Development of polyoxymethylene based nanocomposite and nanofiber materials

Abstract

The present work focuses on the development of polyoxymethylene (POM) and its copolymer based nanocomposite and nanofiber materials. The first part involves clarification of the effects of surfactants used for modifying of clay on the intercalation of the polymer chain and the properties of the nanocomposite obtained. A quaternary ammonium surfactant induces the mixture of intercalated/flocculated nanocomposite structure while a primary ammonium surfactant induces an exfoliated structure of the nanocomposites, together with an improvement in mechanical properties and a significant gas barrier property. The second part considers electrospinning technique to produce nonofiber with unique properties. An electrospun POM nanofiber using a hexafluoroisopropanol (HFIP)-based solvent is successfully prepared by controlling the spinning conditions, i.e. electrostatic field strength and relative humidity and the polymer solution properties, i.e. copolymer content and vapor pressure of the solvent. Nanoporous structure is inevitably formed and is mainly induced via thermally induced phase separation (TIPS) and vapor induced phase separation (VIPS) mechanisms. By controlling the voltage and rotating velocity of disc rotator, the crystalline morphology changes between anextended chain crystal (ECC) and a folded chain crystal (FCC). Herman’s orientation function and dichroic ratio lead us to a conclusion that (i) molecular orientation is parallel to fiber axis in both isotropic and anisotropic POM nonofibers and (ii) a single nanofiber consists of nanofibril assembly with 60-70 Å in size and tilting at a certain degree.