Waterproof Ability Research Articles

Transforming Commercial Polymers into Tough yet Switchable Adhesives by Trident Photoswitch Molecule Doping: Break Adhesion-Switchability Paradox.

Here, a trident molecule doping strategy is introduced to overcome both cohesion-adhesion trade-off and adhesion-switchability conflict, transforming commercial polymers into tough yet photo-switchable adhesives. The strategy involves initial rational design of new trident photoswitch molecules namely TAzo-3 featuring azobenzene and hydroxy-terminated alkyl chains involved rigid-soft tri-branch structure, and subsequent doping into commercial polycaprolactone (PCL) via simple blending. Unique design enables TAzo-3 as a versatile dopant, not only regulating the internal and external supramolecular interaction to balance cohesion and interface adhesion for tough bonding, but also affording marked photothermal effect to facilitate rapid adhesive melting for great photo-switchability. Thus, the optimal TAzo-3-doped PCL (TAzo-3@P) displays markedly-improved bonding performance on diverse substrates compared to linear azobenzene-doped PCL and pure PCL. Impressively, TAzo-3@P on polymethyl methacrylate (PMMA) attains large room-temperature adhesion strength of 6.7MPa - surpassing most reported adhesives and many commercial adhesives on PMMA, along with easy photo-induced detachment with remarkable switch ratio of 2.09×105. Besides, TAzo-3@P can also act as "permanent" adhesives for only adhesion, demonstrating excellent multi-reusability, anti-freezing and waterproof ability. Mechanism studies unveil that the switchable adhesion is closely linked with the dopant molecule structure while rigid-soft coupled trident structures and hydroxy-terminated alkyl chains are key factors.

Experimental and simulation studies on the waterproofing performance of anchored sealing gasket for shield tunnel lining

Anchored sealing gasket can be prefabricated together with prefabricated segment in the prefabrication factory, which can significantly improve the on-site construction convenience and waterproofing performance of shield tunnel segments. This paper proposed a novel anchored sealing gasket with a closed bottom and a symmetric pair of anchored feet on both sides, and the mechanical properties, waterproofing performance, and leakage mechanism of the gasket was investigated by experimental and numerical simulation methods. Test results show that for traditional sealing gasket, leakage occurs at the contact surface between the sealing gasket and the segment, while for anchored sealing gasket, leakage occurs only at the contact surface between the sealing gaskets, which indicates that the anchored sealing gasket feet can effectively prevent leakage between the sealing gasket and the shield segment. Compared with the traditional sealing gasket, the waterproofing ability of the anchored sealing gasket under the same working conditions is increased by 114%. The dynamic simulation of the waterproofing behavior of the anchored sealing gasket, considering the effect of water pressure, was carried out based on the flow-solid coupling model established by the Coupled Euler-Lagrangian (CEL) method. It was found that the waterproofing behavior of the anchored sealing gasket can be divided into four stages: the segment compression stage, the water compression stage, the water wedge stage, and the water breakthrough stage. The water resistance ability between the anchored sealing gasket and the segment is much higher than between the sealing gaskets. The anchor feet can prevent leakage at the interface between the gasket and the segment effectively. In addition, it was found that the test value of the waterproofing capacity of the anchored sealing gasket was close to the peak value of the maximum contact stress between the sealing gaskets during the water wedging stage, and this peak value can be used as a prediction method for the waterproofing capacity of the anchored sealing gasket to investigate the effect of joint deformation on waterproofing capacity. Finally, based on the experimental and simulation results, the waterproofing mechanism of the anchored sealing gasket was revealed, providing a reference for the waterproofing design of anchored sealing gaskets for prefabricated underground structures joints in the future.

Fabrication of hierarchical superhydrophobic structures by silane enriched with nanomaterials for enhancing permeability and freeze-thaw resistance

In this paper, the method of dehydration condensation reaction was used to establish a superhydrophobic cement mortar surface with the contact angle of 159.3° and the slide angle of 6.1° by using organosilane and inorganic nanomaterials. The nanoparticles built roughness and the silane provided low surface energy, which in combination achieved self-cleaning, waterproof and durability improvement. The superhydrophobic coating with good penetration depth is able to show superhydrophobicity after simply brushing and curing at room temperature for 24 hours and maintain hydrophobicity after surface abrasion. A variety of liquid droplets can roll freely from the surface of superhydrophobic cement mortar and carry contaminants rolling down to show self-cleaning performance. In terms of durability, the coating appears good adhesion to the surface of cement mortar, which retained its hydrophobic property after tape-peeling tests and outdoor simulation tests. In addition, compared with ordinary cement mortar, the superhydrophobic cement mortar demonstrates excellent waterproof ability and freeze-thaw resistance through low water absorption and slow quality reduction after multiple freeze-thaw cycles. These key characteristics provide advantages for concrete protection applications in harsh environments.

