Increase In Contact Angle Research Articles

Study on the Water Blocking Capacity and Influencing Factors of Hydrophobic Gravel Beds.

Excess water production is a common and extremely serious problem during the process of reservoir development, especially in the middle and later stages of unconsolidated sandstone reservoirs. High water content ratios will negatively affect the recovery efficiency and equipment safety of oil and gas wells. In this study, a hydrophobic quartz sand proppant was prepared with 1,1,1,3,3, 3-hexamethyldisilazane (HMDS) for gravel packing technology. The capillary resistance of hydrophobic quartz sand beds to water was used to achieve water inhibition and oil enhancement. Then, a theoretical capillary bundle model of a quartz sand bed was developed to predict the capillary resistance and water blocking capacity of the quartz sand bed. An evaluation of the experiment results shows that the activation index is up to 96% and the water contact angle is up to 151° after treatment by 0.6 wt % HMDS, which indicates that the quartz sand after modification has strong hydrophobicity. The calculation results demonstrate that the capillary resistance (CR) and the water blocking capacity (WBC) decrease with increasing quartz sand particle size and porosity of the quartz sand bed. As the water contact angle increases, the CR and WBC are also increased. In addition, to make the WBC of hydrophobic quartz sand bed δ > 20%, the parameters of the quartz sand bed must be satisfied: particle size dg < 50 μm, porosity ϕ < 30%, water contact angle θ > 150°, and production pressure difference Δp < 1 MPa. The results of this study could provide theoretical guidance for the construction parameters of hydrophobic gravel packing in high water-cut oil and gas fields.

Inhibiting wood-water interactions by hydrothermal hemicellulose extraction combined with furfurylation

Abstract Wood-water interactions affect durability and performance of wood products, such as dimensional stability and biodegradation. To upgrade wood, a combined modification via hemicellulose extraction and furfurylation was proposed to inhibit wood-water interactions. More intense hemicellulose extraction caused larger voids and led to higher pore volume. The increment of porosity resulted in more uniform distribution of polymerized furfural resin in cells, as indicated by scanning electron microscopic and confocal laser scanning microscopic observations. The combined modification greatly reduced surface wettability with an increase of water contact angle (CA) of over 134% at 100 s. With hemicellulose extraction, polymerized furfural resin partially occupied the accommodation initially for water molecules and reduced accessible sorption sites, causing water absorption (WA) of wood to decrease by over 30% after soaking in water for 768 h. Dynamic moisture sorption was weakened after combined modification, and the moderate hemicellulose extraction combined with furfurylation reduced the moisture content by over 50% due to incorporative changes of chemical sorption sites and physical porosity. The results confirmed the efficiency of the combined modification in inhibiting wood-water interactions and indicated the importance to accurately control hemicellulose content during modification. This study could provide useful information for sustainably enhancing wood performance and upgrading low-quality wood.

Synthesis, characterization and evaluation of azobenzene nanogels for their antibacterial properties in adhesive dentistry.

The presence of cariogenic bacteria within the prepared tooth cavity at the adhesive resin-dentin interface is detrimental to the long-term stability and function of composite restorations. Here, we report the synthesis and incorporation of methacrylated azobenzene nanogels within bisphenol A-glycidylmethacrylate/hydroxyethyl methacrylate/ethanol (B/H/E) adhesive resins and evaluate their ability to reduce the bacterial invasion of cariogenicStreptococcus mutansbiofilms while preserving the mechanical strength and structural integrity of the critical interfacial connection between the restoration and the tooth. The azobenzene nanogel, with a hydrodynamic radius of<2nm and a molecular weight of 12,000Da, was polymerized withinB/H/E adhesive formulations at concentrations of 0.5wt.%, 1.5wt.%, and 2.5wt.%. While the double-bond conversion, cytocompatibility, water solubility, and sorption of the adhesive networks were comparable, azobenzene nanogel networks showed improved hydrophobicity with a ≥ 25° increase in water contact angle. The polymerized adhesive surfaces formulated with azobenzene nanogels showed a 66% reduction in bacterial biofilms relative to the control while maintaining the mechanical properties and micro-tensile bond strength of the adhesive networks. The increased hydrophobicity and antibacterial activity are promising indicators that azobenzene nanogel additives have the potential to increase the durability and longevity of adhesive resins.

