Shrinkage Temperature Research Articles

Comparison on the properties of bovine pericardium and porcine pericardium used as leaflet materials of transcatheter heart valve.

In order to obtain the smaller delivery diameter, porcine pericardium had been used as a substitute material of bovine pericardium for the leaflet materials of transcatheter heart valve (THV). However, the differences between them had not been fully studied. Therefore, this study compared the microstructure, biochemical and mechanical properties of two materials and hydrodynamics of THV made by the two materials in detail. In this study, firstly, the microstructure of pericardium was analyzed by staining and scanning electron microscope; secondly, the biochemical properties of pericardium after different processes were compared by heat shrinkage temperature test, free amino and carboxyl concentration test, enzyme degradation test, subcutaneous implantation calcification analysis in rats; finally, the mechanical properties were evaluated by uniaxial tensile test before and after the pericardium being crimped, and then, the hydrodynamics of THV was studied according to the ISO5840 standard. Compared with bovine pericardium, after the same process, porcine pericardium showed a looser and tinier fiber bundle, a similar free carboxyl concentration, a lower resistance to enzyme degradation, a significantly lower calcification, bearing capacity and damage after being crimped, a better hydrodynamic and adaption with lower cardiac output and deformation of implantation position. Meanwhile the dehydration process of pericardium almost had preserved all the biochemical advantages of two materials. In this study, porcine and bovine pericardium showed some significant differences in biochemical, mechanical properties and hydrodynamics. According to the results, it was presumed that the thinner porcine pericardium might be more suitable for THV of right heart system. Meanwhile, more attention should be taken for the calcification of THV made by the bovine pericardium.

Experimental Study on Performance of Cement Stabilized Macadam Modified with Composite Agent

In this paper, three composite agents (i.e. emulsified asphalt, EA; styrene butadiene rubber, SBR; rubber powder, RP) were employed to modify the cement stabilized macadam (CSM) for the optimal design of semi-rigid base materials. The feasibility of utilizing EA/SBR/RP composites in the cement stabilized macadam is investigated from the perspectives of the modification mechanism and durability performance. To investigate the effects of different modifiers on the modification mechanism of the cement stabilized macadam, the unconfined compressive strength (UCS), indirect tensile strength (ITS), and compressive resilience modulus (CRM) of the modified samples with the variations in EA/SBR/RP composites groups were tested. Moreover, the drying shrinkage test and temperature shrinkage tests are performed to reveal the effectiveness of EA/SBR/RP composites on durability performance of cement stabilized macadam. The results show that the UCS, ITS, and CRM of the samples decrease with the increasing of EA/SBR/RP composites during 28 days. The average drying shrinkage coefficient (DSC) increases with the increasing of EA/SBR/RP composites. Considering all the above experimental results, the recommended dosage of the composite agent is 2% EA, 0.75% SBR, and 0.6% RP.

Effect of microcracking on the shrinkage cracking and durability performance of cement-treated macadam material

ABSTRACT This study systematically investigates the effect of microcracking on the shrinkage performance and durability of cement-treated macadam (CTM). Microcracks formed in the early stage of microcracking can reduce reflection cracks generated in semi-rigid base asphalt pavements. The shrinkage characteristics and durability of CTM after microcracking are important to consider in the engineering of the CTM base. In this study, indoor shrinkage tests were conducted on the prepared specimens in ten working conditions, and finite element analysis of the water loss shrinkage of the microcracked CTM was conducted using a cohesive zone model (CZM). The CTM durability after early microcracking was analyzed and evaluated through fatigue tests and freeze–thaw cycle tests. The results showed that the drying shrinkage strain and temperature contraction coefficient of the CTM could be effectively reduced by microcracking. The fatigue life of the CTM decreased with 50% microcracking, but was still within the service requirement. Taking the 104 Chinese road reconstruction project as the research background, microcracking should be conducted 35 d before the freezing period to avoid significantly affecting the frost resistance of the CTM base. This study provides a theoretical basis for the promotion and application of microcracking techniques in practical engineering.