Study of waterproof ability and corrosion resistance of basalt fiber-reinforced concrete with superhydrophobic surfaces

Study of waterproof ability and corrosion resistance of basalt fiber-reinforced concrete with superhydrophobic surfaces

Effects of fluorosilane addition on polyurethane electrospun membranes with waterproof and breathable performance

Waterproof and breathable fibrous membrane is a new type of polymer functional material widely used in outdoor protection, sports equipment, industrial production, and other fields. To impart waterproof ability and breathability, a common practice is to modify the electrospun membrane with low surface-energy materials, such as fluorosilane. However, when directly added to the electrospinning solution, the effects of fluorosilane on the property of the prepared membrane have been scarcely reported. Herein, we prepared the electrospun polyurethane membrane by adding two types of fluorosilane into the polyurethane solution. The effects of fluorosilane type and concentration on the conductivity and viscosity of the electrospinning solution were investigated. Moreover, the prepared polyurethane/fluorosilane fibrous membranes are analyzed in terms of their surface morphology, structure, water contact angle, breathable performance, and mechanical properties. Results show that the dual effects of fluorosilane content exert an opposing influence on the jet drawing process, which yields a minimum fiber diameter when the fluorosilane content is 20%. Under this condition, the membrane shows the highest water vapor transmission rate (10.4 kg/(m2·d). In addition the membranes have the maximum water contact angle (138°) and breaking strength (12 MPa) when the fluorosilane content is 40%. This study provides insights into fabricating electrospun waterproof and breathable membranes in equipment for outdoor sports and protection.

A water-resistance and breathable fabric-based sensor with high sensitivity for air and underwater applications

A wearable sensing device, it not only has good breathability to ensure long-term wearing comfort but also needs to have waterproof ability to avoid sweat erosion. However, most reported works only have breathability or waterproof ability, which greatly limits their application. Herein, we designed and fabricated a water-resistant and breathable sensor based on non-woven fabric via the simple methods of 3D direct writing and spray coating. The sensing principle of supercapacitive and the micro uneven structure of fibers endows the sensor with high sensitivity (77.19 kPa−1), wide detection range (0–65 kPa), fast response speed (within 50 ms), cycle stability (over 10,000 cycles). The stearic acid (STA) coating method enables the sensor with excellent hydrophobicity (water contact angle of about 160.9°) and waterproof ability that can work normally in humid environments and even underwater. Benefiting from the natural micropore structure of fibers, the sensor demonstrates excellent air permeability (359.4 mm s−1). As a result, the fabric-based sensor can monitor human motions, and physiological signals and recognize gestures in the normal open-air and underwater environment, demonstrating its huge potential in underwater applications.

Fabrication of breathable superhydrophobic composite fabric with moisture permeability and weak-electric-field bactericidal ability designed for protective clothing applications

Most protective clothing on the market today cannot provide both comfort properties and protectability, which would not match the requirement for preventing or killing the rapidly growing and changing virus. Hence, a novel breathable and waterproof composite fabric used in protective clothing was designed through the hot-press process with three functional layers. The waterproof ability, moisture permeability, mechanical property, electricity and bactericidal ability of three layers and composite fabric were studied. Results showed that the moisture permeability of coated thermoplastic polyurethane (TPU) membrane reached 19854 g m2 d−1. The composite fabric had still excellent moisture permeability of up to 13956 g m2 d−1 and water contact angle of 151.7°. The coated TPU membrane had good tensile strength and acid resistance. The voltage and current of composite fabric after 7 days were approximately 0.336 V and 1.4 μA. The composite fabric had a 97.5 % filtering effect for NaCl aerosols, a 99 % bacteriostatic rate, and the ability to withstand the Phy-X174 phage with a diameter of 0.027 μm. This composite fabric based on the principle of moisture permeability and weak electric field could be used in protective clothing, which would be of theoretical significance and guiding practical production.

