Water Resistance Performance Research Articles

Manipulating morphology and surface engineering of spinel cobalt oxides to attain high catalytic performance for propane oxidation

The selective synthesis of nanomaterials with different morphologies and crystal facets is of great significance for catalytic properties and practical applications. We report a strategy for controllable fabrication of hierarchical Co3O4 materials with various morphologies (ellipsoidal, flowerlike, book-shaped, spindlelike) and study their catalytic properties in propane oxidation. Co3O4-B (book-shaped) is found to exhibit the highest propane oxidation rate (0.86 × 10-8 mol m−2 s−1) and the highest turnover frequency (TOF = 11.49 × 10−3 s−1) at 220 °C. This confirms that Co3O4-B provides a higher specific surface area, a highly exposed {110} facet, and abundant Co3+ cations, which make it exhibit favorable low-temperature reducibility and oxygen mobility and thus improve its catalytic activity. In situ diffuse reflectance infrared Fourier transform spectroscopic analysis reveals that the intermediates, such as carboxylate and carbonate species, are involved in propane oxidation. Furthermore, Co3O4-B shows high water-resistance performance, and no significant deactivation is observed after long-term stability and reusability tests.

Using a magnesia binder to improve the airproof performance of molded composites

Introduction. Water resistance is one of durability criteria of building materials. As a rule, the value of the liquefaction ratio is applied to assess the water resistance. However, even water resistant materials are not always able to withstand cyclical weather impacts that cause linear deformations, reduced strength and cause destruction of building products. Therefore, it is necessary to take into account the resistance of building materials, namely, their resistance to alternating humidification and drying (airproof performance). The purpose of this research is to study the producibility of molded composites containing a modified magnesium binder that features higher resistance to weather impacts.
 Materials and methods. The magnesium binder was modified by the silica fume and high pressure molding to increase the water resistance and airproof performance of the composites. The influence produced by the modifier on the change in the compressive strength of dried and water-saturated molded composites, liquefaction and airproof performance ratios, as well as linear deformations of the reference specimens were studied following a pre-set number of cycles of alternating wetting and drying.
 Results. The water resistance and airproof performance of construction products, containing magnesia binders, may be improved by the micro-silica, added to pressed mixtures, and their compaction by press molding. Compositions of molded composites, containing a modified magnesia binder, were developed for the manufacture of products used to make enclosing structures and for the flooring of rooms having the indoor humidity of over 60 %.
 Conclusions. It is established that molded composites containing a modified magnesia binder feature high resistance to alternating wetting and drying. The proposed method of modifying magnesia binders prevents the destruction of molded stone-like materials containing these binders in case of exposure to alternating stresses; it reduces linear deformations and, as a result, decelerates the fatigue failure. The use of a recyclable material as a mineral additive must contribute to the reduction of the cost of products and allow to consider the method of their production as one of the best technologies available.

Tailoring nanofibrillated cellulose through sonication and its potential use in molded pulp packaging

Nanofibrillated cellulose (NFC) was systematically tailored by ultrasonic-assisted esterification with lactic acid at different amplitudes and times, which led to modified NFC (mNFC) with different degrees of substitution (DS), between 0.21 and 0.55, as confirmed by titration, FTIR, and C13 NMR. A partial fragmentation and decrease in crystallinity of mNFC were revealed by TEM and XRD. To form molded pulp sheets, 5 wt% mNFC was added into a bagasse (BG) pulp slurry, then partially dewatered before hot-pressed. mNFC worked effectively as self-retention aid, partly solving the issue of drainage during sheet forming as commonly observed from unmodified NFC. The BG/mNFC (DS 0.55) sheet exhibited an enhancement in tensile properties. Water resistance and barrier performance of the current sheets were also evidently increased. The results suggested that the higher DS on mNFC can improve water resistance and mechanical properties, simultaneously overcoming drainage challenges in processing of molded pulp products.

Experience Study on Long‐Life Microsurfacing with High Water Resistance Performance

Microsurfacing is a standard preventive maintenance technology developed on the basis of slurry sealing technology. However, the high temperature and rainy season in Guangdong Province affect its expanded application because of its low water resistance and short service life. So, high‐performance microsurfacing, a new microsurfacing technology, has been developed. The key to this technique is an appropriate proportion of water‐based epoxy resin and waterborne epoxy curing agent, which could generate a chemical reaction to form a high‐performance bonding network structure of space. And indoor wet‐wheel wear test shows that its antiwear ability and resistance to water damage are evidently increased (to over 50%) compared with the conventional microsurfacing. Furthermore, from the long‐term road performance results, the antisliding and water resistance performance of high‐performance microsurfacing is much higher than the conventional technique.

