Abstract: This disclosure relates generally to adhesives and particularly to reversible adhesives. This disclosure further relates to generally adhesive articles and particularly to wound dressings comprising such adhesives. The adhesive comprises a core and a shell comprising at least two components. One of the components of the shell comprises a polymer formed by reacting a monomer of a thermally reversible polymer and the other component comprises a polymer formed by reacting a monomer of a polymer of a pressure sensitive adhesive. The wound dressing comprises a substrate and the reversible adhesive, forming a reversible wound dressing. Such wound dressings are particularly suitable for treatment of damaged sensitive tissue, for example wounds formed on a fragile skin.

Abstract: A photomask assembly is disclosed having a photomask substrate and a composite pellicle frame that includes both a metallic frame component and a scavenger component. The metallic frame component has a cross-sectional thickness of at least 100 micrometers in all directions, and the volume percentage of the scavenger component relative to the overall volume of the composite frame is in the range of 0.1 to 95%. The scavenger component has a gas permeability to oxygen or nitrogen greater than about 10 ml·mm/cm2·min·MPa, an average pore size between 0.001 and 10 micrometers, and a pore surface area greater than 10 m2/g. This configuration enables the pellicle frame to have sufficient strength to withstand stresses encountered during normal use, yet also to have the capability of scavenging impurity molecules from the space adjacent to the photomask substrate.

Abstract: A process is suited for producing cylindrical silica glass bodies having refractive index gradients. The process involves providing a cylindrical porous body having an initially uniform dopant distribution, heating the porous body in a halogen-containing atmosphere to produce a dopant gradient sufficient to produce a reduction in &Dgr;n of at least 20% from the center of the body to 90% of the distance from the edge of the body, and completely densifying the porous body at an elevated temperature to produce the glass body. The process is more cost-effective than those previously known, and allows for high reproducibility of the refractive index gradients of the bodies produced.

Abstract: A sol-gel process for producing dry porous gel monoliths, e.g., silica glass monoliths, in which the successive process steps of gelling, aging and drying all occur within a mold formed of a selected porous material, e.g., graphite. The mold is inert to the gel solution and it has sufficient strength to withstand the temperatures and pressures encountered during the process. The mold and gel thereby can remain within a sealed autoclave during these process steps, and mechanical handling of the mold and the gel are minimized. This substantially enhances the process' efficiency. Alternatively, the mold can have a non-porous inner skin to enhance ease of cleaning of the mold, and of removal of the gel.

Abstract: A sol-gel process for producing dry porous gel monoliths, e.g., silica glass monoliths, in which the successive process steps of gelling, aging and drying all occur within a mold formed of a porous material, e.g., graphite. The mold is inert to the gel solution and it has sufficient strength to withstand the temperatures and pressures encountered during the process, yet it has sufficient porosity to facilitate the escape of liquid from the gel pores directly through the mold, itself. The mold and gel thereby can remain within a sealed autoclave during these process steps, and mechanical handling of the mold and the gel are minimized. This substantially enhances the process' efficiency. Alternatively, the mold can have a non-porous inner skin.

Abstract: An improved apparatus, and related method of operation, is described for rapidly drying large monoliths of glass, ceramic and/or composite material, under subcritical conditions, while minimizing the risk of cracking the monolith during the drying process. The apparatus incorporates a pressure chamber for carrying the monolith to be dried, with no significant limitation on the size of the monolith relative to the size of the chamber. The monolith is initially immersed in a suitable drying solvent, and the temperature of the pressure chamber is raised to a predetermined value below the solvent's critical temperature, which raises the pressure to a predetermined value, likewise below the solvent's critical pressure. At a selected time during the drying process the pressure chamber is connected to a diffusion chamber, to draw away and condense solvent vapor.

Abstract: An improved apparatus, and related method of operation, is described for rapidly drying large monoliths of glass, ceramic and/or composite material, under subcritical conditions, while minimizing the risk of cracking the monolith during the drying process. The apparatus incorporates a pressure chamber for carrying the monolith to be dried, with no significant limitation on the size of the monolith relative to the size of the chamber. The monolith is initially immersed in a suitable drying solvent, and the temperature of the pressure chamber is raised to a predetermined value below the solvent's critical temperature, which raises the pressure to a predetermined value, likewise below the solvent's critical pressure. At a selected time during the drying process the pressure chamber is connected to a diffusion chamber, to draw away and condense solvent vapor.

Abstract: A process is disclosed for drying sol-gel derived porous wet bodies without inducing cracks therein. The wet gel preferably is immersed in a liquid solvent before being placed inside a drying chamber capable of withstanding relatively high pressures and temperatures. After the wet gel is loaded, the chamber is sealed from the outside environment, and then is heated from outside the chamber in a controlled manner until a prescribed subcritical pressure is reached. The final temperature and pressure are always lower than the critical temperature and pressure of the drying solvent. The solvent vapor is then evacuated from the chamber in a controlled fashion to decrease the pressure until ambient pressure is reached, while preferably maintaining the temperature inside the chamber at the prescribed level. Thereafter, the inside of the chamber is purged with an inert gas for a prescribed time period, after which the chamber is cooled to ambient temperature and the dry crack-free porous gel is removed.

Abstract: A process and apparatus are described for rapidly drying a wet, porous gel monolith of glass or ceramic, at subcritical temperatures without inducing any cracking of the gel. The wet gel is immersed in a liquid solvent in a chamber, and the liquid solvent is then heated and expelled from the chamber. Further heating, with or without the presence of a flowing inert gas, fully dries the wet gel. When an inert gas is used, the gas is delivered to the chamber with a controlled solvent partial vapor pressure, to correspondingly control the driving force for drying the gel.

Abstract: A sol-gel process for forming a germania-doped silica glass rod that is suitable for use as a preform in the manufacture of high numerical aperture optical fibers. The sol is produced by mixing together prescribed quantities of alkoxides including tetraethyl orthosilicate and tetraethyl orthogermanate, deionized water, ethanol and a precipitation catalyst such as hydrofluoric acid. Premature precipitation of germania is avoided by adding ethanol and deionized water to an alkoxide solution at a controlled, drop-wise rate and by then similarly adding the catalyst at a controlled, drop-wise rate. After drying the resulting gel, sintering is performed by chlorinating the dry gel to remove residual hydroxyl groups, then oxygenating the chlorinated gel to remove the chlorine, and finally heating the oxygenated gel in helium to a temperature of about 1300.degree. C. Chlorinating and oxygenating the gel for extended time durations, and maintaining the gel above 1200.degree. C.

Abstract: A process and apparatus are described for rapidly drying a wet, porous gel monolith of glass or ceramic, at subcritical temperatures without inducing any cracking of the gel. The wet gel in immersed in a liquid solvent in a chamber, and the liquid solvent is then heated and expelled from the chamber. Further heating, with or without the presence of a flowing inert gas, fully dries the wet gel. When an inert gas is used, the gas is delivered to the chamber with a controlled solvent partial vapor pressure, to correspondingly control the driving force for drying the gel.