Properties of Hard Rubber. XIII. Experiments on Thermal Effects during Vulcanization

1944 ◽  
Vol 17 (4) ◽  
pp. 923-928
Author(s):  
H. F. Church ◽  
H. A. Daynes
Keyword(s):  
Thermal Effects ◽  
Thermal Instability ◽  
Exothermic Reaction ◽  
Limiting Factors ◽  
High Grade ◽  
Internal Temperature ◽  
Internal Heating ◽  
Open Steam ◽  
Safe Thickness ◽  
Platen Temperature

Abstract The characteristics and technical importance of the internal heating effect during the vulcanization of hard rubber, due to the exothermic reaction between rubber and sulfur, are recalled, and the conditions under which thermal instability may occur are outlined. The necessity of avoiding even slight increases in internal temperature when vulcanizing material for research purposes is emphasized. Experiments are described in which sheets of rubber-sulfur mixings of various thicknesses were vulcanized in a platen press at various temperatures, and the internal and surface temperatures were measured throughout the vulcanization period by means of thermocouples. The time-temperature curves are reproduced. The relations between internal temperature rise, platen temperature, and thickness of sheet are indicated. The choice of maximum safe thickness for a given platen temperature or of maximum safe platen temperature for a given thickness is shown to be very critical. The rise of temperature is greater in open steam vulcanization than in press-vulcanization, for a reason which is pointed out. It is important that these limiting factors in the use of high-grade rubber-sulfur materials should be taken into account in designing hard rubber articles.

Nitride-Related Compounds Preparation from Waste Aluminum Dross by Self-Propagating High-Temperature Process

2005 ◽  
Vol 486-487 ◽  
pp. 297-300
Author(s):  
Jae Ryeong Lee ◽  
Ikkyu Lee ◽  
Hee Young Shin ◽  
Jong Gwan Ahn ◽  
Dong Jin Kim ◽  
...  
Keyword(s):  
Exothermic Reaction ◽  
Combustion Products ◽  
Low Grade ◽  
High Grade ◽  
Nitrogen Gas ◽  
Aluminum Dross ◽  
High Temperature Process ◽  
Al Powder ◽  
In The Beginning ◽  
Related Compounds

Nitride-related compounds containing AlN and AlON were synthesized from aluminum dross using a combustion reaction, irrespective of the content of Al in Al-dross. The formation of AlON is induced by the exothermic reaction between Al and nitrogen. On the occasion of using high-grade dross, unreacted Al was detected in the combustion products. This may be originated from Al in the dross because Al in dross exists in the dispersed oxide layer. Therefore, its reactivity with nitrogen is relatively lower, compared to Al powder mixed with the dross in the beginning. It is noted that, on the occasion of using low-grade dross, unreacted Al in the product can be controlled by means of adjusting particle size of dross, resulting in improvement of the permeation of nitrogen gas into the compact through the well established open pore channels.

Thermal instability in a star—gas system

1995 ◽  
Vol 54 (2) ◽  
pp. 157-172 ◽  
Author(s):  
S. P. Talwar ◽  
M. P. Bora
Keyword(s):  
Heat Loss ◽  
Thermal Effects ◽  
Thermal Instability ◽  
Composite System ◽  
Stellar Dynamics ◽  
Mhd Equations ◽  
Temperature Dependent ◽  
Gas System ◽  
The Stability ◽  
Loss Mechanisms

A composite interstellar model consisting of stars and optically thin radiating plasma is considered in order to investigate the thermal instability arising from possible radiation and other heat-loss mechanisms. The stellar dynamics is governed by the Vlasov equation, while the gas is supposed to be a hydromagnetic plasma, described by the MHD equations, with a density- and temperature-dependent heat-loss function. It is shown that while with cold stars the system is in general unstable irrespective of thermal effects of the plasma, with warm stars having a Maxwellian distribution the thermal plasma considerably influences the stability of the composite system. It is also shown that the otherwise stable composite (with warm stars) configuration may become unstable in the presence of a radiating plasma because of coupling between the heat-loss mechanisms and stellar populations.

Application of the image-force model to the theory of contact rectification and of rectifier breakdown

1951 ◽  
Vol 207 (1089) ◽  
pp. 156-181 ◽  
Keyword(s):  
Thermal Instability ◽  
Diffusion Theory ◽  
Electronic Conductivity ◽  
Image Force ◽  
Limiting Factors ◽  
Force Model ◽  
Current Voltage ◽  
Intrinsic Conduction ◽  
Subsequent Rise ◽  
Good Agreement

The assumptions underlying the current diffusion theory of rectification are critically examined. By replacing the familiar step-like potential distribution at the rectifying junction by one with a more gradual rise in potential, the theory is extended to cover the range of high inverse voltages, where existing theories fail. On the application of an inverse voltage the height of the barrier is reduced and the leakage current increases. The subsequent rise in temperature in turn causes a further increase in current. With sufficiently high inverse voltages this process can eventually lead to the onset of intrinsic conduction or to thermal instability long before the barrier has been reduced completely. By way of example, the theory is applied to the selenium plate rectifier. It is found possible to choose a consistent set of parameters giving an inverse current/voltage characteristic in good agreement with experiment. Hysteresis as well as a number of certain phenomena observed on breakdown can be explained on the assumption of weak spots in the barrier. The theory predicts the onset of thermal instability with reasonable accuracy. As this instability is one of the limiting factors of rectifier operation it is shown that the choice of materials which make up useful rectifying junctions is restricted to those combining a reasonably large barrier height with a fairly low electronic conductivity of the semi-conductor.