Influence of Water-Repellent Admixtures on the Water-Resistance of Unstabilized and Stabilized Compressed Earth Blocks

The low durability of water action has been the main issue of earth construction since ancient times. In this way, sustainable solutions are needed to improve the earthen building materials water-resistance performance without significantly changing their appearance and eco-friendly nature. This study aims at characterizing the water-resistance of compressed earth blocks (CEB) produced with or without different types of colorless water-repellent admixtures. To this end, different types of unstabilized and 8% cement stabilized CEB were protected with two post-surface treatments, namely a silane-siloxane based surface water-repellent (SWR) and a natural linseed oil (LO), as well as one olein based integral water-repellent (IWR). Unprotected reference CEB were also considered for comparison purposes. More sustainable CEB were produced with 20% replacement of earth by recycling waste building materials. The CEB were tested in terms of compressive and flexural strength, capillary water absorption, immersion absorption, water permeability, low-pressure water absorption, and water erosion resistance from drip and spray tests. The influence of the moisture content on the compressive strength was also analysed. The cement-stabilization and water-repellent treatments were able to overcome the non-water-resistant nature of unstabilized CEB. In general, the best performance was attained with SWR, followed by IWR. The LO was less effective in reducing the long-term absorption but was able to protect unstabilized CEB from light rainfall simulated conditions. Under severe water erosion, the surface treatments were less effective, but water penetration was reduced up to near 40%. The mechanical strength, total porosity, water permeability and immersion absorption were not significantly affected by water-repellent products. Moreover, the mechanical strength reduction of stabilized CEB after saturation was about 30%, regardless of the water-repellent treatment. The main contribution of water-repellent admixtures occurred in all properties involving capillary absorption.

Analysis of effectiveness of wooden floor finishes in some residential buildings in Lagos, Nigeria

PurposeWood is one of the materials that is used for building construction either as structural member or as finishes from ages past to contemporary generation. It is composed of elongated, hollow spindle shaped cells that are arranged parallel to each other along the trunk of a tree. The resistance to water, chemicals, strength properties, appearance and decay rate is dictated by the fibrous cells. The purpose of this paper was to examine the application and use of wooden floor finish (an extract from wood) in residential buildings in Lagos, Nigeria, with a view to determine its effectiveness.Design/methodology/approachThe study adopted a dual stage survey approach before the administration of questionnaire on 100 respondents that were selected through purposive sampling after the initial inquiry on the use of the material from 384 randomly selected samples from the entire population.FindingsThe study shows that the material is applied in all interior spaces except bathrooms and toilets. Minimal adoption is also seen in the kitchen area. Users indicate that wooden floor finish requires little maintenance, has low impact on users' health, considered safe-minimal occurrence of home accidents is recorded, has moderate thermal insulation and affordable.Practical implicationsThe usage has impact on the environment due to continuous lumbering activities and lack of adequate plan for reforestation. This suggests that its sustainability depends on afforestation programmes. Its poor performance in sound insulation, water and fire resistance requires further attention. The maintenance is relatively easy and affordable.Originality/valueThe author made a new foray into investigating the performance of wooden floor finish due to its resurgence in the area bearing in mind the unseasoned condition of wood in circulation in the area. Previous adoptions were done by a less aggressive generation of well-trained artisans. Best places for its usage within the interior spaces are identified.

Ultra-stable Eu3+-doped CsPbCl2Br1 perovskite quantum dots glass for optical temperature sensing

In this work, Eu3+-doped CsPbCl2Br1 in borosilicate glass was successfully synthesized by the melt quenching annealing technique and crystallization method. This work reports a novel Eu3+-doped CsPbCl2Br1 perovskite quantum dots (QDs) glass with high sensitivity for optical temperature sensing. The relation of fluorescence intensity ratio (FIR) with the temperature was studied in the temperature range of 80–440 K. Notably, the maximum absolute temperature sensitivity (Sa) and relative temperature sensitivity (Sr) of Eu3+-doped CsPbCl2Br1 perovskite QDs glass can reach as high as 0.0315 K–1 and 3.097%/K, respectively. Meanwhile, Eu3+-doped CsPbCl2Br1 QDs glass demonstrates good water resistance, excellent thermal and cold cycling stability performance. The Eu3+-doped QDs glass materials can bring inspiration to the future exploration of rare earth ion-doped QDs glass material on the application of optical temperature sensing in the future.

