Lawrence Paul Demejo

Influence of rheology and molecular architecture on the fusing behavior of toners

A series of branched polyester toners was synthesized by design to exhibit a systematic variation in the level of tetrafunctional branching agent and a nearly matched melt viscosity. The branching agent level was varied in five steps from 0 to 5 mole percent of total diol component in the fmal polymer. The various compositions were polymerized by a one-step toner synthetic process to avoid the molecular weight degradation normally associated with the melt compounding step. These materials were then ground to toners that exhibited a broad range of performance characteristics. The toner hot offset temperature was found to be nearly independent of branch agent concentration, while the image glossing characteristics of these materials were found to vary over a broad frequency (or equivalent temperature) range. These results suggest that the hot offset temperature is mainly a function of the melt viscosity of toners with similar chemical and rheological characteristics and the glossing response is determined primarily by their elastic properties above Tg. The change in glossing timescale tracked quantitatively the change in the terminal zone elastic modulus for these and analogous branched polyester toners.