Role of Anionic Chromium Species in Leather Tanning

Chrome tanned leathers are definitely unique in comparison with leather made from any other known tanning agents, especially in terms of thermal stability, cost and its reactive mechanism with collagen fibers. In our current studies, self basifying chrome tanning materials masked with different percentages of organic acid were prepared and applied after the de-liming stage of leather processing. This eliminated the need for pickling and basification steps. Tanned leathers resisted shrinkage up to 103 and 105±2°C while conventional chrome tanned leathers resisted up to 108±2°C. Also, interaction of anionic chrome species in tanning was studied. It was observed that the percentage of anionic species in the experimental chrome tanning material was higher than conventional chrome tanning material and the shrinkage temperature achieved by application of experimental tanning material proves that anionic species do involve in tanning. Tanned leathers were crusted and analysed for strength and organoleptic properties.

The use of non-chrome mineral tanning materials as a preferable environmentally friendly tanning material

Mineral chrome tanning agent is the most widely used tanning agent for various types of leather articles, given its various advantages. Besides its many advantages, there is a negative side to chrome tanneries, namely the presence of waste disposal that is harmful to the environment. Therefore, this study aims to determine the quality of mineral tanning materials other than chrome (aluminium and titanium) as a substitute for leather tanning (free of chrome). The research raw materials were 12 pieces of pickled goatskin. The chemicals used are aluminium tanning agent (Novaltan Al), titanium tanning agent, salt (NaCl), Peramit MLN, Derminol OCS, MgO, NaHCO3, BCG indicator, Rellugan GT 50, Tanigan PAK, Lipoderm Liquor SAF, Dermagen GPA, Derminol SPE, Derminol NLM, Acid dyestuff, formic acid, Sincal DR and anti-fungal. The method used is to carry out the tanning process using aluminium tanning agents with levels of 2%, 4%, and 6% Al2O3, continued the combination between aluminium and titanium tanning agent. The results obtained were analyzed for the cross-sectional and content of the leather using the EDX method, a shrinkage temperature (Ts) test, and physical quality of crust skin. The results showed that the higher the Al2O3 content, the more Al content in the leather, but the lower the wrinkle temperature of the leather. Meanwhile, the longer the processing time, the aluminium content in the skin increases. The use of aluminium and titanium tanning agent can improve the physical quality of the skin, both in terms of tensile strength and skin softness. The conclusion that can be drawn is the use of 2% free of chrome (aluminium) tanning material can produce Ts of 71°C. The physical quality of the crust skin from aluminium and titanium mineral tanning agents is better than the single-use of aluminium.

Improvement of hydrothermal stability and chrome uptake of leather: Amino-terminated hyper-branched polymer as high exhausted tanning auxiliary

Carboxyl-terminated hyper-branched polyester is extensively used as high exhaustion chrome tanning auxiliary owing to its strong coordination ability with trivalent chrome. Owing to lower electronegativity of N than O, the coordination ability with trivalent chrome for hyper-branched polyamide is stronger than polyester. Herein, in this paper, an amino-terminated hyper-branched polyamide (HBPN) is synthesized and used as high exhaustion chrome in tanning of pickling pigskin (HBPN–Cr). The effects of utilization of HBPN in denaturation temperature, shrinkage temperature, chrome uptake, and microstructure structure of wet-blue leather are studied. Moreover, the anti-oxidation stability of wet-blue leather is preliminary studied by heat treatment. The results show that incorporation of 1% HBPN in pickling process can significantly improve chrome uptake to 83.32%. The hydrothermal stability of wet-blue leather is improved due to the formation of higher crosslinking degree of collagen fibers. In addition, for the wet-blue leather without unsaturated fatliquoring agent, through heat treatment, hexavalent chrome does not appear after 24 ​h heat treatment. On the contrary, the chrome complex changes from hydroxyl copolymerization to more stable oxygen copolymerization or chrome oxide for C–Cr and HBPN-Cr tanned leather, respectively. These results will build a data support for the further study of hyper-branched polymer chrome tanning auxiliaries.

