Hot Plate Temperature Research Articles

Recent developments in hot plate welding of thermoplastics

AbstractThis paper considers the hot plate welding process applied to three injection molded thermoplastic materials: polypropylene, high impact polystyrene, and poly(phenylene oxide). Weld quality was assessed by tensile testing. The process was found to be suitable for all three materials, although tolerance to variations in process parameters varied. The parameters in the heating phase, i.e., hot plate temperature and time, were the most important for achieving good welds, whereas parameter variations in the consolidation phase were relatively unimportant.

Dopamine D-1 and D-2 receptor antagonists potentiate analgesic and motor effects of morphine

To examine the role of dopamine receptor subtypes mediating analgesic and motor responses to opioids, rats were pretreated with either saline or a selective D-1 or D-2 dopamine receptor antagonist 10 min prior to morphine (12 mg/kg IP). Analgesic response latency was determined using the hot plate test (52.5°C and 55°C), and catalepsy was assessed using the abnormal posture test. Morphine increased analgesic response latency to 44.5 ± 7.9% of the maximum possible response, but had no cataleptic effect in the abnormal posture test. Pretreatment with either the D-1 antagonist, SCH 23390 (50–100 μg/kg), or the D-2 antagonist, eticlopride (20–150 μg/kg), potently enhanced morphine analgesia as measured on the 52.5°C hot plate. Peak analgesic responses to morphine increased to 100 ± 0% and 91.9 ± 7.5% of maximum with the highest doses of SCH 23390 and eticlopride, respectively. These treatments also produced catalepsy. Increasing the hot plate temperature to 55°C reduced response latency in groups treated with either dopamine receptor antagonist plus morphine. This indicates that the animals were capable of responding at a shorter latency and demonstrates that motor impairment cannot account for potentiation of morphine analgesia by D-1 and D-2 antagonists at 52.5°C. These results show that the relationship between dopamine and opioids with respect to analgesic and motor systems involves both dopamine receptor subtypes.

Effects of lateral hypothalamic lesions on the anorexia induced by ethanolamine-O-sulfate

Intracisternal (IC) injection of the GABA-transaminase inhibitor, ethanolamine-O-sulfate (EOS), has been previously shown to induce dose-dependent anorexia in normal rats as well as to reverse overeating in several rodent models of acute and chronic hyperphagia. To determine if such anorexia might be mediated by cells within or fibers of passage which traverse the lateral hypothalamus (LH), adult female rats received bilateral radiofrequency heat lesions of the LH vs. anesthesia control injections and were allowed to recover normal feeding and drinking responses. Using a longitudinal design, all animals then received 100, 0, and 200 micrograms EOS in 20 microliters deionized water IC with 1 week separating each injection. In addition to daily measures of feeding, drinking and body weight, all animals were screened 24 hr after injections for sensorimotor competence and general health by testing open-field activity, catalepsy, paw-lick responses on a hot-plate and rectal temperature. As reported previously, IC EOS induced dose-dependent hypophagia and weight loss. However, the magnitude and duration of these effects were equivalent in lesioned and control rats. In addition, open-field activity and body temperature were reliably lowered as a function of dosage while catalepsy was increased. Again, this effect was equivalent in lesioned and control rats. Subsequent tests of drinking and feeding in response to hyperosmotic and hypoglycemic challenges, respectively, confirmed that lesioned rats were deficient compared to controls. These findings suggest that an intact LH axis is not required for the anorexigenic effects of IC EOS.

Acute and chronic treatment with selective serotonin uptake inhibitors in mice: effects on nociceptive sensitivity and response to 5-methoxy- N, N-dimethyltryptamine

The tail-flick and increasing temperature hot-plate tests were employed to study the effects of acute or chronic treatment with zimelidine, alaproclate or chlorimipramine on nociception and response to 5-methoxy- N, N-dimethyltryptamine (5-MeODMT) in mice. A single dose of the serotonin (5-HT) uptake inhibitors produced antinociception in the hot-plate test but not in the tail-flick test. After chronic administration, reduced tail-flick latencies were demonstrated 24, 48, 72 and 144 h after withdrawal of zimelidine treatment, 48 h after withdrawal of alaproclate and 48 and 96 h after withdrawal of chlorimipramine treatment. The hot-plate response temperatures were slightly lowered after chronic zimelidine treatment but not after treatment with alaproclate or chlorimipramine. The response to 5-MeODMT was not altered by a single dose of the 5-HT uptake inhibitors, however, after withdrawal of chronic treatment this response was increased in the tail-flick test but not in the hot-plate test. It was concluded that acute and chronic treatment with 5-HT uptake inhibitors modulate nociception differently, and that chronic treatment induces supersensitivity of spinal postsynaptic 5-HT receptors. Different modulation of different 5-HT receptor subpopulations by these compounds may possibly contribute to the test-dependent results.

