Peeling Off Research Articles

Fabrication of Flexible Pyramid Array as SERS Substrate for Direct Sampling and Reproducible Detection.

Rapid extraction and analysis of target molecules from irregular surfaces are in high demand in the field of on-site analysis. Herein, a flexible platform used for surface-enhanced Raman scattering (SERS) based on an ordered polymer pyramid structure with half-imbedded silver nanoparticles (AgNPs) was prepared to address this issue. The fabrication includes the following steps: (1) creating inverted pyramid arrays in silicon substrate, (2) preparing a layer of AgNPs on the surface of the inverted pyramids, and (3) obtaining a substrate with an ordered polymer pyramids array with half-imbedded AgNPs by the molding method. This flexible substrate is capable of rapid extraction via a simple and convenient "paste and peel off" method. In addition, the substrate exhibits great repeatability and good sensitivity thanks to the uniformity and larger surface area of the ordered pyramids. The density of "hot spots" (local electromagnetic field with high intensity) is increased on the structured surface. Semi-imbedding silver particles in the polymer pyramids makes "hot spots" robust on the substrate. In addition, the preprepared silicon template with the inverted pyramids can be reused, which greatly reduces the production cost. With this substrate, we successfully analyzed thiram molecules on the epidermis of apples, cucumbers, and oranges, and the detection limits are 2.4, 3, and 3 ng/cm2, respectively. These results demonstrate the great potential of the substrate for in situ analysis, which can provide reference for the design of ideal SERS substrates.

Flexible and gradually bonded metal organic framework coatings for atomic oxygen protection of polyimide films

Rapid development of coatings with atomic oxygen (AO) resistance, which benefit long-duration exploration mission in low earth orbit (LEO), poses a challenging requirement on flexible coatings with excellent bonding property. Metal organic framework (MOF) has abundant sites and organic–inorganic hybrid chemical composition, which displays potential in increasing AO resistance, flexibility and bonding property simultaneously. Here, we combined surface modification and spin-coating to prepare MIL-53(Al) (a kind of materials of Lavashir skeleton) coated polyimide (PI) thin film exhibiting excellent flexibility, bonding property and AO resistance, which had no cracks after bending 1000 times, had no peeling off and had only 12% erosion yield compared with pristine PI, verified by the bend test, cross-cut tape test and AO exposure experiment respectively. Also, the mechanism of homogeneous film formation was explained, in which MIL-53(Al) seed layer provided binding force between coating and substrate, and the microstructural transformation caused by breathing effect and negative linear compressibility (NLC) prevented the occurrence of coating cracking. This work extends the application range of MIL-53(Al), optimizes the application of MOFs film formation, and offers a new idea to protect the spacecrafts in LEO.

PROPERTY ENHANCEMENT OF PIGMENT PRINTED POLYESTER FABRIC USING PLASMA TECHNOLOGY

Today, the customer is the king of the market and polyester fabric is in high demand as it is more economical and has many good properties when compared with other textile material. Polyester is claiming more than 75percent of the estimated 60 million metric tons of fibres consumed in man-made textiles in the apparel industry over natural fibres. Naseerali (2013) In this study the researcher has made an attempt to improve the absorbency of polyester fabric as well as to reduce its static charge. Air plasma technology was used to treat the surface of 100% polyester fabric at different time durations of 15, 30, 45, 60, 90, 120 minutes. The control and the surface modified fabrics were then printed with water- based pigments which are eco-friendly and without water based pigments which are commercially used. As most of the pigment printed samples get peeled off so it was plasma treated and then printed to evaluate the durability of the pigment prints. The UPF (ultra-violet protection factor) value of all the control and the modified sample were then evaluated to determine the ultraviolet radiation blockage or transmittance by fabrics intended to be used for UV protection. It was further found that better UPF value of the modified non water- based pigment at 90 minutes when compared to water based pigment samples and untreated samples. The fastness properties like rub and color fastness were observed with standard methods. In the rub fastness tests it was observed that the plasma treated with water based pigments for 30 minutes gave better dry rub fastness and it concludes that plasma treatment more than 30 minutes is not required because it gives a better results at 30 minutes. In the color fastness properties the water- based and non-water based pigment printing gave a better result at all-time durations than the control sample, so in concern of energy usage, treatment can be given for less time duration to have better quality products.

