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Describes experiments on properties of leather performed by a science teacher, assisted by senior science students. Concludes that the finish layer contributes a major part of the resistance to air passage, reducing permeability of leather. Flexing increases permeability and may, in its action, discriminate between finishes. (Author/JN)

The purpose of this study is to explore a theoretical idea in relation to a body of empirical material from a reading activity involving a picturebook on shadow. The theoretical idea, sprung from variation theory, entails children's discernment through synchronic simultaneity as a key to their ability to imagine. To explore this idea, an analysis has been conducted on how 5-year-olds, in words and actions, express themselves in a reading activity involving The Black Rabbit (Leathers, 2014) in regard to discerning and imagining about shadow as a light phenomenon. Vygotsky describes children's previous experiences as a key to their ability to imagine. The results of this study imply that children's discernment in the moment, with synchronic simultaneity, appears to be another key that unlocks their ability to imagine explicit depictions in a picturebook. The results also show that when children's discernment with both synchronic and diachronic simultaneity (i.e., discernment in the moment and before the moment) is missing, their ability to imagine remains untapped, as none of the keys to their imagination, which might unlock their ability to imagine implicit depictions in a picturebook, are used. [ABSTRACT FROM AUTHOR]

In order to achieve batch production, we propose a simple and fast method to prepare leather-finished plywood. In this study, ethylene–vinyl acetate was selected as the intermediate layer to prepare EVA/polyurethane (PU) leather composites. ESEM, tensile property test and compressive property test were used to characterize the microstructure and physical-mechanical properties of the composites. The response surface method (RSM) was also used to explore the relationship between hot pressing temperature, hot pressing pressure and hot pressing time. The significance of the factors and the interactions between the two factors were determined by ANOVA, with the most significant effect being that of the temperature. The theoretical optimal hot pressing process conditions were calculated by the regression equation as a temperature of 124.4 °C, a time of 200 s and a pressure of 1.3 MPa. The surface bond strength of the test specimen measured under this condition was 1.89 MPa, it has good finishing properties and the impregnation peel strength and surface bond strength met the requirements of GB/T 15104-2021. [ABSTRACT FROM AUTHOR]

Quantifying the degree of deterioration is crucial for developing prevention strategies for archaeological leather. In this work, the morphology, chemical compositions, and physical properties of artificially aged leather samples were analyzed using a series of test methods to determine non-destructive or micro-destructive technologies for quantifying the degree of deterioration in archaeological leather. Results show that the hydroxyproline (Hyp) content of leather decreases with the increase of deterioration degree because deterioration leads to the gradual destruction of the collagen fiber network of leather. Moreover, the Hyp content of leather can be micro-destructively determined by high-performance liquid chromatography with fluorescence detection. Therefore, the determination of Hyp content is recommended to quantify the degree of deterioration in archaeological leather. [ABSTRACT FROM AUTHOR]

Vegetable tannins are environmentally friendly tanning agents. However, they generally impart a dark colour to the tanned leather and highly contribute to the organic load in wastewaters. In this study, we employed a purification protocol separately on chestnut tannin (CT) and sulfited quebracho tannin (QT) to obtain the purified fractions (PCT and PQT). These samples were characterised by GPC, 1H NMR, 13C NMR, FT-IR, and HPLC–DAD techniques and applied for tanning tests. Through the purification process, non-tannin components and smaller molecules such as gallic acid, glucopyranose, and catechin were effectively removed from CT and QT, which consequently led to the reduced moisture content, pH value, and lighter colour of purified fractions. The crust leathers processed with PCT and PQT showed desirable light shades. Moreover, the organic loads in PCT and PQT tanning wastewater were reduced by 13.5% and 19.1%, respectively, when compared to those in traditional CT and QT tanning wastewater. Additionally, the physical and mechanical characteristics of crust leathers processed with PCT and PQT were comparable to those processed with CT and QT. Thus, purification of vegetable tannins may serve as a feasible strategy for producing light-colored vegetable-tanned leather while minimizing organic pollutant discharge during the vegetable tanning process. [ABSTRACT FROM AUTHOR]