Study on the Dry-Cleaning Process of Mink Fur Based on Subcritical Solvent

It is significant to apply environmentally benign technology to fur processing. In this paper, subcritical extraction with n-pentane was used to dry clean mink fur and the effect on the quality of mink fur was studied. The dispersion degree of the leather fibers and the morphology of the wool fiber were characterized with SEM, the mechanical properties, shrinkage temperature and oil content left in fur were determined and analyzed. The results showed that the fibers of mink fur were well separated and no excess lipids in the fibers or on the surface of mink fur and the hair of the mink fur is not damaged. The tensile strength and elongation of mink fur show slight increase respectively, and the shrinkage temperature of mink fur that was treated by subcritical solvent was significantly increased compared with that of the mink fur treated with tetrachloroethylene by conventional dry cleaning method.

Hydrogen Peroxide-oxidized Soybean Polysaccharides as Novel Masking Agents for Zirconium Tanning

A series of hydrogen peroxide-oxidized soybean polysaccharides (HPS) were prepared using H2O2 and copper catalyst, which were then used as novel masking agents for zirconium tanning. The HPS samples were characterized by Fourier transforms infrared (FT-IR) spectroscopy, dynamic light scattering (DLS), and X-ray diffraction (XRD). FT-IR suggested the formation of carbonyl and carboxyl groups after hydrogen peroxide oxidation. DLS indicated that the HPS particle size decreases with increasing the H2O2 dosage. HPS with carbonyl and carboxyl groups and medium particle size was able to coordinate with zirconium to remarkably facilitate the tanning process. The shrinkage temperature of the tanned leather reached 92oC. Meanwhile, the fullness, softness, and mechanical properties of the leather were greatly improved by the tanning. The function of HPS and its interaction with zirconium were studied by FT-IR, XRD, and it was found that the triple helical structures of collagen fiber were not changed greatly. Scanning electron microscopy (SEM) showed that collagen fibers were dispersed and tanning agents were evenly distributed in collagen fibers. A new strategy for chromefree tanning is suggested and a strong support for the application of zirconium tanning is provided.

Preparation and application of polyethylene glycol triazine derivatives as a chrome-free tanning agent for wet-white leather manufacturing.

Leather manufacturing is the process of transforming animal skin into high value-added commodity. As a crucial step in the leather producing process, conventional chrome tanning could lead to discharge of chromium contaminant due to the low efficiency of chromium uptake. In this paper, a series of polyethylene glycol triazine derivatives' tanning agent (PT) with different molecule weight was synthesized with one-step method and applied in the main tanning of hide. The chemical structure of the PT was detected by FT-IR and 1H-NMR. The application experimental results indicated that after 16% of PT tanning at pH of 6, the wet-white was endowed with shrinkage temperature over 80°C and thickening rate over 108%. The experimental results indicated that the PT tanning leather not only have a better physical and mechanical properties than commercial triazine derivatives tanning agent, but also the leather is endowed with the effects of outstanding thermal properties. Considering that the pickling process became unnecessary, a large number of neutral salts could be avoided, the chromium load in spent liquor decreased from 1288 mg/L to 0, and the total dissolved chlorine in spent liquor decreased from 15,360 to 9581 mg/L; no toxic and harmful substances such as chromium and aldehyde are introduced into the tanning process. Compared with the leather tanned with commercial triazine derivatives' tanning agent, the leather tanned with PT showed a similar overall tanning properties and better environmental friendliness, which makes PT matches the integral requirements of the modern sustainable leather industry.

Study on generalized friction coefficient between base and surface layers of asphalt pavement

PurposeUsing typical structure of asphalt pavement in Harbin area of China, and the formula of generalized friction coefficient between base and surface layers of asphalt pavement in cold area is established.Design/methodology/approachThrough structural characteristics analysis of asphalt pavement in cold area, the generalized formula of friction coefficient between base and surface layers of asphalt pavement in cold area is derived. The formula can quickly calculate the friction coefficient between layers of asphalt pavement.FindingsBased on quantitative analysis to the contacting state between layers of asphalt pavement in cold area, the relationships between generalized friction coefficient and resilient modulus of asphalt mixtures, temperature shrinkage coefficient and temperature have been established.Originality/valueThe findings can enrich the description methods about the contacting state between layers of asphalt pavement, and have a certain theoretical and practical value. Through the application of the formula of generalized friction coefficient between layers, it can provide a technical basis for the asphalt pavement design, construction and maintenance in cold area.