Ablation behavior of C/C-ZrC-SiC composite with gradient distribution of ZrC-SiC ceramics along the thickness

A novel C/C-ZrC-SiC gradient composite (GGC/C-ZS) is prepared via thermal gradient chemical vapor infiltration (TGCVI) technology combined with polymer infiltration and pyrolysis (PIP). And ablation tests are carried out to evaluate the thermal shock and ablation resistance. Results show that the GGC/C-ZS exhibits excellent anti-ablation performance (linear ablation rate is −2.12 μm/s) after ablation for 2 × 40 s (under 2500 °C). The high ZrC-SiC content in the surface region of GGC/C-ZS ensures a dense ZrO2 scale of the ablation center and helps withstand the high thermal stress induced by the ablation. During the ablation, the compact ZrO2 scale can block heat transfer from the surface to the matrix of GGC/C-ZS because of its low thermal conductivity, which can relieve the thermal etching and the massive loss of SiO2 beneath the ZrO2 scale. Besides, the gradient structure can also reduce heat mismatch between the ZrC-SiC ceramics and the C/C matrix, which can avoid the peeling off of the ZrO2 scale after a second ablation process.

Recycled CFRP Plate Retrofitting using Adhesive and TRS for Steel Girders

AbstractThe retrofitting method using CFRP (Carbon Fiber Reinforced Plastic) plates was applied to a steel highway bridge in 2002 for the first time in Japan, where some of CFRP plates have been detected to be peeled from their ends, recently. CFRP plates are light‐weight and anti‐corrosive comparing with steel plates, while they have problems in the durability of adhesives bonding CFRP plates to steel plates. Currently, recycled CFRP plates have been developed for the environmental load reducing. Additionally, long sized CFRP plates are required to retrofit bridge members. In this study, the effectiveness of TRS (Thread Rolling Screw) used to connect the long‐size recycled CFRP plate end to the steel girder bottom flange with adhesives is investigated through static and fatigue loading tests using large size steel girder specimens. As a result, TRS can prevent long‐size recycled CFRP plates from peeling off under allowable stress static loadings, while the long‐size recycled CFRP plates connected by only adhesives without TRS peeled off from their ends. In fatigue loading tests, TRS can also prevent long‐size recycled CFRP plates from peeling, though fatigue cracks were developed from TRS holes under higher stress range.

The long and the short of it: Russian predicate adjectives with zero copula

The present article presents an empirical investigation of the choice between so-called long (e.g., prostoj ‘simple’) and short (e.g., prost ‘simple’) forms of predicate adjectives in Russian, based on data from the syntactic subcorpus of the Russian National Corpus. The data under scrutiny suggest that short forms represent the dominant option for predicate adjectives. It is proposed that long forms are descriptions of thematic participants in sentences with no complement, while short forms may take complements and describe both participants (thematic and rhematic) and situations. Within the “space of competition” where both long and short forms are well attested, it is argued that the choice of form to some extent depends on subject type, gender/number, and frequency. On the methodological level, the approach adopted in the present study may be extended to other cases of competition in morphosyntax. It is suggested that one should first “peel off” contexts where (nearly) categorical rules are at work, before one undertakes a statistical analysis of the “space of competition”.