The hot plate welding of high-density polyethylene

The application of statistical modelling techniques is illustrated in the context of an investigation into the hot plate welding of high density polyethylene. A second-degree polynomial was used as an approximation to the true but unknown response function relating the quality of a weld to variables such as hot plate temperature or heating time. The coefficients of the model were estimated using the results from a series of experimental runs, with control variable settings selected according to a composite rotatable design; the fit of the model was improved by transformation of the response variable.

Thermal Conductivity Measurement with the Plate Apparatus: Influence of the Guard Ring Width on the Accuracy of Measurement

The temperature field in circular and square plate test specimens is calculated and thereby the error from the heat exchange at the outer edge of the guard ring derived for single and double plate devices contact. The error is shown to be proportional to the reduced temperature difference (difference between the mean specimen and the ambient temperatures divided by the difference between the hot and cold plate tem peratures) and the margin of error, therefore, can be optimally reduced by an appro priate adjustment in the ambient temperature. Experiments on an extruded foam confirm the results of the analytical calculations. Diagrams and tables which are de veloped on the basis of the above derived relationships make possible estimation of margin of error for different measuring arrangements for plate devices of usual sizes.

Effect of hot plate temperature on the antinociceptive activity of mixed opioid agonist‐antagonist compounds

AbstractThe effects of four different hot plate temperatures (49.5, 53, 55, and 60°C) on the antinociceptive activity of butorphanol, nalbuphine, pentazocine, and morphine were determined. Antinociception, as measured by an increase in percent maximum possible effect (%MPE) derived from time to paw lick in mice increased with dose for all compounds except nalbuphine at all temperatures. Nalbuphine elicited activity (50% MPE) at one dose (3 mg/kg) at 49.5°C. Butorphanol, 10 mg/kg, and pentazocine, 10 mg/kg, produced 100% MPE and 80% MPE at 49.5°C and 53°C, respectively. Only morphine (20 mg/kg) produced 100% MPE at all temperatures. Since every compound exhibited antinociceptive activity at 49.5°C at some dose below toxicity, it is suggested that this is the preferred temperature to screen for mixed opioid compounds.

Hot-plate alloying for ohmic contacts to GaAs

The fabrication and optimization of ohmic contacts to GaAs prepared by heating the wafers on a hot plate is described. The method offers high throughput and is production adaptable. The apparatus consists of a hot plate constructed of a heat pipe with a high surface temperature uniformity (±2°C over 4-in diameter) located inside a glove box with an ambient controlled to 5 percent H 2 /95 percent N 2 forming gas. Specific resistance and morphology of AuGe/Ni/Au contacts were characterized as a function of hot-plate surface temperature. At the optimum alloy temperature, specific resistances of less than 10-6Ω-cm2were obtained repeatably for VPE GaAs with active layers of n ∼ 1017cm-3and thicknesses of ∼0.4 µm as well as for VPE GaAs with an n+surface layer greater than 1018cm-3. The contact surface morphologies were smoothest for those alloyed at temperatures below the optimum, and, for those alloyed at or above the optimum, they were increasingly less smooth for increasingly higher alloy temperatures. A general discussion of this method's potential application to high-volume GaAs processing is given.

Minimum ignition temperature of a self-raising flour on a standard hot-plate

A hot-plate to the draft specification of the International Electrotechnical Commission (Committee 31H) was constructed and located in a chamber with an air extractor and a transparent door. A commercial self-raising flour was tested to assess the relationship between minimum ignition temperature (MIT) and layer depth (5–40 mm in steps of 5 mm). MIT varied from 311°C for 5 mm to 265°C for 20 mm and to 238°C for 40 mm layers. The results fitted the relationship ln ( δ cT 2 r 2 )= M − ( N T ) , with a correlation coefficient of 0·994 for 4 points above the recommended minimum ratio of sample diameter-to-depth of 5:1 and 0·995 for 8 points above the ratio of 2·5:1. The latter relationship had a slightly flatter slope than the former. The variation in results from the two lines was examined. It is recommended for self-raising flour that more reliable results are obtained from 15 mm layer depth than 5 mm because of the tendency of the latter layers to buckle and crack under test. Relationships between hot plate temperature and (a) time taken for layer to reach plate temperature, (b) maximum temperature generated in sample and (c) percent residue after each test, were obtained for the 15 mm layer at plate temperatures up to 410°C.

