Shrinkage Temperature Research Articles

The Effect of Gamma Irradiation on Shrinkage Activity of Collagen in Vegetable Tanned Leather

The dose dependent effect of gamma irradiation on collagen in vegetable tanned leather was studied by the MHT method. Examination of the irradiated samples at 3 months after the irradiation treatment revealed variations of the main shrinkage temperatures and intervals. Up to 25 kGy, the shrinkage temperature does not vary while the total shrinkage interval decreases suggesting cross-linking as the main process. At higher doses, the decrease of shrinkage temperature is accompanied by the increase of the total shrinkage interval indicating that peptide chain scission becomes predominat. Quebracho-tanned sheep leather shows to be the less resistant to the deterioration effect of gamma radiations, while both mimosa-tanned goat leather and quebracho-tanned calf leather better withstand the destabilization effects.

Properties of polymers as a nanoscale material for fibers in leather

Hyperbranched polymers, an innovative class of nano-polymers, could enhance the properties of fibers owning to their unique structures. In this study, the ester compound (HPAE) of 3-(bis(2-hydroxyethyl)amino)propionic acid and pentaerythritol was treated with undecylenic acid to obtain novel hyperbranched multiterminal alkenyl polymers (HPAE-UAs). The sizes of the HPAE-UAs could be controlled conveniently from 400 to 1300 nm by adjusting the capped fraction of the hydroxyl groups with undecylenic acids. The molecular structures of HPAE-UAs were characterized by means of FT-IR and 1H-NMR. Then, the effect of the HPAE-UAs on the structures, thermal, and mechanical properties of the wet blue leather were investigated. TEM and SEM demonstrated that the spacing between fibers was enlarged. The thermogravimetric analysis showed that the residual volume of leather could reach up to 30.3 % at about 500 °C. Furthermore, the shrinkage temperature increased to 89.4 °C. It was found that the HPAE-UAs used in leather could improve the thermal performance, physical and mechanical properties. All of these results indicate that HPAE-UAs can be used as a fatliquor with retanning in leather process.

Preparation, characterization and application of dispersible and spherical Nano-SiO2@Copolymer nanocomposite in leather tanning

Dispersible and spherical silica nanoparticles (nano-SiO2) were prepared with tetraethyl silicate and different surface-modifiers via a simple method. The silica nanoparticles surface-modified with methacryloxy (propyl) trimethoxysilane (denoted as MPS-SiO2), dimethyl diallyl ammoniumchloride (denoted as DMDAAC-SiO2) and poly (methacrylic acid) (denoted as PMAA-SiO2) which are known as hydrophobic, amphiphilic and hydrophilic modifiers, respectively, exhibited excellent dispersibility in various solvents or polymer matrix. The obtained bare silica nanoparticles, MPS-SiO2, DMDAAC-SiO2 and PMAA-SiO2 were characterized by Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), transmission electron microscope (TEM) and scanning electron microscope (SEM). A series of nanocomposites (denoted as SiO2/P, MPS-SiO2/P, DMDAAC-SiO2/P and PMAA-SiO2/P, respectively) were also prepared with the bare or surface-modified silica nanoparticles and methacrylic acid-co-acrylamide-co-acrylonitrile-co-salicylic acid tetrabasic copolymer (denoted as PMAAS) and applied in leather tanning. Compared with those of the leather tanned with the commercial acrylic resin (CHINATAN OM) and pure tetrabasic copolymer tanning agents, the physical and mechanical properties, rheological properties and thermal stabilities of the leather treated with SiO2/P, MPS-SiO2/P, DMDAAC-SiO2/P or PMAA-SiO2/P founded to be improved in a significant way. Moreover, the highest shrinkage temperature of the wet-white sheepskin tanned with PMAA-SiO2/P reached to 76°C and the thickness increase reached to 105%.

