Search Results (10)

The elastic response of chromium-tanned leather was successfully improved by treatment with XSBR, a carboxylated styrene-butadiene copolymer. The carboxylic groups pending from a styrene-butadiene rubber (SBR) backbone were found to promote penetration of the aqueous polymer dispersion into the fibrous tanned leather and participated in pH-reversible physical crosslinking by H-bonding. The different penetrations of XSBR or SBR were investigated using a micro-FTIR cross-sectional analysis from the grain (outer) to the flesh (inner) side of 18 wt% elastomer-treated samples, based on the shaved leather weight. In particular, the profile of the diagnostic out-of-plane =C-H bending of butadiene and styrene units was consistent with a more effective penetration of XSBR. The leather with XSBR showed a comparatively lower elastic modulus of 10–15% and roughly a 10% increase in elongation at the break, indicating better flexibility and shape recovery. Also, the leather was characterized by a 15% higher burst strength. These results suggest the better swelling of the ionomeric XSBR in the initial stage of retanning performed at a pH higher than the isoelectric point of the leather when both the tanned leather and the XSBR ionomer had a negative surface charge. The high pH favored the penetration of XSBR due to a poor attractive interaction with the tanned fibrous leather network. Subsequent processing in an acid bath caused further physical crosslinking through hydrogen bonding between XSBR and the leather. Full article

This study explores the development and characterization of biodegradable leather using alginate derivatives as sustainable tanning agents, aiming to reduce the environmental impact associated with traditional leather tanning processes. Alginate, a natural polysaccharide derived from brown algae, was modified through ultrasound treatment to reduce viscosity and improve its application in leather tanning. This study investigated the use of sodium alginates as bio-based retanning agents, comparing their performance against that of conventional chromium-tanned and vegetable-tanned leathers, as well as synthetic alternatives such as leatherette, Piñatex^®, and Desserto^®. The physical, chemical, and thermal properties of the resulting leathers were assessed. The results demonstrated that alginate-based tanning agents could produce leather with comparable or superior properties to conventional and synthetic leathers, meeting the quality standards required for high-end footwear and leather goods. This research highlights the potential of alginate derivatives to serve as eco-friendly alternatives in the leather industry. The findings underscore the feasibility of integrating bio-based materials into industrial applications, promoting environmental conservation and resource efficiency. Full article

The tanning industry generates effluents with high chromium content, which require treatment prior to discharge into the sewage system. This article explores the use of magnetic magnetite nanoparticles (MNPs) to remove Cr(VI) from aqueous solutions, such as tanning effluents. The MNPs were synthesized by coprecipitation reaction using the Olea europaea extract as a reducing agent. Subsequently, they were characterized by dynamic light scattering spectroscopy (DLS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). MNPs with irregular morphology and diameters ranging from 73.28 to 162.90 nm were obtained. Cr(VI) removal was performed using jar test methodology, and its efficiency was evaluated in the laboratory for different initial Cr(VI) (mg/L) concentration and nanoparticle (g/L) concentration. A kinetic study was developed and indicated that the equilibrium adsorption mechanism corresponds to a pseudo-second-order model. Furthermore, the isotherm analysis revealed that chromium adsorption best fits the Langmuir isotherm. Finally, Cr(VI) removal rates from 85% to 100% were achieved in tanning and retanning effluents. Full article

The aim of this paper was to develop a biopolymer based on raw materials not originating from petroleum chemistry to reduce the environmental impact. To this end, an acrylic-based retanning product was designed where part of the fossil-based raw materials was replaced with biomass-derived polysaccharides. Life cycle assessment (LCA) of the new biopolymer and a standard product was conducted to determine the environmental impact. Biodegradability of both products was determined by BOD₅/COD ratio measurement. Products were characterized by IR, gel permeation chromatography (GPC), and Carbon-14 content. The new product was experimented as compared to standard fossil-based product, and the main properties of leathers and effluents were assessed. The results showed that the new biopolymer provides the leather with similar organoleptic characteristics, higher biodegradability and better exhaustion. LCA allowed concluding that the new biopolymer reduces the environmental impact of 4 of the 19 impact categories analyzed. A sensitivity analysis was performed where the polysaccharide derivative was replaced with a protein derivative. The analysis concluded that the protein-based biopolymer reduced the environmental impact in 16 of the 19 categories studied. Therefore, the choice of the biopolymer is critical in this type of products, which may or may not reduce the environmental impact. Full article