Effect of structural parameters and service conditions on the tilt angle of double row angular contact ball bearing

In this paper, for double row angular contact ball bearing, a five-degrees-of-freedom bearing analysis model based on quasi-statics is proposed. This model is used to study the influence of structural parameters and service conditions on the tilt angle and limit tilt angle of the bearing. The results show that the radial clearance will increase the ultimate tilt angle. The coincidence degree between the roller and the inner raceway will reduce the ultimate tilt angle, but the coincidence degree between the roller and the outer raceway has the opposite effect. The increase in the external load of the bearing will increase the tilt angle. The moment load has the greatest effect on the tilt angle. The rotation speed of the bearing has no effect on the tilt angle. The coincidence degree between the roller and the raceway will reduce the tilt angle; furthermore, the influence of the coincidence degree between roller and different ring on the tilt angle is also different when different rings are fixed. The tilt angle will decrease with the increase of the initial contact angle, and this effect is more and more obvious. The fixation of different ring has no effect on this influence.

Modeling study on sessile water droplet during freezing with the consideration of gravity, supercooling, and volume expansion effects

Droplet freezing phenomenon widely exists in many fields, including aerospace, power production, and cryopreservation, etc. Considering the effects of supercooling, gravity and volume expansion, a theoretical model of droplet freezing is developed. A good agreement is found between the predicted results of freezing front radius and height and experiments for both hydrophilic and hydrophobic surfaces. The developed model also shows good performance in predicting freezing times. The average prediction deviation is 7.63%, and more than 93% simulation results show the deviation within ±15%. Gravity has a more obvious influence on final freezing times with the increase of cold plate temperature, contact angle, and droplet volume. For the droplet freezing process under various contact angles and cold plate temperatures, the fastest average temperature change rates inside water droplet are -2.48 °C/s and -1.72 °C/s, respectively. This study is beneficial for the better understanding of the droplet solidification as well as the optimization of refrigeration and defrosting technologies.

A high-stable soybean-oil-based epoxy acrylate emulsion stabilized by silanized nanocrystalline cellulose as a sustainable paper coating for enhanced water vapor barrier

Soybean-oil-based polymer is a promising bio-based water barrier coating on paper packaging but the application is challenged due to its poor water dispersibility. In this present study, 3-aminopropyltriethoxysilane (APTES) modified nanocrystalline cellulose (NCC) was used to implement a stable dispersion of acrylated epoxidized soybean oil (AESO) in water and thus synergistically improved the water vapor barrier properties after coating on paper. APTES-NCC was successfully prepared, and displayed a better interface compatibility with AESO through the Michael addition reaction. Compared with NCC, APTES-NCC displayed an improved hydrophobicity and wettability with AESO, with an increase of contact angle from 38.0° to 76.4°, and a decrease of interfacial tension from 91.5 ± 3.5 mN/m to 82.9 ± 1.8 mN/m. As an emulsifier, APTES-NCC can be more effectively adsorbed on the oil–water interface to form a more stable emulsion than NCC, with a decrease of AESO droplets size from 4.8 µm to 3.1 µm, and a remarkable improvement in static and centrifugal stability. In rheological measurement, the APTES-NCC/AESO emulsion showed a wider linear viscoelastic region (3.4%), better viscoelasticity and thermal curing properties than that of NCC/AESO emulsion, which further explained that the stability of APTES-NCC/AESO emulsion were improved. Therefore, APTES-NCC/AESO emulsion as a coating on paper cured into a continuous barrier film can effectively improve the water vapor barrier properties of paper, and the water vapor transmission rate (WVTR) of paper can be reduced from 1392.8 g/m2•24 h (NCC/AESO emulsion-coated) to 1286.3 g/m2 24 h (APTES-NCC/AESO emulsion-coated), both are significantly lower than that of base paper (1926.7 g/m2•24 h). CLSM testing showed that APTES-NCC could interact effectively with AESO to forming a tight barrier on paper surface and at the same time, sealing the pores inside the paper to resist water vapor penetration. The high-stable AESO emulsion prepared by APTES-NCC is expected to facilitate the utilization of NCC and AESO as a value-added material in making sustainable barrier packaging.