Modification of the characteristic melting temperatures of sawdust ashes

This research was focused on one aspect of the use of biomass in energy plants, namely, the problems associated with low melting temperatures of ashes formed after sawdust combustion, which causes serious operational problems associated with agglomeration, slagging, and corrosion. For this research, the selected methodology was evaluated by CEN (European Committee for Standardization), based on the determination of four parameters: shrinkage temperature, deformation temperature, hemisphere temperature, and flow temperature. The above mentioned temperatures were determined for ash samples of sawdust burned in an oxidizing and reducing atmosphere.

Response of stem radial growth of Qinghai spruce (Picea crassifolia) to environmental factors in the Qilian Mountains of China

Exploring the response of intra-annual tree growth to environmental factors is critical for the understanding of the effects of climate changes on tree seasonal growth patterns. We monitored stem radial changes of Qinghai spruce (Picea crassifolia) over two growing seasons (2014 and 2015) in the Qilian Mountains of China using high-resolution point dendrometers. Our results showed that the onset of the main growth period occurred around 11 May. Soil temperature was a key environmental factor influencing the onset of tree growth. Stem radial growth commenced when soil temperature at 40cm depth was >0°C. The timing of radial growth cessation exhibited greater variability than onset, ranging from late July to early August, and was probably unrelated to climatic conditions. We found close relationships between maximum daily shrinkage (MDS) and air temperature, precipitation, soil water content, and soil temperature. Maximum and mean air temperature, relative air humidity, vapor pressure deficit, and precipitation had significant effects on daily stem radial increment (SRI). Precipitation was one of the most important factors influencing stem radial growth. Moreover, the number of precipitation days was more significant in promoting cumulative seasonal growth of Qinghai spruce than total precipitation. With climate warming, the onset of radial growth may occur earlier than before, and seasonal growth patterns of trees may change.

Influence of telopeptides on the structural and physical properties of polymeric and monomeric acid-soluble type I collagen

Currently two factors hinder the use of collagen as building block of regenerative devices: the limited mechanical strength in aqueous environment, and potential antigenicity. Polymeric collagen is naturally found in the cross-linked state and is mechanically tougher than the monomeric, acid-soluble collagen ex vivo. The antigenicity of collagen, on the other hand, is mainly ascribed to inter-species variations in amino acid sequences of the non-helical terminal telopeptides. These telopeptides can be removed through enzymatic treatment to produce atelocollagen, although the effect of this cleavage on triple helix organization, amino acidic composition and thermal properties is often disregarded. Here, we compare the structural, chemical and physical properties of polymeric and monomeric type I collagen with and without telopeptides, in an effort to elucidate the influence of either mature covalent crosslinks or telopeptides. Circular dichroism (CD) was used to examine the triple helical conformation and quantify the denaturation temperature (Td) of both monomeric collagen (36.5°C) and monomeric atelocollagen (35.5°C). CD measurements were combined with differential scanning calorimetry (DSC) in order to gain insight into the triple helix-to-coil thermal transition and shrinkage temperature (Ts) of polymeric atelo collagen (44.8°C), polymeric collagen (62.7°C), monomeric atelo collagen (51.4°C) and monomeric collagen (66.5°C). Structural and thermal analysis was combined with high pressure liquid chromatography (HPLC) to determine the content of specific collagen amino acidic residues used as markers for the presence of telopeptides and mature crosslinks. Hydroxylamine was used as the marker for polymeric collagen, and had a total content of 9.66% for both polymeric and polymeric atelo collagen; tyrosine was used as the marker for telopeptide cleavage, was expressed as 0.526% of the content of polymeric collagen and the partially-reduced content of 0.39% for atelocollagen.