Transient and steady state supersaturation in a thermal diffusion cloud chamber

A theoretical analysis of transient and steady state supersaturation distribution inside a thermal diffusion type cloud nuclei counter is presented for simulation of cloud in the laboratory and also for the measurement of cloud nuclei spectra. Solutions of one-dimensional partial differential equations of water vapour diffusion and heat conduction under appropriate initial and boundary conditions are used in this analysis. The height of the chamber is taken as 2.5 cm in which top and bottom plate temperatures are 35 and 30°C respectively. The lower surface temperature corresponds to a typical average environmental temperature of Poona. Different cases of sample entry are discussed. Analysis shows that transient super-saturation exceeding the steady state value arises if the incoming sample is colder than the hot top plate temperature and saturated at that temperature. Transient subsaturation is created initially inside the diffusion chamber when the sample is saturated at the top plate temperature. The chamber passes gradually from a state of transient subsaturation to steady state supersaturation when the incoming air sample is maintained at either top plate or bottom plate temperature and having certain relative humidity. Operation of the chamber under the above non-steady state conditions can introduce large unpredictable errors into the measurement of cloud nuclei spectra, particularly when the incoming air sample is saturated and colder than the top-plate temperature.

Effects of heat-stress on behavior and the pituitary adrenal axis in rats

Three experiments were performed in order to analyse the behavioral and biochemical correlates of four different intensities of the same stressor. In experiment 1, rats were exposed to heat stress (hot-plate) of varying temperatures for 30 seconds. Activity was recorded in an open field immediately after stress for 30 minutes. The data revealed that the milder temperatures increased (21, 47, 52°C), while the higher temperature (57°C) decreased activity. Experiment 2 assessed the pituitary-adrenal response to the different temperatures by measuring levels of plasma corticosterone 30 minutes after stress. The four levels of hot-plate temperatures induced differential levels of corticosterone which may best be described as an inverted U-shaped function, with only the extreme temperature (57°) inducing a significant elevation in levels of the steroid. Experiment 3 further manipulated the pituitary adrenal axis by administering dexamethasone 25 hr and 1 hr before stress and ACTH 15 min before stress. Both affected activity levels by depressing locomotion regardless of the stress intensity. These results are compared to other studies that have addressed the question of stress-induced activation and it is suggested that stress is not a unitary concept, but interacts with the performance of certain behaviors to produce both facilatory or inhibitory results.

Wärmeleitfähigkeitsmessungen mit dem Plattengerät: Einfluβ der Schutzringbreite auf die Meβunsicherheit

The temperature field in circular and square plate test specimens is calculated and thereby the error from the heat exchange at the outer edge of the guard ring derived for single and double plate devices under conditions of isothermal hot and cold plates and ideal thermal contact. The error is shown to be proportional to the reduced temperature difference (difference between the mean specimen and the ambient temperatures divided by the difference between the hot and cold plate temperatures) and the margin of error, therefore, can be optimally reduced by an appropriate adjustment in the ambient temperature. Experiments on an extruder foam confirm the results of the analytical calculations. Diagrams and tables which are developed on the basis of the above derived relationships, make possible estimation of margin of error for different measuring arrangements for plate devices of usual sizes.

Hot plate welding of plastics: Factors affecting weld strength

AbstractWelded joints were made under a range of conditions in polypropylene, glass fiber reinforced polypropylene and poly (methylmethacrylate) bars. Melt flow in the weld was investigated by microscopy and by contact microradiography, and weld strengths were measured by tensile tests. The fracture toughness of the weld zone was determined by tests on double edge notched specimens. The study shows that weld strength is strongly affected by hot plate temperature, heating time and melt flow during welding. Insufficient heating or melt flow results in incomplete bonding. Excessive melt flow produces strong transverse orientation. Both reduce strength, but in different ways, which can be distinguished by fracture mechanics tests.

Elevated Ion Temperature in a Double-Ended Q Machine

The perpendicular ion temperature of a barium plasma contained in a double-ended Q machine has been measured by a spectroscopic technique. When the plasma is “ion-rich”, good agreement is found between the measured ion temperature and the hot-plate temperature, while in the “electron-rich” regime, the ion temperature is elevated above the hot-plate temperature. The increased ion temperature can be well accounted for by the energy input through the acceleration of ions through the electron sheath and their consequent thermalization.