FORMULASI DAN UJI MUTU FISIK MASKER PEEL OFF PATI KENTANG (Amylum solani) SEBAGAI EKSFOLIASI KULIT WAJAH

FORMULASI DAN UJI MUTU FISIK MASKER PEEL OFF PATI KENTANG (Amylum solani) SEBAGAI EKSFOLIASI KULIT WAJAH

Flexural Performance of Cracked Reinforced Concrete Beams Strengthened with Prestressed CFRP Sheets under Repeated Loads

Because researchers are aiming to restore the deformation and minimize the crack width of existing concrete structures, the strengthening technology of prestressed carbon-fiber-reinforced plastic (CFRP) is currently the focus of many studies and applications. In terms of the strengthening of a prestressed CFRP sheet on the flexural performance of cracked reinforced concrete beams under repeated loads, a four-point bending test of 12 beams was conducted considering the prestress degree reflected by the amount and the prestress force of the CFRP sheet. The longitudinal strengthened CFRP sheet was bonded on the bottom surface of the test beam and fixed by U-jacket CFRP sheets at the ends after tensioning. The strains of concrete, longitudinal tensile steel bars and CFRP sheets were measured at the pure bending segment of test beams, while the cracks, midspan deflection and failure pattern were recorded. The results show that the normal strain on the mid-span section of the strengthened beams by the prestress CFRP sheets was fitted for the assumption of plane section, the cracks and mid-span deflection decreased with the prestress degree of the CFRP sheets to provide better serviceability for the strengthened beams, the load capacity could be increased by 41.0–88.8% at the yield of longitudinal tensile steel bars and increased by 41.9–74.8% at the ultimate state and the ductility at the failure state was sharply reduced by 54.9–186%. The peeling off of broken CFRP sheets played a role in controlling the failure pattern of the strengthened beams under repeated loads. Finally, methods for predicting the bending performance of reinforced concrete beams strengthened by prestressed CFRP sheets were proposed. This study enriches the knowledge about damaged reinforced concrete beams that were strengthened with prestressed CFRP sheets.

On understanding the mechanical properties and damage behavior of Cf/SiC composites by indentation method

Carbon fiber reinforced silicon carbide ceramic matrix (Cf/SiC) composites have the advantages of high temperature resistance, wear resistance, low density, high hardness as well as specific strength. They have been applied extensively in hot-end components of aerospace and braking systems of trains. Nevertheless, grappling with the anisotropy, non-homogeneity, and weak interlayer bonding of Cf/SiC composites presents a major challenge for achieving efficient and low-damage processing. This paper is primarily intended to investigate comprehensively the mechanical properties and damage behavior of Cf/SiC composites by nanoindentation and Vickers indentation tests. The behaviors of indentation damage on the longitudinal section of fiber (LSF), the cross-section of fiber (CSF) and matrix under different loads and the deflection mechanism of matrix crack were analyzed. The findings reveal a pronounced anisotropy between the radial and axial orientations of the fiber, and plastic deformation exists in the matrix. Furthermore, the matrix has the largest hardness and elastic modulus, while the LSF displays the lowest values among the composites. The main forms of indentation damage on the LSF are fiber crack, fiber peel off, fiber cocked up and squamous crack. The main manifestations of indentation damage on CSF are fiber crushing and fiber debonding, with the total surface damage area being comparatively limited. The fiber orientation and interface are influential factors in the crack propagation path of matrix. Notably, the fibers effectively inhibit the crack propagation of the matrix. This investigation provides valuable theoretical guidance for the formation mechanism and suppression strategy of machining damage in Cf/SiC composites.

A facile and high-efficient method to fabricate slippery liquid-infused porous surface with enhanced functionality

Inspired by Nepenthes pitcher, slippery liquid-infused porous surface (SLIPS) has been extensively investigated owing to its potential applications required for water repellence. However, the existing preparation methods for SLIPS involve complicated processing technologies and toxic chemical reagents, which seriously restricts practical applications. Herein, we prepared the SLIPS on Al substrates by nanosecond pulsed laser ablation, low surface energy modification, and infusion of lubricant. The optimal laser parameters for the preparation of the SLIPS were explored. The as-prepared SLIPS showed good slippery performance with a sliding angle smaller than 5° for various liquids. A series of performance tests, including knife scratching, repeated tape peeling off, sandpaper abrasion, heating, hot water jet impacting, and long-term water immersion, were conducted to investigate the mechanical strength and durability of the prepared SLIPS, and the SLIPS showed high mechanical strength and good durability. Moreover, the fabricated SLIPS could also resist corrosion solution, avoid contamination, protect the substrates against freezing rain and have superior water collection efficiency in moist environments. Thanks to the excellent performances, the prepared SLIPS has promising potential for practical applications.