Characteristics of dry shrinkage and temperature shrinkage of cement-stabilized steel slag

The objective of the present study was to investigate the characteristics of dry shrinkage and temperature shrinkage of cement-stabilized steel slag (CSS). The steel slag was intended to be utilized to replace the macadam in cement-stabilized base course to reduce dry shrinkage and temperature shrinkage of semi-rigid base materials. Dry shrinkage and temperature shrinkage tests were performed to analyze the water loss rate, dry shrinkage strain, dry shrinkage coefficient and temperature shrinkage strain of CSS and cement-stabilized macadam (CSM) as functions of time, cement content and gradation types of the material. The water loss rate of CSS increased with the rise in time, and then tended to be flat on about 10th days. The hygroscopicity of coarse gradation CSS was larger than those of intermediate gradation and fine gradation CSS. With the same gradation, the more the cement content was, the greater the water loss rate was. It was suggested that the cement content of CSS should not be more than 4%, which can obviously reduce the dry shrinkage strain. Compared with CSM, CSS with rational adjustment of gradation owned a smaller dry shrinkage strain and would not produce a larger temperature shrinkage strain. It is feasible to replace the base macadam with waste steel slag, which is beneficial to improve the characteristics of dry shrinkage and temperature shrinkage of semi-rigid base material and utilization of waste steel slag. This paper aims to provide a solid theoretical foundation to popularize the wide utilization of CSS in engineering applications.

Effects of glutaraldehyde concentration and fixation time on material characteristics and calcification of bovine pericardium: implications for the optimal method of fixation of autologous pericardium used for cardiovascular surgery.

Autologous pericardium, which is widely used in the field of cardiovascular surgery, is usually fixed with glutaraldehyde (GA) to improve handling and provide biomechanical stability. However, an optimal method of GA fixation of autologous pericardium is not known. The objective of this study was to evaluate the effects of GA concentration and fixation time on material characteristics and calcification of bovine pericardium. Bovine pericardial tissues were fixed with different concentrations of GA (0.3, 0.4, 0.5 and 0.6%) for different exposure times (10 and 20 min). Material characteristics of the fixed tissues were assessed by mechanical test, thermal stability test and pronase test. The tissues were subcutaneously implanted into 3-week-old rats for 2months, and the calcium contents of the explanted tissues were measured. Differences between the groups were evaluated by two-way analysis of variance. Differently treated tissues showed no significant differences in tensile strength. The mean elongation at break of the pericardial tissues fixed with 0.5 and 0.6% was significantly higher compared with 0.3 and 0.4% when fixed for 20 min. The mean elongation at break of the pericardial tissues fixed for 20 min was significantly higher compared with 10 min when fixed with 0.5 and 0.6%. Thermal stability test revealed significantly higher mean shrinkage temperature of the pericardial tissues fixed with 0.6% compared with lower concentrations irrespective of fixation time. The mean shrinkage temperature of the pericardial tissues fixed for 20 min was significantly higher compared with 10 min irrespective of GA concentration. Pronase test revealed significantly lower mean percent remaining weight of the pericardial tissues fixed with 0.3% compared with higher concentrations irrespective of fixation time. The mean percent remaining weight of the pericardial tissues fixed for 20 min was significantly higher compared with 10 min irrespective of GA concentration. The mean calcium content of the pericardial tissues fixed with 0.6% was significantly lower than that of the pericardial tissues fixed with 0.4% irrespective of fixation time. Fixation of bovine pericardium with 0.5 and 0.6% GA for 20 min produced superior results with regard to material characteristics (mechanical properties, degree of fixation and resistance to enzymatic degradation) and postimplantation calcification. These results may have implications for optimal fixation of autologous pericardium used for cardiovascular surgery.

Role of solvent-mediated carbodiimide cross-linking in fabrication of electrospun gelatin nanofibrous membranes as ophthalmic biomaterials

