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In commercial slabstock foaming, liquid CO2 technology is increasingly applied to replace previously used liquid auxiliary blowing agents like CFCs and methylene chloride. Knowledge of physical properties of mixtures which are used in liquidCO2 foaming may contribute to the further development of the liquid CO2 technology. Equations have been determined which do predict, for specific operational conditions and formulations, the pressures which are required in commercial foam operation to keep theCO2 dissolved both in the polyol/CO2 and in the foaming mixture/CO2 solutions. The evident dependence on temperature ofCO2 solubility, established for both polyol and foaming mixtures, strongly supports tight temperature control of the feedstocks in slabstock liquid CO2 foaming. The solubility of CO2 in polyol was found to increase with the EO content of the polyol where the effect of molecular weight was found to be negligible. It was established that small amounts of water and surfactant lower the CO2 solubility, and it is predicted that the commonly used levels of TDI do the same. Based on this information, it is advisable to conduct the mixing of TDI and auxiliary components at pressures a fraction higher than the saturation pressure of the liquid CO2 polyol mixture. A significant decrease of both viscosity and surface tension is quantified for polyol and model foaming systems at increasing liquidCO2 concentration. These decreases may explain why very small cell sizes can be obtained with liquid CO2 foaming, as the nucleation process takes place at high liquid CO2 concentration. The rise in viscosity upon evaporation ofCO2 into the froth may explain the relative stability of the unreacted froth. A cooling capacity of about 1°C per part of CO2 per hundred parts of polyol is determined from two independent experiments. However, for safety reasons, it is advisable to keep the current assumption of 0°C per part of CO2 per hundred parts of polyol in commercial foaming until a further study on the temperature evolution of liquidCO2 blown foaming under practical conditions is conducted.

The collision-induced dissociation reactions of the monocarboxylate anions, generated from the dimethyl and diethyl esters of glutaric acid and its 3,3-dimethyl analogue in a chemical ionization source, were studied as a function of the potential applied to the collision cell in combination with 2 H labelling experiments. It was shown that many of the product anions are formed in consecutive steps. The mechanisms associated with these steps appear to be initiated by a functional group interaction between the carboxylate anion and the ester group, 1,5-hydrogen migrations both to the carboxylate anion and the uncharged ester group and charge remote fragmentation. In one of the collision-induced dissociation channels a methyl anion is generated as a granddaughter product anion, which contains the hydrogen atoms exclusively originating from positions 2 and 4 as shown by the applied 2 H labelling

It is shown that doubly charged α,ω-alkane dicarboxylate negative ions can be formed in the gas phase by collisionally-induced “ion pair” formation from singly charged carboxylate negative ions, generated from aliphatic α,ω-dicarboxylic esters, if the carboxylate groups are separated by more than two carbon atoms.