In the present study, bark, which is the waste part of a tree, was utilized as a source of tannin for leather tanning after its value addition. The barks of Acacia nilotica L. and Eucalyptus globulus, which are abundantly available in Pakistan, were selected in this study. Different extraction techniques including mechanical, soxhlet, reflux and ultrasonic extraction were used for the extraction of tannin from the selected barks. The medium of extraction included aqueous as well as different solvent mixtures in different ratios. The solvent mixtures used in this study were methanol-water and acetone–water. The methanol–water ratio was kept (50:50) and the acetone–water ratio was maintained at (50:50 and 70:30). In the first step, the process of extraction was optimized for solvent mixtures and extraction time by taking a fixed dose (5 g) of each bark and a fixed volume of each extracting solvent mixture (150 mL). The total phenolic contents (TPC) of the bark extracts were determined by colorimetric assay (as mg GAE/g bark), taking gallic acid as the reference standard. The tannin contents (TC) of the bark extracts were determined by using the standard hide powder method (SLC 117). It was concluded that among the different extraction techniques, and among the solvent mixtures acetone–water in ratio (70:30), ultrasonic extraction resulted in maximum extraction of tannin (196.1 and 125.2 mg/g), respectively for A. nilotica and E. globulus. FTIR analyses of the dried extracts obtained from both barks were compared with FTIR of the most commonly used commercial vegetable tanning agent in the leather industry, i.e., mimosa. Results were comparable, which confirmed the presence of condensed tannin in both barks. The extracted tannin was applied on a pickle and wet blue leather to evaluate its tanning and re-tanning capability. Mimosa, the most abundantly used vegetable tanning material in the leather industry, was applied as a reference standard on the same pickle and wet blue leather for comparison. Different physical properties, such as leather shrinkage temperature, leather softness, tensile strength, percent elongation and breaking strength, were measured to evaluate the tanning efficacy of the extracted tannins. The results showed that tannin obtained from A. nilotica showed comparable physical properties to those of mimosa. It was concluded from the results that tannin obtained from locally available bark, i.e., A. nilotica, can be utilized as a vegetable tanning agent for the leather industry. Full article

Leather processing industries consume high volumes of water and chemicals and release effluents into the environment that pollute the surface water and may cause harm to human health. Leather processing involves different wet processing stages such as soaking, liming, chrome tanning, rechroming, neutralization, fatliqouring and dyeing. The pollution generated from the leather processing stages varies in volume, nature and concentrations. Qualitative and quantitative assessments of effluents generated from different stages of leather processing can be useful to understand the stagewise and overall water pollution of leather wet processing and to design and plan pollution abatement initiatives. Water footprints (WF) can help in understanding the total water consumption and water pollution caused by the leather sector. The objectives of this research are to assess the characteristics of effluents generated from different stages of leather processing, calculate the water footprint (WF) and analyze the pollution load of the Bangladesh leather sector. To perform experimental analyses, effluent samples were collected from the following leather processing stages: soaking, liming, deliming and bating, pickling and tanning, wet back, rechroming, neutralization, retanning, dyeing and fatliqouring from four leather processing factories. The key pollution indicating parameters, such as pH, chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solid (TDS) and total suspended solid (TSS) of the effluent samples were analyzed. The experimental study showed that almost 52% effluents generate from beam house and tan yard operations, and about 48% effluents generate from post tanning operations. Due to the presence of high amounts of salt, insecticides and bactericides, the effluent generated from the soaking stage contains high BOD and TDS. On the other hand, effluent generated from liming contains the highest amounts of BOD, COD, TDS, and TSS. The reduction or segregation of soaking and liming effluents will be effective in improving the environmental performance of the wet processing of leather. To assess the total water footprint of the leather sector, the water footprint of feed crops and raw hides were calculated, along with the water footprint of the leather processing stages. The water footprints of bovine and ovine crust leather were found to be 34,000 m³/ton and 17,300 m³/ton, respectively. The blue water footprint is higher in soaking, liming and finishing. The green water footprint of leather is mainly contributed by feed crops of farming animals. The grey water footprint was found higher in the soaking, liming, fatliqouring and dyeing stages. About 97% of the water footprints of tanneries are contributed by the wet processing stages. The grey water footprint is the most significant part of the total water footprint of the leather sector, which indicates the impact of high water pollution by the leather processing stages. This study can help to understand the overall scenario of water consumption and water pollution caused by the leather sector in Bangladesh. This study can also be useful in designing sustainable leather products by reducing the total water footprint per unit of leather goods. The systematic approach of this study could be useful for other countries in leather processing. Full article