Due to their ability to mimic the structure of extracellular matrix, electrospun gelatin nanofibers are promising cell scaffolding materials for tissue engineering applications. However, the hydrophilic gelatin molecules usually need stabilization before use in aqueous physiological environment. Considering that biomaterials cross-linked via film immersion technique may have a more homogeneous cross-linked structure than vapor phase cross-linking, this work aims to investigate the chemical modification of electrospun gelatin nanofibrous membranes by liquid phase carbodiimide in the presence of ethanol/water co-solvents with varying ethanol concentrations ranging from 80 to 99.5vol%. The results of characterization showed that increasing water content in the binary reaction solvent system increases the extent of cross-linking of gelatin nanofibers, but simultaneously promotes the effect of biopolymer swelling and distortion in fiber mat structure. As compared to non-cross-linked counterparts, carbodiimide treated gelatin nanofibrous mats exhibited better thermal and biological stability where the shrinkage temperature and resistance to enzymatic degradation varied in response to ethanol/water solvent composition-mediated generation of cross-links. Irrespective of their cross-linking density, all studied membrane samples did not induce any responses in ocular epithelial cell cultures derived from cornea, lens, and retina. Unlike many other cross-linking agents and/or methods (e.g., excessive vapor phase cross-linking) that may pose a risk of toxicity, our study demonstrated that these nanofibrous materials are well tolerated by anterior segment tissues. These findings also indicate the safety of using ethanol/water co-solvents for chemical cross-linking of gelatin to engineer nanofibrous materials with negligible biological effects. In summary, the present results suggest the importance of solvent-mediated carbodiimide cross-linking in modulating structure–property relationship without compromising in vitro and in vivo biocompatibility of electrospun gelatin nanofibers for future ophthalmic applications.

Influence of metal cations on leather degradation

Abstract In the presence of ions of transition metals, mainly iron and copper, there occurs a heavy damage in historical leathers: loss of firmness, fragility and even powdering. Ions of transition metals are contained in pigments used for leather dying or they come from chemicals used for leather marbling or from direct contact of leather with metal clips etc. After accelerated ageing of samples the influence of transition metal cations was evaluated by determination of changes in mechanical properties, pH values and shrinkage temperatures. Structural changes in leather were examined by means of scanning electron microscope, SDS-PAGE electrophoresis and spectroscopy of electron paramagnetic resonance. In leather samples a semiquinone radical has been detected, which initiates their oxidation. Transition metal cations catalyse this oxidation process thus increasing the damage extent when compared to leathers not containing these ions.

Erratum to: A study of the deterioration of aged parchment marked with laboratory iron gall inks using FTIR‑ATR spectroscopy and micro hot table

A great number of historic manuscripts, drawings, etc., many of which are stored and/or exhibited in museums, archives and various collections contain iron gall inks (IGIs) as base scripting material. Although the severe deterioration effect of IGIs on paper has been recognized and its chemistry has been explored, little focus has been given on IGIs on parchment. A study was designed to investigate laboratory iron gall inks containing ferrous sulphate and gallic acid (LIG formulation) and with added quantities of gum arabic (LIGG formulation). Specimens marked with the above ink types were artificially aged at 80 °C and 80 % RH for up to 32 days. Micro hot table (MHT) thermal analysis showed a decrease in the shrinkage temperatures in inked areas of aged parchment of up to 15.5 °C. Results of FTIR-ATR spectroscopy showed intense migration of sulphate ions from inked spots to neighbouring ink-free areas at the surface of parchment in both ink formulations, also confirmed by SEM microanalysis results. This effect peaked at short-moderate times of artificial ageing, where calcium sulphate was identified and located at the surface of ink-free areas. Moreover, early signs for gelatinization of collagen also resulted from analysis of Amide I and II infrared bands, where the random coil content increased upon ageing as compared to the helical one.

Chromium recovery from tannery sludge by bioleaching and its reuse in tanning process

Bioleaching has been demonstrated as a feasible and effective technology for removing Cr(III) from tannery sludge, but the recovery of bioleachate derived from tannery sludge by bioleaching is rarely reported. The purpose of this study was therefore to figure out the components of bioleachate and develop a chromium-iron tanning agent using the bioleachate and reuse it in tanning process. Component analysis indicated that the bioleachate contained high concentrations of Cr and Fe, as well as small quantities of other elements. The dissolved organic matter in the bioleachate was detected to be less than 1000 mg/L, which was mainly composed of polysaccharide, aliphatic or aromatic carboxylic acid compounds. A chromium-iron tanning agent was then prepared using the bioleachate, iron and chromium salts in a suitable ligand environment, and reused for tanning. In the tanning experiments, the pickled pigskins were tanned with this prepared tanning agent and the results indicated that chromium-iron tanned crust leather presented comparable physical and mechanical properties as well as air permeability when compared with conventional chromium tanned crust leather, but the thermal shrinkage temperature was about 4 °C lower than that of the chromium tanned crust leather. Therefore, this study provides not only a reuse route for tannery sludge bioleachate but also a clean tanning agent for leather processing.

