Abstract:

Cotton fabrics have good water absorption properties, air permeability, non-toxicity, but microorganisms easily damage them. Collagen is a commonly used biomaterial that has properties such as biocompatibility, biodegradability, non-toxicity, but with poor mechanical properties. Glutaraldehyde is the main cross-linking agent for collagen and characterized by antimicrobial properties. ZnO nanoparticles exhibiting antibacterial, antifungal, anticorrosive and protective properties against UV, is widely applicable in medicine. The combination of all these components in one biocomposite with potential antimicrobial properties and healing effect can find application in medical practice. In this study, an attempt was made to improve the properties of cotton fabric by impregnating it with gelatin hydrogel cross-linked with glutaraldehyde and containing ZnO nanoparticles. Three methods of modification were applied, varying the mixing regimes of the components and the conditions. The composite materials were investigated by means of SEM, FTIR, and fluorescence analysis. The morphological analyzes of the samples modified by different methods show that the spherical particles of ZnO have changed into a flower-like structures; the particles are covered by the collagen film; and dispersed and agglomerated in certain places. FTIR analyzes prove interactions between the organic and inorganic components. This is also confirmed by the observed fluorescent properties, which are of different intensity. All these observations suggest good antibacterial properties that will be the subject of future research.

Keratin biomaterials have many different advantages over other biomolecules. A number of techniques have been studied to prepare keratin hydrolysates. Many of them use strong reagents and the processes take place under very drastic conditions. The present study focuses on the following aspects: producing keratin hydrolysates from various animal sources; application of various methods for extraction; comparison of the type of treatment over the degree of hydrolysis. Sheep wool samples were used, respectively native and alkaline pre-treated and samples of goat hair, respectively native and enzyme pre-treated. The methods used for the hydrolysis of keratin materials are: 1) by sulfotolysis with sodium pyrosulfate and urea; 2) with thioglycolic acid and 3) with sodium hydroxide. The obtained hydrolysates were characterized by qualitative reactions, spectrophotometric and FTIR analysis. It was found that the samples from one and the same animal source show very different properties and different degrees of hydrolysis. The highest degree of hydrolysis was achieved for the pre-treated samples. It was proved that the method of hydrolysis with NaOH is the most appropriate for sheep wool and to a much greater extent for the alkaline treated wool than for the native. The reducing agent: sodium pyrosulfate and urea is the most appropriate for enzyme pre-treated samples of goat skin. Therefore, pre-treatment of animal hair samples facilitates the hydrolysis process and makes it easier to break disulfide bonds. The disadvantage of proteins, and in particular keratins, is the difference in the structure of macromolecules, which are obtained from different animal sources. Therefore, this requires a specific approach to the hydrolysis of keratin from each individual animal source.

No abstract

ABSTRACT. The paper proposes a new approach to improve the technological properties of polychloroprene adhesives by changing the mixing regime. This approach has contributed not only to improving the rheological and mechanical properties of the adhesives used, but also for a detailed theoretical explanation of the rheological behavior. The purpose of this work is to study the rheological behavior of modified polychloroprene adhesive compositions in dependence of the amount of the modifying agent and the mixing regimes to achieve the optimal process parameters of bonding and prediction of their technological features. Seven types of polychloroprene-based adhesives were used and a modification with phenol formaldehyde resin was applied. Investigations were made on the influence of modifying agent amount, on rubber compounds processing regimes, on reaction conditions, on the rheological behavior of polymer fluids, on the interactions occurring between the rubber and the other components within the adhesive compositions, on the adhesion properties of the polychloroprene adhesives. Data from rheological analysis were compared with the results of microscopic observations and physico-mechanical properties. Using rheological analysis, it was found that the addition of resin to the rubber on the rolls during the mixing process favors the adhesion, leads to better wetting of the substrates and the formation of a strong glue joint. The optimal amount of the resin as an agent improving the compatibility between the oxides associates and the chloroprene rubber and the associates of the rubber itself was determined. KEY WORDS: chloroprene adhesives, resins, modification, rheology, strength STUDIUL COMPORTAMENTULUI REOLOGIC AL COMPOZITIILOR ADEZIVE POLICLOROPRENICE MODIFICATEREZUMAT. S-a propus o noua abordare pentru a îmbunatati proprietatile tehnologice ale adezivilor policloroprenici prin modificarea regimului de amestecare. Aceasta abordare a contribuit nu numai la îmbunatatirea proprietatilor reologice si mecanice ale adezivilor utilizate, ci si la o explicatie teoretica detaliata a comportamentului reologic. Scopul acestei lucrari este de a studia comportamentul reologic al compozitiilor adezive policloroprenice modificate în functie de cantitatea de agent de modificare si de regimurile de amestecare pentru a obtine parametrii optimi de lipire si pentru predictia caracteristicilor tehnologice ale compozitiilor. S-au utilizat sapte tipuri de adezivi pe baza de policloropren si s-a aplicat o modificare cu rasina fenol-formaldehidica. S-au efectuat investigatii privind influenta modificarii cantitatii de agent asupra regimurilor de prelucrare a compusilor de cauciuc, asupra conditiilor de reactie, asupra comportamentului reologic al fluidelor polimerice, asupra interactiunilor care apar între cauciuc si alte componente ale compozitiilor adezive si asupra proprietatilor de aderenta ale adezivilor policloroprenici. S-a facut o comparatie a datelor din analiza reologica cu rezultatele observatiilor microscopice si proprietatil...