Polyester fibres structure modification using some organic solutions
The treatment causes only minor decrease in fi bre, i.e. yarn strength, while breaking elongation increases signifi cantly, almost up to 150 % in comparison to the untreated sample. Organic solvents, i.e. plasticizer solutions in the organic solvents mixture infl uence fi bre properties in a very favorable way, i.e. they can enable better dyeing, better moisture absorption, easier treatment in further phases of textile products manufacture and generally better usability. X-ray structural analysis was used to examine the infl uence of the treatment of polyester fi bres in the form of fi lament yarn, fi neness 75/26 dtex, with solutions 0.3, 0.6 and 0.9 % hydroquinone and α-naphtole in the solvent mixture which contained chlorophorm and methanol (solubility parameter δ=11.7) on changing of crystalline degree and crystallite size. It was found that treated fi bres showed sharper refl exion on diffractograms than untreated ones, i.e. they showed higher crystalline degree but smaller crystallite size.
Solvent‐ and glow‐discharge‐induced surface wetting and morphological changes of poly(ethylene terephthalate) (PET)
The effects of argon glow discharge and selected organic solvents on the surface wettability of poly(ethylene terephthalate) (PET) and on the wettability decay of glow discharged PET films were studied. Glow discharge in argon (30 W/1 min) drastically reduced the initial water contact angle (CA) measurement of PET from 67.0 to 26.2°. The glow-discharge-induced wetting, however, decayed during the first 7 days and stabilized at 33.1°. Treatments in dimethyl sulfoxide, dimethyl formamide, pyrdine, and water at 80°C caused some improvement in surface wettability as shown by decreases of water CAs in the range of 53–56°. When the solvent and glow discharge treatments were applied consecutively on PET, additive effects on improving surface wettability were observed. The stabilized water CAs of the solvent-and-glow-discharged films ranged from 25.0 to 32.1° depending upon the solvent type. The solvent treatments prior to glow discharge either reduced the extent of CA decay or the time taken to reach stabilization on PET films. Scanning electron microscopic evaluation showed no difference between the solventtreated and the untreated PET surfaces, but a finely etched surface was observed on the glow discharged PET at a 40,000 magnification and above. The distinctly different surface of the DMSO-and-glow-discharged PET indicated that morphological changes on PET surface were induced by the solvent.
Growth from Solutions
Growth from solutions is the crystallization of a compound whose chemical composition differs markedly from that of the initial liquid phase. Commonly used solvents are water, multicomponent aqueous or nonaqueous solutions, and melts of some chemical compounds. Differentiations are made based on growth temperatures and on the chemical nature of the solvent. In growth from low-temperature aqueous solutions, the temperatures generally do not exceed 80–90°C; in growth from superheated aqueous solutions (hydrothermal method), they reach 800°C, and in growth from salt melts (molten-salt, flux, or fluxed melt growth), they usually do not exceed 1200–1300°C, but sometimes reach 1500°C.