Waterproof Properties Research Articles

Waterproof and breathable polyacrylonitrile/(polyurethane/fluorinated-silica) composite nanofiber membrane via side-by-side electrospinning

Abstract

Hot-melt Adhesive Bonding of Polyurethane/Fluorinated Polyurethane/Alkylsilane-Functionalized Graphene Nanofibrous Fabrics with Enhanced Waterproofness, Breathability, and Mechanical Properties.

Waterproof-breathable (WB) materials with outstanding waterproofness, breathability, and mechanical performance are critical in diverse consumer applications. Electrospun nanofibrous membranes with thin fiber diameters, small pore sizes, and high porosity have attracted significant attention in the WB fabric field. Hot-press treatment technology can induce the formation of inter-fiber fusion structures and hence improve the waterproofness and mechanical performance. By combining electrospinning and hot-press treatment technology, polyurethane/fluorinated polyurethane/thermoplastic polyurethane/alkylsilane-functionalized graphene (PU/FPU/TPU/FG) nanofiber WB fabric was fabricated. Subsequently, the morphologies, porous structure, hydrostatic pressure, water vapor transmission rate (WVTR), and stress–strain behavior of the nanofiber WB fabric were systematically investigated. The introduction of the hydrophobic FG sheet structure and the formation of the inter-fiber fusion structure greatly improved not only the waterproofness but also the mechanical performance of the nanofiber WB fabric. The optimized PU/FPU/TPU-50/FG-1.5 WB fabric exhibited an excellent comprehensive performance: a high hydrostatic pressure of 80.4 kPa, a modest WVTR of 7.6 kg m−2 d−1, and a robust tensile stress of 127.59 MPa, which could be used to achieve various applications. This work not only highlights the preparation of materials, but also provides a high-performance nanofiber WB fabric with huge potential application prospects in various fields.

Flexible and Ultrathin Waterproof Cellular Membranes Based on High-Conjunction Metal-Wrapped Polymer Nanofibers for Electromagnetic Interference Shielding.

Ultrathin, lightweight, and flexible electromagnetic interference (EMI) shielding materials are urgently demanded to address EM radiation pollution. Efficient design to utilize the shields' microstructures is crucial yet remains highly challenging for maximum EMI shielding effectiveness (SE) while minimizing material consumption. Herein, novel cellular membranes are designed based on a facile polydopamine-assisted metal (copper or silver) deposition on electrospun polymer nanofibers. The membranes can efficiently exploit the high-conjunction cellular structures of metal and polymer nanofibers, and their interactions for excellent electrical conductivity, mechanical flexibility, and ultrahigh EMI shielding performance. EMI SE reaches more than 53 dB in an ultra-broadband frequency range at a membrane thickness of merely 2.5 µm and a density of 1.6 g cm-3 , and an SE of 44.7 dB is accomplished at the lowest thickness of 1.2 µm. The normalized specific SE is up to 232 860 dB cm2 g-1 , significantly surpassing that of other shielding materials ever reported. More, integrated functionalities are discovered in the membrane, such as antibacterial, waterproof properties, excellent air permeability, high resistance to mechanical deformations and low-voltage uniform heating performance, offering strong potential for applications in aerospace and portable and wearable smart electronics.

Laboratory evaluation of long-term sealing behaviors of two water-swelling materials for shield tunnel gasket

This paper investigates the waterproofing properties of two water swelling gasket materials, i.e. water-swelling rubber (WSR) and water-swelling polyurethane (WSP). Swelling tests were performed to measure the swelling ratios in both compression and free swelling states. A dynamic mechanical analyzer (DMA) was employed to measure the storage moduli under different compression pressures and in different saline environments. Scanning electron microscope (SEM) was performed to investigate the micro-damage morphology for both WSR and WSP. According to the test results, under the compression load of 1.0 MPa, the maximum axial swelling ratio (Sa) and free swelling ratio (Sw) of WSP was nearly four times and twice that of WSR, and the storage modulus E’ of WSP was three times that of WSR. Also, the micro-cracks of WSP were much less and shallow than those of WSR under the same load condition and saline environments. Thus, the WSP specimen showed better water-proof performance than the WSR specimen under the complex submarine condition.