For a long time, the leather industry has considered the chromium tanning process to be the easiest and fastest way to treat raw hides and transform them into valuable products. In the last few decades, increasing attention has been paid to the potential oxidation of the trivalent chromium in tanned leather. This happens for many reasons, such as the quality of the tanning agent or the adoption of good manufacturing practices. Anyway, the main problem, which is difficult to solve, is the sensibility of the free residual chromium tanned leather, which is high enough for possible harmful activity. Given this scenario, this work proposes a solution to decrease hexavalent chromium formation by using antioxidants during the leather tanning process. In this regard, a screening work was started, to find the worst-case scenario for trivalent chromium oxidation. To do this, commercial tanning products were employed, especially fatliquoring agents, which, in some cases, are the main source that could easily react with ROS (Reactive Oxygen Species) to drive chromium oxidation. After the determination of conditions, different groups of common antioxidants were tested to analyse the antioxidation performances and their possible use in the chromium-based tanning process. The results underline the efficient action of the antioxidants studied, paving the way for some interesting perspectives to limit the drawbacks of chromium tanned leather. [ABSTRACT FROM AUTHOR]

Fruit leathers are convenient, delicious and sophisticated alternatives to natural fruits as a source of nutrients, fibers and bioactive compounds. The present study was conducted to develop new fruit leathers by adding 0.5%, 1.0% and 1.5% wild bilberry (BIPP) and blackcurrant (BCPP) pomace powders in pear leather manufactured with honey (5%), pectin (1%) and lemon juice (2.5%) as additional ingredients. The CIEL*a*b* color parameters, titratable acidity, total phenolics content, total anthocyanins content and DPPH radical scavenging activity were determined in the fruit leathers. In addition, the puncturing force, flexibility and adhesiveness of the fruit leathers were measured and sensory analysis was conducted. The results showed that the addition of pomace powders significantly decreased the lightness, chroma and hue angle and increased the titratable acidity of the fruit leathers while a* values decreased in the leathers with BIPP addition. Flexibility slightly decreased while adhesiveness significantly increased with increasing BIPP and BCPP addition level, changes that were perceived as negative in the sensory analysis. The total phenolic content increased by 2.03, 3.26 and 4.45 times at 0.5, 1.0 and 1.5% BIPP addition, respectively, while only by 1.22, 1.42 and 1.60 times at the same levels of BCPP addition. The newly developed fruit leathers could be recommended as alternative snack foods with high nutritional value and functionality. [ABSTRACT FROM AUTHOR]

Natural leather-based materials possess a combination of air permeability, wear resistance, and plasticity. However, conventional leather products have inherent limitations that make them unsuitable for unconventional applications. Therefore, it is necessary to develop new capabilities in order to overcome these limitations. In this study, we explored the conversion of regular leather into a high-strength product with hydrophobic properties through surface engineering. To achieve this, we synthesized polysiloxane-modified fluorinated waterborne polyurethane emulsions as functional coatings using emulsion polymerization. The structure and properties of the treated leathers were characterized using techniques such as Fourier transform infrared, thermogravimetry, X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. The results demonstrated that the synthesized polysiloxane-modified fluorinated waterborne polyurethane successfully penetrated and combined with the fibers of the leather, resulting in excellent hydrophobicity. The water contact angle increased to 124.3°. Furthermore, the tensile strength and tear strength of unfinished leather are 875 N and 114 N, respectively. The application of waterborne polyurethane-derived functional additives as coatings resulted in a significant increase in tensile and tear strength of the leather by 60 N and 16 N, respectively. In addition, the softness of the leather increased from 7.6 mm to 10.09 mm. Overall, the use of this functional waterborne polyurethane coating will contribute to the diversification of leather applications. [ABSTRACT FROM AUTHOR]

