Waterproofing Membrane Research Articles

Environmentally Friendly Waterproof and Breathable Nanofiber Membranes with Thermal Regulation Performance by One-Step Electrospinning

Environmentally Friendly Waterproof and Breathable Nanofiber Membranes with Thermal Regulation Performance by One-Step Electrospinning

Ultra‐Lightweight, Highly Permeable, and Waterproof Fibrous Organic Electrochemical Transistors for On‐Skin Bioelectronics

AbstractRecently emerged on‐skin electronics with applications in human–machine interfaces and on‐body healthy monitoring call for the development of high‐performance skin‐like electrodes and semiconducting polymers. The development of waterproof and breathable membranes that can provide a high level of protection for human skins and a comfortable contact between electronics and skin are the pressing demands for on‐skin electronics. However, major challenges remain, such as the limited mechanical durability and permeability of gas and liquid, hindering long‐term stability and reusability. Herein, a fibrous electrolyte containing polymer matrix and ionic liquid, which is highly robust, breathable, waterproof, and conformal with human skin is reported. Serving as fibrous substrate and electrolyte of organic electrochemical transistors (OECTs), a high transconductance of ≈0.8 mS, stability over pulsing and time (≈1000 cycles and 30 days) are achieved. The softness of fibrous OECTs enables a comfortable contact after attaching to human skin, which can reduce the interfacial impedance to achieve a high‐quality local amplification of the electrocardiography signals (signal‐to‐noise ratio of 21.7 dB) even in skin squeezed state or after one week. These results indicated that our fibrous OECTs have huge potential for versatile on‐skin electronics such as non‐invasive medical monitoring, soft sensors, and textile electronics.

Waterproof and Breathable Graphene‐Based Electronic Fabric for Wearable Sensors

AbstractElectronic skin (E‐skin) is widely used in bionic prosthesis, soft robotics, and wearable electronic devices. Waterproof and breathable membranes that provide a high level of protection and comfort are promising core materials for meeting the pressing demand for E‐skin. However, creating such materials exhibiting waterproofness, breathability, and ease of fabrication has proven to be a great challenge. In this paper, waterproof, breathable Modal‐based knitted fabric E‐skin is proposed by using a simple, low‐cost three‐step process including the graphene oxide (GO) loading, GO‐reducing, and polydimethylsiloxane loading. The prepared E‐skin is insensitive to common liquids in daily life including water, tea, milk, and coffee, showing superior waterproof capability. The breathability is also tested with a water vapor transmission rate of ≈13.6 mg cm−2 h−1. Besides, this E‐skin can achieve reliable human motion monitoring. The authors believe this E‐skin can provide a reliable principle for further design and development of waterproof and breathable electronic skin.

Development of Filled Immiscible Polymers Blend Monofilaments for Water Detection in Composite

In order to avoid environmental pollution by effluents, the incorporation of electrical conductive yarns in a waterproof membrane allows detecting a leak or crack on industrial concrete structure. The membrane is made of composite materials: a glass textile structure equipped with the detector yarns and molded in an epoxy resin. The liquid’s detection and the data’s transmission depend on the yarn’s conductivity variation and its chemical and physical properties. This study aims to develop a water detector monofilament from conductive polymer composites (CPC): an immiscible polymers blend (polyamide 6.6/elastomer) filled with carbon nanotubes (CNT). The addition of elastomer in the CPC yarn is important to withstand the mechanical deformation of the resin structure without breaking. The morphology of the immiscible polymers blend and the localization of the CNT influence the electrical conductivity of the yarn and thus, its property of water detection. Two principles of water detection are investigated with this blend: the short circuit and the absorption. For the short circuit, the presence of liquid is detected when the liquid creates a conductive path between two yarns in parallel. While, the absorption principle is based on the conductivity variation with the yarn’s swelling in contact with water.

