Leather Surface Research Articles

Leather defect classification and segmentation using deep learning architecture

ABSTRACT The defects on a leather surface may be caused by the poor material handling process during the production and manufacturing stages. It is essential to eliminate the natural variations and artificial injuries on the leather surfaces, in order to control the quality of the products and achieve customer satisfaction. To date, the visual inspection of the leather defects is performed manually by human operators. Thus, this paper aims to introduce an automatic defect detection technique by employing a deep learning method. Specifically, the proposed method consists of two stages: classification and instance segmentation. The former stage distinguishes whether the piece of the leather sample contains a defective part or not, whereas the latter is to localize the precise defective location. To accomplish the tasks, the dataset is first collected under a proper laboratory environment. Among 250 defective samples and 125 non-defective samples, the proposed method has been demonstrated its feature learning capability by producing promising performance when considering relatively fewer training samples. Particularly, the defect types focused in this study are the black lines and wrinkles. The best performance obtained is ∼95% for the classification task, whereas the segmentation task reaches an Intersection over Union rate of 99.84%

Shotgun metagenomics of dust microbiome from flight deck and cabin in civil aviation aircraft.

Microbial exposure is related to the health of passengers on commercial aircraft, but no studies characterized the microbial composition at the species level and identified their ecological determinants. We collected vacuum dust from floor and seat surfaces in flight decks and cabins of 18 aircraft, and amplification-free shotgun metagenomics was conducted to characterize the microbial composition. In total, 7437 microbial taxa were identified. The relative abundance for bacteria, eukaryote, viruses, and archaea was 96.9%, 1.8%, 0.3%, and 0.03%, respectively. The top bacterial species mainly derived from outdoor air and human skin included Sphingomonas, Corynebacterium, Micrococcus luteus, Variovorax paradoxus, Paracoccus dentrificans, and Propionibacterium acnes. The abundance of NIAID-defined pathogens was low, accounted for only 0.23% of total microbes. The microbial species and functional composition were structured by the indoor surface type (R2 =0.38, Adonis), followed by the manufacturer of the aircraft (R2 =0.12) and flight duration (R2 =0.07). Indoor surfaces affected species derived from different habitats; the abundance of dry skin and desiccated species was higher on textile surfaces, whereas the abundance of moist and oily skin species was higher on leather surfaces. The growth rates for most microbes were stopped and almost stopped.

Nonequilibrium low temperature plasma in process of collagen containing polymer materials electrical properties modification

The process of treatment with nonequilibrium low temperature plasma allows to reduce collagen materials electric potential due to charges dissipating along leather surface. Under certain conditions the main reason for the generation and accumulation of static electricity is the high hydrophilicity of the material. Leather surface hydrophobization is achieved through water repellent application and bulk nonequilibrium low temperature plasma treatment. Despite material surface hydrophobization nonequilibrium low temperature plasma processing parameters for genuine collagen containing polymer materials hygroscopicity increasement are determined. Collagen containing polymer materials plasma treatment also increases its biological compatibility and antimicrobial properties, improves mechanical characteristics by changing the internal structure of the material.

Nonionic Short-Chain Fluorinated Surfactants in the Fatliquoring of Chrome-Tanned Goat Skin

Surfactants as essential auxiliaries are used in almost all chemical processes in leather production. In this work, a series of nonionic short-chain fluorinated surfactants (Fn-Fn, where n = 2, 4, or 6) were successfully prepared and used as fatliquoring auxiliaries in the fatliquoring process of chrome-tanned goat skin. The chemical structure of these nonionic short-chain fluorinated surfactants was characterized by FTIR and the molecular weight was determined by GPC. The surface tension measurement results revealed that these three fluorinated surfactants showed excellent surface activities. The effect of type and dosage of Fn-Fn as well as fatliquoring temperature on fatliquoring properties of chrome-tanned goat skin were estimated by the softness and physical mechanical properties characteristic of resultant leather. The results revealed that the leather treated with 1 wt% F4-F4 at the fatliquoring temperature of 40oC showed the best overall performance, whose softness and physical mechanical properties were improved significantly. Moreover, the collagen fiber morphology and waterproof performance of leather treated with Fn-Fn were also investigated which showed that the addition of Fn-Fn in the fatliquoring process could promote the loosening of collagen fibers while effectively enhancing the water repellency of the leather surface. Therefore, such types of nonionic short-chain fluorinated surfactants are promising to be as desired fatliquoring auxiliaries in the leather industry.

