No abstract

No abstract

The lifetime of singlet oxygen ( 1 D g ) sensitized by apparently non-fluorescent 9-acetylanthracene (ACA) was determined at pressures up to about 35 MPa in supercritical ethane (SCF ethane;35, 45 and 55 C) as well as in liquid ethane (25 C) from the phosphorescence decay measurements. For all the systems examined, the decay rate constant (t D À1 ) increased significantly at the lower pressure region and monotonically as pressure increased further. It was also found that the pressure dependence of the bimolecular rate constant for quenching, k D , is similar to that of t D À1. The apparent activation volume for k D varied from À120 to À32 cm 3 mol À1 at the lower pressure region and from À24 to À15 cm 3 mol À1 at the higher pressure region. In liquid solution over the pressure range examined, the pressure dependence of k D was interpreted well by a mechanism of the encounter complex formed between the singlet oxygen and the solvent molecules, together with that of the radial distribution function at contact with hard spheres, whereas it was not for the SCF systems in the low pressure region. In SCF solution, the deviation from this model was attributed to the contribution of the local density augmentation around the solute molecule. The degree of the local density augmentation evaluated is compared with that determined from the peak shift in absorption spectra of ACA measured in this work.

ABSTRACT:Highly flame-resistant glass-epoxy laminates without flame-retarding additives such as halogen and phosphorous compounds have been developed to overcome environmental problems caused by these additives. The laminates consist mainly of a self-extinguishing epoxy-resin compound (phenol aralkyl), an incombustible-gas generator (amino-triazine-novolac hardener: ATN hardener), and inorganic materials such as a charring promoter (zinc molybdate on talc: ZMT) and a limited amount of harmless metal hydroxide (aluminum trihydroxide: ATH). They are highly flame-resistant and have other beneficial characteristics, including soldering-heat resistance, humidity resistance, electronic properties, and processing advantages. These qualities make them applicable enough to replace the FR-4 type printed wiring boards (PWBs) that are widely used today. Simultaneously using the ATN hardener and ZMT in the laminates, including the epoxy-resin compound and ATH, greatly improved their flame retardance. We then reduced the amount of ATH to obtain even better flame retardance in the laminates. This reduction of the ATH, consequently, improved other practical characteristics such as solderingheat resistance, humidity resistance, and electronic properties.

No abstract