Application of transmission electron microscopy to polymer thin sections. I. Observations on nylon 66, bulk and filament forms

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Abstract
A study was made on the internal morphology of molding pellets and filaments of nylon 66 by using transmission electron microscopy on ultrathin sections and polarized light microscopy. Nylon specimens embedded in an epoxy–phenolic resin alloy were sectioned to below 500 A. in thickness on an ultramicrotome with a 48° diamond knife. This resin combined good sectioning properties with strong adhesion to the nylon due to the interaction between the phenolic and the nylon. It was established that success in sectioning depended on embedding in a medium with proper wetting characteristics (to permit floating sections away from the knife edge) and obtaining a strong adhesive bond between specimen and embedding material. Contrast in the electron micrographs was enhanced by staining the nylon sections with phosphotungstic acid. Observations on nylon 66 molding pellets resolved the fibrillar structure of spherulites at the 100 A. level. Observations on undrawn monofilaments indicated a cylindrical rather than spherical symmetry of spherulitic crystallization. When the filaments were cold‐drawn, these spherulites retained their radial symmetry but were reduced in diameter.