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This research concentrates on the developmemnt of sustainable formulation of an environmentally friendly structural composite using an innovative approach, incorporating recycled materials. The primary aim of this research is to utilize the industrial wastes as re-circulated input to make structural materials without using new raw materials. Waste plastic, tanned waste leather, and waste glass fiber-reinforced plastic (GFRP) additives. The fabrication employs the hand layup method, and the composite undergoes comprehensive characterization following ASTM standards. According to the results, the composite designation "D" emerged as the most mechanically robust, with a tensile strength of 142 MPa, flexural strength of 195 MPa, compression strength of 156 MPa, interlaminar shear strength of 45 MPa, rail shear strength of 31 MPa, and an impact energy of 4.94 J. Concerning creep behavior, the "E" designation demonstrates minimal creep strain, recording values of 0.0057, 0.0076, and 0.0123 for 5000 s, 10000 s, and 15000 s time frame, respectively. This indicated the addition of 5 vol. % of GFRP additives improved the load-bearing effect. In terms of flammability, the "E" designation exhibits noteworthy flame resistance, with a low flame propagation speed of 10.83 mm/min. Additionally, the "E" designation demonstrates stable hydrophobic behavior, revealing a minimal water absorption percentage of 0.001. This study showcases the potential of the developed composite, emphasizing its mechanical strength, resistance to creep, flame retardancy, and hydrophobic properties, positioning it as an environmentally responsible and versatile material for diverse applications. [ABSTRACT FROM AUTHOR]

This study was based on an epoxy hybrid biocomposite made of silane-treated goat tanned leather that had been toughened with treated chitosan carbohydrate polymer (CCP) and areca fiber that had been treated with silane. The objective was to examine how silane-treated CCP and a hybrid type of fiber and leather enhance the epoxy biocomposite's mechanical and impact toughness. Aqueous solution silane treatment was used to treat the fiber and tanned leather, and the hand layup method was used to create the composites. The mechanical characteristics of the composite material Areca/Leather/Areca (ALA2) with addition 1.0 vol.% of CCP results in improvements to the maximum tensile, flexural, strength and modulus, Izod impact toughness, and hardness test values of 172 MPa, 4.98 GPa, 208 MPa, 5.30 GPa, 7.0 J, and 87 Shore D. The hybrid form of fiber and leather increased the low-velocity impact maximum up to 10.5 J and 11.3 J for reinforcements that were as-received and those had been surface treated as well as introduced with 1.0 vol.% of CCP, respectively. The addition by 1.0 vol.% of CCP for the ALA staking sequence resulted in a maximum fatigue life count of 32847. The composite designation ALA2 is therefore advised for further application, and it is suggested that Areca/Leather/Areca hybrid layup sequences with silane-treated 1.0 vol.% CCP produce the best results. In both surface-treated and as-received conditions, the ALA layup sequences outperformed other composite designations. When a high impact toughening effect is required, such composite materials with higher impact toughness and toughness may be used in the defense, automobile, drone, and structural industries. [ABSTRACT FROM AUTHOR]

The utilization of leather waste (LW) in a polyurethane (PU) matrix makes a smart and novel shape stable phase change material (SSPCM). This is essential for sustainability as it reduces landfill waste after use. The PU is synthesized in bulk with a 90% yield, using biodegradable polycaprolactone diol and bio‐based polyol (castor oil), along with tolylene‐2,4‐diisocyanate. PL and PLG composites are prepared by blending of constituent components PU (P), LW (L), and poly(glycidyl methacrylate) (PGMA, G), as specified by their code names. Role of LW (hydrogen bonding and chemical crosslinking) and morphology are elucidated by FTIR and SEM, respectively. Self‐healing time (2 h), shape fixity ratios (Rf) (PL: 60–80% and PLG: 60–70%) and shape recovery ratios (Rr) (100% for both) are determined at 60°C. PLG displays faster shape recovery in water (<30 s) compared to air (>300 s). Shape stability and thermal properties of the SSPCM are examined using the temperature responsive leakage study, TGA, and DSC. This research introduces a new approach for using leather waste (LW) in SSPCM, with self‐healing and 100% Rr. This material may find application where SSPCM with high durability and flexibility is essential such as textile and footwear materials. [ABSTRACT FROM AUTHOR]