Synthesis of magnetic Fe–Cr bimetallic nanoparticles from industrial effluents for smart material applications

Leather, a unique consumer material, does not offer any smart or advanced applications due to the lack of functional properties. An approach has been made to prepare magnetic nanoparticles utilizing the simulated chromium and iron-containing wastewater. Here, we synthesized bimetallic chromium-iron oxide nanoparticles using a simple co-precipitation technique followed by freeze-drying without any heating or calcination and coated on the surface of the leather to provide distinctive magnetic properties. The as-synthesized bimetallic nanoparticles have 20 ± 3 nm size with a magnetization value of 11 emu/g. The existence of coated bimetallic nanoparticles with the commercial leather finishing dispersion was seen on the leather surface up to 24.7 ± 2.5 μm thickness through the scanning electron microscopy. Vibrating sample magnetometric measurements show that the bimetallic nanoparticles coated magnetic leather exhibits ferromagnetic behavior. We also demonstrate that the bimetallic nanoparticles coated magnetic leathers can be used for adhesive-free interior decoration and electromagnetic interference shielding applications.

Fabrication of water-resistance and durable antimicrobial adhesion polyurethane coating containing weakly amphiphilic poly(isobornyl acrylate) Side chains

Polyurethane (PU) coatings are the most preferred systems in widespread applications on account of their great variability and fine-tuning of material properties. In this work, we have developed an eco-friendly antimicrobial polyurethane with natural-sourced isobornyl antifoulant side chains. A key development is the preparation of weakly amphiphilic poly(isobornyl acrylate) (PIBA) with terminal dihydroxy by thiol-ene ‘click’ reaction under UV catalysis. Then, the macro-polyol rich in isobornyl group is incorporated as a chain extender to achieve the functionalized polyurethane resin (PIBA-PU). Our study shows that the introduction of PIBA pendant long chains slightly affects the thermal behaviors of the soft and hard segments of PIBA-PU, and significantly improves the water-resistance of polyurethane coating as expected. The antibacterial and antifungal adhesion performances of the coatings are both substantially enhanced at higher content of PIBA. Leather-finishing application further indicates that PIBA-PU coated leather surfaces exhibit effective and long-lasting antifungal activity. The results suggest that functionalizing polyurethane with weakly amphiphilic acrylate long chains offers novel options for green coating design, whereby surface hydrophobicity and antimicrobial performances are both satisfactory and suitable for surface finishing.

Synthesis and Characterization of Environmentally-Friendly Self-Matting Waterborne Polyurethane Coatings

A series of self-matting waterborne polyurethanes (WPUs) were successfully prepared by introducing hydrophilic units into both soft and hard segments. By employing a polycaprolactone polyol containing carboxylate groups within the polymer chains to provide hydrophilicity directly, the matting performance of WPU films was greatly improved. The chemical structures of the WPU resins were confirmed by FTIR spectroscopy, and the morphology of WPU films was observed by SEM. The parameters of WPU preparation were investigated in detail. It was found that the surface gloss of WPU films as well as the particle sizes of WPU dispersions were closely associated with the content of hydrophilic units. As the content of carboxylates or sulfonates increased, the particle sizes of WPU decreased, while the gloss increased gradually. When the particle sizes of dispersions were greater than 3 μm, the gloss of WPU films coated on a leather surface was lower than 1. The results of TG showed that, the initial decomposition temperatures of WPU films were higher than 280 °C, which indicated these films also had good thermal stability. The prepared self-matting WPU coatings would have potential application prospects in the field of leather finishing.

