Rate Of Decrease In Weight Research Articles

Dechlorination of poly(vinyl chloride) by microwave irradiation I: A simple examination using a commercial microwave oven

Poly(vinyl chloride) (PVC) was decomposed by microwave (MW) irradiation (2.45 GHz) using a commercial MW oven. The efficiency of dielectric absorption was evaluated quantitatively from the rate of temperature increase on MW irradiation. The efficiency of dielectric heating increased at temperatures above the glass transition temperature ( T g). The decomposition on MW irradiation, monitored using the weight, depended on the initial (preheating) temperature of the sample before irradiation. The degradation time profile with various initial temperatures was shifted along the time axis and was successfully superimposed on a single curve. A pure PVC film was subjected to heating at a constant temperature from 230 °C to 310 °C, and the rate of weight decrease on heating was measured. The apparent activation energy was 84.4 kJ/mol for a single monomer unit.

Effects of Soil Moisture and Temperature on Decomposition Rates of Some Waste Materials from Agriculture and Agro-industry

The effect of soil moisture and temperature on decomposition of waste materials, bagasse, coir dust, rice chaff and rice straw, in soil were examined by measuring the decrease in weight of and CO2 generation from each waste material. The rate of the decrease in weight increased as temperature rose, and was highest in rice straw followed by bagasse, rice chaff and coir dust in this order, irrespective of soil moisture and temperature level. In all waste materials, the rate of decrease in weight was highest in the soil holding the water equivalent to field capacity (saturated soil) followed by submerged soil and dry soil in this order. CO2 generation rate was also highest in rice straw followed by bagasse, rice chaff and coir dust. It was highest in saturated soil followed by half-saturated or submerged soil and dry soil in this order. The rate of CO2 generation from rice straw in saturated soil was highest at the initial period of incubation and it decreased thereafter, but the rate in submerged soil was highest at 40 and 20 days after the start of incubation at 20 and 35ºC, respectively. The rate of CO2 generation from coir dust and rice chaff was very low at all soil moisture levels at either 20 or 35ºC. The content of total N in the waste materials was positively and significantly correlated with the rate of decrease in weight in saturated and submerged soils at a moderate temperature (Oct. – Dec.), and in submerged soil at a high temperature (Aug. – Oct.). It was also significantly correlated with CO2 generation rate in submerged soil at 20ºC. Holocellulose and hemicellulose contents were negatively and significantly correlated with CO2 generation rate in dry soil at 20ºC. Lignin content was also significantly and negatively correlated with CO2 generation in dry soil at 35ºC.

Long-Term Deterioration of GFRP in Water and Moist Environment

This report examines the effects of water and moisture on the durability of pultruded glass-fiber-reinforced polymers (GFRP) with vinylester resin for applications in normal air conditions. Deterioration tests, including both immersion and atmosphere conditions at various temperatures, were conducted to investigate the deterioration characteristics of pultruded GFRP after being permeated by water. The main findings from the tests were that cracks appeared on the surface of the GFRP and that the weight of the materials decreased, which may be attributed in the surface treatment oil for the glass-fiber cloth being dissolved away. The bending strength of the GFRP was also found to be reduced. The rate of weight decrease and the reductions in bending strength were greater in a 60°C water-immersion condition compared to both a 60°C moist-atmosphere condition and a 40°C water-immersion condition. This difference is due to the fact that the glass fiber and matrix resin separated in water at 60°C. Although the matrix resin changed color in air at 60°C, becoming noticeably brown, no chemical changes were found by infrared spectra.

New chitin-based polymer hybrids, 4: soil burial degradation behavior of poly(vinyl alcohol)/chitin derivative miscible blends

Soil burial degradation behavior of miscible blend systems of poly(vinyl alcohol) (PVA)/partially deacetylated chitin (1), PVA/chitin-graft-poly(2-methyl-2-oxazoline) (2), and PVA/chitin-graft-poly(2-ethyl-2-oxazoline) (3) was investigated in comparison with the case of a pure PVA film. The degradation of the blend films was followed by the weight changes, scanning electron microscopic observation, Fourier transform infrared spectroscopy, 1H-NMR, and size exclusion chromatography analyses. The rate of weight decrease in these PVA/chitin derivative hybrids was higher than that of control PVA in the soil burial test. Fourier transform infrared spectra of the recovered samples of the blends showed an apparent increase of the absorption intensity due to β-diketone structure in PVA, which reflects the progress of biodegradation of PVA by PVA-oxidizing enzymes. Scanning electron microscopic observation revealed that these blend films were degraded by bacteria and actinomycetes. The triad tacticity and number-average molecular weight of PVA in the hybrids after soil burial determined by 1H-NMR and size exclusion chromatography, respectively, were almost the same as those before soil burial. These results suggested that enzymatic degradation of the hybrid films occurred mainly on the surface and that degradation of the PVA-based samples in the soil was accelerated by blending the chitin derivatives. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1171–1179, 1999

Physiological phases of nymphal molting defined by mobility, body weight decrease, and excretion in Haemaphysalis longicornis (Acari: Ixodidae).

Based on the rate of body weight decrease, the nymphal premolting period in Haemaphysalis longicornis Neumann was divided into three phases: a period of rapid weight decrease following detachment, a period of slight decrease, and another period of relatively rapid decrease before molting. Phase 1 was characterized by increased guanine excretion and mobility. The rate of weight decrease during phase 1 was greater in males than in females. During the premolting period, excreta consisted only of guanine and were devoid of hematin. In phases 2 and 3, neither excretion nor mobility was observed. Twenty-eight percent of the females and 40% of the males did not undergo phase 3. Adult body weight decreased rapidly until about day 5 after molting, after which weight was maintained until the end of the experiment. Guanine was excreted in large quantities just after molting and in small amounts for 4 d thereafter. Hematin excretion followed guanine excretion and was concentrated in a 3-d period starting 4 d after molting. The beginning of hematin excretion coincided approximately with the point at which body weight was maintained at a constant state. There were no quantitative differences per unit of body weight between the sexes with the exception of the rate of body weight loss during nymphal phase 1.

Natural selection for covariation in growth components in Tribolium castaneum

The relationships between various components of growth were studied, both at the intra- and inter-populational levels, in twelve laboratory populations of Tribolium castaneum with widely different geographic backgrounds. The components of growth related to body weight — at the 13th day of larval life, Lw, at the first day of pupal life, Pw, at the first day of adult life, Aw, — and to developmental time — at pupation, Pt, at emergence of the adults, At. The relationships between those traits, presumably brought about by natural selection, were compared with similar relationships as disclosed in a study using lines artificially selected for some growth components. The correlations between Pw and Aw and between Pt and At are positive in both naturally and artificially selected populations. This is due to the fact that the rate of decrease in weight between Pw and Aw depends on Pw and to the fact that the developmental time between Pt and At is constant. The consistent significant correlation between growth rate, Lw, and both Pt and At contrasts with the absence of association between Lw and either Pw or Aw. This indicates that the rate of growth relates to developmental time and not to the final body weight. This is confirmed by the lack of consistent correlations, both at the intra- and inter-populational level, between weight, Pw and Aw, and developmental time, Pt and At. The balance achieved between those components of growth are discussed in terms of natural versus artificial selection and their bearing on various triats related to fitness are analyzed.