Design features and best practice in podium deck waterproofing : Examples and perspectives from UK industry

Podium decks — a basement roof at, or around, ground level which is not covered by superstructure — are an increasingly common feature in the modern built environment. This increase may be partly attributed to growing awareness of the need for sustainability. Green roofs, sustainable urban drainage, water attenuation and even parks and farms are being located on top of podium decks. Waterproofing of these podium decks is vital in order to use the space created beneath and also to prolong the life expectancy of the structure. This research analyses the available best practice guidance and then compares the key waterproofing design features with opinions from industry. Opinions are gathered first through 78 questionnaire respondents and then interviews with four experienced respondents with unusual views. These findings are then compared with case studies of podium decks with waterproofing failures. This research suggests that robust podium deck waterproofing design comes from the following choices in the fundamental features of waterproofing design for podium decks: a) reinforced concrete structural deck; b) fully bonded waterproofing membrane; c) waterproofing laid to a gradient to falls; and d) provision of a drainage void over the waterproofing layer. As a result of these findings, this paper calls for more authoritative best practice guidance on podium deck waterproofing design in a bid to reduce pressures in procurement that lead to weaker waterproofing design choices. This research may be of interest to built environment professionals because it identifies some fundamental features of podium deck waterproofing design and clarifies which design choices are perceived to deliver more robust waterproofing than others.

Waterproof and Moisture-Permeable Polyurethane Nanofiber Membrane with High Strength, Launderability, and Durable Antimicrobial Properties.

Nanofiber membrane has high biological protection function because of its good waterproof and moisture permeability properties. However, this membrane usually lacks active antimicrobial properties, limiting the application in reusable bioprotective textiles. Herein, waterborne polyurethane-capped Ag nanoparticles (AgNPs) were synthesized by reducing silver nitrate in water by sodium borohydride in the presence of polyurethane. AgNP-embedded thermoplastic urethane (TPU) nanofiber membrane was prepared by electrospinning a mixed solution of AgNPs and TPU. As-prepared membranes with Ag content of 50–300 mg·kg−1 have an average diameter of 0.75, 0.64, and 0.63 μm and good fiber uniformity. The doping of AgNP-embedded nanomembrane showed increased breaking force probably because of the induced crystallization effect. Test results showed that as-prepared TPU nanofiber membrane with silver content as low as 100 mg·kg−1 showed good washing resistance. The antibacterial rates of E. coli and S. aureus remained 99.99% with 50 times of soaping or chlorine washing. The corresponding waterproof and moisture permeability properties of nanofiber membrane with a thickness of 0.1 mm remained nearly unchanged, i.e., moisture permeability of around 2600 g·m−2 per 24 h and the hydrostatic pressure resistance of around 400 Pa after 50 times of soaping or chlorine washing.

Durability and Degradation of PVC-P Roofing Membrane-Example of Dynamic Fatigue Testing.

This paper presents a study of PVC-P waterproofing membrane Specimens. The Specimens were taken from different segments of a flat roof after a service life of 11 years. The reason for analysing the condition of the Specimens was the apparent degradation of the waterproofing, which no longer guaranteed the watertightness of the roof. The analysis of the performance of the Specimens was based on the control of the mechanical properties, which were compared with the declared values. The mechanical properties of the degraded PVC-P waterproofing membranes with a polyester mesh backing, which are prescribed by the standards, do not usually deviate from the declared properties. This often poses a problem for liability and warranty claims due to the poor quality of the waterproofing membrane. There may be several causes of degradation of PVC-P. For this reason, in this paper, we present the possibility of controlling the properties of PVC-P waterproofing membranes using cyclic dynamic fatigue, microstructure analysis using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the cause of the deterioration of the PVC-P waterproofing membranes is often related to dehydrochlorination of the polymer. However, the deterioration of the mechanical properties of the PVC-P waterproofing membranes can be successfully demonstrated by cyclic dynamic fatigue.