Waterproof, Highly Tough, and Fast Self-Healing Polyurethane for Durable Electronic Skin

A stretchable electronic skin (e-skin) requires a durable elastomeric matrix to serve in various conditions. Therefore, excellent and balanced properties such as elasticity, water proof capability, toughness, and self-healing are demanded. However, it is very difficult and often contradictory to optimize them at one time. Here, a polyurethane (BS-PU-3) containing a polydisperse hard segment, hydrophobic soft segment, and a dynamic disulfide bond was prepared by one-pot synthesis. Unlike the normal two-pot reaction, BS-PU-3 obtained through the one-pot method owned a higher density of self-healing points along the main chain and a faster self-healing speed, which reached 1.11 μm/min in a cut-through sample and recovered more than 93% of virgin mechanical properties in 6 h at room temperature. Moreover, a remarkable toughness of 27.5 MJ/m3 assures its durability as an e-skin matrix. Even with a 1 mm notch (half of the total width) on a standard dumbbell specimen, it could still bear the tensile strain up to 324% without any crack propagation. With polybutadiene as the soft segment, the shape, microstructure, and conductivity in BS-PU-3 and BS-PU-3-based stretchable electronics kept very stable after soaking in water for 3 days, proving the super waterproof property. An e-skin demo was constructed, and self-healing in pressure sensitivity, mechanical, and electrical properties were verified.

Fabrication of superhydrophobicity on foamed concrete surface by GO/silane coating

Foamed concrete is a lightweight building material, but its high water absorption is one of its main disadvantages. The objective of this study was to fabricate, characterize and evaluate a GO/silane superhydrophobic coatings on foamed concrete surface. The results showed that the water contact angle of the foamed concrete was 165.5° and water can roll off from the surface easily. Superhydrophobic modification improves waterproof properties of the foamed concrete obviously, the water sorptivity was reduced about 97.2%. SEM results showed that the superhydrophobic surface was mainly due to the rough structure brought by GO and the low surface energy brought by silane.

Effect of calcium sulphoaluminate cement on mechanical strength and waterproof properties of beta-hemihydrate phosphogypsum

Beta-hemihydrate phosphogypsum (β-HPG) as a cementitious material obtained from the dehydration of phosphogypsum (PG) can be widely used for the preparation of building materials. The main problems for its utilization are its low mechanical strength and poor waterproof properties. In this study, calcium sulphoaluminate cement (SAC) was used to improve the properties of β-HPG. The compressive strength, flexural strength, ratio of compressive to flexural strength, water absorption rate and softening coefficient were measured. The volume stability, pore structure and microstructure were characterized to evaluate the effect of SAC. The results show that SAC can improve the mechanical strength and waterproof properties of β-HPG significantly. With the addition of 20% SAC, the increase of drying shrinkage is relatively small, and the compressive strength and softening coefficient were 21.5 MPa and 0.66, increasing by 60.85% and 96.04% respectively compared to the mixture without SAC. Specifically, ettringite and aluminate hydroxide are formed and interconnected with calcium sulfate dihydrate to improve the waterproof properties of β-HPG under the effect of SAC. The crystal morphology of calcium sulfate dihydrate changes from long rods to short columns, and the pore size and total porosity of the mixture decrease, resulting in the improvement of the mechanical strength of β-HPG. The purpose of this work is to optimize the properties of β-HPG and provide a high performance cementitious material for the effective utilization of PG.

Preparation and characterization of low-cost waterproofing sheets from NR-loaded clay

ABSTRACT The importance of polymers is comprised in their industrial and technological applications. A low-cost waterproofing product with good thermal insulation properties is the aim of this paper. Natural rubber (NR)/clay composite was prepared with different concentrations of clay (20, 40, 60, 80,100, 150 and 200) phr. An experimental investigation was carried out to obtain low-cost construction material with desirable mechanical, thermal and waterproofing properties. The influences of clay loading on mechanical, water absorption, swelling, specific gravity and thermal properties were inspected. It was observed that the incorporation of clay into the NR increases the thermal conductivity, the maximum degree of swelling and swelling index decrease with increasing clay content. The tensile properties of NR composite were found to be increased with the increase of clay content due to the increase of crosslinking density the incorporation of clay into the NR decreases the swelling parameters, Crosslink density calculations from both swelling and mechanical measurements have the same trend and order of magnitude. It exhibited some extent of improvement in tensile, hardness and compression set properties with the addition of clay. NR loaded with 60 phr clay was chosen as the reasonable value of thermal conductivity which lies in the range of thermal insulating material and suitable mechanical properties and other concentrations with the higher thermal conductivity can be used as a waterproofing sheet.