Seawater Desalination by Modified Membrane Distillation: Effect of Hydrophilic Surface Modifying Macromolecules Addition into PVDF Hollow Fiber Membrane.

Hollow fiber membranes of polyvinylidene fluoride (PVDF) were prepared by incorporating varying concentrations of hydrophilic surface-modifying macromolecules (LSMM) and a constant amount of polyethylene glycol (PEG) additives. The membranes were fabricated by the dry-wet spinning technique. The prepared hollow fiber membranes were dip-coated by hydrophobic surface-modifying macromolecules (BSMM) as the final step fabrication. The additives combination is aimed to produce hollow fiber membranes with high flux permeation and high salt rejection in the matter of seawater desalination application. This study prepares hollow fiber membranes from the formulation of 18 wt. % of PVDF mixed with 5 wt. % of PEG and 3, 4, and 5 wt. % of LSMM. The membranes are then dip-coated with 1 wt. % of BSMM. The effect of LSMM loading on hydrophobicity, morphology, average pore size, surface porosity, and membrane performance is investigated. Coating modification on LSMM membranes showed an increase in contact angle up to 57% of pure, unmodified PVDF/PEG membranes, which made the fabricated membranes at least passable when hydrophobicity was considered as one main characteristic. Furthermore, The PVDF/PEG/4LSMM-BSMM membrane exhibits 161 °C of melting point as characterized by the DSC. This value indicates an improvement of thermal behavior shows so as the fabricated membranes are desirable for membrane distillation operation conditions range. Based on the results, it can be concluded that PVDF/PEG membranes with the use of LSMM and BSMM combination could enhance the permeate flux up to 81.32 kg·m−2·h−1 at the maximum, with stable salt rejection around 99.9%, and these are found to be potential for seawater desalination application.

Enhancement of Flotation Performance of Oxidized Coal by the Mixture of Laurylamine Dipropylene Diamine and Kerosene

Conventional hydrocarbon oil cannot adhere effectively to oxidized coal, resulting in a low yield of clean coal. In this study, a high-speed homogenizer was used to emulsify LDD (laurylamine dipropylene diamine) and kerosene, which enhanced the flotation efficiency of oxidized coal. The flotation results showed an increase from 4.12% (only kerosene) to 23.33% (emulsified oil). An increase in contact angle indicated that the mixture reagent can increase the hydrophobicity of coal particles, which is attributed to the adsorption of LDD onto the coal particle surface and the decrease of the oil droplet A lower surface tension of LDD allows it to produce a stable layer of froth than the layer generated by kerosene alone.

Post-processing of additively manufactured metal parts by ultrashort laser pulses for high-quality net shape geometries and advanced functionality

Additive manufacturing by means of laser-based powder bed fusion (LPBF) offers high flexibility with respect to the generation of individualized and light-weight metal parts. However, the produced parts are typically attached to support structures and deviate a few tens of micrometers from the targeted final component in geometrical net shape and surface roughness due to the melt-based fusion process. Therefore, different post-processing techniques were examined in the past to resolve the mentioned quality drawbacks. In our work, we investigated the potential of post-processing of LPBF-generated Ti6Al4V parts with ultrashort pulse laser ablation. As a result, the support structures were effectively removed, the surface roughness was reduced by 81% and complex geometries with high shape accuracy were fabricated. Furthermore, the LBPF-generated parts were laser surface structured to investigate the potential of post-processing with ultrashort laser pulses for advanced functionality, such as water-repellent surfaces. The generation of surface structures on the LPBF-generated Ti6Al4V part changed the wetting behaviour from hydrophilic to hydrophobic with an increased contact angle from 73° up to 130°.