Design and analysis of a flexible hydrophone based on PVDF with aluminum film substrate and PDMS encapsulation

Unmanned underwater vehicles (UUVs) need hydrophones for underwater acoustic sensing. However, previous hydrophones were rigid in shape and unable to realize conformal installation. In this paper, a flexible hydrophone with great installation adaptability was presented. Polyvinylidene fluoride (PVDF) piezoelectric film was applied as the transducing material. A flexible aluminum film was selected as the substrate. These two films were sandwiched by polydimethylsiloxane (PDMS) layers. Finite element simulation revealed that the sensitivity and bandwidth of the hydrophone were enhanced by using the aluminum film substrate. The sensing performance improvement was ascribed to the suppressed in-plane stress of the PVDF film. Prototypes were fabricated and tested. The fabricated hydrophone exhibited a sensitivity of −211 dB (ref. 1 V/μPa) at 500 Hz. It owned a 20–500 Hz working frequency range and an omnidirectional pattern. Besides, the sensitivity difference caused by shape changes was within 2.3 dB. Furthermore, the hydrophone showed good waterproofing ability.

Ultra-stable, waterproof and self-healing serpentine stretchable conductors based on WPU sheath-wrapped conductive yarn for stretchable interconnects and wearable heaters

Stretchable conductors (SCs) have shown promising potential in the field of stretchable electronic devices for their lightweight, high flexibility, stable performance, and easy integration. However, the conductivity of most reported stretchable conductive composites is sensitive to deformation, and it is still unsatisfactory due to their poor recoverability and low reliability under large strain. In this paper, we have fabricated a serpentine stretchable conductor (SSC) with high conductivity, stretchability, and ultra-stability by spontaneously wrapping elastic waterborne polyurethane (WPU) sheath on the surface of the multi-walled carbon nanotube (MWCNT)/WPU nanocomposite conductive yarn, which was prepared by a simple wet-spinning method. The WPU elastic sheath endows SSC with long-term tensile durability and recoverability. Remarkably, benefiting from the sharing effect of the serpentine structure on the tensile strain energy, SSC shows distinctive strain-insensitive behavior (ΔR/R0 less than 1.6%) up to 100% strain and ultra-high quality factor (Q = 105) at 80% strain. Furthermore, SSC also has temperature resistance, waterproof ability, and self-healing capability, making it capable of being used in harsh circumstances. The combination of high conductivity, stretchability, and super reliability renders many potential applications for SSC, such as stretchable interconnects and wearable heaters. Such serpentine stretchable device with distinctive strain-insensitive behavior provides a novel design idea for stretchy electronics.

Impact Analysis and Optimization of Key Material Parameters of Embedded Water-Stop in Tunnels

Leakage diseases frequently occur in mountain tunnels, and the lining joints are weak waterproof links. In order to solve the problems such as insufficient waterproof technology for existing tunnel joints, this paper relies on the scientific and technological project of the Hubei Provincial Department of Transportation to optimize the key parameters of the tunnel water-stop material and uses numerical simulation methods to analyze the impact of the hardness of the water-stop and the bond strength between the water-stop and concrete on its deformation and waterproof ability. Through the adhesion test, the optimization method of the bond strength between the water-stop and concrete is explored. The results show that: (1) the deformation stress of the water-stop will increase with the increase in hardness and reducing the hardness of the water-stop can improve its stress deformation state. Considering that low hardness increases the risk of damage and reduces the quality, it is recommended that the hardness be 55–60 (HA). (2) The adhesion between the water-stop and the concrete lining is the key to waterproofing the water-stop. Increasing the adhesion between the water-stop and the concrete is an effective optimization method. However, to prevent excessive deformation stress, it is necessary to optimize the geometric structure of the water-stop simultaneously. (3) Placing an epoxy–quartz sand coating on the surface of the water-stop can increase the adhesive force between the water-stop and the concrete. When the thickness of the epoxy layer is 2 mm, and the particle size of quartz sand is 26–40 mesh, the effect is best.

