Lignin Based Colorant: Modified Black Liquor for Leather Surface Coating Application
Nowadays, much research is focused towards the development of a value-added products from industrial waste. In this concern, the preparation of pigment colorant with good covering power from the paper and pulp industry waste is less explored within the leather world. The paper and pulp industry generate huge quantity of waste, which is commercially known as black liquor. In order to prepare the pigments with good covering property the black liquor was acidified, and the insoluble organic part of black liquor was used for pigment application. In this work, the structural characterization of the prepared pigment products was analyzed by FT-IR, TGA, DSC, BET, SEM and DLS. Further sol-gel method was employed for the preparation of pigment formulation using the insoluble lignin obtained from the black liquor. The applicability of isolated insoluble as brown pigment was evaluated by using it as pigment for leather surface coating. The color characteristics of the pigment coated leather and checkered card were analyzed by using CIELAB color measurement. The results obtained clearly confirm that the insoluble lignin has potential application as a brown pigment in leather finishing application and is compatible with various auxiliaries employed in leather finishing. Utilization of the prepared brown pigment in leather finishing resulted in upgradation of finished leather through excellent surface covering and in addition, no overloading of grain was observed. Thus, this article provides an approach for converting waste black liquor from paper and pulp industry into a value-added material for pigment application.
JALCA Oct 2018
Effect of Cyclic Stress while Being Dried on the Mechanical Properties and Thermostability of Leathers
Various mechanical processes are usually applied in leather making and using, which inevitably affect the structure and properties of leathers, such as mechanical performance and hydrothermal stability. Cyclic stress is very common in leather making, which may cause different changes to leather, compared with constant stress. However, very few results have been reported regarding the influence of cyclic stress on leathers. In the present work, cyclic stresses were applied to leather in drying. The influences of cyclic stress on the mechanical properties, hydrothermal stability and dry heat resistance of leathers were investigated. Also, the cross section of leather was observed with SEM, and the changes of hydrogen bonds in collagen fibers were characterized and discussed with the results of FT-IR. It was indicated that stress in drying leads to orientation of collagen fibres and increased mechanical strength. A balance is set up between tensile strength and elongation at break of leathers with the action cyclic stress. Longer stretching leads to higher tensile strength and lower elongation at break. Meanwhile, stress in drying may prevent the formation of hydrogen bonds inside collagen fibres and change the weaving structure of collagen fibres, resulting in decreased hydrothermal stability of leathers. Cyclic stress may provide leathers with better dry heat resistance than constant stress. Also, a simplified model of collagen fibres movement was introduced, to establish a relationship between processing and properties of leathers from viewpoint of collagen fibre structure.
JALCA Oct 2018
Polyethylene Glycol as a Preservative for Pigskin and Its Interaction with Collagen
Herein, an immersing method for the pigskin preservation by using polyethylene glycol (PEG) with different molecular weights (Mw = 200, 600, 6000) was developed and the influence of PEG on the conformation of type I collagen was investigated. Only PEG200 followed dehydration and rehydration patterns similar to that of salt curing and exhibits reasonably good preservative and bloodstains removal effects. Zeta potential analyses show that the collagen-PEG solutions have good dispersions stability. FT-IR and US-DSC results indicate that collagen triple helixes are kept integrated in the presence of PEG, and the highly hydrated feature of PEG helps to maintain the stability of the protein conformation. Atomic Force Microscope (AFM) images show that the collagen fibrils become more dispersed with the increasing Mw of PEG. The present work gives positive insight to partially replacing sodium chloride for the preservation of raw hide and skin, as well as the development of PEG-collagen biomaterials.