Preparation of Waterproof and Air-Permeable Membrane by Water Surface Spreading Method for Metal-Air Battery

The electrochemical performance of metal–air batteries is sensitive to environmental humidity, which significantly limits its wide application in an air environment. In this paper, a waterproof and breathable polydimethylsiloxane (PDMS) composite membrane has been successfully synthesized by the water spreading method for metal–air batteries. The effects of spreading times and fillers (hydrophobic SiO2 and silicalite-1) on the water vapor and air permeability of the PDMS membrane were investigated. The results demonstrate that increasing the spreading times and adding an appropriate amount of hydrophobic SiO2 can improve the waterproof quality and air permeability of the PDMS membrane. The optimized membrane was assembled into a metal–air battery, and the effects of the membrane on the running resistance, cycle number, and polarization voltage of the battery were evaluated. The hydrophobic SiO2–PDMS membrane significantly reduces the running resistance of the battery and improves the cycle number of lithium–air batteries by 25% and that of zinc–air batteries by 100% in an air environment (40% RH, 25 °C). The polarization voltage is also significantly reduced, indicating great potential in applications.

Environmentally Friendly, Durably Waterproof, and Highly Breathable Fibrous Fabrics Prepared by One-Step Fluorine-Free Waterborne Coating.

Waterproof and breathable membranes (WBMs) have drawn broad attention due to their widespread applications in various scientific and industry fields. However, creating WBMs with environment-friendliness and high performance is still a critical and challenging task. Herein, an environmentally friendly fluorine-free WBM with high performance was prepared through electrospinning and one-step dip-coating technology. The fluorine-free waterborne hydroxyl acrylic resin (HAR) emulsion containing long hydrocarbon chains endowed the electrospun polyacrylonitrile/blocked isocyanate prepolymer (PAN/BIP) fibrous membranes with superior hydrophobicity; meanwhile, crosslinking agent BIP ensured strong chemical binding between hydrocarbon segments and fiber substrate. The as-prepared PAN/BIP@HAR fibrous membranes achieve ideal properties with waterproofness of 112.5 kPa and moisture permeability of 12.7 kg m-2 d-1, which are comparable to the existing high-performance fluorinated WBMs. Besides, the PAN/BIP@HAR membranes also display impressive tensile strength and durability. Significantly, the proposed technology was also applicable to other hydrophilic fiber substrates, such as cellulose acetate and polyamide 6. The successful synthesis of environmentally friendly, durably waterproof, and highly breathable PAN/BIP@HAR membranes not only opens a new avenue to materials design, but also provides promising candidates with tremendous potential in various areas.

Preparation of Fluorine‐Free Waterproof and Breathable Electrospun Nanofibrous Membranes via Thiol‐ene Click Reaction

AbstractClothes that are comfortable and functional are important in daily life; however, the manufacture of fluorine‐free functional fabrics with excellent waterproofness and breathability using simple and environmentally friendly methods still presents several technical challenges. Currently, the ultraviolet (UV) radiation‐initiated thiol‐ene click reaction is used for the construction of hydrophobic surfaces due to its high efficiency and the mild reaction conditions involved. Therefore, in this work, the electrospinning technique and the UV‐initiated thiol‐ene click reaction to introduce hydrophobic octadecanethiol (thiol) and 2,4,6,8‐tetramethyl‐2,4,6,8‐tetra‐vinylcyclotetrasiloxane (TMTVSi) into the silicon‐based polyurethane/polymethyl methacrylate (Si‐PU/PMMA) nanofibrous membranes is combined. After UV irradiation, the sulfhydryl groups of the thiol react with the carbon–carbon double bond of the TMTVSi, resulting in cross‐linking between the nanofibers. The fluorine‐free Si‐PU/PMMA/TMTVSi‐thiol‐30 waterproof and breathable electrospun nanofibrous membranes are observed to show excellent properties, which include a hydrostatic pressure of 64.43 kPa, water vapor transmittance (WVT) rate of 7879 g m−2 d−1, and robust tensile stress of 10.04 MPa, all of which enable the membrane to be widely used in the field of protective garments and oil–water separation.

