electric Capacitance ◽  
Barium Strontium ◽  
Spectroscopy Studies ◽  
Pressure Changes

Abstract. This report presents the results of high-pressure and broadband dielectric spectroscopy studies in polyvinylidene difluoride (PVDF) and barium strontium titanate (BST) microparticles composites (BST/PVDF). It shows that the Arrhenius behaviour for the temperature-related dynamics under atmospheric pressure is coupled to Super-Arrhenius/Super-Barus isothermal pressure changes of the primary relaxation time. Following these results, an explanation of the unique behaviour of the BST/PVDF composite is proposed. Subsequently, it is shown that when approaching the GPa domain the negative electric capacitance phenomenon occurs. Graphical abstract

Absolute Viscosity of Air down to Cryogenic Temperatures and up to High Pressures

1973 ◽  
Vol 15 (4) ◽  
pp. 266-270 ◽  
Author(s):  
B. Latto ◽  
M. W. Saunders
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Atmospheric Pressure ◽  
High Pressures ◽  
The Other ◽  
Cryogenic Temperatures ◽  
Temperature Range ◽  
Absolute Viscosity ◽  
Correlating Equations ◽  
Better Than

The absolute viscosity of gaseous air was determined experimentally for the general pressure and temperature range 100–15 000 kPa and 90–400 K respectively, using a series capillary transpiration-type viscometer which has been developed by the authors. The accuracy of the experimental data is believed to be better than ± 1 per cent. Two general correlating equations, one for atmospheric pressure and the other for medium high pressure (i.e., densities up to 400 kg/m3), have been obtained.

Cyclone Bomb hits Southern Brazil in 2020

2020 ◽  
Vol 3 (3) ◽  
Author(s):  
Ricardo Gobato ◽  
Alireza Heidari
Keyword(s):  
High Pressure ◽  
Atmospheric Pressure ◽  
High Speed ◽  
Satellite Images ◽  
The State ◽  
Southern Brazil ◽  
Santa Catarina ◽  
High Area ◽  
South Of Brazil ◽  
Rapid Drop

An “explosive extratropical cyclone” is an atmospheric phenomenon that occurs when there is a very rapid drop in central atmospheric pressure. This phenomenon, with its characteristic of rapidly lowering the pressure in its interior, generates very intense winds and for this reason it is called explosive cyclone, bomb cyclone. With gusts recorded of 116 km/h, atmospheric phenomenon – “cyclone bomb” (CB) hit southern Brazil on June 30, the beginning of winter 2020, causing destruction in its influence over. One of the cities most affected was Chapecó, west of the state of Santa Catarina. The satellite images show that the CB generated a low pressure (976 mbar) inside it, generating two atmospheric currents that moved at high speed. In a northwest-southeast direction, Bolivia and Paraguay, crossing the states of Parana and Santa Catarina, and this draft that hit the south of Brazil, which caused the destruction of the affected states.  Another moving to Argentina, southwest-northeast direction, due to high area of high pressure (1022 mbar). Both enhanced the phenomenon.

Atmospheric pressure changes in the Arctic from 1801 to 1920

2012 ◽  
Vol 33 (7) ◽  
pp. 1730-1760 ◽  
Author(s):  
Rajmund Przybylak ◽  
Przemysław Wyszyński ◽  
Zsuzsanna Vízi ◽  
Joanna Jankowska
Keyword(s):  
Atmospheric Pressure ◽  
The Arctic ◽  
Pressure Changes

scholarly journals Comparison of bacterial microleakage of three bioactive endodontic sealers in simulated underwater diving and aviation conditions

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Mehdi Dastorani ◽  
Behnam Malekpour ◽  
Mohsen AminSobhani ◽  
Mohammadsadegh Alemrajabi ◽  
Arezoo Mahdian ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Mineral Trioxide Aggregate ◽  
In Vitro Study ◽  
Chi Square ◽  
Custom Made ◽  
Single Cone ◽  
Registration Number ◽  
Chi Square Test ◽  
Pressure Changes

Abstract Background Bacterial microleakage is an important cause of apical periodontitis and endodontic treatment failure. This study aimed to assess the bacterial microleakage of nano-mineral trioxide aggregate (nano-MTA) as a sealer, Endoseal MTA, and GuttaFlow Bioseal sealers in atmospheric pressure, and simulated underwater diving and aviation conditions. Methods In this in vitro, experimental study, 180 extracted single-rooted teeth were cleaned and shaped, and were then randomly divided into three groups for single-cone obturation using Endoseal MTA, GuttaFlow Bioseal, or nano-MTA as a sealer. Each group was then randomly divided into three subgroups, and subjected to ambient atmospheric pressure, 2 atm pressure (to simulate underwater diving), and 0.5 atm pressure (to simulate aviation) using a custom-made pressure chamber. The teeth then underwent microbial leakage test using Streptococcus mutans (S. mutans), and the percentage of samples showing microleakage was recorded for up to 1 month, and analyzed using the Chi-square test. Results The three sealer groups were significantly different regarding bacterial microleakage (P < 0.05). The nano-MTA group showed significantly higher microleakage after 15 days than the other two groups (P = 0.006). The effect of pressure on bacterial microleakage was not significant in any sealer group (P > 0.05). Conclusion Within the limitations of this in vitro study, it may be concluded that single-cone obturation technique using nano-MTA as a sealer results in lower resistance to bacterial microleakage compared with the use of GuttaFlow Bioseal, and Endoseal MTA. Pressure changes in simulated underwater diving and aviation conditions had no significant effect on bacterial microleakage. Trial Registration Number This is not a human subject research.