A Porous Media Leakage Model of Contact Mechanical Seals Considering Surface Wettability

The fluid leakage channel found in contact mechanical seals belongs to the microchannel category. Thus, upon further inspection, the influence of surface wettability and other factors neglected in previous studies becomes obvious. The porous leakage model of contact mechanical seals considering the surface wettability presented in this paper was based on the Cassie model and slip theory. The variations of the microchannel slip length and the velocity under various wettability conditions were studied and the relationship between the slip length and the apparent contact angle was established. Moreover, using porous media theory, the theoretical model of the leakage rate in contact mechanical seals considers the surface wettability depending on various parameters. The observed parameters included the surface contact angle, sealing medium pressure, viscosity coefficient, fractal dimension, and maximum pore diameter. The simulation results obtained using the proposed model have shown that the leakage rate increases with the increase of the apparent contact angle. Particularly when the contact pressure is small, the influence of the surface wettability is more significant. Furthermore, the leakage rate results obtained via the proposed model were compared to those of existing models. The comparison confirmed that the proposed model is applicable and that the necessity of considering wettability significantly affects the leakage rate calculation accuracy. The proposed model lays a foundation for further improving the calculation accuracy, making it easier for both the researchers and practitioners to suppress the leakage in contact mechanical seals.

Cinnamon Essential Oil Encapsulated into a Fish Gelatin-Bacterial Cellulose Nanocrystals Complex and Active Films Thereof

In this study, cinnamon essential oil (CEO) nanocapsules were stabilized by means of bacterial cellulose nanocrystals (BCNCs) and encapsulated using fish gelatin as the main polymer phase. Emulsions were prepared at pH 5 using different CEO concentrations (0.03, 0.06, 0.12, 0.24, 0.36, and 0.48% v/w) and a fixed amount of fish gelatin (3% w/w) and BCNCs (0.06% w/w). The controlled release of the essential oil was assessed by release studies, which revealed that the higher the CEO concentration, the lower the release rate of CEO. In addition, modelling of experimental data using five different equations showed that the best fitting was obtained for the Korsmeyer-Peppas model, according to which the CEO release obeyed a non-Fickian behavior. Films obtained from the same formulations were characterized in terms of optical properties (light transmittance and haze), surface wettability, barrier (oxygen, carbon dioxide, and water vapor transmission rates) and mechanical properties. It was observed that an increased amount of CEO in the films did not significantly affect both transparency and haze, while it yielded an increase in surface hydrophobicity (~ 120% increase in water contact angle over the control) and elongation. Finally, the barrier performances of films against O2, CO2, and water vapor suggest a potential application of CEO/GelA-BCNC matrices as antimicrobial layers (in the form of coatings deposited on plastic films or directly on food) in living foods that have a respiratory metabolism, such as modified atmosphere-packaged crustaceans and mollusks as well as fruits and vegetables.Graphical abstract

Effect of processing environment on the wettability behavior of laser-processed titanium

The wettability properties of two types of titanium surfaces structured by femtosecond laser are studied. Samples that are textured in air, demonstrated superhydrophilic properties immediately after laser structuring. In contrast, just prepared samples, which are processed in vacuum, show an increase in the water contact angle compared to the unprocessed Ti. Since the surface morphology of both samples was similar, the observed superhydrophilic behavior of the samples prepared in air is attributed to the partial oxidation of Ti surface during laser texturing. High temperature post-annealing of the samples that were laser-structured in vacuum completely oxidized the Ti surface. This in turn led to the formation of a permanent hydrophilic surface that could not be changed even after storing in vacuum or ambient atmosphere for a long time.

Fractionated Lignosulfonates for Laccase-Catalyzed Oxygen-Scavenging Films and Coatings.

