Effect of water uptake

When dealing with partially crystalline materials, such as those produced by milling, the effect of water uptake is intensified. The amorphous component likely absorbs greater quantities of water than its crystalline counterpart, leading to reduced Tg, increased molecular mobility, and both physical and chemical instability. 

The tensile properties of BCB/BMI are not affected by the absorption of water as shown in Table II. Future studies will be done to determine the effect of water uptake on the mechanical properties at elevated temperatures. 

Table V. Effect of Water Uptake on a Sulfonated EPDM° Neutralized with a Quaternary Phosphonium Ion...

Measuring the resistivity on a very local scale inside concrete using small embedded electrodes has been shown to be a good method for measuring and monitoring the effects of water uptake and drying, as a function of depth, binder type and environment [42, 43]. 

Fig. 5 Effect of water uptake on glass transition temperature and the determination of bound vs free water in a polyurethane SMP. Immersion in water at room temperature (a) results in a Tg reduction. Absorbed water consist of two fractions The free water, which can be removed by drying under moderate conditions without effects on Tg (b), and the bound water, which is in closed interaction with the polymer and requires further heating for desorption (c). Adapted with permission from [24], Copyright 2005, American Institute of Physics...

Natural fiber/PP-composites absorb moisture from the environment. This moisture absorption does not lead to a change in width or length but to an alteration in thickness (about 1% at 1% water absorption). The tensile and flexural properties depend also on the moisture content. So the effects of water uptake are only partly reversible. The relative... 

High initial cost and environmental restrictions prevent use of oil and synthetic muds in many cases where shale problems are expected. It is necessary then to treat a water-base mud to minimize the destabilizing effect of the drilling fluid. Salts, polymers, and other organic materials are added to the mud to reduce the water sensitivity of the shale, shale sweUing, and weakening arising from mud contact, or the rate of water uptake by the shale. 

Everall, N.C., N.A.A. Macfarlane, and R.W. Sedgwick. 1989b. The effects of water hardness upon the uptake, accumulation and excretion of zinc in the brown trout, Salmo trutta L. Jour. Fish Biol. 35 881-892... 

Dyer, S.D., J.R. Coats, S.P. Bradbury, G.J. Atchison, and J.M. Clark. 1989. Effects of water hardness and salinity on the acute toxicity and uptake of fenvalerate by bluegill (Lepomis macmchirus). Bull. Environ. Contam. Toxicol. 42 359-366. 

Atkinson, M. J. and Bilger, R. W. (1992). Effects of water velocity on phosphate-uptake in coral reef-flat communities, Limnol. Oceanogr., 37, 273-279. 

Thomas, F. I. M. and Atkinson, M. J. (1997). Ammonium uptake by coral reefs effects of water velocity and surface roughness on mass transfer, Limnol. Oceanogr., 42, 81-88. 

GraysonBT, Webb JD, Factors offecting the performance and crop phytotoxicity of a new rice herbicide, cinmethylin. 1. Effects of water depth and soil type on the distribution and uptake of anmethylin by transplanted and direct-seeded rice,... 

Plain water crosses the walls of the intestine by osmotic action alone. However, if sodium and sugars are also present then the active transport mechanisms described earlier operate and water absorption can be enhanced. The effect is dependant on concentrations the maximum rate of water uptake occurs when the concentrations give a slightly hypotonic solution (200-250 mOsm/kg, cf. 287 mOsm/kg for isotonicity) (Wapnir and Lifshitz, 1985). Conversely, when the lumen contents are significantly hypertonic, water is secreted from plasma into the intestine by osmotic action this is a dehydrating effect. 

Reid, C. P. P. Bowen, G. D. (1979b). Effect of water stress on phosphorus uptake by mycorrhizas of Pinus radiata. New Phytologist, 83, 103-7. 

Water uptake in ionomeric membranes has been studied intensively. There are significant differences in water uptake by such membranes from liquid and vapor phases. We will first discuss some data on water uptake from the liquid phase by various membranes and the effect of the thermal history of the membrane on such uptake. We will then concentrate on the uptake of water from the vapor phase. Both modes of water uptake could be important under PEFC operating conditions. 

The tendency of a solid to take up water from the atmosphere, as it is subjected to a controlled RH program under isothermal conditions, is referred to as hygroscopicity (35). The hygroscopicity of a solid can be classified based on the amount or rate of water uptake when a solid is exposed to controlled RH values at a specified temperature (Table 1 from Ref. 35). The RH of a saturated solution of the API, RHo, can also be of importance. From a preformulation perspective, it is important to know the effect of water sorption on the pharmaceutically relevant properties of the API. 

---