The subject of moisture-induced failure in glass-resin composite materials is reviewed. Emphasis is given to the fundamental surface chemistry and fracture mechanics involved. These disciplines offer substantial information about water adsorption on polar solids, including glass, and about the fracture of solids. However, this information is shown to be inadequate in describing the mechanisms involved in the failure of glass-resin materials. Some insight into these mechanisms is possible from various studies of the moisture-induced failure of bulk glass and adhesive/adherend systems. Also, some light is shed on moisture-induced failure by considering the empirical methods used to improve composite wet-strength, especially the use of silane adhesion promoters. Recent research on the silanes suggests that their action may involve a modification of the resin in the vicinity of the glass/resin interface.

Water at the Interface

The existence of the exclusion zone (EZ), a layer of water in which plastic microspheres are repelled from hydrophilic surfaces, has now been independently demonstrated by several groups. A better understanding of the mechanisms which generate EZs would help with understanding the possible importance of EZs in biology and in engineering applications such as filtration and microfluidics. Here we review the experimental evidence for EZ phenomena in water and the major theories that have been proposed. We review experimental results from birefringence, neutron radiography, nuclear magnetic resonance, and other studies. Pollack and others have theorized that water in the EZ exists has a different structure than bulk water, and that this accounts for the EZ. We present several alternative explanations for EZs and argue that Schurr's theory based on diffusiophoresis presents a compelling alternative explanation for the core EZ phenomenon. Among other things, Schurr's theory makes predictions about the growth of the EZ with time which have been confirmed by Florea et al. and others. We also touch on several possible confounding factors that make experimentation on EZs difficult, such as charged surface groups, dissolved solutes, and adsorbed nanobubbles.

Exclusion zone phenomena in water -- a critical review of experimental findings and theories

Investigations of the phase behaviour on freezing and subsequent melting and of other properties indicate that anomalous water is a solution containing a fixed amount of relatively involatile material in normal water. There seems to be no need to postulate the existence of a new polymer of water in such solutions. If only water and silica are present, the properties are consistent with those of a silicic acid gel.

Colligative properties of anomalous water.

Hydrogen bonding and polywater in clay-water systems*

SINCE the discovery of “anomalous water”1, several models2–12 have been proposed for its structure. I derive here a model based on present experimental knowledge, and then explain its mechanism.

Structure of Anomalous Water and Its Mechanism

1.

A structurally modified state of water and of a number of other polar liquids, arising under dynamic conditions of condensation of incompletely saturated vapors in quartz capillaries, was detected.




2.

Structurally modified liquids are distinguished by increased density and viscosity, increased saturated vapor pressure, and a different course of the thermal expansion and phase transformations.




3.

The possible causes of the formation of a structurally modified state of liquids were discussed.

The modified state of water and other liquids

In experiments performed by various methods and on different objects, it has been shown that the properties of water in boundary layers and in fine pores are substantially different from the bulk properties. These differences play an important role in various technological processes. For example, the stability of thin films of water often determines flotation conditions and the mass transfer in drying porous solids. The presence of boundary layers of water with changed properties increases the stability of a number of colloidal systems, and this must be taken into account in developing measures for water treatment to remove suspended matter. Finally, the special properties of boundary layers of water, in particular their lower dissolving power, are finding broad practical applications in the technology of reverse osmosis separation of solution and in water desalination.

N. V. Churaev

Papers

The modified state of water and other liquids

Structure and properties of boundary layers of water