Lignin derivatives have potential as antioxidants in advanced packaging materials through their ability to scavenge oxygen in reactions catalyzed by phenol-oxidizing enzymes, such as laccase. The effects of size fractionation of lignosulfonates on laccase-catalyzed reactions were investigated in experiments with aqueous solutions, films, and coated paperboard. Four industrial lignosulfonate preparations were compared: Feed (unfractionated), Prod (5–60 kDa enriched), Conc (≥60 kDa enriched), and Perm (≤60 kDa enriched). Extraction of lignosulfonates from films showed that the enzymic reaction increased the average molecular weight from <10,000 to up to 66,000. The enzymatic reaction resulted in an increase in the water contact angle of the films from the range 25–49° to 56–81°. The four preparations showed relatively small differences with regard to their ability to scavenge oxygen in aqueous solution and in experiments with coated paperboards in sealed chambers. Coatings with lignosulfonates where the contents of low-molecular weight material had been reduced (i.e., Prod and Conc) showed improved water resistance after the enzymic reaction. Thus, in both aqueous and solid media, fractionation of lignosulfonates had little effect on oxygen scavenging, but fractionation was beneficial for other reasons, such as improved cross-linking resulting in higher molecular weight and superior water resistance.

Enhanced hydrophobicity of polyurethane with the self-assembly of perfluoropolyether-based triblock copolymers

The self-assemblies of poly(isobornyl methacrylate)m-b-perfluoropolyether-b-poly(isobornyl methacrylate)m (BCPm) in mixed 1,1,2-trichlorotrifluoroethane/N,N-dimethylformamide (F113/DMF) solvent were used to improve the surface hydrophobicity of polyether-based polyurethane (PU). With the loading of BCPm micelles into the PU, the surface roughness and the fluorine content in the surface were effectively enhanced, leading to the significant increase of water contact angle (WCA) from 73° to 140°. This improvement was much more pronounced than that of PU containing only perfluoropolyether units at the same fluorine content level due to higher surface roughness. For the hybrid coatings prepared from BCPm with different degrees of polymerization (DP) of poly(isobornyl methacrylate) blocks, the water repellency reached the maximum at the DP of 10. In addition, the hybrid coatings exhibited excellent mechanical durability and acid-alkali resistance, which is beneficial for broadening the application scenarios of cotton fabrics. Altogether, the self-assembly of perfluoropolyether based copolymers with high surface hydrophobicity shows potential applications in the protection of polymeric materials.

Visual Detection of Adenosine Triphosphate by Taylor Rising: A Simple Point-of-Care Testing Method Based on Rolling Circle Amplification.

Rapid and sensitive point-of-care testing (POCT) is an extremely critical mission in practical applications, especially for rigorous military medicine, home health care, and in the third world. Here, we report a visual POCT method for adenosine triphosphate (ATP) detection based on Taylor rising in the corner of quadratic geometries between two rod surfaces. We discuss the principle of Taylor rising, demonstrating that it is significantly influenced by contact angle, surface tension, and density of the sample, which are controlled by ATP-dependent rolling circle amplification (RCA). In the presence of ATP, RCA reaction effectively suppresses Taylor-rising behavior, due to the increased contact angle, density, and decreased surface tension. Without addition of ATP, untriggered RCA reaction is favorable for Taylor rising, resulting in a significant height. With this proposed method, visual sensitive detection of ATP without the aid of other instruments is realized with only a 5 μL droplet, which has good selectivity and a low detection limit (17 nM). Importantly, this visual method provides a promising POCT tool for user-friendly molecular diagnostics.

Low Energy X-ray Photons Induced Changes in Lexan Films

40 keV Synchrotron X-ray photons were made to fall on Lexan polycarbonate films at different exposure time. The low energy X-ray photons assisted modification in terms of physico-chemical properties of Lexan films were studied using Fourier Transform Infrared (FTIR) spectrophotometer, X-Ray Diffractogram (XRD), Vicker’s Microhardness Tester,Scanning Electron Microscope (SEM) and Contact Angle Meter. FTIR result mainly includes decrease in the C=C stretching and C-C stretching of aromatics after irradiation. XRD analysis shows a slight decrease in the crystallinity after irradiation. Vicker’s microhardness test reveals the decrement in microhardness of Lexan films after irradiation. SEM result shows irradiation induced changes in the surface morphology. Contact angle measurement shows increase in the water contact angle in irradiated Lexan films.