Distribution, Source, and Ecological Risk Assessment of Persistent Organic Pollutants in Surface Sediments of Boao Coastal Waters

Persistent organic pollutants (POPs) in the environment have the characteristics of persistence, bioaccumulation, teratogenicity, carcinogenicity, and mutagenicity. Long-term exposure of low-content POPs will also have a certain impact on marine ecosystems and human beings. The contents of three typical persistent organic pollutants[polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polycyclic biphenyls (PCBs)] of surface sediments were analyzed using gas chromatography and mass spectrometry (GC-MS) to assess the pollution characteristics of persistent organic pollutants in Boao coastal waters. The distribution and source of persistent organic pollutants were analyzed in this study, and the ecological risk was assessed using three different methods:the effect interval low/median method (ERL/ERM), mean effect interval median quotient method (M-ERM-Q), and mean potential impact concentration quotient method (M-PEC-Q). The results indicated that the contents (measured by dry weight) of ΣPAHs, ΣOCPs, and ΣPCBs in the study area were 4.5-367.50, 3.99-175.30, and ND-2.89 ng·g-1, respectively, which were at a low level, and the overall distribution showed a trend of gradually increasing toward the sea. The results of POPs source analysis showed that the PAHs in the study area were mainly from the combustion of wood and coal. Among OCPs, the HCH was mainly from lindane, the historical land-based input had been completely degraded, and the DDT was mainly the traditional DDTs pesticides, with additional continuous DDT input. The PCBs were primarily pentachlorobiphenyls, which might have come from the release of paint on the bottom of the hull in the early stage of shipping and the peeling off of paint from old ships. The ecological risk assessment results showed that there was little difference among the assessment results of the three methods, which showed that only phenanthrene monomer of PAHs in the study area had a slight negative impact, and the DDT and the γ-HCH among PAHs would cause great ecological risk, whereas PCBs and other pollutants would not cause ecological risk. On the whole, the possibility of comprehensive ecological risk caused by the three pollutants was very small.

Comprehensive Research on the Layered Corrosion of Archaeological Copper Wares: A Case Study from Qinghai, China

ABSTRACT In this study, copper wares excavated from tombs in the Qinghai Province of China were investigated. Using varied analysis methods, this study analyzes the layered corrosion products of copper ware. Furthermore, it discusses the relevant corrosion mechanism along with the burial environment, condition, and manufacturing craft. The forged copper wares appear to be in a state of stratified corrosion in the burial environment. Beginning from the outside and moving toward the inside, the following layers were observed: malachite and azurite; atacamite and clinoatacamite; cuprite and clinoatacamite; and the innermost layer, which is a residual metal layer in some regions. In the cuprite layer, the presence of clinoatacamite was observed to destroy the structure of the cuprite and form fine stratification, which, in turn, promoted the further development of chlorine-containing corrosion products and led to the ‘peeling off’ of copper ware. This study explores the destructive corrosion caused by Cl in copper ware.

Investigation on deterioration mechanism of geopolymer cemented coal Gangue-Fly ash backfill under combined action of high temperature and salt corrosion environment