Przegląd metod badań technologicznych zabytkowych kodeksów na przykładzie Codex Aureus Gnesnensis

In 2012 Codex Aureus Gnesnensis called the „Gold Codex” from the Archdiocesian Archive of Gniezno (item „BK Ms 1a”) was investigated by scientific workers from the Nicolaus Copernicus University in Toruń. The codex was made on parchment, reachly illuminated, block covered with wooden boards and leather, and decorative silver elements were set to the cover. All basic elements and substances of the object were investigated: metal elements, wooden boards, leather, pigments and binders, parchment, paper products, textile materials, materials used for reparation. Attempts were also put on investigation of degradation products of materials and decayed areas. Several methods applied to characterise meterials the object consists of. They were as follows: A). non-invasive methods: observation in ViS light, rentgenography (RTG), reflectography in the UV light, UV induced fluorescence, NIR reflectography, X-ray fluorescence, FTIR spectroscopy, False IR analysis, pH measure of paper products, B). microdestrucive analyses on samples: X-ray fluorescence, observation of morphological features under optical microscopes (VIS, PL, UV), SEM with energy dispersive X-ray spectrometer (EDX), FTIR spectroscopy, False IR analysis, gas chromatography, collagen shrinkage temperature (MHT), fiber identification of paper products and textiles (morphological features, Herzberg stain, Schweizer reagent), lignin detection in paper products (phloroglucin), microchemical identification of organic substances (saponification test, hydroxyroline test, ninhydrin, sudan black, malachite green, amido black). Also the microbiological investigations were performed (nondestructive: ATP, insects identification; microdestructive: observation of sampled microorganisms under optical microscope). Results of investigations allowed dating of parts of the codex as well as realisation of the conservation-restoration project.

Biodeterioration process of chromium tanned leather with Penicillium sp.

For getting a clear and detail process of chromium tanned leather biodeteriorated with Penicillium sp. as a reference for future research and providing a cleaner chromium containing leather waste disposal method. The chromium tanned leather (CTL) and chromium tanned hide powder (CTHP) were biodeteriorated with the Penicillium. The CTL was biodeteriorated at first to verify the biodeterioration effect, and then the changes of the CTHP structure and thermal properties after the biodeterioration were analyzed by Scanning Electron Microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), Thermal Gravimetric Analyzer (TG) and Differential Scanning Calorimeter (DSC). The deterioration degree of the CTHP was characterized by the contents of hydroxyproline and total nitrogen in the filtrate, the Penicillium number was counted too during the process. The results showed that the CTL could be biodeteriorated with the Penicillium as shrinkage temperature and mass decreasing even though the biodeterioration degree was not ideal enough. After the process of CTHP biodeteriorated with the Penicillium, the surface morphology and structure of the CTHP were damaged. The thermal resistance and thermal denaturing temperature reduced which showed the detanning effect happened in the biodeterioration process. With the increasing of biodeterioration time, the hydroxyproline and total nitrogen in the filtrate increased. The Penicillium number maximized at 96 h and protease was produced in the process with enzymatic activity reaching to 9.23U mL−1. These phenomena demonstrated the Penicillium grew through digesting chromium tanned leather and produced metabolites. To sum up, the biodeterioration process of chromium tanned leather with Penicillium was a synergistic effect of chromium detanning and the Penicillium growth.

