Mechanical Properties Of Leather Research Articles

Zinc Oxide Nanoparticles in Leather Conservation: Exploring the Potential of Hydroxypropyl Cellulose/Zinc Oxide Nanocomposite as a Leather Consolidation Agent

This research presents a comprehensive study on the application of hydroxypropyl cellulose/zinc oxide nanocomposite (HPC/ZnO NC) as an effective consolidant in leather conservation. The critical focus is to prevent photooxidative degradation, a significant challenge in preserving historical leather artifacts. The nanocomposite was evaluated for its protective capabilities against environmental stressors like UV radiation and moisture, mechanical robustness, and potential to stabilize acid-damaged leather. The uniform dispersion of ZnO NPs in the HPC matrix was revealed as crucial for improving leather properties, which was confirmed through SEM imaging. The HPC/ZnO NC coating effectively prevented UV-induced microcracks, surface degradation and collagen denaturation. It also demonstrated enhanced mechanical resistance, inhibiting the reduction in leather’s maximum tolerable force and increasing the elongation index, even after aging. Additionally, it exhibited improved water-repellent properties and increased the pH of the leather, offering potential benefits for the treatment of acid-degraded leathers. Overall, the findings affirm that the application of HPC/ZnO NC significantly augments the physical and mechanical properties of leather, providing enhanced resistance to environmental degradation.

Utilization of Collagen Wastes as Bioretanning Agent and Effects on the Mechanical Properties of Leather

A bioretanning agent was developed as an alternative to conventional synthetic retanning agents to pave the way for sustainability in the leather industry. Tanned solid waste shavings obtained from leather processing was utilized to produce a proteinic sub-structure for constitution building block of the bioretanning agent's backbone. The protein hydrolyzates were acquired with different molecular weights and the hybrid biopolymers were obtained by grafting the hydrolyzates with acrylic acids (AAc) and acrylamides (AAm). To evaluate the properties imparted by the designed bioretanning agent, it was incorporated into the leather in the retanning processes and compared to the control samples fabricated with conventional procedures. Penetration of hybrid biopolymer into the matrix for retanning was achieved easily, and using low and high molecular weight biopolymers have been recorded by 20% and 23% of improvement on the mechanical performance of the leather samples, respectively. The ratio of the hydrolyzate and AAm/AAc was found to be fitted at 1:2 for both. Furthermore, as per the evaluation of the leathers retanned by novel biopolymer, the results were promising in terms of technical viability and revealed that the biopolymer usage could enhance the mechanical performance of the leather while benefiting from the waste-to-wealth approach.

Functional nanocomposite based on waterborne polyurethane and layered double hydroxide as a flame retardant for leather

Incorporation of multifunctional nanomaterials into collagen fibers is considered as a promising approach to fabrication of multifunctional leather. In this study, an effective approach for improving the flame retardancy of leather and promoting absorption of anionic dyes and fatliquoring agents on leather through introduction of layered double hydroxide (LDH) into waterborne polyurethane (WPU) by physical blending method to prepare WPU/LDH nanocomposite as leather retanning agent has been reported. The results indicate that the original form and intercalated form of LDH both coexist in the WPU/LDH composites, and the LDH is evenly dispersed in WPU. Moreover, hydrogen bond and electrostatic interaction exist between LDH and WPU. The penetration and dispersion of LDH in collagen fibers improves the thickening rate, dye uptake, softness and mechanical properties of leather. Moreover, the introduction of LDH also improves the flame retardancy of the resulting leather. Compared to the leather treated with WPU, the ignition time, the length of charring, and the mass loss rate of the leather treated with WPU/LDH-8% are reduced by 74.2%, 58.6% and 46.2%, respectively, and the limiting oxygen index (LOI) value increases from 23.6% to 26.0%. The peak heat release rate (PHRR) and total heat release (THR) of the leather treated with WPU/LDH-8% decreased by 34.4% and 28.7% compared to that of the leather treated with WPU. The excellent flame retardancy of leather can attributed to the barrier effect of highly reinforced carbonaceous char, retarding the escaping of flammable volatiles in the leather and shielding the further damage of the leather by external heat irradiation. The high performance nanocomposites are promising for applications in the manufacture of flame-retardant leather. In addition, the reduction of BOD and COD of the WPU/LDH post-tanning systems is beneficial to reduce the impact of retanning agents on the environment, which is of great significance to “cleaner production”.