The geopolymer cemented coal gangue-fly ash backfill (GCGFB) is pumped to the goaf to maintain the stability of surface subsidence, which is inevitably affected by the high temperature caused by geothermal heat and ion erosion of mine water. To study the deterioration mechanism of GCGFB caused by salt corrosion and high temperature of mine water, in this study, a customized temperature-controlled corrosion chamber was used to carry out the corrosion experiment of GCGFB. A three-factor and three-level orthogonal experiment was designed. The uniaxial compressive strength (UCS), relative dynamic elastic modulus (RDEM) and weight deterioration of GCGFB under different combinations of temperatures, solution concentrations, and solution types were analysed. The deterioration mechanism of GCGFB was analysed through the testing of scanning electron microscopy (SEM)-energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). From the results, the most significant factors on the deterioration of GCGFB is solution type. Cl− and SO42− caused chemical-physical erosion on GCGFB, and the UCS, RDEM and weight of GCGFB increased first and then decreased with ages. The reason for the increase was due to the compacting effect of Friedel 's sat, ettringite, and gypsum filled in GCGFB. The reason for the decrease was due to the expansion pressure on the inner wall of the pores of the GCGFB caused it to crack or even peel off. The GCGFB was corroded in 20 % Na2SO4 solution at 40 °C for 90 days, and the UCS increased by 164.90 % compared to that of the uncorroded specimen. Mg2+ brought chemical erosion on GCGFB, and a decreasing law of the UCS, RDEM and weight with ages was shown. During the Mg2+ erosion, there are more and more M−S−H in matrix, which reduced the density of specimen apparently. The GCGFB was corroded in 5 % MgCl2 solution at 40 °C for 180 days, and the macropore area distribution of GCGFB is increased to 23.499% than that of uncorroded group. The expansion stress of corrosion products would squeeze the inner pore wall, resulting in microcracks inside GCGFB and high temperatures would accelerate the migration of ions and the formation of corrosion products. Overall, this study can provide a new insight or valuable data for the designing of ultra-high performance, low-caron, eco-friendly, and durable GCGFB structures in the harsh mining environments.

Construction and performance evaluation of novel compound oil displacement system for enhanced oil recovery

Conventional methods of flooding leave behind a significant amount of oil films that adhere to the rock surfaces. Developing novel compound oil displacement system to achieve efficient oil film peeling and migration is of great significance for further enhanced oil recovery. Herein, a novel compound oil displacement system was developed through optimization experiments using a binary surfactant mixture composed of SDBS and BS-18, along with a wetting regulator known as CAS. The minimum interfacial tension attained of compound oil displacement system was 0.0042 mN/m, indicating an ultra-low level. Meanwhile, the compound system could alter the rock surface wettability from oleophilic to strong hydrophilic, with the underwater oil contact angle substantially increasing from 18° to 123.1°. The compound system demonstrated remarkable stability at high water salinity (60000 ppm) and high temperature (90 °C). The surface strong hydrophilicity contributed to the excellent oil film peeling performance of compound system, leading to an 89.14% reduction in the oil film area within 12 h. The superior ability in interfacial tension reduction and wettability alteration of the compound system facilitated the “peeling off” and “migrating out” process of the residual oil film, and impressive enhanced oil recovery of 18.68% was achieved compared to that of the surfactant mixture SDBS/BS-18 (7.23%) and wetting regulator CAS (7.64%). It is believed that the outcomes of this work provide valuable insights into the design and optimization of effective oil displacement systems for residual oil development.

Hf and Ta co-doping MCrAlY alloy to improve the lifetime of coatings

Thermal barrier coating (TBC) is one of the key components of an aircraft turbine or stationary gas turbine. NiCoCrAlY is the most commonly used bond coat (BC) and its composition and impurities have an impact on the lifetime of the TBC. However, the performance of NiCoCrAlY is very unstable due to the influence of impurities. Reactive elements (RE) Hf and Ta are co-doped into the bond coat to improve the adhesion of thermally grown oxide (TGO) layers to extend the lifetime of TBC. Yttrium stabilized zirconia (YSZ) is sprayed on free-standing alloys of NiCoCrAlY and NiCoCrAlYHfTa, respectively. The samples are cyclically oxidized at 1050 °C until the peeling off of coatings. The lifetime of NiCoCrAlY coatings is only 240 h, while the lifetime of NiCoCrAlYHfTa coatings reaches 2664 h. The morphology and structure of the oxide scale are characterized to study the mechanisms of lifetime extension.

