Vapour pressures of hydroxybenzophenone UV absorbers

A thermogravimetric method was used to measure the vapour pressures of a series of hydroxybenzophenone UV stabilisers. Enthalpies of vaporisation were determined from the slope of a plot of the logarithm of the vapour pressure against reciprocal absolute temperature. Enthalpies of sublimation were measured either directly by the same method or by summing the enthalpy of vaporisation with the enthalpy of fusion determined by differential scanning calorimetry. Values of the vapour pressure at the melting temperature are given along with extrapolated values at 258C and the estimated normal boiling temperature. Decreasing the hydrogen bonding potential within a series of compounds increases the volatility whereas increasing molecular weight has the opposite effect. # 1999 Elsevier Science B.V. All rights reserved.