Surface chemistry regulation of nanoparticle coatings on activated carbons for rapid and long-lasting adsorption of organic pollutants

The nature of activated carbons (AC) to possess large specific surface areas and highly developed internal channels, is beneficial to absorb a variety of organic pollutants for practical applications in widespread areas, such as odor removal, flue gas cleaning and water purification. However, the domination of water affinity on AC could promote the adsorption to saturation in a short period, hindering the adsorptive performance on organics and reducing the service life severely. Thus, a simultaneous demonstration of the remarkable adsorptive property along with moisture resistance is of great significance. In this work, the superhydrophobic ACs with selective adsorptive property were fabricated via the combination of pretreatment to roughen the surface and grafting of propyl trimethoxysilane on superhydrophobic nanoparticles. The design was verified by the theoretical calculation of density functional theory accompanied with surface grafting ratio, and the as-prepared ACs presented favorable damp- and water-proof ability in the long term, showing only 11.8% weight increment for up to 180 days in high humidity. More importantly, superhydrophobic ACs exhibited effective capture of organics for continuous adsorption under aqueous phase and humid conditions, with removal efficiency over 90%.

An experimental study on the influence of fly ash and crumb rubber on the mechanical property and permeability of Engineered Cementitious Composite (ECC)

Interest in using Engineering Cementitious Composites (ECC) for waterproof reinforcement has rapidly risen in recent years. Many studies revealed the excellent mechanical properties and waterproof ability of ECC, and analytical models have been proposed for predicting the permeability of ECC at different strain levels. However, the tailoring theory of ECC leads to the fact that the mechanical properties and waterproof ability can be further improved by incorporating different binders and aggregates and adjusting their proportions. Therefore, the applicability of current permeability models on the ECC with different mix proportions still needs to be researched. This paper focuses on adding fly ash and crumb rubber to enhance the waterproof ability of ECC. Mechanical properties and permeability experiments at different tensile strain were conducted for ECC with various mix proportions, and the effects of fly ash and crumb rubber on the improving the ductility and reducing permeability were revealed. In addition, the accuracy of the model for different mix proportions and different strain levels was studied. It is revealed that both fly ash and crumb rubber lead to a higher ductility, denser crack pattern and lower permeability, and ECC with fly ash has a better performance than ECC with crumb rubber at high strain level. The analytical model for permeability of ECC was proved to be accurate when few crumb rubber is added, while overestimate is observed for high crumb rubber content experiments. The findings of this research will contribute to the mix proportion design of ECC for waterproof reinforcement application.

Superelastic Conductive Fibers with Fractal Helices for Flexible Electronic Applications

AbstractThe widespread application of flexible electronic devices places higher demands for stretchable conductors as crucial components owing to their stable and consistently high conductivity and high stretchability. In this study, a superelastic conductive fractal helix fiber (FHF) consisting of a thermoplastic polyurethane fiber and Ag wire is developed, which exhibits excellent waterproofing ability. The maximum strain of the FHF can be improved to 8300% by increasing the helical index C and Ag wire winding density. A high conductivity of 6.3 × 107 S m−1 and ultra‐high Q value of 3.37 × 104 at a strain of 5600% are realized for the conductive fiber owing to its fractal helical structure. The elastic limit point A of the FHF can be obtained by the relative resistance change (0.166%) to ensure that elastic deformation only occurs when stress is applied. In the elastic strain range, FHF demonstrates high electrical reliability under repeated deformation (over 10 000 cycles of stretching with a strain of 5600%) with a negligible increase in resistance. Moreover, the FHF can be easily integrated with the fabrics as an interconnection for wearable electronics. The newly developed twined FHF can also be used as a capacitive strain sensor to monitor human activity.

Insight on Atmospheric Hydrothermal Aging for Polyester and Polyimide Film Used in Dry-Type Reactor

The breakdown of the dry-type reactor induced by being exposed to moisture needs to be further explored. For this purpose, as the common insulating films in the dry-type reactor, PET and PI films were targeted to investigate the effects of atmospheric hydrothermal aging on the microstructure, thermal stability, and mechanical properties of the films. As the result of hydrothermal aging, the moisture-based thermal degradation obviously occurred on the surface of both PET and PI films, even at a low temperature. More defects and flaws can be observed on the surface of PET than that of PI film, which were responsible for decreasing the transmittance and tensile strength of films. According to the statistical analysis with a one-sample t test, the thermal stability of aged PET and PI films has no significant difference with raw films during the hydrothermal aging. Compared with thermal stress, the hydrolysis of ester linkage and the imide ring are the main factors of hydrothermal aging for PET and PI films, respectively. Improving the waterproof ability of PET and PI films can be effective to prevent deterioration of the interturn insulation performance of the dry-type reactor.

Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn4+ and Mg2.

In this report, red-emitting alumina nanophosphors doped with Mn4+ and Mg2+ (Al2O3:Mn4+, Mg2+) are synthesized by a hydrothermal method using a Pluronic surfactant. The prepared samples are ceramic-sintered at various temperatures. X-ray diffraction shows that Al2O3:Mn4+, Mg2+ annealed at 500 °C exhibits a cubic γ-Al2O3 phase with the space group Fd3m-227. The tetragonal δ-Al2O3 and rhombohedral α-Al2O3 phase is obtained at 1000 and 1300 °C, respectively. Cube-like nanoparticles in a size of ∼40 nm are observed for the alumina heated at 500-1000 °C. The size and red-emitting intensity of the phosphors remarkably increased with annealed temperature ∼1300 °C. Emission spectra of the phosphors show strong peaks at 678 and 692 nm due to 2 E g → 4 A 2 transitions of the Mn4+ ion, under a light excitation of 460 nm. A strong zero-phonon line (ZPL) emission is observed in the luminescence spectra of δ-Al2O3:Mn4+, Mg2+ at 298 K, whereas a weak one is observed in those of α- and γ-Al2O3:Mn4+, Mg2+. The alumina phosphors exhibited an excellent waterproof ability during 60 days in water and good thermal stability in the range of 77-573 K. A warm-white light-emitting diode (WLED) fabricated using In x Ga1-x N nanowire chips with Al2O3:Mn4+, Mg2+ red-emitting nanophosphors presents a high color rendering index of ∼95.1 and a low correlated color temperature of ∼4998 K. Moreover, the current-voltage characteristic of the nanowire LEDs could be improved using Al2O3:Mn4+, Mg2+ nanophosphors which is attributed to the increased heat dissipation in the nanowire LEDs.

Experimental investigation on thermal management system of composite phase change material coupled with serpentine tubes for battery module

• Paraffin/carbon nanotube/boron nitride/silicone gel (PCBS) composite has designed. • PCBS exhibits anti-leakage, reignite resistance and prominent waterproof property. • Batteries with PCBS can decrease interface heat resistance by pouring technology. • Composite material coupled with serpentine tubes is designed for battery module. • The battery module with PCBS can exhibits excellent thermal management effect. As an advanced thermal management method for battery modules, phase change material with many advantages have attracted much attention; however, many significant challenges still exist. In this study, a novel paraffin/carbon nanotube/boron nitride/silicone gel composite material was designed and fabricated. Owing to the combination of phase change material with the large latent heat and silicone gel as a thermal interface material, the paraffin/carbon nanotube/boron nitride/silicone gel exhibits outstanding properties such as anti-leakage, mechanical flexibility, re-ignition resistance, and outstanding waterproofing ability. Compared with the pre-solidification process, the results reveal that the battery with composite material can obtain a low-interface thermal resistance between the composite materials and batteries through an in-situ pouring technology, which exhibits a faster thermal response than that without PCBS. In addition, the paraffin/carbon nanotube/boron nitride/silicone gel coupled with serpentine liquid-cooling tubes have been utilized in the battery module, which can control the maximum temperature below 55 °C at 1 C discharge rate, it is obviously lower than that without composite material. This research is expected to provide insights into the design and optimization of thermal management systems in various energy storage fields.

