Jadranka Akalović’s research while affiliated with University of Zagreb and other places

Kako bi se utvrdila promjena obojenja odn. postojanost obojenja, uzorak vegetabilno štavljene kože podvrgnut je močenju u alkalnoj otopini znoja kako bi se izlučio višak tanina i drugih netaninskih tvari koje zbog svoje velike količine unutar stukture kože imaju snažan antimikrobni učinak, te u tom slučaju naknadna obrada nije potrebna. Remisijskim spektrofotometrom uzorci kože snimljeni su prije i nakon procesa močenja kako bi se utvrdila promjena obojenja objektivnim mjerenjem kolorističkih prametara boje i ukupne razlike u boji. Učinkovitost obrada ekološki prihvatljivom plazmom i biopolimerom hitozanom potvrđena je kod nekih uzoraka kože mikrobiološkim analizama spram dvije bakterijske vrste Staphylococcus aureus i Klebsiella pneumoniae , provedbom kvalitativnog testa difuzije.

For a long time, the production and processing of cowhide was based on the use of chrome tanning. However, the growing problem with chromium waste and its negative impact on human health and the environment prompted the search for more environmentally friendly processes such as vegetable tanning or aldehyde tanning. In the present study, we investigated the DNA-damaging effects induced in HepG2 cells after 24 h exposure to leather samples (cut into 1 × 1 cm2 rectangles) processed with different tanning agents. Our main objective was to determine which tanning procedure resulted in the highest DNA instability. The extent of treatment-induced DNA damage was determined using the alkaline comet assay. All tanning processes used in leather processing caused primary DNA damage in HepG2 cells compared to untreated cells. The effects measured in the exposed cells indicate that the leaching of potentially genotoxic chemicals from the same surface is variable and was highest after vegetable tanning, followed by synthetic tanning and chrome tanning. These results could be due to the complex composition of the vegetable and synthetic tanning agents. Despite all limitations, these preliminary results could be useful to gain a general insight into the genotoxic potential of the processes used in the processing of natural leather and to plan future experiments with more specific cell or tissue models.

The influence of differently tanned and finished bovine leather on thermophysiological properties was investigated. In addition, it was investigated whether sampling has a significant influence on the thermophysiological properties. The back of the tested leathers is thicker than the neck because of better microstructure regularity and uniformity as well as thicker and denser distributed fibrils than in the neck parts. The neck parts have a greater proportion of air-filled spaces between the fibrils, resulting in a higher thermal resistance of the leather neck parts. Considering the thickness of synthetic and chrome-tanned leathers (dyed and hydrophobized), the thinner chrome-tanned leathers (0.063 W m ⁻¹ °C ⁻¹ for the neck part, 0.090 W m ⁻¹ °C ⁻¹ for the back part part) have almost the same thermal conductivity as synthetic ones (0.065 W m ⁻¹ °C ⁻¹ for the neck part, 0.089 W m ⁻¹ °C ⁻¹ for the back part). Their thermal and water vapour resistance show considerable differences. There is no significant difference in water vapour resistance of the neck and back part of chrome tanned, dyed and hydrophobized leather (25.27 m ² Pa W ⁻¹ for the neck part; 25.15 m ² Pa W ⁻¹ for the back part) in contrast to equally treated synthetically tanned leather (30.38 m ² Pa W ⁻¹ for the neck part; 26.96 m ² Pa W ⁻¹ for the back part).The presented study could help in choosing the appropriate point of sampling, tanning as well as finishing agents for obtaining satisfying thermophysiological comfort in the wide range of leather application.

Full grain refers to the strongest and most durable part of the cattle hide, consisting of the grain layer and the part of the underlying corium, and has not been sanded or buffed to remove any imperfections, that means it displays the more natural characteristics of leather. Leather quality changes with sampling location and were also affected by tanning and finishing processes utilized during production. Full grain leather, instead finishing, sometimes go only through an ironing process for the desired sheen is obtained. Therefore, with the purpose of analysing the influence of the leather processing level, and sampling location on their usage quality, in this paper, differently tanned semi processed cattle full grain leathers, sampled from the bend, shoulder and belly of side leather cuts were evaluated. Their applicability for footwear uppers were assessed by measuring leather thickness, mass per unit area, apparent density, tensile strength and percentage elongation at break, as well as flexibility using penetrometer and flexometer, all according to the standardised test methods.KeywordsFull grain leatherSemi processed cattle leatherLeather testingUsage qualityFootwear