Effect of ethanol on wetting and adhesion properties of rhamnolipid

The wetting and adhesion properties of the surfactants and biosurfactants play a very important role in the processes occurring in practice. These properties can be changed by the addition to the aqueous solution of the surfactants and biosurfactants different kinds of the substances influencing the structure of water and the hydration of the head and tail of the surfactants molecules. Therefore, we studied effect of the ethanol on the wetting and adhesion properties of rhamnolipid by the measurements of the contact angle of the aqueous solution of rhamnolipid in the presence of ethanol on the polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA) and quartz surface. The obtained results of the contact angle were analyzed in the light of the surface tension components of the solids, water, ethanol as well as the head and tail of the rhamnolipid surface tension. Based on these analyses the adsorption of the ethanol and rhamnolipid at the solid-solution, the dependence between adhesion and surface tension, the dependence between the adhesion work of the solution to the solid surfaces and solution surface tension as well as the critical surface tension of solid wetting were considered. The critical surface tension was compared to the surface tension of the solid. From above mentioned consideration, it appeared, among other things, that on the basis of the PTFE-aqueous solution of ethanol (ET) and PTFE-aqueous solution of rhamnolipid (RL) interface tension, it is possible to predict the contribution of ET and RL adsorption at the PTFE-solution of RL and ET mixture. It also appeared that it is possible to determine the Gibbs standard free energy of ET and RL adsorption at the solid-air and solid-solution interfaces, by using the Gibbs excess concentration of ET and RL at these interfaces determined on the basis of contact angle in Langmuir equation modified by de Boer. • Replacement of RL by ET molecules in interfaces layer can cause contact angle increase. • Above ET CAC contact angle depends practically on its adsorption at interfaces but not RL. • Parameter changes linearly as a function of logarithm from sum of and but not • Solution of ET and RL mixture spreads complete over PMMA and quartz at C of ET higher than its CAC. • For PMMA and quartz there is linear dependence between adhesion work and

Wearing Cushioning Shoes Reduce Load Rates More Effectively in Post-Fatigue than in Pre-Fatigue during Landings.

Simple SummaryAthlete experience high impact forces during landing, which is a contributing factor to injury risk potentials. As a potential factor of affecting the impact force, previous study of the effects of footwear cushioning effect on landing biomechanics were inconsistent. Furthermore, limited efforts have been exerted on the relationship between footwear cushioning and fatigue. In this study, the footwear cushioning effects on bipedal landing biomechanics before and after acute exercise-induced fatigue protocol were explored. The results of this study suggest that footwear cushioning can reduce landing-related rearfoot impact forces regardless of fatigue conditions. In a situation where the neuromuscular activity is reduced or absent, e.g., post-fatigue, wearing better cushioning shoes show superior attenuation, as indicated by low forefoot and rearfoot impacts.Purpose: this study aimed to investigate the footwear cushioning effects on impact forces and joint kinematics of the lower extremity during bipedal drop landings before and after acute exercise-induced fatigue protocol. Methods: in this case, 15 male collegiate basketball athletes performed drop landings from a 60 cm platform wearing highly-cushioned shoes (HS) and less cushioned shoes (control shoes, CS) before and after acute fatigue-inducing exercises (i.e., shuttle run combined with multiple vertical jumps). Force plates and motion capturing systems were synchronised to measure ground reaction forces and kinematic data during drop landings. Maximum jump height was analysed with one-way ANOVA. Two-way repeated measure ANOVAs were performed on each of the tested variables to examine if there was significant main effects of shoe and fatigue as well as the interaction. The significance level was set to 0.05. Results: rearfoot peak impact forces and loading rates significantly reduced when the participants wore HS in pre- and post-fatigue conditions. The peak loading rates in forefoot significantly reduced when HS were worn in post-fatigue. Compared with pre-fatigue, wearing HS contributed to with 24% and 13% reduction in forefoot and rearfoot peak loading rates, respectively, and the occurrence times of first and second peak impact forces and loading rates were much later. In the post-fatigue, a significant increase in the initial contact and minimum angles of the ankle were observed in HS compared with CS. Conclusion: these findings suggest that footwear cushioning can reduce landing-related rearfoot impact forces regardless of fatigue conditions. In a situation where the neuromuscular activity is reduced or absent such as post-fatigue wearing better cushioning shoes show superior attenuation, as indicated by lower forefoot and rearfoot impacts.