Countermeasures combined with thermosyphons against the thermal instability of high-grade highways in permafrost regions

2020 ◽  
Vol 153 ◽  
pp. 119047 ◽  
Author(s):  
Zhongrui Yan ◽  
Mingyi Zhang ◽  
Yuanming Lai ◽  
Wansheng Pei ◽  
Tao Luo ◽  
...  
Keyword(s):  
Thermal Instability ◽  
High Grade ◽  
Permafrost Regions

A Model of Optimization and Control the Thermite Kit for Aluminothermic Welding

2016 ◽  
Vol 254 ◽  
pp. 83-90
Author(s):  
Mihai Branzei ◽  
Mihai Ovidiu Cojocaru ◽  
Tudor Adrian Coman ◽  
Ovidiu Vascan
Keyword(s):  
Iron Oxides ◽  
Thermal Effects ◽  
Exothermic Reaction ◽  
Exothermal Reaction ◽  
Aluminium Powder ◽  
Aluminothermic Reaction ◽  
Optimization And Control ◽  
Effect Of Particle Size ◽  
And Control ◽  
Heat Amount

Thermite welding (TW) is now widely used all over the world to weld, maintenance and modernization railway and tram rails [1]. The main materials from the thermite composition (TC), results from manufacturing scraps, which can be retrieved all over the country. Exothermic welding (EW) which is based on the exothermal reaction between iron oxides (FeO, Fe2O3 and Fe3O4) and aluminium powder, takes place at temperatures up to 3500 °C and during casting rail ends are melted in order to be welded.In was studied the thermal effects of the aluminothermic reduction reactions of the iron oxides, which were dosed in different percentages. The aluminothermic reaction efficiency is given by strictness in the ratio of the TC selection and mainly in the iron oxides types. Their correct dosage makes possible the control the exothermic reaction (ER) effect. Also it is revealed the effect of particle size from thermite powder (TP) on the thermite dynamics reactions. Is also presented a model of optimization and control the thermite kits (TK) for aluminothermic welding (AW). Finally, the TK composition can be calculated from "QUARK1" Diagram, as function of the heat amount necessary for the welding.

Thermal Instability in High-Speed Gearing

1961 ◽  
Vol 83 (1) ◽  
pp. 91-103 ◽  
Author(s):  
W. P. Welch ◽  
J. F. Boron
Keyword(s):  
Thermal Expansion ◽  
Steady State ◽  
Experimental Verification ◽  
Thermal Effects ◽  
High Speed ◽  
Thermal Instability ◽  
Point Of View ◽  
State Point

Thermal-expansion effects in gearing have usually been considered from a steady-state point of view. A theory of thermal instability is developed which takes into account the tendency of the thermal effects to be regenerative. This theory provides an adequate and complete explanation for several previously unexplained cases of tooth failure in high-speed high-horsepower reduction gears. Experimental verification of the theory is presented and some of the conditions for avoiding thermal instability are described.

Thermal instability in drawing viscous threads

2007 ◽  
Vol 570 ◽  
pp. 1-16 ◽  
Author(s):  
JONATHAN J. WYLIE ◽  
HUAXIONG HUANG ◽  
ROBERT M. MIURA
Keyword(s):  
Steady State ◽  
Thermal Effects ◽  
Thermal Instability ◽  
Radiative Heat ◽  
Physical Mechanism ◽  
Surprising Result ◽  
Downstream Location ◽  
The Stability ◽  
Steady State Solutions ◽  
Oscillatory Instabilities

We consider the stretching of a thin viscous thread, whose viscosity depends on temperature, that is heated by a radiative heat source. The thread is fed into an apparatus at a fixed speed and stretched by imposing a higher pulling speed at a fixed downstream location. We show that thermal effects lead to the surprising result that steady states exist for which the force required to stretch the thread can decrease when the pulling speed is increased. By considering the nature of the solutions, we show that a simple physical mechanism underlies this counterintuitive behaviour. We study the stability of steady-state solutions and show that a complicated sequence of bifurcations can arise. In particular, both oscillatory and non-oscillatory instabilities can occur in small isolated windows of the imposed pulling speed.

A Review of Journal Bearing Thermal Effects on Rotordynamic Response

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Dongil Shin ◽  
Jongin Yang ◽  
Xiaomeng Tong ◽  
Junho Suh ◽  
Alan Palazzolo
Keyword(s):  
Thermal Effects ◽  
High Performance ◽  
Thermal Instability ◽  
Reynolds Equation ◽  
Dynamic Properties ◽  
Critical Role ◽  
Journal Bearings ◽  
Constant Viscosity ◽  
Bearing Design ◽  
Dynamics Models

Abstract Traditional analysis of journal bearings assumed a constant viscosity which simplified the solutions for static and dynamic characteristics and responses. Today's high-performance machinery requires more accurate models wherein temperature and viscosity distributions in the film must be calculated. Thermal effects in journal bearings have a strong influence on both static and dynamic properties, and consequently play a critical role in determining rotor-bearing system performance. This paper presents an extensive survey of the thermal modeling methods and effects in journal bearings. The subjects include various bearing types, and recent progress in thermal bearing design and thermal instability problems observed in fluid and gas film hydrodynamic bearings. The extent of the survey ranges from conventional Reynolds equation models to more advanced computational fluid dynamics models.

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