JALCA Oct 2018
Preservation of Bovine Hide using Less Salt with Low Concentration of Antiseptic, Part II: Impact of Developed Formulations on Leather Quality and the Environment
The traditional method for bovine hide preservation requires approximately 40-50% sodium chloride on raw hide weight or 95% saturated brine solution in case of wet salting. This salt resides in wastewater after the soaking process and generates a huge environmental pollution in the form of total dissolved solids (TDS) and chlorides (Cl-) during leather processing. The current research has developed antiseptic based hide curing formulation using 45% saturated brine solution which reduces 50% salt usage in compare to traditional method. The newly developed formulations have been found more effective in limiting microbial growth on cured hide than the conventional method preserving the bovine hide for more than 30 days. In this study, post-leather analysis e.g. grain pattern, scanning electron microscopic images, mechanical properties and organoleptic evaluation reveal that the crust leather produced from alternatively cured hides are comparable to the control obtained from traditionally preserved hide. The efficacy of the alternative system is also assessed by monitoring the environmental impacts caused by the leather processing effluents on the basis of TDS and chloride content, total solids (TS), total aerobic bacterial counts in soaking liquor, Bio-Chemical oxygen demand (BOD) and Chemical oxygen demand (COD). The environmental advantages of the alternative hide curing method are determined particularly by 50% reduction of TDS and chloride content. Therefore, this new method is feasible and industrially preferable to the traditional hide curing process.
JALCA Oct 2018
The impact of natural ageing on the hydrothermal stability of new and artificially aged parchment and leather samples
The paper discusses the effects of a 4-year natural ageing on hydrothermal stability of new and previously accelerated aged parchments and leathers. It was observed that natural ageing generally lowers the denaturation temperature (measured using DSC), but in a different way for the two types of these collagen-based materials. Thus, for parchments the largest effect (up to 7 °C) was observed for the new samples, while for the strongly aged ones the temperature shift was negligible. For leathers, no relevant dependence of the denaturation temperature shift (3.0 ± 1.0 °C in average) with the previous accelerated ageing time was observed. For parchment, the enthalpy of denaturation decreases substantially following natural ageing, while for leathers no significant alteration was observed. It was also found that the 1-day accelerated ageing performed in 2013 had comparable effects on the denaturation temperature of these materials as the 4-year natural ageing, making the possibility of predicting the effects of natural ageing on patrimonial artifacts manufactured from parchment and leather
ThermoThermochimica Acta Nov 2018
Enzymatic dehairing: A comprehensive review on the mechanistic aspects with emphasis on enzyme specificity
Enzymatic dehairing as a part of the efforts for greener leather processing has reached progressive advancement with the tradition-bound tanning industry being now more receptive to cleaner processing methods due to increasing pressure from environmental groups. The dehairing mechanism is vaguely understood at present from the point of view of the enzyme specificity, which is needed for consistent and satisfactory hair removal without deleterious effect on the leather quality. Gaining insight into the dehairing specificity would help in designing efficient dehairing process. This paper attempts to review the literature pertaining to all the relevant and critical issues in detail to clearly delineate the right kind of substrate specificity required to attack only the potential targets for hair removal, and for making fine quality leather without adverse effect on other desired leather making components of the skin matrix. The gap in understanding of these critical issues is discussed with recommendation for further scientific studies in the area.
International Journal of Biological Macromolecules 2018
A sustainable and cleaner speedy tanning system based on condensed tannins catalyzed by laccase
Condensed tannins, a sustainable and environmental-friendly vegetable tanning agent, is confined in the wide application of leather industry owing to its poor shrinkage temperature (Ts). In this work, the tanning effect of condensed tannins was enhanced by the green biocatalyst laccase. Meanwhile, the molecular weight and chemical structure of condensed tannins catalyzed by laccase were observed. Its polydispersity index (PDI) was decreased from 2.88 to 1.77 and the Mw from 6354 to 4041. The changes of relative molecular mass were confirmed by Gel permeation chromatography (GPC) analysis. The UV evisible spectroscopy (UVevis) and X-ray photoelectron spectroscopy (XPS) spectra provided evidence for the catalyzing change from o-hydroxylation to o-quinones. From the aspects of the thermal stability, tensile strength, breaking elongation, tear strength, thickening percentage and morphological analysis, the leather tanned by catalyzed condensed tannins (BA) was proved to have more excellent physical properties contrast with that of the leather tanned by untreated BA. This indicates that the physical properties of leather tanned by BA were improved significantly, whilst the catalyzed sustainable agent can be independently used as a promising quick tanning agent of sheepskin light leather.