Shrinkage behaviour of superplasticised RCCP and its relationship with internal temperature

ABSTRACTShrinkage properties of roller-compacted concrete pavement (RCCP) and its relationship with internal temperature variations in superplasticised RCCP were studied. The control and superplasticised RCCPs containing different amounts of sodium naphthalene sulphonate superplasticiser between 1 and 4% by weight of cement were compacted at their optimum water content. The short- and long-term shrinkage and internal temperature variations were monitored in isolated and non-isolated conditions. Micro-structural analysis was implemented using the electron scanning microscope and X-ray diffraction methods. The initial internal temperature of superplasticised RCCP during the first hours of setting was higher than the control mix. A dormant period of low internal temperature was found for superplasticised mixes which started after about 7–13 and 6–10 h in non-isolated and isolated conditions, respectively. For non-isolated condition, the dormant period lasted about 3 days. Under isolated condition, similar trend was found after 4–8 days. During the first day of curing, the total and drying shrinkages of the control RCCP were considerably higher than the superplasticised mixes. On the contrary, the long-term monitoring indicated higher total and drying shrinkages in superplasticised mixes. Based on statistical analysis, the relationship between the autogenous shrinkage and area under the internal temperature diagram was significant.

A comprehensive evaluation of physical and environmental performances for wet-white leather manufacture

This paper presents the comprehensive evaluation results of physical and environmental performances for a novel wet-white (chrome-free) leather manufacturing. The tanning process is optimized as 15 wt% tannic acid (TA) combination with 4 wt% Laponite nanoclay, giving the leather with shrinkage temperature (Ts) above 86 °C. Inductively coupled plasma-atomic emission spectrometry (ICP-AES) measurements indicate that Laponite can be evenly and tightly bound within the leather matrix, which is further confirmed by scanning electron microscopy and energy dispersive X-ray (SEM-EDX) spectroscopy analysis. The resultant wet-white leathers have reasonable good physical properties that can meet the standard requirements for furniture leather without containing hazardous Cr(VI) and formaldehyde. Further life cycle assessment (LCA) studies shows that tanning process is the main contributor to environmental impact categories in the wet-white tanning process, and tannic acid is the most significant substance factor. Compared to conventional chrome tanning, the wet-white tanning process exhibits much lower abiotic depletion potential (ADP), and reduced global warming potential (GWP) and human toxicity potential (HTP) impacts due to the nature of vegetable tanning; whereas, GWP excluding biogenic carbon and energy consumption are higher owing to prolonged run time.

Application of an amphoteric polymer for leather pickling to obtain a less total dissolved solids residual process

A clean approach of less total dissolved solids residual process based on an amphoteric polymer has been attempted. Amphoteric polymer was added in the pickling as experimental process. The amount of common salt reduced from 8% to 2% and the amount of basic chrome sulfate was 4%. 8% common salt was added in pickling and 4% basic chrome sulfate was added in tanning as control. The tanning waste water, wet blue and crust leathers were analysed. The results showed that the amphoteric polymer resulted in increment of Cr2O3 content in leather by 10.8%, and the amphoteric polymer offered leather showed better chromium distribution and collagen fibers distribution properties than conventional leather. The mechanical properties, colour value and shrinkage temperature of the leather treated with amphoteric polymer were close to those of the conventional leather. What's more, the Cr2O3 content of experimental tanning waste reduced by 53.5%, and the reduction in Cl− content is 78.3%, and the total dissolved solids in the experimental waste reduced to 178.11 g/L. From the results obtained, it is suggested that without affecting the quality of the finished leather, the amphoteric polymer offered process could reduce the pollution of tanning waste, and promote the development of cleaner production.