Study on Fatigue Test and Life Prediction of Polyurethane Cement Composite (PUC) under High or Low Temperature Conditions

There are many diseases in the deck pavement of long‐span steel bridges under the action of vehicles, rainwater, and freezing. It is necessary to study a new type of pavement material with high waterproof property, light weight, and high bonding performance for steel deck pavement. Polyurethane cement composite (PUC) can be used for steel deck pavement. In order to find out the temperature effect on fatigue properties of PUC, the four‐point bending fatigue test was carried out at different temperatures. In this paper, the optimum mix ratio of PUC was selected by compressive and flexural tests, and then the bending fatigue test was conducted under strain control mode. Under temperature and external force coupling condition, a method for predicting fatigue life of PUC is proposed by the combination of theoretical deduction and experimental research. The results show that the proposed formula can effectively describe the fatigue life and fatigue limit of PUC. Finally, compared with three different asphalt mixtures for steel deck pavement, it is found that the fatigue performance of polyurethane cement is better than that of asphalt mixture.

Effective Waterproofing of Railway Culvert Pipes

The composition material for waterproofing of the railway infrastructure objects, in particular, culvert pipes is suggested in the article. The waterproof composition contains an acrylic polymer and a filler. The comparison of the composition properties with two kinds of the fillers (silica sand and Portland cement) is carried out. The following properties are defined – water absorption, corrosion stability, stability in an aggressive environment, frost resistance to evaluating the suitability of the proposed composition for waterproofing. These properties are determined for three batches: an acrylic polymer without a filler, an acrylic polymer with silica sand, and an acrylic polymer with Portland cement. The test results show that the composition with silica sand possesses the best waterproofing properties. Wherein the quantity of silica sand is 1.5 mass parts to the quantity of polymer. Compared to the non-filled acrylic polymer the offered composition is characterised less water absorption, more significant corrosion stability and stability in an aggressive environment, better frost resistance. The mix with Portland cement shows a bit worse results at a higher cost of the material in whole.

Water Absorption Properties of Geopolymer Foam after Being Impregnated with Hydrophobic Agents.

Geopolymer foam is classified as a lightweight material with high porous in its matrix which has great offer for applications requiring fire-resistant, thermal, and acoustic properties. However, the high sensitivity to humid environments can be a major barrier of geopolymer foam that limits the variety of applications of this material. Based on this drawback, two types of hydrophobic agent (Lukosil M130 and Lukofob ELX) were used as an impregnator to treat the surface of geopolymer foam samples. This paper presented the results of water absorption properties of the untreated and treated geopolymer foam composites. The obtained properties were flexural strength, compressive strength, density, total water absorption, the rate of water absorption, and water absorption coefficient. The results showed that the samples after being impregnated with hydrophobic agents improved significantly their waterproof property especially using Lukosil M130. Moreover, the samples treated with Lukosil M130 had positive impact on their mechanical strength.

Design and development of energy efficient re-roofing solutions

Although the study of roofing systems (from coverings to structure of the roof) is of great significance to energy efficiency and sustainable development, design and construction of new roofs on top of existing roofs in buildings has not received sufficient attention. This study discusses re-roofing as one of the key options to reduce energy consumption and improve overall building performance. The more conventional choice and more frequently chosen option for building energy retrofit is vertical building envelope components, however, this paper presents the case study of a proposed retrofitting concept for the roof of an existing building. Using a simulation methodology, the research demonstrates how the proposed retrofitting concept improves the energy performance using electricity generated and external conduction gain as evaluation metrics. The proposed novel re-roofing concept consists of thermal insulation, waterproofing and electric energy generation properties. More specifically, the design concept includes a three-layer roofing system consisting of (from exterior toward interior): a PV panel, an EPDM membrane and an insulation layer. The main goal of this study is to develop a concept for an innovative re-roofing solution that demonstrates the feasibility of turning an old building into a watertight and energy producing system.

Thermal transfer and moisture resistances of nano-aerogel-embedded foam concrete

The objective of the present study is to develop a new material through the nano-aerogel application for improving the thermal transfer and moisture resistances of preformed foam concrete. Thus, this pioneering study focused on estimating the feasibility of developing high-performance foam concrete with good thermal transfer resistance and waterproof properties by uniformly embedding a highly adiabatic and hydrophobic aerogel with nanosized pores in the porous structure of foam concrete. Methyltrimethoxysilane (MTMS), a silica-based precursor, and tetraethyl orthosilicate (TEOS) were used to manufacture the nano-aerogel material. The nano aerogels were embedded under negative pressure environments of 5–10 torr within the airtight chamber. The test results show that the nano-aerogel-embedded foam concrete possesses a thermal conductivity of approximately 0.08 W/m·K, which corresponds to be 30–50% of that measured for conventional foam concrete. The waterproof capacity of the nano-aerogel-embedded foam concrete was significantly improved, resulting in a water contact angle of 120.8° and exhibiting 75% lower water absorption at an age of 24 hours when compared with the conventional foam concrete. The integrated reactive group of the nano-aerogel materials was uniformly distributed throughout the foam concrete pores. Thus, our results suggest that nano-aerogel-embedded foam concrete has great potential as a source material for insulation in building structures.

