James Henry Aubert

Note: Thermally removable epoxy adhesives incorporating thermally reversible diels-alder adducts

Thermally reversible adhesives are prepared through the reaction of aliphatic diamines and a diepoxy compound containing two Diels-Alder adducts. The diepoxy compound is formed via the Diels-Alder reaction between two epoxy-containing furans and a bismaleimide. The adhesive displays a T g of m 40°C and a constant shear modulus up to approximately 90°C. At temperatures exceeding 90°C the retro Diels-Alder reaction occurs, which leads to a significant loss in modulus. The loss of modulus is reversible with temperature. A thermally reversible adhesive is proposed based upon the loss of modulus at an elevated temperature, i.e., adhesives bonds are easily broken at elevated temperature where the modulus is low.

Solubility of carbon dioxide in polymers by the quartz crystal microbalance technique

The use of a quartz crystal microbalance (QCM) has been demonstrated to be an accurate and relatively easy technique to measure gas solubility in polymers at high pressures. The technique is reversible and could be used for real-time monitoring of a process. We have compared solubility measurements of CO2 into numerous polymers with literature data, obtained from measurements using a gravimentric approach, with good agreement. With improved electronic sensitivity, this technique could be extended to measure the partitioning of a component present at low levels of CO2 into polymers. This would provide a direct measurement technique that would provide value to investigations into the use of CO2 as an agent to infuse chemicals into polymers.

Interfacial properties of dilute polymer solutions

Abstract The linearly elastic dumbbell is used to model dilute polymer solutions with an interface which preferentially attracts or repels the polymer. Expressions are derived for the three-dimensional solution properties near the surface, such as the number density of dumbbells and stress, and also the two-dimensional properties which can be assigned to the surface, such as adsorption, surface tension, and surface rheological properties. A relationship is found between surface equilibrium properties and surface rheological properties, suggesting a method to predict the dynamic properties of the surface solely from measurements of equilibrium surface tension. The surface rheological properties are anisotropic, indicating that for most shearing flows a single surface viscosity is insufficient to describe the flow. In thin films a stabilization mechanism occurs when single polymer molecules straddle the film. This could retard the draining of thinning films.

The mechanical behavior of microcellular foams

The mechanical behavior of microcellular open-cell foams prepared by a thermally induced phase separation process are investigated. The foams studied were prepared from isotactic polystyrene, polyacrylonitrile, and poly(4-methyl-1-pentene) (rigid foams), and polyurethane and Lycra (elastomeric foams). Their densities were in the range 0.04--0.27 g/cm3. Conventional polystyrene foams were used for comparison. The moduli and collapse stresses of these foams were measured in compression and compared with the current constitutive laws which relate mechanical properties to densities. A reinforcement technique based on the in-situ precipitation of silica was used to improve the mechanical properties. 13 refs., 4 figs., 3 tabs.

Low-density microcellular polymer foams: Applications in biomaterials

Microcellular polymer foams are of interest as biomaterials for uses such as artificial skin, synthetic vascular replacements, artificial organs, and for use in permeable drug delivery systems. This report describes the use of thermally induced phase separation as a technology by which a variety of polymer foams can be prepared. This process permits control of foam morphology, cell size, and density. The phase separation process results in fully open-celled foam structures. Additives such as small molecules and functionalized polymers have been incorporated into these microcellular foams resulting in polymer surfaces with controlled porosity and chemical modification. Microcellular polyurethane foams, with chemically modified surfaces, have potential application as small diameter vascular replacements. 6 refs., 3 figs.

N‐(4‐Hydro­xy­phenyl)male­imide

In the title compound, C10H7NO3, the malamute ring is rotated by 52.75 (5)° with respect to the phenyl ring. There is a weak O—H⋯O intermolecular hydrogen bond between the hydroxyl group and one of the malamute O atoms, with an O⋯O distance of 2.820 (2) A.

Compatibility of Fluorinert, FC-72, with selected materials.

Removable encapsulants have been developed as replacement materials for electronic encapsulation. They can be removed from an electronic assembly in a fairly benign manner. Encapsulants must satisfy a limited number of criteria to be useful. These include processing ease, certain mechanical, thermal, and electrical properties, adhesion to common clean surfaces, good aging characteristics, and compatibility. This report discusses one aspect of the compatibility of removable blown epoxy foams with electronic components. Of interest is the compatibility of the blowing agent, Fluorinert{trademark} (FC-72) electronic fluid with electronic parts, components, and select materials. Excellent compatibility is found with most of the investigated materials. A few materials, such as Teflon{reg_sign} that are comprised of chemicals very similar to FC-72 show substantial absorption of FC-72. No compatibility issues have yet been identified even for the few materials that show substantial absorption.