Prilog proučavanju dobijanja hemijskih dvokomponentnih vlakana specijalnih svojstava na bazi polisaharida

Abstract

U teorijskom dijelu ovog rada dat je pregled dosadašnjih dostignuća i objavljenih radova iz proučavane oblasti, sa posebnim osvrtom na strukturu i mehanizam rastvaranja celuloze i hitozana kao osnovu za dobijanje hemijskih vlakana na bazi ovih polisaharida. U eksperimentalnom dijelu rada su istraživane mogućnosti dobijanja visokokvalitetne celuloze iz kratkih vlakana konoplje, rastvaranje celuloze i hitozana u N-metilmorfolin-N-oksidu (NMMO) i oblikovanje rastvora celuloze i hitozana u vlakna i filmove. Rastvorljivost i kristalisanje dobijenih rastvora su praćeni korištenjem polarizacionog mikroskopa. Poređena su reološka svojstva rastvora celuloze iz vlakana konoplje i bukove tehničke celuloze u NMMO, kao i fiziko-mehanička svojstva vlakana dobijenih iz ovih rastvora. U radu su korištene instrumentalne metode: infracrvena spektroskopska analiza (IR), spektroskopija fotoelektrona emitovanih X-zracima (XPS) i skenirajuća elektronska mikroskopija (SEM). Istraživane su i mogućnosti dobijanja dva tipa dvokomponentnih biološki aktivnih vlakana na bazi celuloze i hitozana. Za dobijanje vlakna tipa fibrili-matrica korišten je postupak oblikovanja mješavine rastvora celuloze iz vlakana konoplje i rastvora komercijalno dostupnog hitozana u NMMO. Za dobijanje vlakna tipa omotač-jezgro primijenjen je dvostepeni postupak. Prvi stepen uključuje oksidaciju liocel vlakna s kalijum perjodatom pri čemu nastaje dialdehidna celuloza (DAC), koja je sposobna da formira Šifovu bazu sa hitozanom. U drugom stepenu su, obradom oksidisanih liocel vlakana s rastvorom hitozana u sirćetnoj kiselini, dobijena liocel vlakna naslojena hitozanom, odnosno vlakna tipa omotač-jezgro. Vlakna tipa fibrili-matrica nisu pokazala zadovoljavajuća fiziko-mehanička svojstva, zbog čega su za dalji rad odabrana vlakna tipa omotač-jezgro. Uticaj primijenjenog dvostepenog postupka na hemijska i fizička svojstva vlakana je praćen određivanjem gubitka mase, sadržaja karbonilnih grupa, finoće i prekidna jačine, kao i sadržaja hitozana u kompozitnim vlaknima celuloza-hitozan. Antibakterijska aktivnost liocel vlakna naslojenih hitozanom prema bakterijama Escherichia coli i Staphylococcus aureus, potvrđena je in vitro eksperimentima. Ostvareni rezultati ukazuju na mogućnost dobijanja visokokvalitetne celuloze iz kratkih vlakana konoplje i oblikovanja rastvora dobijene celuloze u NMMO u vlakna i filmove istih ili poboljšanih fiziko-mehaničkih svojstva u poređenju sa vlaknima od tehničke bukove celuloze. Pored toga, razvijen je efektivan dvostepeni postupak za dobijanje dvokomponentnih biološki aktivnih vlakana na bazi kompozita celuloza-hitozan.

In theoretical part of this work, an overview of up to date achievements and papers related to this field of studing, with special attention to structure and mechanism of cellulose and chitosan dissolution, as a ground for obtaining chemical fibers on the basis of these polysaccharides is given. In the experimental part of the work, possibilities of obtaining high quality cellulose from the short hemp fibers, dissolution of cellulose and chitosan in N-methylmorpholine-N-oxide (NMMO) and fibers and films forming from the cellulose and chitosan solutions, were investigated. Dissolution and subsequent crystallization of obtained solutions were observed using a hot-stage polarized light microscope. The rheological properties of the solutions of hemp and beech cellulose in NMMO were compared, as well as a physical and mechanical properties of fibres obtained from these solutions. In this study the following instrumental methods have been used: Infrared Spectroscopy (IR), X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). Possibilities of obtaining two types of bicomponent biologically active fibres based on a cellulose and chitosan were examined. A fibril-matrix type of fiber was prepared by method for fibers forming from the mixture of solution of cellulose obtained from hemp fibers and solution of commercial chitosan in NMMO. For a cover-core type of fiber an effective two-stage method was developed. The first stage involves the formation of dialdehyde cellulose by the potassium periodate oxidation of lyocell fibers, which is able to form Schiff’s base with chitosan. In the second stage, chitosan coated lyocell fibers, namely cover-core type of fibers, were prepared by subsequent treatment of oxidized lyocell fibers with a solution of chitosan in aqueous acetic acid. Since fibril-matrix type of fibers did not show satisfactory physical and mechanical properties, for further examination the cover-core type of fibers were selected. The impact of this two-stage procedure on chemical and physical properties of fibers was evaluated by determining weight loss, carbonyl group content, fineness and tensile strength of fibers, as well as chitosan content in the composite cellulose-chitosan fibers. Antibacterial activity of the chitosan coated lyocell fibers against bacteria Escherichia coli and Staphylococcus aureus, was confirmed by in vitro experiments. Achieved results are indicative of possibility of obtaining high quality cellulose from the short hemp fibers and formation of fibres and films from solutions of obtained cellulose in NMMO, of the same or improved physical and mechanical properties compared to those made of technical beech cellulose. An effective two-stage method for obtaining bicomponent biologically active fibres based on a composite cellulose-chitosan was also developed.