Enzymatic activity of alkaline protease from Bacillus cereus TD5B and its application as sheep skin dehairing agent

This study aims to determine the enzymatic activity of extracellular alkaline protease from Bacillus cereus TD5B and its potential application as a sheep skin dehairing agent. The B. cereus TD5B was screened for extracellular alkaline protease production on skim milk agar media, while its alkaline protease activity and the application were measured at 1%, 1.5%, and 2%. The application of alkaline protease from B. cereus TD5B as a sheep skin dehairing agent was observed through histological examination and physical properties measurement after chrome-tanning with lime and Na2S as control. The study was conducted in a completely randomized design, and the quantitative data were analyzed using Duncan’s Multiple Range Test. The results showed that a clear zone was seen surrounding B. cereus, indicating the bacteria’s proteolytic activity. The protease activity measurement showed that 2% of alkaline protease had the highest enzymatic activity at 144.75 U/mL/min. The highest tensile strength of sheep leather was obtained after dehairing at 1% alkaline protease concentration (350.26 kg/cm2), even though the highest elongation was obtained at 2% (34.92%). In contrast, different concentrations showed similar shrinkage temperatures at 90°C. This study concludes that the optimum alkaline protease concentration from Bacillus cereus TD5B as a sheep dehairing agent was 2%.

Spark plasma processing of semi-conductive titanium carbide dispersed alumina composites

ABSTRACT The spark plasma sintering behavior of the alumina ceramic composite that is modified by the spatial distribution of electrically semi-conductive sub-micron scale titanium carbide particles was investigated. Titanium Carbide was reinforced to the alumina composites in different weight percent concentrations of 20, 25, 30, and 35. The influence of titanium carbide particle distribution on the thermal profile, micro-hardness, and wear resistance of alumina ceramic composites was studied. Homogenous spatial distribution of sub-micron scale semi-conductive titanium carbide particles in the composite were noticed through scanning electron microscopy, excluding the 35 weight percent sintered sample. In the spark plasma sintering processed samples, X-ray diffraction results revealed strong α-alumina and titanium carbide peaks. The obtained experimental results show that a higher titanium carbide concentration causes an earlier onset of shrinkage temperature, which positively impacts densification. The addition of titanium carbide particles accelerates the sintering kinetics and improves the properties. Among all composites, the sample with 30 weight percent has the highest relative density of 98.80% and hardness of 20.56 GPa. Besides, the highly densified sample of 30 weight percent has superior wear resistance to all other composites, and can be used for high-temperature sliding applications.

Shrinkage Stress and Temperature Variation in Resin Composites Cured via Different Photoactivation Methods: Insights for Standardisation of the Photopolymerisation.

The literature has shown that there is no consensus regarding the best resin composite photoactivation protocol. This study evaluated the efficiency of the conventional, soft-start, pulse-delay and exponential protocols for photoactivation of resin composites in reducing the shrinkage stress and temperature variation during the photopolymerisation. The photoactivation processes were performed using a photocuring unit and a smartphone app developed to control the irradiance according each photoactivation protocol. These photoactivation methods were evaluated applying photoactivation energies recommended by the resins manufactures. Three brands of resin composites were analysed: Z-250, Charisma and Ultrafill. The cure effectiveness was evaluated through depth of cure experiments. All results were statistically evaluated using one-way and multi-factor analysis of variance (ANOVA). The use of exponential and pulse-delay methods resulted in a significant reduction of the shrinkage stress for all evaluated resins; however, the pulse-delay method required too long a photoactivation time. The increases on the temperature were lower when the exponential photoactivation was applied; however, the temperature variation for all photoactivation protocols was not enough to cause damage in the restoration area. The evaluation of the depth of cure showed that all photoactivation protocols resulted in cured resins with equivalent hardness, indicating that the choice of an alternative photoactivation protocol did not harm the polymerisation. In this way, the results showed the exponential protocol as the best photoactivation technique for practical applications.