Transformation of 1-Butene over Synthetic Zeolites

1992 ◽  
Vol 57 (4) ◽  
pp. 869-881 ◽  
Author(s):  
Italo Ferino ◽  
Roberto Monaci ◽  
Vincenzo Solinas ◽  
Lucio Forni ◽  
Antonio Rivoldini ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Continuous Flow ◽  
Liquid Mixture ◽  
Isomerization Reaction ◽  
Reaction Conditions ◽  
Title Reaction ◽  
Y Zeolites ◽  
Temperature Range ◽  
Flow Microreactor ◽  
Synthetic Zeolites

The behaviour of several zeolites as catalysts for the title reaction has been investigated by means of a continuous flow microreactor. Runs performed at atmospheric pressure indicated that at 423 K the completely protonic forms of the zeolites catalyze just the isomerization reaction. In the case of Y zeolites, oligomerization occurs only over the partially decationated samples, in the temperature range between 373 and 423 K and W/F between 0.2 and 22 gcath/g1-but, to an extent which depends on the reaction conditions. Most of the catalysts were tested also under pressure (4.05 MPa) at 423 K. The protonic forms of Y and ZSM-5 zeolites seem promising catalysts in terms of both conversion and selectivity to oligomers. The 1-olefins account for 30% of the entire olefinic mixture. The octenes, which account for 70% of the liquid mixture, are mostly formed of dimethylhexenes. Trimers are also formed during the reaction and, in the very particular case of H[B]ZSM-5, tetramers are produced.

The Effect of Ge Segregation on Oxidation of Si

1987 ◽  
Vol 105 ◽  
Author(s):  
E. C. Frey ◽  
N. R. Parikh ◽  
M. L. Swanson ◽  
M. Z. Numan ◽  
W. K. Chu
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Epitaxial Layer ◽  
Atmospheric Pressure ◽  
Oxidation Rate ◽  
Oxidation Temperature ◽  
Pressure Oxidation ◽  
Enhanced Oxidation ◽  
High Pressure Oxidation

AbstractWe have studied oxidation of various Si samples including: Ge implanted Si, CVD and MBE grown Si(0.4–4% Ge) alloys, and MBE grown Si-Si(Ge) superlattices. The samples were oxidized in pyrogenic steam (800–1000°C, atmospheric pressure) and at low temperature and high pressure (740°C, 205 atm of dry O2). The oxidized samples were analyzed with RBS/channeling and ellipsometry.An enhanced oxidation rate was seen for all Ge doped samples, compared with rates for pure Si. The magnitude of the enhancement increased with decreasing oxidation temperature. For steam oxidations the Ge was segregated from the oxide and formed an epitaxial layer at the Si-SiO2 interface; the quality of the epitaxy was highest for the highest oxidation temperatures. For high pressure oxidation the Ge was trapped in the oxide and the greatest enhancement in oxidation rate (>100%) was observed.

Wide-Temperature-Range Dielectric Permittivity Measurement under High Pressure

2017 ◽  
Vol 34 (4) ◽  
pp. 040701
Author(s):  
Zhen Yuan ◽  
Jin-Long Zhu ◽  
Shao-Min Feng ◽  
Chang-Chun Wang ◽  
Li-Juan Wang ◽  
...  
Keyword(s):  
High Pressure ◽  
Dielectric Permittivity ◽  
Wide Temperature Range ◽  
Temperature Range ◽  
Permittivity Measurement

scholarly journals Supershort avalanche electron beam generation in gases

2008 ◽  
Vol 26 (4) ◽  
pp. 605-617 ◽  
Author(s):  
V.F. Tarasenko ◽  
E.H. Baksht ◽  
A.G. Burachenko ◽  
I.D. Kostyrya ◽  
M.I. Lomaev ◽  
...  
Keyword(s):  
High Pressure ◽  
Electron Beam ◽  
Atmospheric Pressure ◽  
Electron Beams ◽  
Solid Angle ◽  
Generation Mechanism ◽  
Full Width ◽  
Half Maximum ◽  
Electron Beam Pulse ◽  
Supershort Avalanche Electron Beam

AbstractThis paper reports on the properties of a supershort avalanche electron beam generated in the air or other gases under atmospheric pressure and gives the analysis of a generation mechanism of supershort avalanche electron beam, as well as methods of such electron beams registration. It is reported that in the air under the pressure of 1 atm, a supershort (<100 ps) avalanche electron beam is formed in the solid angle more than 2π steradian. The electron beam has been obtained behind a 45 µm thick Al-Be foil in SF6 and Xe under the pressure of 2 atm, and in He, under the pressure of about 15 atm. It is shown that in SF6 under the high pressure (>1 atm) duration (full width at half maximum) of supershort avalanche electron beam pulse is about 150 ps.

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