Journal of Cleaner Production 2018
Application of green cationic silicon-based gemini surfactants to improve antifungal properties, fibre dispersion and dye absorption of sheepskin
In view of conventional surfactants, cationic silicon-based gemini surfactants possess three more advantages imparted by unique structure. Therefore, in this paper, a series of green cationic silicon-based gemini surfactants (Cm-PSi-Cm) with different hydrophobic chain length (m = 8, 12, 18) were used in sheepskin soaking and dyeing processes firstly. Then the properties of sheepskin after Cm-PSi-Cm treatment were studied and their waste bath was analyzed. Meanwhile, traditional soaking scheme (JFC and commercial fungicide) and commercial dye-fixing agent as comparisons were also used in sheepskin soaking and dyeing processes, respectively. The results showed that all performance of sheepskin after C12-PSi-C12 treatment was the most outstanding. Antifungal properties and fiber dispersion of sheepskin after C12-PSi-C12 treatment were almost similar to or even better than traditional soaking scheme. C12-PSi-C12 was conductive to remove the interfibrillary protein among the collagen fibres, but did less damage to collagen fibre in the soaking process. Most importantly, the dosage of C12-PSi-C12 was only half of the traditional soaking scheme, dramatically reducing the use and waste of the resource. Moreover, C12-PSi-C12 was beneficial to the absorption and fixation of the dye by sheepskin. Compared with commercial dye-fixing agent, the dye concentration in dyeing waste bath using C12-PSi-C12 decreased notablely from 3.13 mg/L to 1.75 mg/L. So C12-PSi-C12 can replace traditional soaking scheme and commercial dye-fixing agent using in leather soaking and dyeing processes. In short, C12PSi-C12 as a kind of eco-friendly substance has been presented, which can improve antifungal properties, fibre dispersion and dye absorption of sheepskin synchronously, and can reduce environmental pollution and provide the way for sustainable development of cleaner leather processing.
Journal of Cleaner Production 2018
Layer-by-layer assembly of antibacterial composite coating for leather with cross-link enhanced durability against laundry and abrasion
Due to the breathable and soft nature, leather has been selected as flexible material to produce comfortable shoes. However, due to the intimate contact between leather surface and foot skin, bacteria growth and rapid colonization on leather surface can lead to biofilm formation which will bring potential risk of foot infection. Especially for those patients with diabetic foot, such foot infection can be life threatening. In this work, a composite coating was facilely fabricated onto leather surface via the layer-by-layer assembly of positively charged chitosan (CS) and negatively charged gallic acid modified silver nanoparticles (GA@AgNPs), with subsequent immobilization on leather by chemical cross-linking. Such cross-linked CS/GA@AgNPs coated leather exhibited efficiently antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) through a “kill-release” strategy, which was mainly attributed to the synergistic effect of contact-killing of CS layer, Ag+ ions release and bacterial repelling of anionic GA@AgNPs layer. Furthermore, the stability of the composite coating on leather surface was investigated, and the results revealed that the cross-linking could enhance the durably antibacterial activities of leather against laundering and mechanical abrasion. Therefore, based on the efficiently and durably antibacterial properties, such cross-linked CS/GA@AgNPs layers coated leather is a promising candidate for producing leather shoes for diabetic patients.
Applied Surface Science 2018
The Leather Trades’ Engineers of Massachusetts: Vaughn Morocco Machine Co. 1883-1891 Vaughn Machine Co. 1892-1904 Vaughn-Rood Machine Co. 1903-1905 Part 1
This paper traces the rise of an internationally important engineering concern developed by the Vaughn family in Salem and Peabody, Massachusetts (MA), United States. Initially established to serve the needs of a specific local industry, the Vaughn Morocco Machine Co. was started in the early 1880s by Joseph Warren Vaughn and his three sons. The business name was changed to the Vaughn Machine Co. in 1892, after the company had expanded its sales more generally into leather manufacture. New machinery developments and continuous improvement of the ʻVaughnʼ product range are detailed and illustrated; machinery which would eventually instigate major changes in leather manufacture worldwide. European demand for the companyʼs equipment justified a sales and service depot being established in Germany with satellite marketing and repair branches in France and Britain. Part 2 pursues new machinery developments and the rise of a specific engineering rival. This new competitor combined with a different approach by management at the Vaughn Machine Co. ultimately led to the formation of new challenger – the Vaughn-Rood Machine Co.