Assessment of Stone Protective Coatings with a Novel Eco-Friendly Encapsulated Biocide

The conservation of stone monuments is a constant concern due to their continuous weathering, in which biofouling plays a relevant role. To enhance the effectiveness of biocidal treatments and to avoid environmental issues related to their possible toxicity, this research aims at formulating and characterizing a coating charged with an eco-friendly biocide and showing hydrophobic properties. For this purpose, zosteric sodium salt—a natural biocide product—has been encapsulated into two silica nanocontainers and dispersed into a tetraethoxysilane-based (TEOS) coating also containing TiO2 nanoparticles. The coatings were applied on four different types of stone: brick, mortar, travertine, and Carrara marble. The effectiveness of the coating formulations and their compatibility concerning the properties of coated stones were assessed. The results showed that all coatings conferred a hydrophobic character to the substrate, as demonstrated by the increase of the static contact angle and the reduction in the capillary water absorption coefficient. The transmission of water vapor of the natural stones was preserved as well as their natural aspect. Furthermore, the coatings were homogeneously distributed on the surface and crack-free. Therefore, the protective capability of the coatings was successfully demonstrated.

Mitigation of fouling during milk processing in polytetrafluoroethylene‐titanium dioxide coated plate heat exchanger

AbstractAn attempt was made to mitigate fouling during milk processing in plate heat exchanger by modifying SS316 surface with the coating of polytetrafluoroethylene (PTFE) and titanium dioxide (TiO2) nanoparticles. The surface characteristics of PTFE‐TiO2 coated and conventional SS316 plates, and their thermal performance during heating of milk in batches for 8 hr were compared. It was observed that the static contact angles of water on SS316 and PTFE‐TiO2 coated plates were 66.8 ± 6.3° and 112.8 ± 0.8°, while for milk they were 61.0 ± 6.1° and 97.5 ± 1.1°, respectively. The increase in contact angle for coated surface was suggestive of weaker interaction between the fluid and surface, and enhancement in hydrophobicity. Overall heat transfer coefficients for uncoated and coated plates ranged from 354.36 to 952.26 Wm−2 K−1 and 477.11 to 593.73 Wm−2 K−1, whereas the fouling factor was 1.723 × 10−3 and 0.412 × 10−3 m2KW−1, respectively. As deposition of foulants occurred, the overall heat transfer coefficient of SS316 and coated surfaces dropped by 62.15 and 19.40%, respectively, from the initial value, resulting in crossover of the curves at 310 min of heating milk. After 480 min of heating milk, the fouling factor of SS316 plates was at least four times higher than that of PTFE‐TiO2 coated plates. The PTFE‐TiO2 coating mitigated the deposition of milk foulants by 20 times than that of SS316 surface.Practical ApplicationsFouling of plate heat exchangers (PHE) during milk processing is an unsolved problem causing significant loss in heat transfer performance, increased pressure drop in flow between plates, loss of process time due to cleaning and impairment of product quality. The high surface free energy and hydrophilic adhesion of SS316 to milk act as stimulants to fouling. Modification of SS316 plates in PHE with coating of polytetrafluroethylene and titanium dioxide nanoparticles mitigates fouling. Coated plates maintain the heat transfer performance of the plates for extended time and reduce the cleaning requirement. Also, savings in harsh chemicals, water, and pumping costs could be realized.