The objective of this study was to develop a novel melamine-based resin suitable for producing formaldehyde-free leather with improved retanning properties. The resin was prepared by optimized condensation of melamine, glyoxal and metanilic acid. The novel resin was compared with a commercial resin against different parameters. Functional group analysis of the polymer structure and the route of synthesis was verified with the help of FT-IR spectroscopy. A Leica metallurgical microscope coupled with a CCD camera was used for SEM analysis. The results revealed that the mechanical and organoleptic properties of the novel resin were better than those of the commercial melamine resin. Tensile strength, tear strength and percentage elongation of leather were increased by 17.43%, 10.41% and 8.62%, respectively, in the direction parallel to the backbone, while the increases in these parameters were 15.17%, 9.79% and 6.0%, respectively, in the direction perpendicular to the backbone at the same dose. We observed a 100% reduction in free formaldehyde content in retanned leather as well as in effluent produced by the novel melamine resin. Pollution load study of effluent showed reductions in chemical oxygen demand, total suspended solids and total dissolved solids by 9.21%, 5.60% and 6.97%, respectively, for the novel melamine resin, reflecting its improved exhaustion. The fiber structure of the leather produced by the novel melamine resin was more orderly arranged, showing its improved retanning. These results prove that the novel melamine resin is an effective retanning agent suitable for producing formaldehyde-free leather with a reduction in effluent pollution load. This work introduces an alternative to formaldehyde for amino resins to address its carcinogenic effects. Full article

In leathers, formaldehyde is currently analyzed according to EN ISO 17226-1 standard, by reversed phase liquid chromatography after off-line precolumn derivatization with 2,4 dinitrophenylhydrazine (DNPH) in strong acidic conditions. We first demonstrate that this standard is not adapted to leather retanned with resins likely to release formaldehyde by hydrolysis. Indeed, formaldehyde content may be largely overestimated due to concomitant resin hydrolysis (in harsh acidic conditions) that releases formaldehyde during the derivatization step and during the waiting time on autosampler before analysis. Therefore, we thoroughly studied the derivatization step in order to propose new derivatization conditions. Replacing orthophosphoric acid by less acidic buffer solutions is not enough to avoid hydrolysis. A derivatization without adding acid is realized by solubilizing DNPH in acetonitrile instead of orthophosphoric acid. These conditions lead to a complete derivatization of formaldehyde in 3 h at 50 °C (in a water bath) while avoiding the hydrolysis of co-extracted dicyandiamide and melamine resins. The as-obtained leather extracts are stable over time. Formaldehyde contents found with this method agree with the formaldehyde content measured immediately at the end of derivatization reaction in standard conditions or with formaldehyde content measured by a home-designed flow injection analysis with acetylacetone online derivatization and UV detection. Full article

Over last few years, polyurethane (PU) has been applied in a number of areas because of its remarkable features, such as excellent mechanical strength, good abrasion resistance, toughness, low temperature flexibility, etc. More specifically, PU can be easily “tailor made” to meet specific demands. This structure–property relationship endows great potential for use in wider applications. With the improvement of living standards, ordinary polyurethane products cannot meet people’s growing needs for comfort, quality, and novelty. This has recently drawn enormous commercial and academic attention to the development of functional polyurethane. Among the major applications, PU is one of the prominent retanning agents and coating materials in leather manufacturing. This review gives a summary of academic study in the field of functional PU as well as its recent application in leather manufacture. Full article

Enzymatically processed animal biomass derived from treated bovine hides (wet blue scraps) is herein used as building block for the synthesis of a novel biopolymer. An enzymatic hydrolysis process allows to produce water-soluble lower molecular weight proteins (Bio-A), which are then reacted with glycerol and maleic anhydride (MA) in order to obtain a new intermediate (Bio-IA). With Bio-IA in hand, co-polymerization in the presence of acrylic acid is then carried out. Hydrolysed biomass, intermediates and the final biopolymer (Bio-Ac) have been characterized by means of NMR, FTIR and GPC analysis. Bio-Ac shows good performance when used as retanning agent to produce leather. Physical and mechanical properties of the leather treated with Bio-Ac have been compared with acrylic resin retanned leather, showing similar performance. The reported protocol represents an environmental-friendly interesting alternative to traditional petrochemical based retanning agents, commonly used by the leather industry. Full article