Polyurethane-based retanning agents with antimicrobial properties

Abstract Polyurethane-based retanning agents with antimicrobial properties were synthesized by the chemical incorporation of ciprofloxacin (CPFX) units into polyurethane chains. The chemical structures were characterized by Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). Then, the retanning agents were applied in the leather retanning process. Owing to the conjugation of CPFX into polyurethane chains, the molecular weight increases, further leading to the decrease in hydroxyl value and increase in particle size. The shrinkage temperature was improved after retanning. Owing to the filling of retanning agents in the gap of collagen fibers, the average thickness of leather increased by 65.8%. The mechanical properties of leather were visibly improved because of the large number of –COOH coordinate with Cr3+ and more hydrogen crosslinking with carboxyl group, amino group, and hydroxyl group of leather collagen. Furthermore, leather retanned by these polyurethane-based retanning agents presented good antimicrobial properties. The antibacterial activity could be conserved above 89% even after rinsing for ten times.

Tanning Chemicals’ Influence in Leather Tensile and Tear Strength Review

For over 100 years of tanning research, it is still arguable whether tanning chemicals weaken, strengthen or have an effect on the skin's original collagen fibers.
 The current paper is a review of the literature regarding the impact of the tanning process on the mechanical properties of leather specifically, tensile and tear strength, that raises several questions about this topic. A call is made for the scientific and technical community to address these questions

The Quality of Leather Estimated from Airborne Ultrasonic Testing of Hides

High-quality hides are paramount for competitiveness in both domestic and export markets. Currently, hides are visually inspected and ranked for quality and sale price, which is not always reliable when hair is present on the hides. Advanced technologies are needed to nondestructively and accurately characterize the quality of hides and enable one to estimate the qualitative and mechanical properties of leather. We were the first to carry out research for airborne ultrasonic (AU) methods to nondestructively characterize the quality of hides. The developed nondestructive method is based on measuring the AU waves transmitted through the hide samples. Research results demonstrated that the average amplitude distribution received from the ultrasonic wave transmitted through the hide samples yielded the best correlation with the AU test variables: gain, speed, and frequency. Observations showed AU parameters derived from the average distribution values for amplitude (AMPa) and time of flight (TOFa) have a correlation with the quality of leather. This study demonstrated that the fullness, overall characteristic, tensile strength, stiffness, elongation, and toughness of leather could be nondestructively estimated by the ultrasonic quantities obtained from AU testing of hides.

Mechanical properties and preferences of natural and artificial leathers, and their classification with a focus on leather for bags

In this study, the mechanical properties and preferences of natural and artificial leathers were analyzed. The leathers were classified based on mechanical properties affecting their preferences. The mechanical properties of the leathers were measured via the KES-FB system, and an expert survey was conducted to evaluate leather preference. Leathers possess different mechanical properties depending on the manufacturing process and structural characteristics. Furthermore, differences were observed in the mechanical properties of natural and artificial leather. The mechanical properties of the leathers were related to the preferences for hand and bags. Accordingly, the leather was classified into three clusters. The leathers that were preferred for hand were not preferred for bags, and those preferred for bags were not preferred for hand. Therefore, different development strategies are needed, depending on the type of leather. Natural leather for bags should be light and have good compression elasticity along with its existing mechanical properties, whereas artificial leather should be light and have improved tensile resilience.

Greener Approach for Leather Tanning Using Less Chrome with Plant Tannins and Tannins Mediated Nanoparticles

Making out animal skins or hides to leather is commonly called as tanning. This research was done for utilizing tannins of some medicinal plants and tannin induced green-synthesized silver nanoparticles along with minimal concentration of chromium to enhance the physical and mechanical properties of leather and thereby reducing the pollution caused by chromium in effluent which crucially affect the soil fertility, ground and surface water. In this study, Cassia alata, Euphorbia hirta, Thespesia populnea and Wrightia tinctoria were collected and tannins were extracted from the leaves. Tannins were utilized for production of silver nanoparticles. The extracted tannins and tannin induced silver nanoparticles were characterized, where the silver nanoparticles were found to be crystalline. Further, the tannin and tannin induced silver nanoparticles were used in leather processing either alone or in combination with chromium. The quality of tannin/silver nanoparticle treated leather was compared with chemically tanned leather for its tensile strength, tear strength, shrinking temperature, etc.

Effect of punching on physical and mechanical properties of leathers: Focus on car seat covers

As a lot of time is spent in the car, the comfort of not only the car seat but also the car seat cover itself has become of increasing importance. With increasing use of ventilated seats, the control of the physical and mechanical properties of leather in response to punching has become of prime importance in the design of car seats. This study evaluated the changes in the physical and mechanical properties of leather due to punching and proposes optimum punching intervals for car seats. Sixteen types of leather, punched at three spatial intervals (2, 3, and 5 mm), were evaluated in terms of their apparent density, softness, coefficient of friction, warm-cool feeling, and mechanical properties. Leather punching affected its physical and mechanical properties. However, there were differences in punching intervals that significantly affected each property, including the mechanical properties. Depending on the performance required when developing a product, a suitable punching interval must be selected. Therefore, punching at 5 mm intervals is preferred for obtaining physical and mechanical properties similar to those of untreated leathers, and punching at 3 mm intervals is recommended for achieving more softness. On the contrary, punching at 2 mm intervals increases air permeability but decreases dimensional stability.