Self-crosslinked alkaline polyelectrolyte membranes with exceptional stability under dry-wet alternating conditions

The emergence of alkaline polyelectrolytes (APEs) with high stability and high ionic conductivity has greatly improved the power density of alkaline polyelectrolyte fuel cells (APEFCs), now the cell stability has become an urgent problem to be addressed. The uneven distribution of humidity and hydration state inside large-scale electrodes will cause the membrane to swell and shrink repeatedly, resulting in the membrane rupture and/or the peeling off of catalyst layers, which is a fatal problem affecting the stability of APEFCs. In the present work, we report a new APE, self-crosslinked quaternary ammonia poly (N-methyl-piperidine-terphenyl and 7-bromo-tri-fluoro-heptanone), denoted as xQAPTF. The crosslinking network inside the membrane can be formed without introducing additional crosslinking agents, and can effectively limit the membrane swelling degree in water (only 4% at 80oC). More importantly, the xQAPTF membranes exhibit excellent mechanical strength and flexibility even after multiple all-wet-all-dry cycles. Under the dry-wet alternating condition (RH repeatedly switched between 100% and 50%), the APEFC using xQAPTF membrane run stably, with the cell voltage switching accordingly and steadily. Such a unique quality of APE membranes has so far not been reported in the literature, which strongly enhances the practicality of APEs, as well as the APEFC and relevant technologies.

Mechanical properties and corrosion behavior in molten zinc of Mo–ZrO2 alloys

The effect of the ZrO2 doping amounts on the corrosion properties and mechanical properties of the molybdenum alloys in molten zinc was investigated. Among them, the Mo-1.5 wt% ZrO2 alloy has good corrosion resistance (at 460 °C) and excellent mechanical properties. Compared with that of pure molybdenum, the tensile strength of the Mo-1.5 wt%ZrO2 increased by 16.69% in the rotary forged state and 58.26% in the 1200 °C annealed states, and the compressive strength increased by 16.53% and 84.46%, respectively. At a corrosion temperature of 460 °C, a MoZn7 corrosion layer was formed, which isolates the molybdenum matrix from direct contact with the molten zinc. The distribution of ZrO2 particles in the corrosion layer, which changes the diffusion path of zinc and molybdenum atoms, thus slowing down the corrosion process. The thickness of the corrosion layer gradually decreases with increasing doping amount, where the corrosion layer thickness of the Mo-2.0 wt% ZrO2 is 45.21% lower than that of the pure molybdenum. At a corrosion temperature of 560 °C, the molybdenum matrix is exposed to molten zinc and the grains peel off. As the bond between Mo grains is better than the bond between Mo grains and zirconia, the grain spalling of the zirconia-doped molybdenum alloys is severer than that of pure molybdenum.

Formulasi Sediaan Masker Peel Off dari Ekstrak Buah Alpukat (Persea Americana Mill.) dengan Variasi Konsentrasi Polivinil Alkohol (PVA)

Face mask peel off is a skin care product that when applied to the skin will dry out which can be peeled off from the skin of the face. Avocado Flesh (Persea americana Mill.) has powerful antioxidants that can be used in moisturizing and anti-aging products. This study aims to produce mask preparations to peel off gel from avocado fruit extract (Persea americana Mill.) to moisturize facial skin. This study used the maceration method to obtain a thick extract from avocado fruit. Mask formulation peel off made in a variety of polyvinyl alcohol (PVA) bases, namely 10% (F1), 12% (F2) and 14% (F3) as a film-forming agent. The evaluation is based on physical parameters including organoleptic, homogeneity, spreadability, pH, viscosity, flow properties, drying time and measurement of facial skin moisture levels. The evaluation results on the pH test, homogeneity and drying time showed that all formulas met the standard parameters, namely the PVA pH test 10% = 6.46; PVA 12% = 6.4; PVA 14% = 6.35, in the long test the drying time of 10% PVA = 18.97 minutes; PVA 12% = 20.82 minutes; and 14% PVA = 24.66 minutes. Meanwhile, in the organoleptic test,viscosity, the three formulas were pharmaceutically unstable, namely in the organoleptic test the three formulas experienced a change in consistency, in the spreadability test the spreadability value of PVA 10% = 5.41; PVA 12% = 4.75; PVA 14% = 4.03, in the viscosity test of the three formulas after forced conditions = E (error: the viscosity value exceeds the maximum limit of the viscometer). Based on the results of the facial skin moisture test, it shows that Avocado fruit extract with a concentration of 0.6% can provide effectiveness as a moisturizer for facial skin.