JSLTC Sept/Oct 2018
Leather surface refinement with application of the TiO 2 -SiO2 -GLYMO nanocomposite and lacquer coating
In the present study the effect of TiO2-SiO2-GLYMO nanocomposite on surface properties of leather was investigated. The TiO2-SiO2-GLYMO composite was prepared through the sol-gel route from tetraethoxysilane (TEOS) and titanium n-butoxide (TBO). 3-glycidoxypropyltrimethoxysilane (GLYMO) was added as coupling agent to provide a stable bond between metal oxides and leather substrate. The prepared composite was applied by spraying on the top coat of leathers in finishing. The surface properties observed by scanning electron microscopy (SEM) showed an even and homogenous coating obtained on leather by application of the composite in the presence of lacquer. The chemical structure of composite films was examined via Fourier transform infrared (FTIR) and Si-O-Ti bond and opening of epoxy rings of GLYMO were revealed. The presence of Ti and Si in the composite treated leather samples was ascertained by inductively coupled plasma optic emission spectrometer (ICP-OES). The results of the physical and fastness tests indicated that the use of TiO2-SiO2-GLYMO nanocomposite improves some performance characteristics of leather such as finish adhesion, dry and wet rubbing fastness, colour fastness to light and UV light. The results are promising for the refinement of leather surface with the application of the nanocomposite in the finishing process.
JSLTC Sept/Oct 2018
Leather goods notified to the RAPEX System in the years 2004-2017 – Notification analysis for countries of manufacture and notifying countries
This paper analyses information pertaining to notifications of unsafe leather goods submitted to the EU Rapid Exchange of Information System (RAPEX) in the years 2004-2017. The number of leather goods reported in the system has been compared to total number of notifications on dangerous products classified in the category ʻClothing, textiles and fashion itemsʼ that includes leather goods. The notifications were analysed for the country of origin of leather goods as well as for the notifying country. This allows identification of countries from which the largest number of dangerous leather goods come, i.e., China, India and Pakistan, as well as countries most active in detecting them in their own domestic markets, i.e., Germany, Spain and Estonia. The article presents also results of surveys related to opinions of Polish consumers towards the safety of leather goods they purchase as well as their awareness about the presence and functioning of the RAPEX system. The research showed that most of Polish consumers cannot clearly indicate whether the leather goods they buy are safe for health or not. Moreover, most of Polish customers have no knowledge of the presence and functioning of the RAPEX system.
JSLTC Sept/Oct 2018
Study on possibility of oil migration according to fatliquoring agent characteristics
The natural leather used for car interior materials is a traditional and high-quality material that can be applied to diverse purposes such as the steering wheel, knob, seat and internal trim. However, continuous friction and sweat from the driver causes the hydrolysis of high-molecular resins and plasticisation, which facilitates the abrasion of coated layers. During the summer season, in particular, the painted surfaces weakened under the high-temperature conditions of the car interior often lead to slipperiness and increased lustre owing to the migration of the fatliquoring agent. Thus, this study investigated the bonding between the leather and different types of fatliquoring agents, and their influence on oil migration by facilitating ageing (hydrolysis). The results revealed that the silicon- and lecithin-based fatliquoring agents had a significant influence on oil migration owing to the low bonding to the leather under the ageing condition.