Dissymmetry Gemini Sulfosuccinate Surfactant from Vegetable Oil: A Kind of Environmentally Friendly Fatliquoring Agent in the Leather Industry

Compared with surfactants synthesized from petrochemicals, those synthesized from vegetable oil have outstanding environmental friendliness and superior surface activity. Dissymmetric gemini surfactants, a new class of gemini surfactant, have superior properties. Dissymmetry gemini sulfosuccinate surfactant (DGSS) was synthesized from vegetable oil. The structure of the product was confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) analyses. The properties tests of DGSS showed that the DGSS can significantly reduce the surface tension and has good emulsification ability, good wetting ability, and poor foaming performance. DGSS was applied as a fatliquoring agent in leather for lubricating collagen fibers and improving physical and mechanical properties of leather. Compared with leather treated with 14 wt % commercial fatliquoring agent, leather treated with 8 wt % DGSS can reach the same fatliquor effect. The biochemical oxygen demand (BOD5) per chemical oxygen demand (CO...

Preparation, Characterization and Application of Siloxane Succinate Fatliquor

The silicone succinate surfactant (PMPS) was synthesized by ring-opening reaction using polyether alcohol amine modified polysilosane (PAPS) with maleic anhydride (MA) as the raw materials, and p-toluenesulfonic acid (PTSA) was used as the catalyst. Sulfated castor oil and sulfated rapeseed oil were combinated with PMPS to prepare a new leather fatliqour (PMPSF) composed mainly of PMPS. The molecular structure of PMPS was characterized by FTIR spectra; the thermal properties of PMPS was characterized and analyzed by TGA. PMPSF was used in sheepskin wet blue leather and compared with oxidative sulfited vegetable oils (L-3) and RF-1 fatliquor; the waterproof and mechanical properties of the leather were measured. The results show that the thermal decomposition temperature of PMPS is 192.8°C. Fatliquor PMPSF provids a good level-dyeing property, the leather oiled by it has good flexibility and fullness, the waterproofness and mechanical properties of leather are also good. Moreover, compared with the leather fatliquored by L-3, the thickening rate of leather oiled by PMPSF reaches 13.7%.

Studies on the application of ultrasound in leather enzymatic unhairing

Enzymatic unhairing is a clean technology for leather industry. However, one problem hinders the utilization of enzymes in leather unhairing is the slow diffusion of enzymes through skins. As another clean technology, ultrasound can be applied to accelerate the diffusion of enzymes through skins. In this work, effects of ultrasound on the enzymatic unhairing were investigated. Effect of frequency of ultrasound on the enzymatic unhairing was compared, and 20 kHz was chosen in this work. Under our conditions, ultrasound has little effect on enzyme activities, and also has little influence on the physical and mechanical properties of leather. Ultrasound can enhance the diffusion of enzyme through skins, thus improving the unhairing capacities of enzymes. It is noted that amylase can interact with proteoglycans by attacking saccharide side chains, thus having some unhairing capacity. Ultrasound can improve the unhairing capacity of amylase more effectively. Furthermore, amylase does no harm on the collagen fibrous structure and can be used safely without the need for a high degree of control. So it is possible to use amylase in enzymatic unhairing in combination with protease. In short, using ultrasound in amylase and protease unhairing is a promising clean technology.

The mechanical properties of leather

The many uses of leather have largely relied on the range of mechanical properties which it can provide, according to the raw material employed in its manufacture and the manufacturing processes themselves. The contrasting behaviour of a stiff sole leather and of a fine gloving leather exemplify this point. The last twenty years have seen intensive investigation of many mechanical properties of leather and the design of test methods now accepted internationally. At ambient temperatures and humidities most types of leather show mainly elastic behaviour, although delayed elastic effects may give the semblance of plasticity. The stress relaxation-time relation for constant linear strain shows the stress decaying linearly with log (time). The stress decay becomes discontinuous after sufficient time. The stress-strain relation for extension of leather strips is often markedly non-linear even at low strains (<2%). Two dimensional extension of leather has been analysed using an instrument allowing independent extension in two perpendicular directions. To a first approximation each stress component is linearly related to the two elastic strain components in the perpendicular directions. As with other materials of biological origin, the mechanical behaviour of leather varies from place to place in the skin, not only over its area, but also through its thickness. The extent of variation is briefly discussed and related to the underlying fibre structure. Leather which has been strained and then subjected to either heat alone or heat and moisture, shows much more extensive plasticity than occurs at lower temperatures. This behaviour has been used to enable leather to be given appropriate shapes, as in the heat setting of upper leathers. Quantitative studies of heat setting are reported and the influence of such variables as temperature, moisture content of the applied air stream, the air stream velocity and the duration of treatment are discussed. The plastic deformation obtained in this way is contrasted with “run” in gloving leather.