Optical measurement of the ion temperature in a barium Q plasma

The ion temperature in a single-ended barium Q machine has been determined optically, with and without current drawn through the machine. Ion temperatures which were consistent or slightly higher than the hot-plate temperature of 0.25 eV rose to 5–7 eV when an electron drift was initiated. The ion temperature rose to 1 eV if an ion current was drawn along the column. These phenomena are independent of magnetic field.

Heat Transfer by Natural Convection through V-Corrugated Plates

An experimental investigation is performed on natural convection heat transfer through a square enclosure of V-corrugated vertical plates. The objective of this investigation is to study the variation of heat transfer rate through the square enclosure with the variation of both hot and cold plate temperatures. Hot plate temperature is varied by heat input. To vary cold plate temperature two parameters are considered: one is mass flow rate of water used to remove heat from cold plate and the other is the inlet temperature of water. Air is the media to transfer heat from the hot V-corrugated plate to cold V-corrugated plate. The result shows that the increase of mass flow rate increases the heat transfer rate and the decrease of water inlet temperature increases the heat transfer rate.Journal of Mechanical Engineering Vol.36 Dec. 2006 pp.1-5DOI = 10.3329/jme.v36i0.804

1633. Experimental study of radiative heat transfer between parallel plates.: T J Love and J S Gilbert, Rep ARL-66-0103; AD-643307, June 1966, ( Oklahoma Univ Norman).

Abstract : An apparatus was constructed for the experimental determination of radiative heat transfer between parallel plates. Two plates, approximately twelve inches square, were mounted in a vacuum system. One plate was electrically heated and the other was cooled by circulating water. A guarded heater section was constructed at the center of the hot plate so that the radiative flux at the center could be metered. The distance separating the plates was adjustable. Both plates were faced with prepared stainless steel in order to standardize the measurements. The surface was sandblasted so that the radiation was approximately diffuse. Measurements were made over a range of hot plate temperatures ranging up to approximately 750F. Plate spacings ranged from 0.5 inches to 3.0 inches. Measurements were in good agreement with computations based on the assumption of infinite gray plates for the 0.5 inch spacing. By enclosing the edges of the plates with foil reflectors, the measurements indicated agreement with the infinite gray plate assumption at 1.0 inch separation and reasonable agreement to 3.0 inch separation. Use of the apparatus for measurement of radiative heat transfer between the plates with a cloud of scattering dust separating the plates is discussed. (Author)

On the analysis of linear pyrolysis experiments

Linear pyrolysis experimental data have been used as surface boundary conditions in the analytical treatment of solid propellant combustion problems. The surface boundary conditions required for the analysis are functional relationships between normal regression velocity, gaseous reactant density, total pressure, temperature, and possibly derivatives of these quantities as well, evaluated at the interface between condensed and gaseous phases during combustion. Available experimental data indicates that a relation based upon equilibrium conditions prevailing at the interface is not generally valid. There are available for many substances, however, hot-plate linear pyrolysis data which give an explicit relation between regression velocity of the condensed phase and a measured hot-plate temperature. This hot-plate temperature has been assumed to be also the temperature at the interface. However, this assumption is thought in some cases to be questionable. In addition, the use of such a rate law in combustion analysis would imply that the total pressure and the gascous reactant partial pressures or densities, which are greatly different for the pyrolysis test as compared to the combustion, have a negligible effect on the rate. This implication again is questionable. The present paper seeks to answer in part these questions on the validity of using linear pyrolysis data. A one-dimensional hot-plate linear pyrolysis experiment is proposed which uses a porous heated plate in place of the present impervious plate. The proposed experiment, having simpler fluid dynamics than present hot-plate experiments, is capable of a reasonably precise analytical description. The analysis is carried out for a general case and is then specialized to simple and chainlike surface gasification processes. Conditions are developed to determine whether the surface process is either a rate process or is one of near-equilibrium. A description is presented of the possible use of data from the proposed pyrolysis experiments to compute the accommodation coefficient and the vacuum sublimation rate as functions of surface temperature. With this information, the surface boundary condition for a given material will then be specified. The pyrolysis rate of potassium chloride is calculated as an example of the use of the derived formulas. If fluid dynamic effects are not too important in the present experiments, and in some respects it is estimated that they are not, interpretation from the results of this analysis serves present pyrolysis data as well. Interpretations are carried out for a number of compounds which have interest in propellant combustion studies. From published data on ammonium perchlorate, for example, revised values are estimated for the heat of sublimation, for the activation energy in linear pyrolysis, and for the difference between the hot-plate temperature and the surface temperature in linear pyrolysis.