Marmaray (Bosphorus Crossing)

It is possible to construct deeper and longer immersed tunnels when the connection to land, ventilation, emergency evacuation systems, connection details between elements and similar key features are assessed and designed appropriately. Being the deepest and one of the most challenging immersed tunnels constructed to date, the Bosphorus Crossing included various innovative techniques.The Bosphorus Crossing project is located in Istanbul, Turkey, connecting the European and Asian sides of the city. The works included a double-track railway immersed tunnel with a length of 1387 m at a maximum depth of approximately 60 m below sea level. The tunnel consists of a total of 11 tunnel elements 15.3 m wide and 8.6 m high. Elements were constructed as reinforced concrete (RC) with an external steel waterproof membrane and with a transition to sandwich section for the element joint areas. Element no.11 also had a full-sandwich section in the vicinity of the access shaft connection. Design life of the permanent structures is 100 years. Elements were prefabricated in two drydocks approximately 40 km from the immersion site. Due to the expected severe seismic shaking, a sand foundation was unsuitable. A gravel foundation was placed low and roughly levelled using a remotely operated blade. Under-base grouting was injected from inside the tunnel elements to fill all gaps between the gravel foundation and the bottom slab.The tunnel is in a high seismic zone of Magnitude 7.5, which was considered in the design. Towards the Asian end of the tunnel, ground improvement using compaction grouting was used to minimize the risk of soil liquefaction. A total of 1.2 million m3 of seabed was excavated, of which 118,000 m3 was contaminated soil that had to be dumped in a confined disposal facility created on land nearer the Black Sea. The adjacent bored tunnels were constructed using tunnel boring machines (TBMs) that were driven at depth through pre-mixed soil into receiving chambers at the two ends of the immersed tunnel.

Waterproof, breathable and infrared-invisible polyurethane/silica nanofiber membranes for wearable textiles.

Waterproof and breathable membranes, which have great potential in applications such as membrane distillation, self-cleaning, and multifunctional clothing, have attracted a lot of attention due to their superior performance. Superhydrophobic and infrared-invisible polyurethane (PU)/silica (SiO2) nanofiber microporous membranes were prepared by facile electrospinning and a hydrothermal-assisted sol-gel method. Compared with pure PU nanofiber membranes, silica nanoparticles act as an adhesion layer, which can provide the rough surface and low surface energy of fibrous membranes. Therefore, the grafted PU/SiO2 nanofiber membrane was endowed with a good superhydrophobic effect, and its water contact angle (WCA) reached 161°. The nanofiber membrane exhibited comfortable waterproof and breathable properties, in which the air permeability and water vapor transfer rate was 5.18 mm s-1 and 7.85 kg m-2 d-1, respectively. When the PU/SiO2 nanofiber membrane was irradiated by infrared light, the surface of the fiber membrane showed a green, low-temperature state. These waterproof and breathable nanofiber membranes with superhydrophobic properties could be used in anti-icing, outdoor concealment, and camouflage applications.

Directional Water Transport Janus Composite Nanofiber Membranes for Comfortable Bioprotection.

The Janus membrane has a huge prospect for personal comfortable protection. However, there still is a huge imbalance between the comfort and protection of the existing Janus membrane. There is an urgent need to further improve the comprehensive performance of the protective membrane to realize both protection and comfort. Herein, we report the Janus membrane with directional water transport capacity and dust rejection performance by compounding the polyvinyl chloride hydrophobic nanofiber membrane and polyamide-6 blended polyvinyl pyrrolidone hydrophilic nanofiber membrane. This Janus composite nanofiber membrane exhibited an excellent dust rejection efficiency of 99.99%, air permeability of 42.15 mm/s, which was 76 times that of the commercial waterproof and breathable PTFE membrane, water vapor transmission rate of 4.89 kg/(m2 × 24 h), and accumulative one-way transport capacity of 888.7%. In addition, the breakthrough pressure of the Janus membrane in the reverse direction (i.e., hydrophilic layer to hydrophobic layer) was four times that in the positive direction (i.e., hydrophobic layer to hydrophilic layer), suggesting it to be a potential substrate for comfortable bioprotection with a comprehensive protection capability.