Environmentally friendly waterproof and breathable electrospun nanofiber membranes via post-heat treatment

Waterproof and breathable nanofiber membrane (WBM) is the core of the waterproof and breathable textile. At present, it is difficult to achieve simultaneous improvement of waterproofness, breathability and mechanical properties due to the limitation of material property and preparation technology. Herein, environmentally friendly and high-performing fluorine-free silicon-based polyurethane/polymethyl methacrylate/polyvinyl butyral (Si-PU/PMMA/PVB) WBMs were prepared via a facile electrospinning technology and post-heat treatment. By heating treatment, inter-fiber adhesion was achieved due to the melt of PVB, leading to a decrease in the maximum pore size of the fiber membrane, which enhances the waterproof ability. At the same time, the generated inter-fiber adhesion enhanced the interaction force between fibers, and thus improved the mechanical properties. The as-prepared PU/PMMA/PVB-40 WBM exhibits good water resistance with a hydrostatic pressure of 65.29 kPa, exceptional breathability with a water vapor transmission rate (WVTR) of 7.0 kg m−2 d−1, together with a high tensile strength of 11.52 MPa. The obtained Si-PU/PMMA/PVB WBMs have broad application prospects in special protective clothing and outdoor equipment.

Printable, flexible, breathable and sweatproof bifunctional sensors based on an all-nanofiber platform for fully decoupled pressure–temperature sensing application

Flexible bifunctional sensors that mimic the function of human skin are essential as they provide critical interacting information with human and environment for intelligentization. However, the problem of the interference between sensing signals from different stimuli and the deficiency of comfortability for a long-time skin-attaching wearing still exist. Herein, we present an ultrathin and flexible bifunctional sensor based on two measurable parameters of pressure-induced supercapacitance and temperature-induced resistance with neglectable crosstalk between the two. The sensor consists of a planar iontronic supercapacitor underneath a serpentine resistor with assembly of total seven layers integrated on an electrospun thermoplastic polyurethane (TPU)-based nanofiber platform. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based sensing electrodes are patterned by a direct ink writing method with addition of graphene nanoflakes and Co3O4 nanoparticles to enhance the sensing performance. A high pressure sensitivity (147.19 kPa−1, 0–7 kPa; 4.41 kPa−1, 25–85 kPa) and a high temperature sensitivity (0.040 °C−1, 25–50 °C; 0.002 °C−1, 50–100 °C) are simultaneously achieved. The sensor also has the advantages of humidity inertness, waterproof ability and air permeability, which is breathable to obtain a wearing comfortability. Decoupled pressure–temperature sensing applications of detecting various subtle pressures by objects of different temperatures are demonstrated in a wireless and real-time mode. The proposed bifunctional sensor shows great potential in wearable healthcare monitoring.

Failure Mechanism Analysis and Optimization Analysis of Tunnel Joint Waterstop Considering Bonding and Extrusion

In waterproofing mountain tunnels, the tunnel joint is the weak link. To explore the waterproof failure mechanism of the tunnel joint waterstop belt and to propose an optimization method for the waterstop belt, this paper combines tests and numerical simulations, summarizes the waterproofing mechanism of the waterstop belt, establishes a finite element model of the waterstop belt considering bonding and extrusion, and studies the waterproofing ability and mechanical properties of the waterstop. The main conclusions are as follows: (1) The waterproofing capacity of the water stop belt depends on its surface contact pressure and bonding force. (2) Waterstop deformation will partially destroy the bonding between the waterstop and concrete, reducing the reliability of the waterproofing mechanism. (3) When the deformation of the waterstop belt reaches a certain degree, its stress value is too large to meet the requirements of its service life. (4) The design can be optimized from two aspects: the bond between the waterstop and concrete, and the size of the waterstop.

Effect of PDMS content on waterproofing and mechanical properties of geopolymer composites

The present study mainly studies the effect of polydimethylsiloxane (PDMS) content on the waterproofing and mechanical properties of geopolymer composites. Firstly, hydrophobic modified geopolymer composites (HM-GC) were prepared by adding PDMS during the mixing process. Secondly, the surface wettability characteristics, water absorption, uniaxial compressive and tensile properties of HM-GC were investigated. The effect of PDMS content on the waterproofing and mechanical properties was further discussed. Finally, considering the waterproofing and mechanical properties, the optimal PDMS content was proposed. The results showed that with increasing PDMS content, the contact angle of geopolymer composites rapidly increase at first and then stabilizes. The geopolymer composites with 4% and 5% PDMS content exhibit overhydrophobic surface wettability. In addition, the water absorption gradually decreases with increasing PDMS content, indicating an improvement in the waterproofing ability. The incorporation of PDMS can enhance the compressive properties of geopolymer composites while reducing the tensile properties. Comprehensively considering the waterproofing and mechanical properties, it is reasonable to select 4% as the optimal PDMS content used in practical marine engineering.