The Effect of Incorporating Hydroxyapatite and Silica Nanoparticles in Polyethylene Surface Treatment of Natural Leather
Leather is a natural material which is used widely in different industries. It is prone to lose moisture due to environmental conditions. Consequently, leather becomes hard and fragile, which leads to poor durability. A novel mixed system of Poly (ethylene glycol), Hydroxyapatite, plus Silica nanoparticles enhanced the mechanical, thermal, optical, and aging properties of the natural leather properties. This system also enabled the retention of moisture in leather. Thanks to the reinforcing properties of hydroxyapatite/silica nanoparticles, and the lubricating effect of poly (ethylene glycol), these modifying agents enhanced the mechanical and thermal properties of leather and preserved the leather’s natural color and gloss.
JALCA Oct 2019
Effect of an Amphoteric Chromium-free Polymer Retanning Agent with Reactive Aldehyde Groups on Collagen Fibers
A chromium-free amphoteric polymer retanning agent was prepared by free radical polymerization reaction of undecylenic aldehyde (UAL), acrylic acid (AA) and dimethyl diallyl ammonium chloride (DADMAC) as raw materials. The structure of amphoteric polymer retanning agent was characterized by FT-IR and 1H-NMR. Amphoteric polymer retanning agent was applied to the retanning of vegetable-tanned light leather to investigate the binding ability of crust leather to anionic dyes, fat liquoring agent and physical-mechanical properties of the crust leather. The results showed that the synthesized amphoteric polymer retanning agent was successfully prepared. The application trial indicated that the amphoteric polymer retanning agent can improve the binding capacity between leather and anion dye and fat liquoring agent in the retanning process. The dye absorption rate of the crust leather was up to 99.58% and the dyeing liquor was clear. Furthermore, color of the crust leather was uniform and full and its K/S value and drywet rub fastness, thickening rate and physical-mechanical properties were higher than that of the retanned leather by acrylic resin retanning agent. In addition, the crust leather after retanning with amphoteric polymer retanning agent has good softness, and the absorption rate of fat liquoring agent was 99.62%. The above results showed that amphoteric polymer retanning agent possessed the good retanning property in vegetable tanned sheep garment leather.
JALCA Oct 2019
Determination of Free Formaldehyde in Leather Chemicals
Formaldehyde is widely used in the synthesis of various leather chemicals due to its high reactivity and low cost. It is probably introduced into leather when applying the chemicals to processing, and then released during storage and use of leather, which may pose a potential risk to human health. Existing method for determining formaldehyde in leather is helpless to deal with the complicated chemicals. In this study, a method was optimized for determination of free formaldehyde in leather chemicals based on ISO 27587. A 0.5-2.0 g sample of leather chemical (formaldehyde could range from 1.25 to 1250 mg/kg) was heated at 90°C in nitrogen atmosphere. The released formaldehyde was purged at a flow rate of 300 mL/min for 30 min, captured and derivatized using a bubble absorption tube containing 2,4-dinitrophenylhydrazine absorption solution, and then detected by HPLC-diode array detector. The recovery rate of formaldehyde standard solution was 91.0% with relative standard deviation (RSD) of 4.87% in seven times repeated trials. The repeated determinations of aldehyde tanning agents showed the formaldehyde recoveries higher than 90% and RSD lower than 7%, indicating the accuracy and precision of the method. Powdery amino resins were determined to contain a tiny amount of free formaldehyde using this method. However, it should be noted that hydrolyzed formaldehyde will be formed when the amino resins were dissolved in water and used in retanning, leading to the potential for bringing leather with high content of formaldehyde.
JALCA Oct 2019
Effect of Ionic Liquids Pretreatment on the Extraction of Collagen from Calf Skin
The use of ionic liquids (ILs) for collagen extraction should be premised of not destroying the triple helix structure of collagen. Herein, the effects of pretreatments by two imidazolium based ILs with different anions, 1-ethyl-methylimidazolium dicyanamide ([EMIM][N(CN)2]) and 1-ethyl-methylimidazolium tetrafluoroborate ([EMIM][BF4]), on the extraction of collagen from calf skins were studied. The dependences of ILs pretreatments on ILs species and concentrations (30%, 50%, and 70% (w/w)) were examined, in terms of the fiber morphology of skins as well as the extraction rate, structural integrity, thermal stability, and aggregation behaviors of collagens. The results of histological analysis and scanning electron microscopy showed that the skin fibers were effectively loosened by the IL s pretreatments. The extraction rate of collagen was improved as the increase of ILs concentration and polarity with the highest value of 28.79%. Moreover, sodium dodecyl sulphatepolyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy confirmed that the structural integrity of collagen was maintained after ILs pretreatments, although the thermal stability of collagen was determined to be slightly decreased by ultra-sensitive differential scanning calorimeter. Finally, pyrene fluorescence analysis and atomic force microscope indicated that the aggregation behavior of collagen was weakened when increasing the ILs concentration and polarity. The green ILs pretreatment of calf skins might be used as an effective approach for the extraction of bioactive collagen with improved yield and purity.