Unilateral NMR and thermal microscopy studies of vegetable tanned leather exposed to dehydrothermal treatment and light irradiation

Unilateral nuclear magnetic resonance (NMR) and imaging thermal microscopy (imageMHT) were performed on newly obtained and artificially aged vegetable tanned leathers. Calf and sheep leathers tanned with vegetal extracts of mimosa bark, quebracho and chestnut wood were compared. Ageing was simulated by exposing the leather samples to heating at 70°C in controlled atmosphere at 30% relative humidity and irradiating them with 4000lx in the visible light region for 8, 16, 32 and 64days. Proton spin-lattice relaxation times T1 and effective spin-spin relaxation times T2eff were measured at room temperature and their trend variation compared with the corresponding variations of shrinkage temperature Ts and total length of shrinkage interval measured by imageMHT. Newly obtained leather displayed different proton relaxation times and shrinkage temperatures depending on both the collagen origin and tannin type. Effective spin-spin relaxation values shown to be discriminative for collagen origin and sensitive to the cross-linking degree, whereas spin-lattice relaxation values were more sensitive to the tannin type. Both NMR relaxation times were sensitive to the changes in the water dynamics upon ageing due to the formation of collagen damaged intermediate states and shown a sudden change when the tannin matrix was depleted (e.g. de-tanning).

Enhancement of chromium uptake in tanning process of goat garment leather using nanocomposite

In the present study, a greener approach to tanning process based on nanocomposite assisted chrome tanning has been attempted. Nanocomposite was offered prior to basic chrome sulfate of chrome tanning process during goat garment making. It was found that the shrinkage temperature of the wet blue tanned by nanocomposite associated with less chrome was above 100 °C and the Cr2O3 content in tanning wastewater of nanocomposite associated with less chrome systerm decreased to 165.6 mg/L which brought about better chromium uptake and reduction of chromium load in the wastewater compared to where the 3% and 8% chrome was offered alone. The mechanical properties of crust treated with nanocomposite were close to those of the crust tanned by 8% chrome and the addition of nanocomposite could endow crust with good handle feeling, filling property and softness. The scanning electron microscopy and atomic force microscopy showed that the grain surface of the crust treated with nanocomposite was flat and smooth. The scanning electron microscopy analysis also indicated that the crust treated with nanocomposite contained well-dispersed fibrils and did not destroy the microstructure of collagen. Additionally, The energy dispersive spectrometer analysis revealed that the nanocomposite associated with less chrome tanning process also afforded uniform distribution of chromium in the leather. More specifically, the significant reduction in biochemical oxygen demand, chemical oxygen demand in the wastewater and appeared that suspended solid in the effluent when compared to tanning with 3% and 8% chrome alone conventional tanning method were revealed from environmental impact assessment studies. Most importantly, nanocomposite could bring about the enhancement of chrome uptake, resulting in environmental, economic and social positive impacts to accelerate the sustainable development of leather industry.

Influence of pullulan hydrogel on sutureless wound healing in rats

Carbohydrate polymers have been used to make wound dressings since many years. Pullulan is a carbohydrate polymer, found abundant in nature, produced by various strains of Aureobasidium. In this study, pullulan hydrogel (10%) has been used to test its healing efficacy on suture-less wounds in rats. Male Wistar rats weighing between 150 and 200 g body weights were used for this study. The animals were divided into 3 groups, each group comprising of six animals and a 3 cm full thickness incision was made on the dorsum of the rats. To group I rats, 500 μl of the hydrogel was applied on the wounds followed by finger clamping for 2 min. Group II (positive control) rats were applied with povidone-iodine and group III rats (control) were left untreated. The drug was given once a day until the wounds healed completely. The healing rate was assessed by observing the number of days required for complete healing. The incision wounds of hydrogel treated rats healed within 6 days whereas the wounds of positive control and control rats had taken 11 days and 15 days respectively, for complete healing. The animals were sacrificed and wound breaking strength of the incisions was measured. A two fold increase in the tensile strength was observed in the pullulan hydrogel treated wounds when compared to the control and positive control wounds. The tensile strength of pullulan hydrogel treated wounds was found to be (3.63 MPa) when compared to control (1.17 MPa) and positive control (1.34 MPa) rats. Shrinkage temperature was also remarkably augmented (more than 25%) when compared to control. Histopathological evaluations showed enhanced proliferation of fibroblasts and faster epithelialization of wounds in pullulan hydrogel treated rats. The increased rate of healing in pullulan hydrogel treated wounds might be due to its energy giving and anti-oxidant properties.