Chromic Acid Etching of Polypropylene Filaments

Abstract

Chromic acid etching is shown to effectively remove successive layers of polypropylene filaments and render the interior morphology accessible to electron microscopic examination. Using this technique a range of as spun, hot-drawn, and deformed filaments has been examined. Current theories of semicrystalline polymer morphology have usually been derived from observations on carefully prepared thin films or single crystals. The morphological detail exposed by etching confirms the existence of similar structures in the textile filaments examined. The factor limiting the efficiency of the etch process appears to be the ease of penetration of the etchant into the filament. When the structure is opened up by fibrillation or voiding, the rate of etching increases dramatically. Little difference is observed in etch rates for unvoided samples, between unaligned and highly-oriented structures.