Petar Skundric

The effects of hemicelluloses and lignin removal on water uptake behavior of hemp fibers.

This study investigated the individual influences of hemicelluloses and lignin removal on the water uptake behavior of hemp fibers. Hemp fibers with different content of either hemicelluloses or lignin were obtained by chemical treatment with 17.5% sodium hydroxide or 0.7% sodium chlorite. Various tests (capillary rise method, moisture sorption, water retention power) were applied to evaluate the change in water uptake of modified hemp fibers. The obtained results show that when the content of either hemicelluloses or lignin is reduced progressively by chemical treatment, the capillary properties of hemp fibers are improved, i.e. capillary rise height of modified fibers is increased up to 2.7 times in relation to unmodified fibers. Furthermore, hemicelluloses removal increases the moisture sorption and decreases the water retention values of hemp fibers, while lignin removal decreases the moisture sorption and increases the water retention ability of hemp fibers.

Biosorption of heavy metal ions from aqueous solutions by short hemp fibers: Effect of chemical composition

Sorption potential of waste short hemp fibers for Pb(2+), Cd(2+) and Zn(2+) ions from aqueous media was explored. In order to assess the influence of hemp fiber chemical composition on their heavy metals sorption potential, lignin and hemicelluloses were removed selectively by chemical modification. The degree of fiber swelling and water retention value were determined in order to evaluate the change in accessibility of the cell wall components to aqueous solutions due to the fiber modification. The effects of initial ion concentration, contact time and cosorption were studied in batch sorption experiments. The obtained results show that when the content of either lignin or hemicelluloses is progressively reduced by chemical treatment, the sorption properties of hemp fibers are improved. Short hemp fibers are capable of sorbing metal ions (Pb(2+), Cd(2+) and Zn(2+)) from single as well as from ternary metal ion solutions. The maximum total uptake capacities for Pb(2+), Cd(2+) and Zn(2+) ions from single solutions are the same, i.e. 0.078mmol/g, and from ternary mixture 0.074, 0.035 and 0.035mmol/g, respectively.

Microencapsulation in the textile industry

The application of microencapsulation techniques offers the possibility of producing novel products with many advantages compared to traditional textile products. The microcapsules can introduce important new qualities to garments and fabrics, such as enhanced stability and the controlled release of active compound(s). Although microencapsulation has found application in other business sectors during the last few decades (food, cosmetics Pharmaceuticals), a significant number of microcapsule-based commercial products appeared in the textile industry during the 1990s, while many potential new products are still in the research and development stage. The most attractive examples are fabrics with durable fragrances, T-shirts with UV-ray absorbing microcapsules, T-shirts with thermo-changeable dyes military uniforms with microencapsulated insecticide, thermo-regulation vehicle seats, ski suits, and gloves. In spite of important success in developing new products, there is a lot of space for further research especially in order to improve the mechanical strength of the obtained microcapsules and the kinetics and the mechanism of the release of active compound(s). Therefore, numerous research has focused on the development of new methods of applying of microcapsules on textile, new immobilization techniques and materials, are underway.

Some Properties of Antimicrobial Coated Knitted Textile Material Evaluation

The aim of this work was to investigate the antimicrobial activity of knitted fabric intended for medical purposes as well as the influence of antimicrobial treatment on the compression work, volume resistivity, water sorption. and water retention of the examined material. Polyamide/elastane plain jersey knitted fabric was treated with a polymer matrix of chitosan gel in which either gentamicin sulfate or autochthonous essential oil of Picea abies was incorporated as an active substance. The treated fabrics showed a wide range of antimicrobial activity on microorganisms (Staphilococcus aureus, Escherichia coli, Klebsiella and Candida albicans ) and therefore may have various medical applications. However, antimicrobial treatment changed the mechanical and physical-hygienic properties of the knitted fabric. The antimicrobial coatings decreased the total, elastic and irreversible compression work, water sorption, and volume resistivity, and increased the water retention of the fabrics. Antimicrobial treatment with chitosan and gentamicin sulfate produced a knitted fabric with good antimicrobial properties. However, if good mechanical and physical-hygienic properties are required, antimicrobial treatment with chitosan and essential oil of Picea abies has the advantage over treatment with gentamicin sulfate.

Wetting Properties of Hemp Fibres Modified by Plasma Treatment

Abstract The influence of dielectric barrier discharge (DBD) on the physico-chemical properties of hemp fibres was studied in this paper. Plasma-modification of hemp fibres was performed at atmospheric pressure. The source of the DBD was developed in the Quantum Optics Laboratory of the Faculty of Physics in Belgrade as a device prototype with plane-parallel geometry, for the continuous plasma-modification or treatment of textile materials. The capillary rise method was applied to evaluate the improvement in water uptake of the DBD treated hemp fibres. The plasmamodified hemp fibres have highly improved wetting properties without changing physico-mechanical properties (tensile strength and elongation).

