Thermal head

The thermosensitive recording paper itself is white like a plain sheet of paper. With the application of heat by means of a thermal pen or thermal head, the color-forming components in the thermosensitive layer are brought into reactive contact in the area delineated by the heat pattern... 

White pigments such as calcium carbonate, aluminum hydroxide, silica, kaolin, or urea-formaldehyde resin are used as filler. The filler functions as an absorbent of melted components to prevent their adhesion on the thermal head. Thus, the filler is required to be high in oil absorption and not to wear the thermal head. 

Colour formers such as compounds 243 and 245 are not inherently thermochromic. For example, they melt without any change in colour. However, they may be used to generate colour thermally, either irreversibly or reversibly, as composite materials. In thermally sensitive paper, the colour former and an acidic developer, usually a phenol, are dispersed as insoluble particles in a layer of film-forming material. When brought into contact with a thermal head at around 80-120 °C, the composite... 

It appears therefore that during the operation of all usual calorimeters, temperature gradients are developed between the inner vessel and its surroundings. The resulting thermal head must be associated, in all cases, to heat flows. In isoperibol calorimeters, heat flows (called thermal leaks in this case) are minimized. Conversely, they must be facilitated in isothermal calorimeters. All heat-measuring devices could therefore be named heat-flow calorimeters. However, it must be noted that in isoperibol or isothermal calorimeters, the consequences of the heat flow are more easily determined than the heat flow itself. The temperature decrease... 

Using nitrile oxides, various compounds and materials possessing valuable properties have been prepared. Among them are thin-film resistors useful for a thermal head and comprising a nitrile oxide, ruthenium and oxygen, a method for manufacturing the resistor by coating or deposition (529), isoxazole and/or isoxazoline polyheterocyclic systems like 458, which are useful for development of a new class of ionophores (530). 

An adiabatic calorimeter is a calorimeter that has a jacket temperature adjusted to follow the calorimeter temperature so as to maintain zero thermal head, and the test method (ASTM D-2015, ISO 1928) consists of burning the coal sample in the calorimeter, and the jacket temperature is adjusted during the burning so that it is essentially the same as the calorimeter water temperature. The calorific value is calculated from observations made before and after the combustion. In the isothermal method (ASTM D-3286 ISO 1928), the calorific value is determined by burning a weighed sample of coal in oxygen under controlled conditions, and the calorific value is computed from temperature observations made before, during, and after combustion with appropriate allowances made for the heat contributed by other processes. The value computed for the calorific value of coal... 

A variation on these themes allowed Alder and Bellus to realize a thermal head-to-tail [2 + 2] addition of two acrylic units (69 - 70). ... 

In the case of the dynamic method, the constant heat supply to the sample is obtained by maintaining a constant thermal head between the sample and... 

Mr. Lutherer reasoned that the opaque soot particles in luminous flames would increase radiation to furnace loads and refractory crown, and that if clear flames then momentarily replaced them, that would allow the refractory to radiate to the load and dump its accumulated high-thermal-head heat on the load. 

T = temperature t =time K = constant Tq= thermal head w = stirrer correction R = rate of temperature change... 

The graph in Fig. 4.32 and the data in Table 4.2 show a typical example of calorimetry with a liquid calorimeter. The experiment is started at time t, and temperature Tj. The initial rate of heat loss is determined in the drift measurement. If the thermal head of the calorimeter, T , is not far from the calorimeter temperature, a small, linear drift should be experienced. The measurement is started at t2, 2 This process may be combustion, mixing of two liquids, or just dropping a hot or cold sample into the calorimeter. A strong temperature change is noted between tj and tj. 

Graphically, T can be found by assuming that the heat losses change proportionally to the changes in the amplitude of the curve—i.e., T is fixed at a value that makes the two shaded areas of the figure equal in size (note that the thermal head, T, drops out of the calculation). ... 

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