Autoclavable, Breathable, and Waterproof Membranes Tailored by Ternary Nanofibers for Reusable Medical Protective Applications

Autoclavable, Breathable, and Waterproof Membranes Tailored by Ternary Nanofibers for Reusable Medical Protective Applications

Primary and Secondary Emissions of VOCs and PAHs in Indoor Air from a Waterproof Coal-Tar Membrane: Diagnosis and Remediation

Primary and secondary emissions of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) from a waterproof coal tar membrane and their effect on the indoor air quality were investigated through a case study in a residential building situated in Madrid, Spain. The air contaminants were analyzed in situ using photoionization method and several samples of contaminants were taken using three sorbents: activated carbon, XAD2 and Tenax GR. It was found that various VOCs such as toluene, p- and m-Xylene, PAHs such as naphthalene, methyl-naphthalenes, acenaphthene, acenaphthylene, phenanthrene and fluorine, volatile organic halogens including chloroform and trichlorofluoromethane, and alkylbenzene (1,2,4-trimethylbenzene) were found at concentrations, which exceeded the limits established by international and national agencies (WHO, EPA, OSHA). Some of the above organic compounds were found also in the samples of construction and building materials, which were obtained at different heights and places. The analysis of possible sources of the contaminants pointed at the original coal-tar membrane, which was applied on the terrace to be waterproof. During a posterior reparation the membrane was coated with a new one that hindered dissipation of emitted contaminants. The contaminants leached out and were absorbed by construction materials down in the dwelling. These materials then acted as secondary emission sources. To remediate the emission problem as the contaminated materials were removed and then a ventilation system was installed to force the gasses being emitted from the rest of contaminated slab outside. Follow-up has validated the success of the remediation procedure.

Research on a new adaptive roof waterproofing membrane to improve water resistance of traditional Chinese timber buildings

ABSTRACT The roof configurations of traditional Chinese timber buildings are unique and noticeably different from those of modern buildings, and their roof waterproofing performance is typically very poor. To improve their waterproofing performance, a new adaptive waterproofing membrane was developed and examined. First, typical roof configurations of traditional Chinese timber buildings were investigated and categorized. Then, finite element models of four typical roofs were established in ANSYS, and the stress distributions at the interfaces between the waterproofing membrane layer and adjacent roof layers were studied. Finally, a new adaptive roof waterproofing membrane for traditional Chinese timber buildings was developed, and relevant experiments on its material properties and mechanical performance were carried out. The properties of the new membrane were compared with those of ethylene propylene diene monomer, styrene-butadiene-styrene and atactic polypropylene waterproofing membranes. The results showed that the new waterproofing membrane has very good material properties and can meet the structural safety requirements for the roofs of traditional Chinese timber buildings. This membrane may also provide an adaptive conservation solution for such buildings and can substantially improve the waterproofing performance and durability.

The Benefit of Horizontal Photovoltaic Panels in Reducing Wind Loads on a Membrane Roofing System on a Flat Roof

The present paper proposes a measure for improving the wind-resistant performance of photovoltaic systems and mechanically attached single-ply membrane roofing systems installed on flat roofs by combining them together. Mechanically attached single-ply membrane roofing systems are often used in Japan. These roofing systems are often damaged by strong winds, because they are very sensitive to wind action. Recently, photovoltaic (PV) systems placed on flat roofs have become popular. They are also often damaged by strong winds directed onto the underside, which cause large wind forces onto the PV panels. For improving the wind resistance of these systems, we proposed to install PV panels horizontally with gaps between them. Such an installation may decrease the wind forces on the PV panels due to the pressure equalization effect as well as on the waterproofing membrane due to the shielding effect of the PV panels. This paper discusses the validity of such an idea. The pressure on the bottom surface of a PV panel, called the “layer pressure” here, was evaluated by a numerical simulation based on the unsteady Bernoulli equation. In the simulation, the time history of the external pressure coefficients, measured at many points on the roof in a wind tunnel, was employed. It was found that the wind forces, both on the PV panels and on the roofing system, were significantly reduced. The reduction was large near the roof’s corner, where large suction pressures were induced in oblique winds. Thus, the proposed method improved the wind resistance of both systems significantly.