Achieving superiorly highheat‐dimensionalstability, high strength, and good electrochemical performance for electrospun separators in powerlithium‐ionbattery through building unique condensed structure based on polyimide and poly (m‐phenylene isophthalamide)

AbstractIt is still a challenge for simultaneously achieving high heat resistance, high strength and outstanding electrochemical performance for separators in power lithium‐ion battery (PLB). Herein, new high performance electrospun separators are developed through building unique structure based on polyimide (PI) and poly (m‐phenylene isophthalamide) (PMIA). Orthogonal tests (44) show that the magnitude order of electrospinning factors on the morphology of membrane is concentration>injection rate>receiving distance>voltage. With the optimum factors, the electrospun membrane (PI/PMIA) was prepared, which was further pressed at 100°C for 10 min to get treated membrane (H‐PI/PMIA). Interestingly, the comprehensive performance of PI/PMIA is not a simple combination of those of PI and PMIA; instead, PI/PMIA has much better thermal and mechanical properties than both PI and PMIA, proving that PI/PMIA has a synergistic effect. PI/PMIA and H‐PI/PMIA not only have good ionic conductivity and electrochemical stability, but also have superiorly high properties including dimensional stability (thermal shrinkage temperature>300°C), tensile strengths (24.1 MPa for PI/PMIA, 34.3 MPa for H‐PI/PMIA) and capacity retentions (97.9%, 99.2%) compared with electrospun membranes for PLBs reported in the literature so far (SCI database). The mechanism behind these attractive performances is discussed from condensed structure of membranes.

Extraction, characterization and biocompatibility evaluation of silver carp (Hypophthalmichthys molitrix) skin collagen

Collagen as a biomaterial is commonly obtained from terrestrial animals. However, nowadays, the use of collagen with terrestrial animals' sources due to possible transmission of infectious diseases and religious beliefs is restricted. This study was conducted to evaluate the physicochemical characterization, morphology, and biocompatibility of extracted collagen from silver carp fish skin by-product. Type I collagen was extracted from the silver carp fish skin by-product using acetic acid and pepsin enzyme. The results showed that the extraction yield of ASC and PSC was 43% and 59% (on a dry weight basis), respectively. The presence of two different α-chains confirmed the type I collagen structure for both collagens. Moreover, FTIR spectra investigation demonstrated the triple helical in ASC and PSC collagens. The PSC showed higher imino acids content than ASC. Hence, the fractional viscosity and DSC curves revealed higher denaturation temperature (30 °C), shrinkage temperature (81 °C), and melting temperature (209 °C) for PSC than ASC (29 °C, 77 °C, and 187 °C, respectively). Finally, observations of the microscopic and the cell viability evaluation confirmed biocompatibility and suitable structure to cell growth. Accordingly, the obtained collagen from silver carp fish skin can be a proper alternative for terrestrial animals’ collagen and a safe biomaterial for biomedical use.

Features of thermal relaxation of oriented organic glasses with a partially crosslinked and linear srtructure

The effect of temperature impacts on the relaxation behavior of oriented plexiglass with a linear (AO-120 brand) and with partially cross-linked (AO-120C brand) structure has been studied. The shrinkage temperatures of oriented plexiglas at complete heating of the material have been determined experimentally. The basic characteristics of organic glasses of partially cross-linked and linear structure in undirected and oriented states are studied.

