Thermal history studies

When power cables are energised, some heating takes place as a result of resistive and other effects. Cables are therefore designed with these effects in mind and such that they can accommodate the rated load for the circuit without overheating and consequent accelerated 

It win be noted that there is a small event between 50 and 60°C.Thisisa result of a thermal cycle in manufacturing to remove by-products of the cross-linking process. 

These measurements were carried out under nitrogen purging, at a heating rate of 10 K/min. Samples were approximately 7 mg in weight and held in crimped (unsealed) pans 

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In preparation for thermal-history studies, specimens were first dried (19) and melted at 290°C to form 0.6-mm-thlck sheets... 

Semiconducting Ceramics. Most oxide semiconductors are either doped to create extrinsic defects or annealed under conditions in which they become non stoichiometric. Although the resulting defects have been carefully studied in many oxides, the precise nature of the conduction is not well understood. Mobihty values associated with the various charge transport mechanisms are often low and difficult to measure. In consequence, reported conductivities are often at variance because the effects of variable impurities and past thermal history may overwhelm the dopant effects. 

Thermal transitions can be studied by DSC. The crystallization transition is usually sharp with a good baseline. The melting transition is more complex and often not a single transition (Fig. 3.19)48 as it depends on the thermal history of the sample and the structural changes that can take place upon heating. In warming, solid-state transitions can take place in the unit cell, the lamellae can thicken, and secondary crystallization can also take place. The heats of crystallization and... 

Sample Preparation. Samples for mechanical studies were made by compression molding the polymers at 150°C between Teflon sheets for 15 minutes followed by rapid quenching to room temperature in air. These will be referred to as PQ (press-quenched or simply quenched) samples. The thickness of the PQ samples was around 10 mils (0.25 mm). The thermal history of all of the PQ samples (HBIB, HIBI, and LDPE) were essentially the same. They were used within one week after they were pressed. Samples for morphology, SALS and SEM studies were prepared from toluene solutions. These films were cast on a Teflon sheet at 80 C from a 1% (by weight) solution in toluene. These films were about 5 mils in thickness. When the polymer films had solidified (after 5 hrs), they were stored in a vacuum oven at 80°C for two days to remove residual solvent. These samples will be designated by TOL (solution cast from toluene). 

In the present work, we use quantitative solid-state 13C NMR spectroscopy to study the polymerization process of multiacrylates and the effects of thermal history/aging on the free radical life in polymultiacrylates. 

This group covers aromatic nuclei bearing one nitro group most mono-nitro benzenes can be persuaded to detonate by a tetryl booster few are an immediate danger in tbe absence of other sources of energy. Calorimetric studies [1] suggest tbat nitroaiyl compounds decompose by an autocatalytic mechanism, and thus stability may depend upon thermal history. Individually indexed compounds are ... 

The effects of thermal history on the nucleation characteristics of CaCl2 6H20 melt without nucleation agent and the same melt with nucleation agent were studied experimentally by the cooling method at constant rate of IK/min. 

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