Novel fluorinated compound for imparting sustainable functionalities to cellulose-containing substrates

Herein we present an intensive investigation into the application of a copolymer formed through iodine transfer copolymerization of vinylidene fluoride with 2,3,3,3-tetrafluoro-1-propene. The unique properties of the pre-formed copolymer advocate it for inducing sustainable, multi-functionalized cotton-based textiles. The application of the preformed copolymer is carried out via the treatment of the cotton and cotton/polyester blend fabrics with the copolymer. The improvement of the physico-mechanical properties as well as the encapsulation of the copolymer within the cotton structure alone and in combination with polyester were affected by the absence and presence of epichlorohydrin as a crosslinking agent. A system consisting of the fiber-copolymer-crosslinking agent may result in mechanical entrapping and deposition of the copolymer in the structure of cotton. They work together with encapsulation for sustainable fixation of the copolymer in the overall structure of the fabrics either 100% cotton or cotton/polyester blend fabric (50/50). The augmentation was barely significant in smoothness and elongation at break of fabrics treated with the copolymer along with the crosslinking agent. SEM discovered that the treated fabrics are covered with a deposited film with tiny particles that can penetrate the fabric. EDX analysis confirms the presence of both fluorine and iodine. Also found was a polymer coating based on fluorine and iodine deposition leading to a hydrophobic product. Values of WRA of the treated fabrics place them in easy-care category with marginal losses in tensile strength and with the certainty that the treated fabric acquires waterproof properties.

Waterproof and Antiscour Properties of Asphalt-Based Composite Seals for Airfield Base Layer

A new type of three-layer waterproof structure was developed to reduce the scour problem of concrete slabs by paving an asphalt-based composite seal layer between the cement-stabilized base and the cement concrete pavement. The asphalt-based composite seal layer consists of an upper layer (microsurfacing), a transition layer (microsurfacing), and a bottom layer (synchronous chip seal). A new construction method was proposed to guide the construction of the asphalt-based composite seal layer. The waterproof and antiscouring properties of the asphalt-based composite seal layer were evaluated by a permeability test, a high-resolution industrial computed tomography (CT) scanner, a scouring test, and a direct shear test. The permeability test showed that the three-layer structure possessed good waterproofing properties. The CT scans results showed that the asphalt-based composite seal layer was very dense due to effective compaction during the construction process. The scouring test indicated that the scouring resistance of the asphalt-based composite seal layer was much better than that of the cement-stabilized base. The results showed that the asphalt-based composite seal possessed decent resistance to scour and could effectively protect the base from the threat of scour. The cost analysis results showed that the proposed asphalt-based composite seal layer has a more competitive unit price compared with an asphalt concrete layer.

Study on the improvement of the waterproof and mechanical properties of hemihydrate phosphogypsum-based foam insulation materials

Hemihydrate phosphogypsum was used as a raw material to investigate the effects of different waterproofing agents (three organic agents and slag) and fibers (polypropylene (PP) and polyvinyl alcohol (PVA)) on the waterproofing and mechanical properties of hemihydrate phosphogypsum-based foam insulation materials (HGFMs), and HGFMs with low density, high strength and good water resistance were successfully prepared. The results show that the three organic waterproofing agents have no effect on the waterproofing performance of the HGFMs, but a small amount of slag can effectively improve the waterproofing performance and softening coefficient of the HGFMs. Both the PP and PVA fibers can increase the mechanical properties of the HGFMs, but the PVA fibers improve the mechanical properties more effectively. In addition, short fibers have a better effect on the compressive strength of the samples but a worse effect on the flexural strength of the samples compared with samples containing long fibers.