Pestil, also known as fruit leather, has emerged as a promising non‐dairy carrier for probiotics, utilizing apricots and incorporating probiotics into its formulation. This study aimed to develop a healthy snack bar by incorporating three distinct strains of probiotic bacteria, both in free and encapsulated forms, into the recipe of apricot leather. The physicochemical, bioactive, microbiological, and textural attributes of the resulting apricot pestils were evaluated over a 120‐day storage period. Fluctuations in pH (4.74–4.97) were observed during storage, whereas water activity (0.31–0.45) and moisture content (8.05%–13.40%) exhibited a decreasing trend over time. Incorporating free or encapsulated bacteria resulted in a darker surface, attributed to the intermolecular interactions between probiotics and the pestil matrix. The initial total phenolic content was highest and declined significantly during storage (52.13–291.73 mg gallic acid equivalent/100 g) (p < 0.05). Viability was found to be higher in the encapsulated forms of bacteria at the conclusion of the storage period. Overall, apricot pestil emerged as a promising matrix for viable probiotics, facilitating their delivery and hosting in both free and encapsulated forms during storage. [ABSTRACT FROM AUTHOR]

One of the most crucial components in any industrial operation is energy. However, the supply is not limitless. One of the key ingredients in cement production is energy, whose cost share ranges from 8 to 15% of overall production costs in developed nations but is much more in undeveloped nations. Therefore, the objective of this extensive research was to carry out a thorough energy conservation audit at the Sheba leather factory, located in the city of Mekelle, in the north region of Ethiopia. The specific objective of this research was to analyse the patterns of power consumption, identify energy-saving techniques, as well as to propose energy-saving recommendations for their implementation. It was obtained using primary and secondary data from the industry personnel. As a result, a total of 19 recommendations for energy saving were found and were forwarded for consideration. These recommendations have the potential to save a total of about $ 29900 annually, but their implementation would cost close to $ 15900, with a payback period of seven months. These recommendations also cover the utilities of the boiler, motors, blower, air compressors, cooling tower, and lighting. In order to lower their energy use, economic benefits are also considered. [ABSTRACT FROM AUTHOR]

For a long time, the leather industry has considered the chromium tanning process to be the easiest and fastest way to treat raw hides and transform them into valuable products. In the last few decades, increasing attention has been paid to the potential oxidation of the trivalent chromium in tanned leather. This happens for many reasons, such as the quality of the tanning agent or the adoption of good manufacturing practices. Anyway, the main problem, which is difficult to solve, is the sensibility of the free residual chromium tanned leather, which is high enough for possible harmful activity. Given this scenario, this work proposes a solution to decrease hexavalent chromium formation by using antioxidants during the leather tanning process. In this regard, a screening work was started, to find the worst-case scenario for trivalent chromium oxidation. To do this, commercial tanning products were employed, especially fatliquoring agents, which, in some cases, are the main source that could easily react with ROS (Reactive Oxygen Species) to drive chromium oxidation. After the determination of conditions, different groups of common antioxidants were tested to analyse the antioxidation performances and their possible use in the chromium-based tanning process. The results underline the efficient action of the antioxidants studied, paving the way for some interesting perspectives to limit the drawbacks of chromium tanned leather.

Abstract Vegetable tannins are environmentally friendly tanning agents. However, they generally impart a dark colour to the tanned leather and highly contribute to the organic load in wastewaters. In this study, we employed a purification protocol separately on chestnut tannin (CT) and sulfited quebracho tannin (QT) to obtain the purified fractions (PCT and PQT). These samples were characterised by GPC, 1H NMR, 13C NMR, FT-IR, and HPLC–DAD techniques and applied for tanning tests. Through the purification process, non-tannin components and smaller molecules such as gallic acid, glucopyranose, and catechin were effectively removed from CT and QT, which consequently led to the reduced moisture content, pH value, and lighter colour of purified fractions. The crust leathers processed with PCT and PQT showed desirable light shades. Moreover, the organic loads in PCT and PQT tanning wastewater were reduced by 13.5% and 19.1%, respectively, when compared to those in traditional CT and QT tanning wastewater. Additionally, the physical and mechanical characteristics of crust leathers processed with PCT and PQT were comparable to those processed with CT and QT. Thus, purification of vegetable tannins may serve as a feasible strategy for producing light-colored vegetable-tanned leather while minimizing organic pollutant discharge during the vegetable tanning process. Graphical Abstract