Improving electrical conductivity of leather surface: a new technology versus industrial applications

The present study takes into account the consumer requirement of an even more massive use of touch screen devices, where the leather has to compete with the modern textile fibers in terms of technological performances, with particular reference to the newest technologies for the production of conductive gloves and other kinds of conductive goods, like shoes, garments, and others. Most of the known technologies able to provide materials with a unique ability to discharge static electricity and conductivity comparable with the human body concern the use of textile fibers. On the other hand, the goal of the present work is to delve into the application of technologies for leather matrix, with particular reference to the use of carbon-based nanomaterials, and attention to economical and/or practical aspects.

Copper (0) Mediated Single Electron Transfer-Living Radical Polymerization of Methyl Methacrylate: Functionalized Graphene as a Convenient Tool for Radical Initiator.

Polymer nanocomposites have been synthesized by the covalent addition of bromide-functionalized graphene (Graphene-Br) through the single electron transfer-living radical polymerization technique (SET-LRP). Graphite functionalized with bromide for the first time via an efficient route using mild reagents has been designed to develop a graphene based radical initiator. The efficiency of sacrificial initiator (ethyl α-bromoisobutyrate) has also been compared with a graphene based initiator towards monitoring their Cu(0) mediated controlled molecular weight and morphological structures through mass spectroscopy (MOLDI-TOF) and field emission scanning electron microscopy (FE-SEM) analysis, respectively. The enhancement in thermal stability is observed for graphene-grafted-poly(methyl methacrylate) (G-g-PMMA) at 392 °C, which may be due to the influence ofthe covalent addition of graphene, whereas the sacrificial initiator used to synthesize G-graft-PMMA (S) has low thermal stability as analyzed by TGA. A significant difference is noticed on their glass transition and melting temperatures by DSC. The controlled formation and structural features of the polymer-functionalized-graphene is characterized by Raman, FT-IR, UV-Vis spectroscopy, NMR, and zeta potential measurements. The wettability measurements of the novel G-graft-PMMA on leather surface were found to be better in hydrophobic nature with a water contact angle of 109 ± 1°.

A Multi-Level Colour Thresholding Based Segmentation Approach for Improved Identification of the Defective Region in Leather Surfaces

A Multi-Level Colour Thresholding Based Segmentation Approach for Improved Identification of the Defective Region in Leather Surfaces

Ultrasonic welding of artificial leather products with simultaneous surface embossing

It has been established that artificial leathers based on polyvinyl chloride belong to the group of polymer materials which need finding optimal welding methods and techniques in each specific case.The technology of ultrasonic welding with simultaneous embossing of the surface of artificial leather has been developed, which provides welded joints with high strength characteristics and a good appearance of embossing of the skin surface.

Investigation of finishing of leather for inside parts of the shoes with a natural biocide

The prevention of decrease of quality caused by microbial activity in footwear materials entails the use of biocides. However, these substances may pose a hazard to humans and to the natural environment. The paper presents the results of antimicrobial effect investigation for cowhide leather treated with oregano oil. In these studies oil was applied by spraying onto the finished leather surface and examined to determine its antimicrobial activity by using the Agar Diffusion Plate Test. These results were compared with those where a cowhide leather was treated with oil at the stage of fatliquoring. In addition, the oregano oil toxicity level was assessed and compared with biocides used in the tanning industry. Introducing oregano oil into the leather at the stage of fatliquoring provides a better antimicrobial effect than by spraying, however hygienic finishing of leather can be obtained by introducing oil into the raw material by these both methods. The oregano oil is characterised by the lowest number of hazards and toxicity as compared with commercial biocides. The use of essential oils as natural biocides in the tanning industry seems to be especially important and suitable solution considering the harmful effects of synthetic biocides to humans and the environment.