Stretchable conductive nonwoven fabrics with self-cleaning capability for tunable wearable strain sensor

With the fast growth of wearable intelligent devices, tunable strain sensors with broad strain sensing range and high sensitivity are in urgent demand. Furthermore, the merits of excellent waterproof property, self-cleaning, and anti-corrosion are also imperative for the practical applications of them. Herein, a tunable wearable micro-cracked non-woven fabrics (NWF) strain sensor with broad strain sensing range and high sensitivity was successfully developed based on the electrically conductive cellulose nanocrystal (CNC)/graphene (G) coating with controllable micro-crack density, which was achieved through changing the G loading of the coating layer, and its superhydrophobicity was achieved by simply dip-coating in the hydrophobic fumed silica (Hf-SiO2)/ethanol dispersion. As a result, a broad working range of 98% and GF value up to 2.36 × 104 are simultaneously achieved for the prepared strain sensor (G content is 25 wt%). In addition, it possesses an ultralow detection limit as low as 0.1%, short response time (33 ms) and good sensing stability over 1000 cycles. What's more, the NWF strain sensor presents excellent waterproofness (WCA = 154°), anti-corrosion ability, outstanding self-cleaning and stability. Due to the excellent response performances, the NWF strain sensor can successfully monitor various human activities from subtle deformations (e.g. speech recognition, pulse waves) to vigorous body movements (e.g. finger, elbow joint and wrist movement). Specially, owing to its excellent superhydrophobic characteristic, the strain sensor also exhibits superior self-cleaning capability and good applicability in a humid or underwater harsh outdoor environment.

Preparation of a novel asymmetric wettable chitosan-based sponge and its role in promoting chronic wound healing

Cutaneous chronic wounds are characterized by an impaired wound healing which may lead to infection. To surmount this problem, a novel quaternary ammonium chitosan nanoparticles (TMC NPs)/chitosan (CS)composite sponge with asymmetric wettability surfaces was successfully prepared. The optimum concentrations of TMC NPs and CS were 0.2 mg/mL and 2.0%, respectively. The incorporated TMC NPs could improve the antibacterial activity of the CS sponge. Asymmetric modification enables the CS sponge to have hydrophobic outer surface and hydrophilic inner surface. The hydrophobic surface of the sponge shows waterproof and anti-adhesion contaminant properties, whereas the hydrophilic surface preserves water-absorbing capability and efficiently inhibits the growth of bacteria. More importantly, in vivo chronic wound healing model evaluation reveals that TMC NPs/CS composite sponge promotes the wound healing and accelerates re-epithelialization and angiogenesis. And in vivo anti-infection test shows the TMC NPs/CS composite sponge could effectively prevent wound infection. These findings demonstrate that TMC NPs/CS composite sponge is a promising dressing material for chronic wounds.

Potential use of waste cotton in production of biomass composites

Mechanical and waterproof properties were evaluated for hot-pressed cotton boards produced from different layers (3, 4, and 5) of cotton veneers under the same weight of cotton fibers and melamine-urea-formaldehyde adhesive. The mechanical and waterproof properties of cotton boards exceeded the specifications for particleboard and medium-density fiberboard of the China national standard requirements, and the four-layer cotton boards performed better. Scanning electron microscopy images showed that fibers were intertwined to form a dense network structure after hot-pressing with water, and thicker veneers were not conducive to the penetration of adhesives after cold-pressing. Fourier transform infrared spectra indicated that hydrogen bonding, physical, and mechanical bonding took place in the cotton veneers, and stronger absorption peaks were shown for the chemical functional groups of the five-layer and four-layer cotton boards. X-ray diffraction spectra revealed that the cellulose crystallinity of the cotton boards (3, 4, and 5 layers) increased to 74.5%, 74.4%, and 73.2%, respectively. Thermal gravity/ differential thermal gravity curves showed that the thinner cotton veneers of the cotton boards showed better thermal stability. These results showed promise for the revaluation of this textile waste to produce biomass composites and for its potential use as a raw material in the preparation of biomass composites.

NiCo2S4 nanosheets and polypyrrole anchored porous micro-3D suede villus for flexible and waterproof energy storage

In current work, a polyester suede is initially coated with Ni through a facile electroless deposition method as the conductive scaffold, followed by the growth of conductive and pseudocapacitive NiCo2S4 nanosheets. Besides, to achieve the aim of standardized batch processing of the flexible SCs, sewing and polydimethylsiloxane (PDMS) sealing techniques are employed, and SC devices are successfully assembled and encapsulated. It's worth noting that the resulting SCs demonstrate stable electrochemical performance with a high specific capacitance of 83.59 F/g at a current density of 2 A/g and a high energy density of 22 Wh/Kg at a power density of 750 W/Kg under the working voltage window of 1.5 V, as well as effective waterproof properties.