JALCA Oct 2019
Life cycle assessment of leather shoe manufacturing process based on Simapro
The Eco-indicator 99 ecological index was used to do the life cycle assessment of the manufacturing process of cotton-padded shoes [leather winter shoes with cotton or fur padding] and the ʻnudeʼ shoes [ladies court shoe styles often with a pigskin lining]. The study was based on the total life cycle assessment (LCA) and the SimaPro software. The results showed that the basic skill stages of nude/court shoes and the vamp process of the same shoes had the greatest impact on the environment. The effect was 45.66 % and 52.05 %,respectively. The weighted and single value results for nude/court leather shoes and cotton-padded/winter shoes were concentrated on the effect on human health, reaching 78.62% and 79.01%, respectively. In addition, the cotton-padded/winter shoes had the largest contribution.
JSLTC Sept/Oct 2019
Preparation and properties of matting waterborne polyurethane with polybutadiene
A matting waterborne polyurethane (MWPU) emulsion was prepared using polybutadiene diol (HTPB), polybutylene adipate diol (PBA) and isophorone diisocyanate (IPDI) as the main raw
materials, dimethylolpropionic acid (DMPA) as a hydrophilic chain extender and ethylene diamine as a post chain extender, this was applied to the surface treatment of the leather. The surface
microstructure of the MWPU film was studied by SEM. The results showed that when the content of HTPB increased, the particle size of MWPU emulsion increased, the stability decreased, the mechanical properties and surface roughness of MWPU film increased, the elongation at break, water absorption and light transmittance decreased. Combined with the matting effect, the gloss of the MWPU film was as low as 23GU, and the surface particles of the film were more obvious. The folding fastness was free from cracking, and the abrasion resistance could reach 154 circles [rubs], which meets the testing standard of leather.
JSLTC Sept/Oct 2019
A study of photocatalytic degradation of dyeing and printing wastewater by ZnO@zeolitic imidazolate framework (ZIF)-8
As a semiconducting material with outstanding properties, ZnO has been playing a key role in the chemical industry, light industry, ceramics, electronics, national defence, healthcare and other hightech industries. In recent years, great efforts have been made in studies of ZnO as photocatalyst in the treatment of organic wastewater by virtue of its high reaction rate, excellent applicability and environmentally friendly products. The metal-organic frameworks (MOFs) exhibit large specific surface area and good stability, and calcination of zeolitic imidazolate framework (ZIF)-8 in atmosphere leads to generation of ZnO@MOF. With relatively large specific surface areas, ZnO nanoparticles can generate a large quantity of hydroxyl free radicals under visible light and these radicals can nonselectively oxidise most organics (strong organic-oxidising capability). ZIF-8 was synthesised using the hydrothermal method and calcinated at different temperatures to obtain ZnO nanoparticles of different sizes. Then, the photocatalytic performances of these ZnO nanoparticles were tested by degradation of methylene blue (MB) under visible light. Additionally, the ZnO samples were applied in photocatalytic degradation of dyeing and printing wastewater produced by leather retanning. The chemical oxygen demand (COD) removal rate and the total organic carbon (TOC) mineralisation rate exceeded 70% and 35%, respectively. Tannery wastewater refers to the industrial wastewater discharged by tannery yards. It contains
considerable organics and non-degradable dyes, which increase the oxygen consumption of water. Indeed, organics and non-degradable dyes are severe environmental hazards as their treatments (to meet the emission standards) are extremely challenging. Current treatment methods include physicochemical treatment, biochemical treatment and combined method. However, these methods have their respective limitations in treatment of organic pollutants. Recently, studies of semiconductors as photocatalysts for degradation of various pollutants have attracted great attention both in China and globally.