Introduction: Leather has been a significant source of chromium (Cr) allergy in Denmark since the 1990s. More recently, cobalt (Co) allergy has been identified in leather as a source of allergic contact dermatitis. Objectives: To measure Cr and Co levels in Danish leather goods. Methods: A total of 87 leather samples were collected, all tanned in Europe. Handheld X‐ray fluorescence (XRF) device was used to screen for the presence of Cr and Co. The 20 leather samples with the highest concentrations of Co and Co were tested using International Organization for Standardization (ISO)‐standards. Results: XRF analysis showed Cr in 78/87 (83.9%) samples and Co in 52/87 (59.7%), with average concentrations of 41 mg/kg (range: 0.0–77 mg/kg) and 0.22 mg/kg (range: 0.0–2.9 mg/kg), respectively. ISO 10195 and 17 075–1 testing identified Cr (VI) in 7 out of 20 samples (1.4; 0.3–4.2 mg/kg), while ISO 17072‐1 detected Co in 6 of 20 samples, averaging 3.95 mg/kg (range: 0.22–7.9 mg/kg). Conclusion: Most leather samples contained Cr, which was expected, while Cr (VI) was detectable in seven out of twenty tested samples but only detected in one product above the regulatory limit of 3 mg/kg. A potentially significant concentration was found for Co. [ABSTRACT FROM AUTHOR]

Global demand for the water monitor's skin, Varanus salvator, has made it a valuable wildlife commodity. Leathercraft manufacturing must consider not only beauty but also the strength and flexibility of the leather, which is determined by its structure in the skin. Therefore, this study analyzed and evaluated the fiber type characteristic of the water monitor's skin. Skin samples were collected from 10 Sumatra water monitors with a Snout-Vent Length size of 39-89 cm and were divided into small (39-59 cm) and large (60-89 cm) groups. The skins from the dorsocervical, lumbosacral, and ventral regions were proceeded for histological sections. Histochemical approaches utilized were Hematoxylin Eosin, Picrosirius Red, and Elastin Verhoeff's Hematoxylin staining methods. Thick fibers are the main component in the skin, ranging from 69-73%, respectively, while thin fibers varied greatly and were observed predominantly in the reticular dermis. Fiber size in the reticular dermis of small lizards was lower than that of larger ones. Elastic fibers were observed abundantly at the border of the reticular dermis and subcutaneous layer in both small and large lizards. Moreover, the skin of the small-sized lizard also has a lower morphometric than that of a large-sized lizard, both in thickness and fiber type percentage. Therefore, the skin of small-sized lizards was considered less tough than that of large-sized lizards. [ABSTRACT FROM AUTHOR]

PT ASA is a leather tanning company. Almost 65% of the company's assets are allocated for the procurement of raw leather, which consists of goat and sheepskin. In addition to being expensive, the availability of raw leather is also very limited. The company faces a trade-off where, on one hand, the raw material is easily decayed, but on the other hand, its availability is extremely limited, and if there is not enough inventory, the production process will be disrupted. In this research, a multi-objective optimization model is developed for controlling the inventory of raw leather using the Fuzzy Goal Programming approach. The objectives to be achieved are to minimize the total inventory cost, maximize the total quantity of raw leather that meets standards, and minimize the total cost of losses due to decayed raw leather. Based on the calculations, the fuzzy goal programming membership function value is obtained at 0.9155, with a total inventory cost over the planning horizon of IDR 10,341,630,000, a total of 1,279,542 sq ft of raw leather meeting standards, and a total loss cost due to decayed raw leather of IDR 142,911,691.

Hides and skins, the main raw materials for leather industries, are traditionally preserved with sodium chloride (NaCl). Due to the excessive use of salt (around 40 to 50% w/w) in the curing process, total dissolved solids (TDS), and salinity are produced in large quantities by the soaking effluent during the leather processing. To address the resulting environmental threat from the tanneries and replace traditional curing, plant-based curing is a cutting-edge green technology. In this study, Tamarindus indica leaves were used as a combination of 5% powder + 10% salt and 10% paste + 10% salt to preserve goat skin for 28 days. The organoleptic characteristics, hydrothermal stability, moisture content, nitrogen content, and bacterial load were periodically monitored. After curing, the goatskin was processed into leather, the environmental impact of the wastewater was evaluated, and its physical and fibre strength was assessed. The TDS value, chloride content, biochemical oxygen demand, and chemical oxygen demand were reduced up to 65.62%, 69.38%, 31.08%, and 27.06% respectively. The prepared shoe-upper leather exhibited equivalent physical properties compared to the control. Scanning electron microscopy (SEM) image ensured the conformity of the fibre structure of the experimental leather with control. A significant correlation was seen among the skin preservation efficiency parameters, while the strongest correlation was (r = -0.996, p

