Steam Heat Treatment Research Articles

CHANGES OF THE PROPERTIES OF KEVLAR TIRE CORDS INDUCED BY STEAM- AND DRY-HEAT TREATMENT AND FATIGUE

(1) The tensile strength and ηinh of Kevlar tire cord decreased markedly by steam-heat treatment above about 160°C for 1 hr., but they did not change by dry-heat treatment at 200°C for 1 hr. The specific gravity increased with the increase in treating temperature. From these results, it was concluded that the decrease in the degree of polymerization by hydrolysis and the change of fine structure of the steam-heat treated Kevlar tire cords are the causes for the decrease in the tensile strength and fatigue resistance.(2) Heat shrinkage of Kevlar tire cords was lower than that of nylon 6, polyester and rayon tire cords. Change of X-ray wide angle diffraction pattern in steam-heat treated (tensionless state) Kevlar filaments was very small as compared with that of nylon 6 filaments. On the other hand, we found by DTA and TGA analysis that the decomposition of Kevlar begins at about 500°C and it decomposes at about 605 C. From these results, it was considered that the change of entropy (ΔS) in Kevlar by heat is very small as compared with that of nylon 6, because the molecular conformation of Kevlar is in trans-form and has extended-chain structure with very little flexibility.(3) a: We observed the fibrillation of Kevlar filaments at the fracture after fatigue test and also at the broken area of the Kevlar tire cords which were tested after steam- and dry-heat treatments by the tensile strength test.b: Fatigue resistance increased with increasing twist of Kevlar tire cords, but the tensile strength decreased with increasing twist.c: During fatigue test, the temperature of the air in rubber tube samples which contain Kevlar tire cords was lower than that of polyester tire cords and was equal to that of nylon 6 tire cords.

The poisoning of a steam hydrocarbon gasification catalyst

The factors which affect the loss of activity of a nickel alumina catalyst for the gasification of sulfur-free light hydrocarbons with steam at temperatures below 500 °C have been examined. These are sintering or loss of active surface area due to heat treatment in steam, and poisoning of active sites by a much slower parallel reaction to gasification involving constituents of the hydrocarbon feedstock. The second of these modes of activity loss is much more important at temperatures between 400 and 500 °C and normal operating pressures around 25 atm. This second mode of poisoning is independent of total pressure but rises rapidly with the boiling point of the hydrocarbon feedstock and the hydrocarbon steam ratio supplied. Increases in temperature favor the gasification reaction at the expense of poisoning. With finely divided catalyst particles, the rate of the gasification reaction is chemically controlled and zero order with respect to steam and hydrocarbon. With larger particles (0.3 cm diam) the rate is controlled by gaseous diffusion in the pores of the catalyst and, in line with this, the reaction rate becomes proportional to the particle size, the reaction order rises, and the activation energy falls. Rate control is probably by Knudsen diffusion in the micropores, though bulk diffusion in the macropores cannot be ruled out. The poisoning rate falls sharply at first on entering the region of diffusional control as the particle diameter is increased, but ultimately becomes independent of size. An attempt is made to interpret this phenomenon in terms of the effects of diffusional rate control on steam hydrocarbon ratio and temperature.

DIFFUSION OF NAPHTHALENE FAST ORANGE 2 GS IN HEAT-TREATED NYLON 6 FIBRE BY MSP METHOD

The effect of heat-treatment on diffusion of Naphthalene Fast Orange 2 GS in nylon 6 has been studied by means of microspectrophotometric (MSP) method, While the apparent diffusion coefficient by Kramer's method _??_ exhibits a minimum at 170°C, the concentration dependence of diffusion coefficient D (c) decreases with rising temperature of dryheat-treatment.Dry-heat-treated nylon 6 adsorbs less dyes at equilibrium in the middle region of pH than untreated one does, corresponding with the change of the amount of amino end groups, but the amount of adsorption in the higher pH increases by treatment.In the steam-heat treatment, both the _??_ and the D (c) increase, but the concentration dependence decreases. The higher the treating temperature becomes, the more remarkable these tendencies become.The amount of the amino end groups does not change regardless of steam-heating, A possible explanation on these results is discussed.

Effect of Direct Steam Heating and Vacuum Treatment on Levels of Pesticide Residues in Milk

Milks containing added DDT (p,p′-), heptachlor, lindane, and dieldrin were passed through commercial steam distillation—vacuum processing equipment. This process, developed to expel volatile off-flavors, removed the following percentages of pesticides: dieldrin, 3.0; heptachlor, 0; lindane, 23.8; and DDT (p,p′-), 8.4.

Effects of Direct Steam Heating and Vacuum Treatments on the Chemical Composition of Milk with Especial Reference to Substances Involved in Oxidized Flavor Development

Summary Milk was heated with live steam to from 190 to 240° F. and subjected to vacuum treatments of approximately 9 in. of mercury in one vacuum chamber and 20 in. of mercury in a second vacuum chamber. The direct steam heating and vacuum equipment were used in conjunction with a H.T.S.T. pasteurizing system and a homogenizer. The combined steam heating and vacuum treatment was found to produce a significant denaturation of whey proteins, as measured by the increase in the activity of sulfhydryl groups and the decrease in whey protein nitrogen. The decrease in whey protein nitrogen was shown to be approximately that which would be expected from published data on the effect of indirect heating. However, the extent of activation of sulfhydryl groups was lower than had been expected. The possibility that the vacuum treatment removed some of the volatile sulfhydryls was discussed. Increased activation of sulfhydryl groups was observed upon homogenization, particularly after direct steam heating. It was suggested that sulfhydryl activation may be a factor contributing to the high resistance of homogenized milk to oxidized flavor development. The lack of correlation between the nitroprusside test and cooked flavor is believed to indicate that the nitroprusside test is less sensitive than flavor perception, or that cooked flavor is not necessarily due to nitroprusside reactive substances. A high retention of ascorbic acid was observed in milk subjected to direct steam heating and vacuum treatment. This effect, along with resistance to oxidized flavor development, was noted even in milks to which copper was added. The removal of oxygen by the vacuum treatment and the activation of sulfhydryl groups by the heat treatment were considered to be contributing factors. Homogenization was also shown to contribute to the stability of ascorbic acid and flavor. However, homogenization alone was less effective than the combination of homogenization with steam heating-vacuum treatment.