Changing the properties of natural fibres by coating and of synthetic fibres by infiltration

摘要

The Thesis deals with the development of new concepts for improving the properties of natural and synthetic textile fibres. A natural fibre, cotton, has been chosen as fibrous material. The focus of the modification has been directed towards its handle properties, which usually are improved at the expense of moisture up-take. The silicon based compounds were used for this work. Polylactic acid and polypropylene have been chosen as synthetic fibres whose textile potential is hindered by their poor dyeability and low moisture sorption capacity and which can be modified at spinning stage with suitable additives. The focus here has been directed on using recyclable natural materials as additives for achieving an improved comfort property of the synthetic polymer. Two chemical processes, namely coating and infiltration, were considered for applying functional polymers on the fibre surface and, respectively, for modifying the bulk of a polymer via infiltration of particles into the matrix. The coating of cotton with two hydrophilic silicon softeners, a silanol compound and a PDMS compound, was carried out from water, as a classical method, and from supercritical CO2, respectively, as a new approach. The coating process and the change of the fabric properties were investigated by using Scanning Electron Microscopy (SEM), elemental identification Energy Dispersive X–Ray Spectroscopy (EDX), Fourier Transform Infra-Red Spectroscopy (FTIR), X-Ray Photoelectron Spectroscopy (XPS), moisture analyser and Kawabata Evaluation System (KES-FB). The results allowed optimising the route of silicon product application and put into evidence the benefits of the treatment, independently of the fabric structure. The polylactic acid and polypropylene based composites were produced via melt infiltration of powders of chitosan, cotton or keratins into polymer matrix. The prepared powders were characterised using FTIR, NMR, Raman microscopy and amino acid analysis. The distribution of the powders into the matrix was investigated by SEM analysis. The composites show good thermal and mechanical properties demonstrated by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) and miniature material tester (MiniMat2000). The ability of absorbing and keeping the moisture was highly improved for all materials, as shown with IGA sorb moisture analyser. Polylactic acid based composites proved also an improved ability for dyeing with reactive and acid dyes at 100°C. Summing up the fibres properties can be controllable improved by selecting the appropriate synthetic polymer structure for coating natural fibres, or the appropriate natural additive for infiltrating the matrix of the synthetic fibre.