Recycling leather waste, which accumulates in large quantities in tanneries, and producing packaging paper with improved properties reduces the environmental burden and is at the same time economically efficient. A modified fibrous mass of waste from tanned and untanned leather scraps, waste paper, and acrylic emulsion was obtained and packaging paper based on them was produced. Alkaline modification of tanned leather waste - chrome shavings - leads to an increase in the electrokinetic potential and, accordingly, the stability of the fibrous suspension, partial hydrolysis of skin collagen occurs with the formation of new polar groups, and at the same time, the degree of cross-linking of the skin increases. In the paper composition, new intermolecular bonds are formed between cellulose and skin collagen. The microstructure, elemental composition, morphology, thermal and physical-mechanical properties of modified chrome shavings and composite paper were determined. A significant improvement has been achieved in the main parameters of paper: surface density (decrease by 16-25%), breaking load and breaking length (increase by 15-23%), number of double bends (increase by 2-6 times) in comparison with paper obtained from pure waste paper, and also to a greater extent compared to paper obtained from unmodified leather waste.

For commercial leather processing, chrome tanning is the most used approach but it significantly contributes to environmental pollution. Vegetable tannins, which are large polyphenolic compounds, form strong interactions with proteins and carbohydrates, thereby enhancing the adaptability and value of vegetable-tanned leather as well as reducing environmental impact. In this study, vegetable tannins were extracted from the leaves of Guava plants (Psidium guajava) using ethanol as the solvent, facilitated by ultrasound. Extracted tannins were quantified using the Folin–Ciocâlteu reagent with ultraviolet-visible spectroscopic method. Ultrasound enhanced the extraction process producing a high yield in less time due to its mechanical, thermal, and cavitation impacts. The extracted tannins were characterized by a variety of spectroscopic techniques, including Proton (1H) Nuclear magnetic resonance, Fourier-transform infrared, and ultraviolet-visible spectroscopy. The effect of various process variables, such as temperature, solid-liquid ratio, ultrasonic power, extraction period, and powder fineness, were also investigated to optimize the extraction process. Finally, the extracted tannins were employed in leather tanning processes to assess their potential as tanning agents. The extracted tannins ensured uniform diffusion of tannins, improved thermal stability and reduced the number of tannins in effluent by 68% making it an environmentally friendly leather tanning process.

Abstract A comprehensive evaluation of collagen-based historical artifacts is crucial for the preservation and inheritance of cultural relics, necessitating interdisciplinary approaches that integrate scientific knowledge with practical expertise to develop effective conservation strategies. The present work was focused on a piece of historical leather armor housed in Turpan Museum, Xinjiang, China. SEM–EDS, XRD, ATR-FTIR, and NMR were carried out on this historical leather armor from macro and micro perspectives, mainly including morphology observation, composition analysis, structural assessment, which could provide both quantitative and qualitative insights into the deterioration of the historical leather armor. Additionally, the non-destructive sampling methods and the third-generation sequencing technology (TGS) were employed to identify a total of 13 bacterial species and 8 fungal species, and their metabolic pathways were predicted, providing guidance for preventive conservation and restoration strategies. By the present work, necessary fundamental knowledge might be provided for the effective preservation and inheritance of collagen-based historical artifacts. Graphical Abstract

