Toughening of epoxies via craze-like damage

The fracture behavior of a core-shell rubber (CSR) modified epoxy is investigated using both fracture mechanics and microscopy tools. The CSR-modified epoxy is found to be toughened via numerous line-array cavitations of the CSR particles, followed by plastic flow of the epoxy matrix. The toughening effect via the above craze-like damage process is found to be as effective as that of the well-known widespread rubber cavitation/matrix shear yielding mechanisms. The conditions for triggering the craze-like damage appear to be both stress state and rubber concentration dependent. The type of rubber tougheners utilized also plays a critical role in triggering this rather unusual craze-like damage in epoxy systems. © 1993 John Wiley & Sons, Inc.     

EXTRARETINAL PHOTORECEPTION IN CHICKENS: ENTRAINMENT OF THE CIRCADIAN LOCOMOTOR ACTIVITY RHYTHM

Abstract— The Circadian locomotor activity rhythm of blinded chickens entrained to, or was synchron ized by, light in light dark cycles.     

Control of methanol oxidation by ionic behavior in supercritical water

In supercritical water the rate of methanol oxidation was controlled by ionic behavior as follows: the oxidation rate of methanol decreased with increasing proton and hydroxide ion concentration, possibly due to stabilization of the reactant, while that of CO was suppressed by added protons and enhanced by added hydroxide ions.     

Revised analysis of the structure of the v1 band of methane

The CARS spectrum of the v₁ band of ₁₂CH₄ at a pressure of 14 mbar was recorded using cw excitation in the cavity of a ring argon ion laser. The analysis of the intensity profile of the obarred spectrum led to the detection of inconsistencies with the hitherto proposed calculated positions of transitions with J = 7 to J = 10 and to a relocation of the corresponding lines.     

On the modeling of absorption band shapes and resonance raman excitation profiles

Some general expressions for the modeling of absorption band shapes and Raman excitation profiles are presented. These expressions are shown to be exact representations of the “transform” theory of Hizhnyakov and Tehver. Examples of a calculation are presented which utilize closed-form analytical solutions for the absorption band shape and resonance Raman excitation profile.     

Gel permeation chromatographic analysis of polyurethane prepolymer synthesis kinetics II. The effects of stoichiometry and type of diisocyanate

The kinetics of formation of polyurethane prepolymers is studied by an analytical technique which involves reactive quenching of the isocyanate, separation of the oligomeric species by GPC, and measurement by UV absorbance of the quenched moieties. The precision of the kinetic parameters and the ratios of the oligomers are determined. The effect of changes in reactant stoichiometry on the ratio of oligomers is measured and compared to the value predicted by an equation from Flory. Toluene diisocyanate is shown to give fewer high oligomers than predicted, while methylene diphenylene diisocyanate gives nearly the predicted values. Tetramethylxylene diisocyanate gives more high oligomers than predicted, an unexpected but possibly important result. Catalyst is shown to increase the reaction rate of the last by more than 200 times. © 1994 John Wiley & Sons, Inc.