Nanoscopic investigation on TiO2-SiO2-GLYMO nanocomposite coated and plasma treated leathers

ABSTRACT In this study, the modification of leather surface by application of TiO2-SiO2-GLYMO (3-Glycidyloxypropyltrimethoxysilane) nanocomposite coating and plasma treatment with N2 gas activation is investigated by using Small and Wide Angle X-ray scattering methods. The protective properties were tried to be developed with TEOS and HMDSO polymers’ usage in the coating process by following and controlling nano scale structural changes. The main aim was the controls of nanoscaled surface modifications and determination of the best coating process by keeping natural structure of the leathers. These scattering methods were useful to investigate the coating effects on the PTLs (Plasma Treated Leathers)’ internal structures including collagen microfibers and nanofibers which are hierarchical structures of triple helix collagen. The main purpose of the work was investigate whether the structural change in the natural form of the leather is present or not in the molecular-nanoscopic and microscopic scales after the coating and the applied physico-bio-chemical processes. On the other hand, the successful protective coatings and surface modifications were determined with SAXS analyses by controlling the shape, size and distance distributions of the appeared nanoglobular aggregations. The observations of structural changes taking place within collagen fibrils as a result of surface modification provides new insight into the nature of finishing and informs future processing developments.

A Novel Framework for Classifying Leather Surface Defects Based on a Parameter Optimized Residual Network

Existing works on leather surface defects are mainly focused on the defect detection without performing the classification automatically. On the other hand, the manual classification has the disadvantages including a misjudgment, the occurrence of cumbersome labors and a high cost. To address these issues, this paper proposes a framework for classifying the leather surface defects based on a parameter optimized residual network. In this framework, an ultra high definition imaging system is first utilized to obtain the images of the leather surface. Then, two important network parameters are optimized. They are the size of the image data set and the size of the sliding patch window. Here, the size of the image data set is determined by achieving the tradeoffs between the evaluated workload and the classification accuracy. On the other hand, the size of the sliding patch window is obtained by the least squares method. In order to mitigate the limitation of the gradient disappearance in a deep network, a residual module is introduced to the proposed framework. Finally, the defect classification is performed based on the extracted features using multi-layer convolution and pooling operations. Computer numerical simulation results show that the leather surface defects can be classified effectively by the proposed framework. Also, the classification accuracy can reach 94.6%.

Automatic recognition and defect compensation for calf leather

Various defects existed on the surface of calf leather could affect its usable area and the salable price. No international criterion specifies the compensatory credits for calf leather surface defects which cause additional cost between supplier and purchaser in complicated negotiation process. This paper is to develop an artificial intellectual technique to implement the automatic recognition for types of leather defect and to compensate for leather defective unusable area in order to bridge trading gap. Data of calf defects from sample is extracted to develop an automatic recognition system via artificial intellectual techniques – ANN learning process is introduced to make a sustainable automatic recognition system used to identify types of categories for upcoming leathers under inspection, business transaction; the mean error rate of recognising leather defect is less than 2.16% and the mean deviation rate for compensation area is 0.03% under this simulated transaction.

Machine vision on-line detecting system for effectively eliminating non-detection zone of surface defects

针对皮革表面类缺陷用机器视觉在线检测时，某些缺陷成像质量对照明方向呈现各向异性甚至无法显现而形成检测盲区的问题，研究设计了一套可消除该类检测盲区的在线检测系统。基于缺陷处的散射和信息采集机理得出缺陷特征光强随照明方向的变化规律，并以压印和油墨类缺陷为例进行实验研究，发现2类缺陷特征光强分布均与照明方向相关，缺陷的检测盲区与有效区呈正交态。据此，采用自主设计的侧入式均匀照射离轴面光源，设计出线阵和面阵正交复合的在线检测系统，采用垂直目标面采集信息、45°角暗场正交照明，线阵相机和线光源组成主检测系统，面阵相机和离轴面光源辅检测系统，对随机出现的各向异性缺陷进行上百个样本检测,实验证明，缺陷检测盲区被有效消除，缺陷识别率提升了近22%，检测效率也得到大幅度提高。

Polyacrylate crosslinked with furyl alcohol grafting bismaleimide: A self-healing polymer coating