The aim of this research was to assess the hazardousness and ecotoxicity of paiche leather (Arapaima gigas) dyed with natural colourants (turmeric and purple corn) versus synthetic colourants (anilines). To determine hazardousness, the methodology included the assessment of flammability, corrosivity, reactivity to H2S and HCN, toxicity from metals, and organic compounds of dyed leather. Additionally, its ecotoxicity was determined using the California red worm (Eisenia fetida) as a bioindicator through a bioassay, with treatments at 0.02, 0.04, 0.08, 0.16, and 0.20 g of leather/g of substrate, including undyed leather and a negative control in the investigation. The hazardousness analysis results indicated that leather samples dyed with both natural and synthetic colourants are not hazardous. However, the concentrations of chromium, nickel, cadmium, and lead exceed the permitted values for their use in footwear according to the European Union. Regarding ecotoxicity, the results demonstrate that acute toxicity to E. fetida is lower for natural colourants compared to synthetic colourants, where 100% mortality occurs at concentrations between 0.04 and 0.08 g of leather/g of the substrate. Concerning chronic toxicity, after 12 weeks of exposure, the tolerance concentration for undyed paiche leather is 0.035 g of leather/g of the substrate, and for leather dyed with purple corn and turmeric, it is 0.2 g of leather/g of the substrate. It is shown that the active compounds of natural colourants have a positive effect on worm survival, and it is concluded that paiche leather dyed with these colourants presents environmental advantages over leather dyed with synthetic colourants.

Environmental pollution caused by wastes generated from chrome tan is a major concern nowadays. This study aimed to develop an eco-friendly alternative tanning agent using graphene oxide (GO) based nanocomposite materials. GO was synthesized by a new approach with modification of the Hummers method. Two types of GO-based nanocomposites, GO-TiO2 (GT) and GO-TiO2-PEG (GTP) were prepared by adding TiO2 nanoparticles and polyethylene glycol (PEG) as surface modifiers. They were successfully applied to leather tanning processes at different concentrations (2%, 4%, and 6%). Both synthesized GO, GO-nanocomposites, and the resulting tanned leathers were characterized by Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Fourier-transform Infrared Spectroscopy (FT-IR). Different physico-mechanical properties of leathers tanned with nanocomposites were evaluated and the results were compared with chrome-tanned leathers. The tensile strength of chrome-tanned leather was 223 (kg/cm) whereas the maximum tensile strength was found at 228 (kg/cm) and 233 (kg/cm) in 6% GO-TiO2 and GO-TiO2-PEG tanned leathers respectively. The environmental pollution impact of the effluents generated by the new tanning process was assessed. The COD of effluents generated from chrome tanning was 4800 ppm which was significantly reduced to 2400-1440 ppm and 2880-1920 ppm when GO-TiO2 (GT) and GO-TiO2-PEG (GTP) were applied in leather tanning respectively. The TDS and BOD were found at 183.8 and 200 ppm in conventional chrome-tanned wastewater which were significantly reduced to the range of 47.5-18.3 and 100-50 ppm respectively in liquid wastes obtained from the GO-composite tanning process. The maximum reduction of COD, BOD, TDS, and TSS in leather waste liquid was found with the application of 2% GO-nanocomposites in tanning. The results revealed that leathers tanned with nanocomposites possess characteristic properties which were very similar to those observed in chrome-tanned leathers whereas the new tanning agents drastically reduced the intensity of pollutants in leather effluents. The application of new nanocomposites in the leather tanning process is an innovative effort. This new nanocomposite-tanning method showed minimal consequences regarding environmental pollution with the generation of less toxic effluents from the respective tanning process.

Abstract Melamine resin (MR), traditionally synthesized using melamine and formaldehyde, is widely used in the leather industry. However, the emission of free formaldehyde poses a significant challenge for conventional MR. To address the issues of aldehyde in MR, extensive research has been conducted. This paper introduces a novel aldehyde-free MR (LTSL) retanning agent synthesized using cyanuric chloride, l-lysine, and sodium sulfanilate. The chemical structure of LTSL was analyzed via Fourier transform infrared spectroscopy, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. The presence of amino, carboxyl, and sulfonic acid groups in LTSL enhanced its storability and imparted LTSL with an amphoteric character. The isoelectric point of LTSL was optimized to reach 4.37, and LTSL exhibited an appropriate size distribution with an average particle size of 254.17 nm and achieved high absorption rates of 87.77% and 95.84% for retanning and fatliquoring agents, respectively. Consequently, the thickness rate of LTSL reached up to 37%, with no detectable formaldehyde. Notably, LTSL also demonstrated excellent physical and mechanical properties, primarily attributed to the coordination and electrostatic interactions between the chrome-tanned collagen fiber and amino/carboxyl groups in LTSL. This research presents an innovative approach for developing an aldehyde-free MR retanning agent, significantly contributing to the sustainable development of leather manufacturing. Graphical Abstract