New functionalities in cellulosic fibers developed by chemical modification

This paper gives an overview of the current state in the field of cellulosic fibers functionalization by chemical modification. The emphasis is placed on the selective (periodate and TEMPO oxidation) and non-selective (permanganate and peroxide) cellulose oxidation, non-conventional methods for obtaining man-made cellulosic fibers, methods for obtaining antimicrobial cellulosic fibers, as well as method for obtaining two-component polysaccharide fibers. To provide evidence on the achieved functionalities we mainly used capillary rise method, moisture and iodine sorption method, water retention power, NaOH uptake, different ions sorption, Cu-number, carbonyl-and carboxyl-selective labelling and antimicrobial tests.

Oxidized cotton as a substrate for the preparation of hormone-active fibers-characterization, efficiency and biocompatibility

Oxidized cellulose has a long history of safe and effective use in medical applications. In this paper, research has been directed towards obtaining hormone-active cellulose fibers in the form of an artificial insulin depot, and examination of its biocompatibility regarding cytotoxicity, sensitization, and irritation. The procedure of obtaining the fibrous insulin depot is based on the modification of cotton fibers with sodium periodate, followed by chemisorption of insulin from insulin aqueous solutions. In order to optimize the insulin chemisorption process, the influence of the fiber structure parameters, i.e. the aldehyde group content and iodine sorption value (ISV) on the chemisorption capacity was examined. The obtained artificial depot, containing ≈55 mg insulin/g of fibers, has been characterized in vitro by investigation of the desorption kinetics of the insulin from the fibrous depot. It has been shown that insulin is controllably released in quantities of 1.3-1.6 mg of insulin during 24 hours, in the course of 20 days. The results of biocompatibility tests have shown that the examined artificial depot neither shows irritating effects nor provokes sensitizing or cytotoxic effects. Therefore, these materials are acceptable for use in a direct contact with tissue of a living organism.

Antimicrobial Bioactive Band-Aids with Prolonged and Controlled Action

ABSTRACT The paper discusses the antimicrobial bioactive band-aids, a modem means of wound management and healing, which are effective against a wide spectrum of microorganisms. Ion-exchange fibres and nonwoven textile materials composed of PP/viscose blend were used as a textile basis. Antimicrobial bioactive band-aids were manufactured in two routs: - by chemisorption of gentamicin sulfate by ion-exchange fibres; and - by adhesion of gentamicin sulfate on nonwoven material with the aid of a polymer carrier (chitosan). For assessment of antimicrobial activity, the diffusion method on an agar medium has been used. Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella, Escherichia coli and Candida albicans have been utilised. The kinetics of active substance desorption has been examined through dissolving rate of medical substance from transdermal band-aid in vitro. Physical-chemical foundations and kinetics of desorption of gentamicin sulfate in vitro are described by a mathematical model which can be used for prognosis of prolonged release of medical substance from band-aid as a transdermal system.

ANTIBACTERIAL ACTIVITY OF SELECTIVELY OXIDIZED LYOCELL FIBERS

The purpose of this research was to study antibacterial activity of selectively oxidized lyocell fibers with incorporated silver particles against gram (+) and gram (-) pathogens. Antibacterial properties were accomplished by incorporation of silver ions into modified lyocell fibers by chemisorption from aqueous silver nitrate solution. In order to improve sorption properties of lyocell fibers, the selective TEMPO-mediated oxidation, i.e. oxidation with sodium hypochlorite and catalytic amount of sodium bromide and 2,2´,6,6´-tetramethylpiperidine-1-oxy radical (TEMPO), was applied. The influence of oxidation conditions оn the amount of sorbed silver, and thus on the degree of antibacterial activity was determined. It was found that the maximum amount of sorbed silver was 0.996 mmol/g cell. The antibacterial activity of the TEMPO-oxidized lyocell fibers with silver particles was confirmed in vitro against two strains: Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922). The silver-loaded TEMPO-oxidized lyocell fibers showed better antimicrobial activity against strain Staphylococcus aureus.

ANTIBACTERIAL FIBERS BASED ON CELLULOSE AND CHITOSAN

Cellulose and chitin are the most abundant polysaccharides in nature. Chitin is the natural amino polysaccharide and is estimated to be produced annually almost as much as cellulose. These resources are renewable and inexhaustible if rationally utilised. Unique properties of chitin and chitosan (chitin derivative obtained by the deacetylation of chitin), such as antibacterial activity, biocompatibility, non-toxicity and bioresorptivity make these materials very suitable and important biomaterials. During our studies, we examined the possibilities of obtaining composite, biologically active cellulose-chitosan fibres. Аn effective two-stage procedure for obtaining antibacterial fibers based on cellulose and chitosan was developed. The first stage involves the formation of dialdehyde cellulose by potassium periodate oxidation of cellulose fibers, which is able to form Schiff’s base with chitosan. In the second stage, chitosan coated cellulose fibers were prepared by subsequent treatment of oxidized cellulose fibers with a solution of chitosan in aqueous acetic acid. Maximum percentage of chitosan introduced into/onto the cellulose fibers was 0,51 % (w/w). Antibacterial activity of cellulose fibers coated with chitosan as the active component against bacteria Escherichia coli and Staphylococcus aureus, was confirmed by in vitro experiments .