Leather surface is easily scratched and then discarded somewhere, which might result in a great waste of resources and economics. Self-healing materials could efficiently solve this problem. In this study, furfuryl alcohol (FA) and bismaleimide (BMI) were introduced to polyacylate for preparing self-healing polyacrylate emulsion (PA/(FA-BMI)), which was used as a finishing agent in leather process. Fourier transform infrared spectroscopy indicated that Diels-Alder reaction had taken place between FA and BMI. The dynamic light scattering, transmission electron microscopy and scanning electron microscopy results showed that FA and BMI were dispersed uniformly in polyacrylate. Thermogravimetric analysis results indicated that the addition of FA and BMI increased the thermal stability of polyacrylate. The ultra depth of field microscope (UDFM) results showed that the damaged PA/(FA-BMI) could be self-healing completely when the amount of FA and BMI was 5 %. The leather after finishing with PA/(FA-BMI) could be fully self-healing in 5 h at 50 °C. PA/(FA-BMI) endowed the finished leather good self-healing performance towards scratches on the surfaces. Meanwhile, physical and mechanical properties of the leather finished by PA/(FA-BMI), such as tensile strength, tear strength, wet and dry rub resistance, were also improved obviously.

Leather dyeing using a new liposome-based process assisted by dense gas technology

Liposomes are spherical vesicles characterized by a double lipidic layer surrounding an inner aqueous core; they have been employed in several fields, such as pharmaceutical, cosmetic and nutraceutical. In this work another possible application is explored: the deposition of dyes on sheep leather is attempted, using liposomes as dye vehicles to obtain a better adhesion of dye on leather surface. A supercritical assisted method called SuperLip is proposed to load red aniline into liposomes, for leather coloration. Process parameters have been optimized such as dye and lipid concentration in the system, water flow rate for vesicles inner core production and Gas to Liquid Ratio of the Expanded Liquid to control size and particles distributions.Nanometric liposomes of about 150 nm diameter have been obtained, with a red aniline Encapsulation Efficiency (EE) of about 75%; micrometric vesicles of about 2 μm were also produced with EE up to 82%, in order to provide large dimensions for covering macroscopic surfaces. A conventional dyeing method and the new liposomal method were compared in terms of deposition time, and color resistance. Liposomes, produced in this work, speeded up dye deposition from 60 min to 30 min, and resulted in a higher resistance to heat exposure; indeed, a discoloration down to 2.3% was observed using the proposed method and 25.1% using conventional method.

Study of solvent-free sulfonated waterborne polyurethane as an advanced leather finishing material

A solvent-free waterborne polyurethane was synthesized via one-component crosslinking using N-[(2-amionoethyl)-amino] ethane sulphonated sodium as the post-chain extender. The effects of the N-[(2-amionoethyl)-amino] ethane sulphonated sodium and polyol content on the properties of waterborne polyurethane were investigated. The results indicate that at the optimum post-chain extender (6 mol%) and polyol (15.5 mol%) content, the waterborne polyurethane demonstrated best comprehensive properties. A clear advantage of the approach is that, in contrast with the traditional synthesis technique of waterborne polyurethane, the reaction process did not need any organic solvents to reduce the system viscosity. Also, a more natural optical appearance was obtained by the drying process of waterborne polyurethane itself. The as-developed waterborne polyurethane coating can be extensively used on the artificial leather and synthetic leather surfaces.

Quality inspection of natural leather using non-destructive testing technique

ABSTRACT Results of a novel method of testing natural, tanned hides, in particular full grains, for both internal and external structural defects are presented. Such defects may occur while the animal is still alive or during the hide tanning and finishing processes. The method, still under development, uses a specially designed lamp to produce a thermal excitation impulse and an infrared camera to measure the surface temperature distribution. A newly developed algorithm is employed to process a series of thermograms recorded while the natural leather surface is heated and cooled in turn. Presented are selected results of experimental investigations carried out both on a specially prepared sample and other specimens of natural leathers. The Matlab environment was used to carry out numerical calculations. The solution discussed here represents a part of the project aimed at developing an industrial device for detecting structural flaws of leathers used for luxury upholstered furniture.