R. Sakamoto

Heat capacities and latent heats of LiNO3, NaNO3, and KNO3

Enthalpies of fusion and transition together with heat capacities in both solid and liquid phases have been measured on LiNO3, NaNO3, and KNO3 with a high accuracy by differential scanning calorimetry (DSC). Polynomial expressions of heat capacities are given.

Investigation of latent heat thermal energy storage materials: V. thermoanalytical evaluation of binary eutectic mixtures and compounds of NAOH with NaNO3 OR NaNO2

Abstract Differential scanning calorimetry was applied to the evaluation of binary eutectic mixtures and compounds of NaOH with NaNO 3 or NaNO 2 as latent heat thermal energy storage materials. There are two compounds and three eutectic mixtures consisting of NaOH and NaNO 3 and one compound and two eutectic mixtures consisting of NaOH and NaNO 2 . The heats of fusion of all compounds and mixtures were more than 200 J g −1 . The thermal behaviour of these materials was observed, and some compounds and mixtures show a great tendency to supercool. The specific heat capacity was also measured. Because the eutectic mixture 18.5 mol.% NaNO 3 -81.5 mol.% NaOH is the most promising material for use in a nuclear power plant, this mixture made from industrial products was examined further. After 1000 cycles of melting and crystallization in bench-scale equipment the material shows little change.

Investigation of latent heat-thermal energy storage materials. I. Thermoanalytical evaluation of modified polyethylene

Abstract Differential scanning calorimetry is used to evaluate polyethylene for latent heat-thermal energy storage. Polyethylene is a suitable material from the points of view of latent heat, behavior of melting and crystallization, and material cost. The thermal stability is satisfactory when it is used in a closed system with heat transfer media, such as silicone oil, alkyldiphenyl, alkyldiphenylethane, Caloria HT and ethylene glycol, which shield polyethylene from air. Surface-crosslinking by ion bombardment prevents polyethylene from mutual adhesion and it retains its form after melting. Surface-crosslinked polyethylene with silicone oil or ethylene glycol is the most promising, while the heat transfer media, such as alkyldiphenyl, alkyldiphenylethane and Caloria HT, which dissolve polyethylene, decrease the melting point, but have little effect on the latent heat and sharp DSC peaks of melting and crystallization. Thus, the composite of polyethylene with these media can also be used at an adjusted and desirable operating temperature.

Investigation of latent heat-thermal energy storage materials. IV. Thermoanalytical evaluation of binary eutectic mixtures of NaOH with LiOH or KOH

Abstract Differential scanning calorimetry is used to measure the heat capacity and heat of fusion of binary eutectic mixtures of NaOH with LiOH or KOH, which are promising materials for latent heat-thermal energy storage materials. These binary mixtures are concluded to be useful for thermal energy storage, when residual water, which has a large influence on their thermal characteristics, is exclusively eliminated. The thermophysical data obtained are also useful in R&D of the technology as well as design of the equipment.

Investigation of latent heat-thermal energy storage materials. II. Thermoanalytical evaluation of urea

Abstract Urea is a very suitable material for latent heat-thermal energy storage in the temperature range 100–150°C with respect to the heat of fusion and material cost. Differential scanning calorimetry and thermogravimetry were applied to observe melting and crystallization behavior and to evaluate the thermal stability. Heating and cooling curve methods were also used. It has been revealed that urea has two serious drawbacks; one is a large supercooling tendency and the other is its low thermal stability. By forming a eutectic mixture with potassium chloride or ammonium chloride, the supercooling tendency is remarkably decreased and addition of sebacic acid is also effective for the purpose, but the low thermal stability is not improved by the addition of these compounds. Urea is thus unsuitable for latent heat-thermal energy storage because of its low thermal stability, though the latent heat and the material cost of urea are superior to those of polyethylene which is selected to be a promising material for latent heat-thermal energy storage in the same temperature range.

Mass spectrometric thermal analysis of poly(methyl methacrylate) of high molecular weight

Abstract Mass spectrometric thermal analysis (MTA) of poly(methyl methacrylate) of high molecular weight is made, and MTA curves observed are analyzed to obtain kinetic parameters by two methods proposed by one of the authors. Satisfactory results are obtained by both methods.

EVOLVED GAS ANALYSIS OF POLY(METHYL METHACRYLATE)

Abstract The thermal decomposition of various types of poly(methyl methacrylate) under vacuum was investigated by evolved gas analysis with a mass spectrometer. Though the volatilized product is mainly methyl methacrylate due to unzipping, four steps of volatilization were observed, and decompositions depend on the molecular weight and the polymerization process. The mechanisms of these four steps are elucidated by comparison of the amount of the volatilized product found at each step with the molecular weight and the polymerization process. The first step is a depolymerization initiated at the weak bond of copolymerized oxygen, and the second and third steps consist of depolymerization initiated at the chain ends, which occur due to disproportionation in propagating radical termination during polymerization. The fourth and final step is a depolymerization initiated by random scission in the main chain.