Preliminary investigation on the transient hygrothermal analysis of a CLT-based retrofit solution for exterior walls

This paper investigates the transient hygrothermal performance of an innovative energy and seismic renovation solution for reinforced concrete (RC) framed buildings, based on the addition of Cross-Laminated Timber (CLT) panels to the outer walls, in combination with wood-based insulation. This solution is being developed in the framework of a four-year EU-funded project called e-SAFE. The investigation relies on numerical simulations in DELPHIN 6.1, by considering combined heat and mass transfer (HAMT) due to water vapour diffusion and capillary transport. The proposed solution is tested in three different climates in Italy, to verify whether the CLT layer and the outer waterproof vapour-open membrane, inserted to protect the wood-based insulation from rain, still allow the effective drying of the vapour accumulated in liquid form in the walls, while also preventing mould formation. The results show that the increased thermal resistance of the wall assembly significantly reduces the total water content, although moderate risks of mould growth in the wooden materials may occur in coldest climates.

Preparation of zinc oxide loaded polyurethane/polysulfone composite nanofiber membrane and study on its waterproof and moisture permeability properties

Herein, zinc oxide Nanoparticles (ZnO-NPs) were bonded to the surface of polyurethane/polysulfone (PU/PSF) electrospun nanofiber membrane, it was then hydrophobically modified with Hexadecyltrimethoxysilane (HDTMS), and a new waterproof and moisture permeable composite nanofiber membrane with excellent ultraviolet (UV) resistant function was finally prepared. In this study, the effects of different PU/PSF mass ratio on the waterproof, moisture permeability and thermodynamic properties of nanofiber membrane were discussed. According to the static water contact angle, air permeability and moisture permeability, the effects of ZnO and HDTMS on the waterproof properties of composite nanofiber membrane were analyzed. The results have revealed that when the mass ratio of PU to PSF was 7:3, PU/PSF composite membrane has the best fiber morphology, thermal stability and waterproof and moisture permeability properties. After the surface of the composite film was successfully loaded with ZnO-NPs and treated with 2 wt% HDTMS, its contact angle reached 149°, the moisture permeability was 9.6 kg/m 2 /d and UPF value up to 1117.67 which shows excellent UV resistance.

Pre-applied mechanical bonded waterproofing membranes: Macroscopic nonwoven behavior during the concreting process

Pre-applied bonded waterproofing membranes are used as positive-side waterproofing membranes on concrete basements. They are installed prior to concrete works and form a bond with the fresh concrete, inter alia, by the use of nonwovens. However, it is not yet known how the nonwovens behave during the concreting process, which is preventing any optimization. This is why this article aims to understand the macroscopic changes of nonwovens during concreting and identifies beneficial nonwoven properties for a waterproof bond. Seven nonwoven bonded pre-applied membranes are installed using fresh concrete and varying installation parameters and are afterward investigated using microsections, hydrostatic tests and micro-CT scans. During the installation process, the nonwovens are first compressed due to the fresh concrete load and behave like exposed to a mechanical load. Then, as vibration compaction begins, cement paste separates from the fresh concrete in a filtration process and fills the nonwoven. The fresh concrete pressure is then transferred via the cement paste so that the nonwovens can decompress due to the residual stress of the fibers. The final nonwoven thickness depends on compaction equipment, compaction time, and orientation of the nonwoven in the concrete. With the onset of compaction, the porosity within the nonwoven decreases fast so that acceptable lateral water migrations are present after 2–3 s using strong compaction equipment. The void volume of the nonwoven is decisive for the compaction time needed, so new nonwovens should be designed with low void volumes concerning a waterproof bond.