JSLTC Sept/Oct 2018
The aggregation behaviour of leather collagen fibres during drying
The rule for the changes and mechanism influencing the structure of leather during drying were studied from the point of view of fibre movement, based on the stress state and combination mode of collagen fibres. The effect of capillary pressure difference force (CPDF) and hydrogen bonds on the aggregation behaviour of leatherʼs collagen fibres during drying was investigated. The results showed that, during hang drying, under the action of CPDF, collagen fibres will move towards each other and bond by hydrogen bonds thus making the structure of dried leather stable. During freeze drying, the collagen fibres are not affected by CPDF and the fibres tend to maintain the original dispersed state. During hang drying, when the hydrogen bond force between collagen fibres is weakened by fatliquoring, the aggregate structure of collagen fibres is unstable, and collagen fibres can be easily re-dispersed by milling. The results of this research confirmed that, during drying, the change in the collagen fibresʼ aggregate structure is due to the process in which collagen fibres move and combine under the action of ʻforceʼ. The final dried leather structure is determined by the stress state and combining ways of collagen fibres during drying.
JSLTC Sept/Oct 2018
Effects of PAA on the different scales of leather structure
In this article, the topology of fibrils and the aggregate structure of leather fibres were characterised by TEM and SEM to reveal the effects of PAA on the different scale of the structure of leather. The results show that PAA has little influence on the collagen molecules array and collagen fibres aggregate structure in the wet state. But, during air-drying PAA observably influences the collagen fibres aggregate structure. After being PAA retanned, the air-dried leather fibres become thinner and the space between fibres increases.
JSLTC Sept/Oct 2018
Tetraselmis sp. isolated from a microalgae consortium for tannery wastewater treatment
Microalgae have been the subject of several studies in the wastewater treatment field due to their ability for the removal of various nutrients, organic load and to be a clean and economical way to treat pollutants. The effluents from leather finishing processing steps contain chemical pollutants due to the use of dyes, surfactants, toxic metals, emulsifying agents, retanning agents, oils, pigments, resins, among other chemicals added. In this work, the isolated microalgae Tetraselmis sp. was obtained from a microalgae consortium and evaluated for their ability for the treatment effluents collected from a tannery. The growth of microalgae biomass in these effluents in mixotrophic cultivation was analysed, as well as, the capacity of removal of total nitrogen (TN), total organic carbon (TOC), total carbon (TC), inorganic carbon (IC), ammonia (N-NH3), phosphorus (P-PO4), chemical oxygen demand (COD) and biological oxygen demand (BOD). The removal values observed for the 50R50T (50% raw/50% treated effluent) and 75R25T (75% raw/25% treated effluent) concentrations were 96.59% and 99.81% for phosphorus, 99.90% and 89.2% for ammoniacal nitrogen, 89.06% and 54.78% for TN, 40.46% and 43.54% for COD, 59.24% and 57.90% for TOC, 32.70% and 44.73% for BOD, respectively. The microalgae Tetraselmis sp. showed notable growth in mixotrophic cultivation, and the efficient removal of the controlled parameters indicate an enormous potential for application in tannery wastewater treatment.
JSLTC Sept/Oct 2018
Studies of structure changes of archeological leather by FTIR spectroscopy
Fourier transform infrared spectroscopy was used to investigate protein structures in new vegetable tanned and artificially aged leather as well as in waterlogged archaeological leather dating from the Warring State Period (475BC-221BC). The obtained quantitative and qualitative information on protein structure changes was useful to characterize the deterioration of the archaeological leather during ageing in the buried environment. Compared with those in new vegetable-tanned leather, the amide A and amide II bands in the artificially aged and archaeological leather shifted to lower wave numbers, suggesting hydrogen bonding in the collagen in the artificially and naturally aged leather was weakened. The estimation of the relative percentages of collagen secondary structures based on the peak area of component bands in the amide III showed that ɑ-helix structure of collagen converted into a random coil structure in the artificially aged and archaeological leather. Besides, the characteristic absorption peaks of tannins appeared in the spectra of all archaeological leather samples, but the tannins content decreased, indicating that tannins present in the archaeological leather could be degraded or detanned. The results showed that there was an increase in disorder structures in the collagen molecular structure and that the cross-linking between the tannins and collagen was disrupted in archaeological leather. This study will help us to elucidate the deterioration mechanism and guide the conservation of archaeological leathers.
JSLTC Sept/Oct 2018