FORMULASI DAN EVALUASI FISIK MASKER GEL PEEL OFF EKSTRAK DAUN TURI (Sesbania grandiflora (L.) Poir.)

Turi leaves contain flavonoids, saponins and tannins which can function as Propionibacterium acnes antibacterials so that they can be used to make peel-off gel masks. PVA in a peel off gel mask functions as a gelling agent and film forming agent. The aim of the study was to determine the formulation of turi leaf extract peel off gel masks, physical evaluation of the preparation, and to determine the effect of variations in PVA concentration on the physical properties of the preparation. This study uses a descriptive experimental method. The simplicia extraction method uses maceration with a ratio of turi leaf simplicia and 96% ethanol (1:7). Variations in the concentration of PVA used were 10%, 13%, 16%. Each formula was subjected to organoleptic tests, homogeneity tests, pH tests,adhesion tests, spreadability tests, drying time tests and viscosity tests. The results showed that the peel off gel mask preparations on F1, F2, F3 were respectively dark green in color, had a distinctive odor of turi leaf extract, slightly runny, slightly thick and viscous, had a homogeneous preparation. pH test results 5,75±0,39; 5,88±0,30; 6,17±0,32. Stickiness test results 19,69±5,89 seconds; 36,11±0,65 seconds; 54,02±3,11 seconds. Spreadability test results 5,40± 0,49 cm; 4,57±0,28 cm; 3,70±0,22 cm. Drying time test results 20,06±1,49 minutes; 18,23±1,01 minutes; 16,53±0,73 minutes. Viscosity test results 21173±3609,32 cPs; 48917,33±1,15 cPs; 48938±13,58 cPs. The results of the physical tests were followed by the One Way Anova and Kruskal Wallis statistical tests, showing that variations in PVA concentration significantly affected the physical test results of adhesion, spreadability, viscosity and drying time, but did not significantly affect the pH value.

Computational fluid dynamics simulation of natural gas hydrate sloughing and pipewall shedding temperature profile: Implications for CO2 transportation in subsea pipeline

The continuous flow assurance in subsea gas pipelines heavily relies on the assessment of temperature profile during hydrate sloughing and pipewall shedding caused by hydrates, with similar implications for carbon dioxide (CO2) transportation under hydrate-forming conditions. Hydrate sloughing is the peeling off of some hydrate deposits from the pipeline inner surface. Similarly, pipewall shedding by hydrates involves the direct interaction of hydrates with the pipeline inner surface, resulting in the detachment or removal of hydrate deposits from the pipewall. While sloughing occur within the deposit of hydrates, pipewall shedding is related to direct interaction of the gas phase with the thin layer of hydrates on the pipewall. In this study, a computational fluid dynamics (CFD) simulation approach is employed, using a validated CFD model from the literature for predicting hydrate deposition rates (Umuteme et al., 2022), by applying a subcooling temperature to the pipe wall at hydrates forming condition. We have deduced the presence of hydrates based on the stable temperature profile of natural gas hydrates along the pipeline model. The study shows that the simulated temperature contours align well with the reported hydrate deposition profile in gas pipelines (Di Lorenzo et al., 2018). The conversion of the consumption rate of natural gas to hydrates was achieved using the equation proposed in the literature (Umuteme et al., 2022). Two shear stress regimes have been identified for hydrate sloughing and pipewall shedding in this study, with the latter resulting in higher shear stress on the pipewall. Presently, there is a growing concern regarding the potential leakage of CO2 in pipelines (Lu et al., 2020; Wang et al., 2022; Wareing et al., 2016), which may escalate due to pipewall corrosion caused by hydrates (Obanijesu, 2012). The findings in this research can provide further knowledge that can enhance the safe transportation of CO2 in pipelines under stable hydrate forming conditions.