Chromium-free and waterless vegetable-aluminium tanning system for sustainable leather manufacture

Intensifying researches in leather sector are focusing on eco-benign tanning chemicals with less environmental impact processing route. The present study aims to design an eco-acceptable shoe upper leather process that could potentially eliminate use of chrome from the leather industry. Possible conversion of Cr3+ to Cr6+ in suitable oxidant environment during leather manufacture is always a threat to the ecosystem. Water load for leather processing is very high, also becoming a precious resource that needs to be reduced for industrial applications. Further without water usage for a process, generation of wastewater could be averted. With this context, a combination tanning using wattle and aluminium has been developed in a pickle-less and waterless medium. The experimental leather possesses a shrinkage temperature of 84 °C with a fully loaded compact fibre structure indicating that tannin penetration is not affected in waterless medium. Experimental leathers exhibit better physical strength and comparable organoleptic characteristics. The process enjoys environmental benefits as it shows significant pollution load reduction in Biological Oxygen Demand (BOD), chemical oxygen demand (COD), Total Dissolved Solids (TDS) by 88, 89, and 97%, respectively. Hence, a viable option is made available to manufacture eco-acceptable leather without water usage and chrome salts in tanning.

Enzymes for Leather Processing: Effect on Pickling and Chroming.

Recently, increasing attention has been paid to the application of enzymes in a wide variety of leather production processes. The aim of the present study was to investigate the action of enzymatic pickling on derma’s collagen and the influence of this action on subsequent processes and properties of chromed and finished leather. The application of active in acidic medium proteolytic enzymes in the pickling process led to an additional impact on derma structure: collagen was more strongly affected and the porosity of the pelt dermis was reduced, but the hide became more thermally stable. The enzymatically pickled pelt bonded more chromium and reached higher shrinkage temperature while chroming; dyes penetrated deeper; such leather bonded more fatliquors. On the other hand, the action of enzymes worsened the physical–mechanical properties of the leather, as the experimental leather was weaker than the conventional one. The first was characterised by weaker grain layer and had significantly higher relative elongation. Therefore, as some properties improve and others worsen during such a process, the application of every enzyme should be carefully investigated and optimized to produce a leather with defined properties.

Combination chrome and mangrove (Rhizophora mucronata) bark crude extract on Epinephelus sp. leather quality

Almost all tanning leather industry used chrome sulphate mineral because it has a high tannic power and produce tanned leather with good quality. However. as much as 25% chrome in tanning is wasted as liquid waste. Chrome as waste product from tanning process is categorized as dangerous waste which is toxic to the environment. The aim of this study was to determine the effect of combination chrome and mangrove bark crude extract on tanned Epinephelus sp. skin. The results showed that the best grouper skin was tanned on 8% tanner extract. which was demonstrated a tensile strength value by 228.91 kgf/cm2, tear strength by 23.43 kgf/cm, elongation by 24.03%, and shrinkage temperature by 55.23° C. This studied promised application of mangrove extract could replace chrome as tanned agent for greenly method.

Selective degradation and oxidation of hemicellulose in corncob to oligosaccharides: From biomass into masking agent for sustainable leather tanning

Chrome-free metal tanning agent has been considered as eco-friendly in the leather industry. However, extensive crosslinking reactions of metal species on the leather surface restrain their uniform penetration into the hierarchical nanoscale leather matrix. Thus, masking agents with appropriate coordination ability are needed. Herein, the selective degradation of hemicellulose in corncob was achieved with 92.5% of conversion in an AlCl3–H2O system, obtaining oligosaccharides masking agent with high purity and leaving cellulose and lignin in the solid residue for other valuable use. Subsequently, H2O2 oxidation was performed to introduce –CHO/–COOH into oligosaccharides and reduce their molecular weights, thereby enhancing coordination ability and reducing ligand dimension. The post-oxidized reaction fluids together with additional Zr species were subjected to leather tanning, in which the oligosaccharides could coordinate with Al/Zr species and promote the penetration of metal species into the leather matrix. By controlling the hemicellulose degradation and oligosaccharide oxidation, an appropriate concentration of oligosaccharides with proper –CHO/–COOH contents allowed the efficient masking effect of the oligosaccharides. As a result, a uniform distribution of Al/Zr species was observed on the cross section, and 83.5 °C of shrinkage temperature was obtained for the chrome-free tanned leather.