JSLTC Sept/Oct 2019
Inhibitory mechanism of hexavalent chromium formation in chrome-tanned leather with combined inhibitors
The perfect inhibition of Cr6+ formation in Cr-tanned leather has been reported using combined inhibitors consisting 3(2)-t-butyl-4-hydroxyanisole (BHA), ascorbic acid (AsA), and collagen peptide (CP-9). In this study, the inhibitory mechanism of the combined inhibitors was investigated with respect to: (i) Inhibiting the conversion of Cr3+ to Cr6+ by scavenging lipid radicals and peroxy radicals in free lipid of Cr-tanned leather; (ii) strengthening the reductivity within Cr-tanned leather; and (iii) stabilising Cr3+ complexes by coordination with CP-9. Electron spin resonance (ESR) of free lipid extracted from the Cr-tanned leather treated with combined inhibitors showed that free radicals considerably reduced with BHA and AsA. AsA markedly depressed peroxide value (POV), indicating strong effectiveness of the reducing action of AsA. The CP-9-added extract with 0.1 mol/L potassium phosphate buffer (pH 5.5) of the Cr-tanned leather before changing from pH5.5 to 8.0 showed that the conversion of Cr3+ to Cr6+ showed concentration-dependent inhibition, suggesting stabilisation through CP-9 coordination. Therefore, perfect inhibition of Cr6+ formation in Cr-tanned leather using combined inhibitors was concluded to be caused by the multiple inhibitory actions of BHA, AsA, and CP-9, such as radical scavenging, radical scavenger regeneration, reducing action, and Cr3+ stabilisation.
JSLTC Sept/Oct 2019
Formaldehyde release from Chekiang lambskin, characteristic parameter determination and influencing factors
VOC emissions may cause poor indoor (vehicle cabins included) air quality (IAQ). Recent studies have been conducted on the characteristics of volatile organic compounds (VOCs) emissions, most of them are focused on wood-based building materials, fur or fur imitations are scarcely mentioned. However, formaldehyde or formaldehyde-containing chemicals are often used in the production of fur, resulting in a certain amount of formaldehyde remaining in the finished product. This paper takes formaldehyde (FA) as an example to study its diffusion in fur. In order to understand and control the behaviour of the formaldehyde emission characteristics. Based on detailed mass transfer analysis of the emission process in a ventilated chamber, this paper measured the three emission characteristic parameters, i.e., the initial emittable concentration (C0), the diffusion coefficient (Dm) and the partition coefficient (K). The influence of different factors on the release parameters was also studied, as well as the time required for the emission of formaldehyde under different ventilation rates; we also compared the formaldehyde results of different test methods. The results showed that both Dm and C0 increased as temperature rose, but C0 increase is significant. With the increase of relative humidity, Dm decreased but C0 increased. In addition, the prediction model agrees well with the experimental data. The greater the ventilation rate, the faster the improvement of air quality standards in the cabin; The initial concentration was less than 43% of the formaldehyde content obtained through the extraction method and less than 4.6% of the formaldehyde content obtained by the distillation method.
JSLTC Sept/Oct 2019
Tanning properties of 4-((4,6-Dichloro-1,3,5-Triazin-2-yl) amino) benzene sulfonic acid
In this work, a triazine tanning agent of 4-((4,6-dichloro-1,3,5-triazin-2-yl)amino) benzenesulfonic acid (SAT) was prepared with cyanuric chloride and sodium p-aminobenzene sulfonate, its structure was confirmed by FTIR spectroscopy, and its tanning property was investigated. The results indicate that SAT can raise the Ts of tanned skin to around 75°C at the optimised dosage of 3%. The stability of tanned leather was tested by washing with aqueous solution of 10w% urea, 10w% NaCl and 1:1 acetone. The results of washing show that the tanned leather of SAT has excellent stability and there are stable covalent bond interactions between SAT and collagen fibres. Based on the results of washing and the structure characteristics of SAT, a tanning mechanism of SAT was given in which the second Cl and the third Cl on the triazine ring can both react with collagen fibres under mild tanning conditions of 35°C to 45°C.
JSLTC Sept/Oct 2019
Preparation of formaldehyde-free melamine resins using furfural as condensing agent and investigation of their retanning performance
Sulfonated amino resins are an important class of polymers which are used as retanning agents in the leather industry. There is challenge for such resins to be synthesised without formaldehyde to satisfy the strict regulation in leather goods. In this work, formaldehyde-free melamine based retanning agents have been synthesised by acid catalysed process using furfural as condensing agent and sodium metabisulfite as the sulfonating agent. Sulfonated melamine furfural (SMFr) resins were synthesised using different molar ratio of melamine, sodium metabisulfite and furfural. Stable and water-soluble resins were produced without etherification. The sodium metabisulfite to melamine ratio (SMB/M) was changed from 0.5-2.0 and furfural to
melamine mole ratio (Fr/M) was varied from 2-6. The viscosity behaviour of the produced resins was evaluated with the increasing trend of sulfonation and increasing mole ratio of furfural to melamine. Functional group analysis and conversion of reactants into product was elucidated by FTIR. Synthesised formaldehyde-free resins (SMFr) were comparatively evaluated as retanning agents on goatskin wet-blue against a commercially available sulfonated melamine formaldehyde (SMF) resin. The retanning performance of synthesised resins was studied and found better than that of the commercial SMF resin.
JSLTC Sept/Oct 2019