Development of a Headspace-Solid Phase Micro Extraction Method for the Analysis of Volatile and Semi-Volatile Organic Compounds from Polyurethane Resins for Leather Finishing

Volatile organic compounds (VOCs) and Semi-Volatile Organic Compounds (SVOCs) arise from the chemicals used in the various stages of the leather manufacturing process. An important aim of the tanning industry is to minimize or eliminate VOCs and SVOCs, without lowering the quality of leather. This paper shows the development of a new headspace-solid phase micro extraction coupled with gas chromatography–mass spectrometry (HS-SPME/GC-MS) method for the identification of VOCs and SVOCs emitted by newly designed polymers for the leather finishing operation. These new polymers are polyurethane resins designed to reduce the VOC and SVOC concentration. This method enables a simple and fast determination of the qualitative and semi-quantitative content of VOCs and SVOCs in polyurethane-type finishing resins. The chemicals that are of concern in this paper are the following: Dipropylene glycol Monomethyl Ether (DPGME), DBE-3 (a mixture of dibasic esters) and Triethylamine (TEA). The test conditions that have been determined to carry out the HS-SPME assay are the following: incubation time (2 hours), extraction temperature and time (40°C; 5 minutes) and the desorption conditions (280°C, 50 seconds). Ten samples of laboratory scale resins were tested by HS-SPME followed by gas chromatography (GC-MS). DPGME and DBE-3 (a mixture of dimethyl adipate, dimethyl glutarate and dimethyl succinate) have been identified effectively. The compounds are identified by a quantitative method using external calibration curves for the target compounds. The technique is not effective to determine the TEA compound, since the chromatograms shown poor resolution peaks for the standard.

Hybrid Pigments Based on Montmorillonite and Anionic Dyes for Leather Finishing

The work is focused on obtaining hybrid pigments by adsorption of anionic dyes on positively charged montmorillonite. Modification of the sodium form of montmorillonite by chromium hydroxocomplexes was provided to ensure effective adsorption of anionic dyes on the surface of mineral particles. A high level of adsorption of anionic dyes as a result of steric factor was revealed. It was shown that the adsorption of dyes depended on the pH of the medium and was characterized by a maximum level at pH 4.5 – 6.0. The scheme of obtaining hybrid pigments, which were characterized by good сovering ability, resistance to stratification, especially saturated and intense colour was proposed.

Isolation and characterization of fungal and bacterial proteolytic strains from chrome shavings

The chrome shavings waste obtained as a result of the leather finishing process accumulates in a large volume in tanneries and represent a major problem for the environment. This waste are particularly resistant to attack of microorganisms, due to the significant concentration of chromium and are thus difficult to degrade. In this study, chrome shavings were analyzed microbiologically by determining the total number of germs and the number of yeasts and molds on specific culture media. Several bacterial and fungal strains were isolated from the cultures in Petri dishes, after the growth of the colonies. These strains were characterized in terms of the production of proteolytic enzymes, by a method of screening on the media with casein, which allows the determination of proteolytic indices of microorganisms. As a result of the tests performed, five bacterial strains probably belonging to the genus Bacillus and two fungal strains from the genera Penicillium and Cladosporium were selected.

Collagen hydrolysate from chromed shavings for leather finish

Chrome shavings are posing a pollution threat. An alkali-enzymatic hydrolysis method was utilized to get collagen hydrolysate (CH) as possible constituent for leather finishing formulations. The new enzyme preparation Vilzim PRO Conc was exploited for the hydrolysis. The dependence of CH properties on conditions of hydrolysis was explored. The direct addition 5% CH into finishing compositions increases tensile strength and relative elongation of films obtained from the compositions. Further increase of the collagen hydrolysate content in the films leads to worse mechanical properties of the films.

The influence of TiO2 and N-TiO2 nanopowders in natural leather finishing for heritage or modern binding

The methods for processing raw hides over time, have been numerous: smoke, fat, fermented milk, egg, volcanic soils, plants (shells, fruits, leaves) and so on. The books binding with leather has its origins in the Orient and are known various types of goatskin and calfskin, tanned with sumac finished marbled (sapphire), in black (Moroccan), by floating and dyeing in various colors (Cordoba leathers). Preoccupations regarding the assurance of optimal characteristics for the binding leathers, respectively the durability of the leathers for the restoration of the patrimony objects or of the modern binding were of the most topicality in the last decades, abroad and also in our country. The paper describes the finishing of vegetable and alum tanned leather samples that have been functionalized with titanium dioxide (TiO2) or nitrogen-doped titanium dioxide (N-TiO2) nanopowders, in different concentrations. To simulate soiling in real conditions, four types of soiling agents were applied: tea, coffee, beetroot extract and pen paste. The samples were exposed to irradiation in a photoreactor with various light sources for up to 192 hours. The evaluation of the photocatalytic degradation was performed by the CIELab technique.

Special effect finish for bookbinding leather

The art of bookbinding requires not only skills in the old craft of bookbinding but also materials that can transform a simple book into a high-quality artistic product. Due to its unique properties, leather still remains the first-choice material in the case of art and archival bindings. However, the long-term durability of modern leather is not known since there is little commercial interest in long periods of durability and the market of leather for art, design and archival purposes is very small. It is worth noting that deterioration is influenced by the manufacturing technology, and especially by the chemical ingredients used in the various steps of leather making, from dehairing to tanning and finishing. It is therefore very likely that modern and contemporary artworks made of/with modern leather undergo faster degradation than ancient and medieval artworks. Thus, leather finishing is very important for both artistic and sustainable points of view. In fact, finishes with special effects such as antique, bicolour, printed, cracked, waxy are highly sought for vegetable tanned leather used for artistic and luxury bookbinding, archival bookbinding and restoration purposes. The evolving leather finishing technology of chrome-free leather (i.e. vegetable tanned leather) has enabled us to protect and improve the quality, look and feel of leather and to make it suitable for contemporary art bindery.