Dennis J. Massa

Use of carbon–carbon nuclear spin diffusion for the study of the miscibility of polymer blends

This high‐resolution solid‐state NMR work explores the usefulness of carbon–carbon nuclear spin diffusion to probe the miscibility of polymer blends. Experiments involving one‐ and two‐dimensional NMR spectra, applied to blends of poly(ethylene terephthalate) (PET) and bisphenol‐A polycarbonate (BPAPC), show that spin exchange occurs between carbon‐13 nuclei located in monomer units that belong to the two different homopolymers. Carbon spin diffusion, which strongly depends on the internuclear distance, is explored as a possible probe for specific interactions between polar groups of the two polymers. Our results clearly show that the PET/BPAPC blends studied are homogeneously mixed at distances of 4.5 to 6 A.

Measuring the dynamic moduli of glassy polymers: analysis of the Rheovibron

A mechanical model for the Rheovibron DDV‐II, an instrument for measuring the dynamic tensile moduli of polymers, has been proposed and analyzed to derive expressions for the moduli which take into account system compliance, sample yielding within the tensile grips, and system inertia. These effects require a correction to the raw data of 20–30% for glassy polymer samples in the tensile geometry, and the correction factor varies substantially with temperature, frequency, sample width and thickness, and among different polymers. In addition to the standard tensile grips, a new sample holder was introduced which adapts the Rheovibron to the flexural geometry. Experiments were carried out on samples of poly(methyl methacrylate) (PMMA) in tension and in flexure, on rigid aluminum samples, on a PMMA tensile sample with variable system inertia, and on a tensile specimen of bisphenol‐A polycarbonate at various temperatures, the model describing the behavior of the system quantitatively. It is concluded that for ...

P‐145: Polymer C‐Plate Retarders: History and Future

A brief review is given of the surprisingly long history of C plates made from polymeric materials. Previous work dating from the early 1900s is discussed. A new class of amorphous polymers is identified, and aspects of their structure, properties, and performance are shown.

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.