Investigations, which are related to plasma efficiency on the treated leather surface, are significant in the development of ecologically and economically friendly processes in obtaining material of desired functional properties. Through the pretreatments using plasma different chemical-physical reactions in the surface layer of treated leather are occurred resulting in improved reactivity. In this paper, modification and functionalization of bovine leather using 1,2,3,4-butantetracarboxylic acid and chitosan were explored. Pretreatments of leather samples were realised using argon and oxygen plasma to assess various influence of chemically reactive oxygen and inert argon gas. Two different bovine leathers -chrome tanned leather and leather tanned with synthetic tanning agent (Cr-free) were chosen for treatments. Analyse of the surface morphology was conducted with SEM microscopy, while the chemical changes using ATR-FTIR spectroscopy. Antimicrobial effectiveness of treated leather was tested with qualitative Agar diffusion plate test against two bacterial Staphylococcus aureus and Klebsiella pneumoniae . Obtained results indicated how applied oxygen and argon plasma pretreatments in optimized process conditions contribute to the improvement of tested functional properties. Achieved surface changes positively affected on leather surface reactivity and antimicrobial effectiveness, particularly Cr-free leather.

Full grain leather refers to the strongest and most durable part of the cattle hide, consisting of the grain layer and the part of the underlying corium, and has not been sanded or buffed to remove any imperfections, that means it displays the more natural characteristics of leather. Leather quality changes with sampling location, depending on variation present in the leather fibrous structure. Leather properties were also affected by tanning and finishing processes utilized during production. Full grain leather, instead finishing, sometimes go only through an ironing process for the desired sheen is obtained. Therefore, with the purpose of analysing the influence of the leather processing level, and sampling location on their quality, in this paper, the physical and mechanical properties of differently (synthetic and chromium) tanned finished and non-finished cattle full grain leathers, sampled from the bend, shoulder and belly of side leather cuts were evaluated. Their applicability for footwear uppers were assessed by measuring leather thickness, mass per unit area, apparent density, tensile strength and percentage elongation at break, all according to the standardised test methods.

U radu su ispitana svojstva otpornosti na zapaljenje i širenje plamena dvaju uzoraka vatrootpornih goveđih koža te njihova otpornost na djelovanje topline uz praćenje plinovitih produkata koji se javljaju prilikom toplinske razgradnje. Uzorci su podvrgnuti termogravimetrijskoj analizi (TGA) uz praćenje plinovitih produkata razgradnje (TG-IR) tijekom dekompozicije. S obzirom na rezultate gorivosti zaključeno je da ispitivani uzorci glatke goveđe kože pokazuju zadovoljavajuću stabilnost na djelovanje plamena i topline, dok je perforirana brušena vatrootporna koža s umjetnim licem djelomično pougljenila i skupila se u području neposrednog dodira s plamenom. Oba uzorka pokazuju slično ponašanje tijekom TGA, no razlike su uočene prilikom analize plinovitih produkata razgradnje.

This paper aims to investigate fire resistance properties of two samples of fireproof bovine leather; both with smooth and perforated brushed surfaces. Apart from flammability and flame spreading, an important property is heat resistance and the development of gaseous products that occur during heat degradation. For the purpose of characterizing those properties, cowhide leather samples were exposed to thermogravimetric analysis (TGA) of monitoring gaseous degradation products (TG-IR) during decomposition. Considering the results of fire resistance, it can be concluded that tested samples of smooth bovine leather show satisfactory stability to the influence of flame and heat, while perforated brushed fireproof leather with artificial surface was partially pouched and gathered in the area of direct contact with flame. Both samples show similar behavior during TGA, but differences have been observed in the analysis of gaseous degradation products.

Functionality and appearance are key aspects of good footwear. Developments in recent science and technology offer a wider scope of innovations, contributing to diversity and higher complexity of the production concept of footwear. Contemporary industrial footwear market offers a practically limitless number of new design and fashion solutions, often of quite similar appearance, but with significant differences in quality level, both regarding manufacture, raw material content, durability, and in some special functional finishes. The materials for footwear manufacture are functionalized for functional protective purposes, such as antimicrobial, waterproofing, fire resistant, wear and tear resistant, and recently for some therapeutical purposes. Novelties in material functionalization for the materials built in the footwear are most often promoted and presented on tags and labels and are used as advertisement issues, while some functionalities have become a logo for some brands.