A study of hybrid organo-silicate coatings on wool textiles

摘要

Hybrid organic-inorganic coatings impart desirable properties to textiles, but can adversely affect properties such as bending rigidity and extensibility. This study aimed to develop effective organo-silicate coatings for wool textiles.Formulations based on silanes with contrasting properties were applied to fabrics by padding and to single fibres and rovings by dip coating, and examined by microscopy. The bending rigidities and water repellencies of fabrics, and the tensile properties of rovings were determined. The silanes used were methyltriethoxysilane (MTES) and (3-glycidoxypropyl)trimethoxysilane (GLYMO). Methylimidazole (MI) was used to catalyse the reaction between the epoxy groups of GLYMO and the amine groups of wool. MTES coatings of up to 3.0% solids on mass of wool could be applied to woven fabric without causing unacceptable stiffness. MTES coatings of as little as 0.3% solids on mass of wool imparted water repellency. The water repellency was increased by adding hydrophobic compounds to the formulation. Hydrophilic GLYMO-MI formulations gave greater wetting and coverage of dip coated single fibres than MTES formulations, due to the greater reactivity of the fibre surface towards GLYMO, and the flocculation of hydrophobic MTES during drying. On roving, inter-fibre bonding masked the differences between MTES and GLYMO-MI coatings observed in single fibre studies.At low levels (0.05% by mass of formulation solids), a non-ionic surfactant improved the ability of GLYMO-MI coatings to wet-out wool, while at higher levels it caused flocculation. The surfactant had an inconsistent effect on MTES coatings. Increasing the critical surface tension of wool by chlorination, lowered the minimum GLYMO-MI solids level needed for continuous coating from 4.0% to 3.0%. In contrast, chlorination gave only small improvements to MTES coatings. The surface of wool accommodates extension by the separation of cuticle scales. Continuous coatings hinder this separation and crack at the scale junctions. It has been shown that these undesirable effects are avoided with discontinuous coatings, such those produced by MTES formulations.This work has shown that organo-silicate coatings can be tailored by choice of silane precursors, addition of surfactant, controlling reactivity between coating and wool, and modifying wool's surface energy, to effectively coat wool textiles.