Structure and properties of edible packaging film prepared by soy protein isolate-eggshell membrane conjugates loaded with Eugenol

Abstract In this study, we reported a facile and economical strategy for producing a functional protein-based composite film that was based on soybean protein isolate (SPI), eggshell membrane (ESM) and eugenol (Eu). The composite films were also characterized by mechanical, water vapor permeability (WVP), UV barrier, water resistance, hydrophobicity, antioxidant and antimicrobial activity. The results suggested the appropriate content of ESM could significantly enhance the mechanical, barrier, water resistance and hydrophobicity performances of the film. The addition of Eu into the SPI/ESM film could improve not only these properties, but also antimicrobial and antioxidant properties. The intermolecular interaction between SPI, ESM and Eu was mainly hydrogen bond confirmed by the Fourier-transform infrared spectroscopy (FTIR). The scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated a good compatibility existed between SPI and ESM, and the Eu could be well emulsified and dispersed into the SPI/ESM film matrices network. Such edible films carried potentially developed in active packaging applications.

Design of Highly Adhesive and Water-Resistant UV/Heat Dual-Curable Epoxy-Acrylate Composite for Narrow Bezel Display Based on Reactive Organic-Inorganic Hybrid Nanoparticles.

To attain the narrow bezel characteristic of information displays, functional sealing composite materials should possess high adhesion strength and water barrier performance due to their narrow line widths. In this study, highly adhesive UV/heat dual-curable epoxy–acrylate composites with outstanding water-resistant performance have been proposed using photoreactive organic–inorganic hybrid nanoparticles that can react with an acrylate resin, creating a crosslinked nanoparticle network within the sealing composite. The hybrid nanoparticles consisted of reactive methacrylate groups as a shell and an inorganic core of silica or aluminum oxide, and were facilely synthesized through sol–gel reaction and chemisorption process. The curing characteristics, adhesive strength, and moisture permeability of the proposed sealing composite have been compared to those of a conventional epoxy–acrylate composite containing inorganic silica particles. The composites including hybrid nanoparticles exhibited high UV and heat curing ratios owing to the numerous methacrylate groups on the nanoparticle surface and high compatibility with organic resins. Moreover, the proposed sealing composite showed high adhesion strength and extremely low water permeability due to the creation of densely photocrosslinked network with matrix resins. In addition, the sealing composite exhibited excellent narrow dispensing width as well as relatively low viscosity, suggesting the potential application in narrow bezel display.

Enhancing the mechanical and water resistance performances of bamboo particle reinforced polypropylene composite through cell separation

Abstract It is frequently observed that bamboo particle composites (BPCs) do not show higher mechanical performances than the corresponding wood particles composites (WPCs), although bulk bamboo is much stronger than wood in mechanical performances. Herein this phenomenon was demonstrated from the cell compositions in the applied bamboo particles. To address that, a simple method to physically separate bamboo fibers (BFs) and bamboo parenchyma cells (BPs) from a bamboo particle mixture was developed. Polypropylene (PP) composites with pure BFs, BPs, a mixture of BFs and BPs (BFs + BPs), wood particles (WPs) as fillers were prepared. The flexural and dynamic mechanical properties, water absorption, and thermal properties were determined. The BF/PP composites showed the best mechanical performances (MOR at 35 MPa, MOE at 2.4 GPa), followed by WP/PP, (BF + BP)/PP, and BP/PP. They also exhibited the lowest water absorption and thickness swelling. Little difference was found for the thermal decomposition properties. However, a lower activation energy of BF/PP compared with BP/PP implied an uneven dispersion of BFs and weaker interfacial interaction between BF and PP. The results suggest that the mechanical performances and water resistance of bamboo particle/polymer composites can be significantly improved through cell separation. However, interface modification should be applied if higher performances of BF/PP composites are required.

High moisture resistance of an efficient Mn4+-activated red phosphor Cs2NbOF5:Mn4+ for WLEDs

Mn4+-activated fluoride red phosphors, the most important red phosphors for warm white light emitting diodes (LEDs), usually suffer from inherent poor moisture resistance which is a major obstacle to their long-lasting outdoor applications in a high humidity environment. Surface modification of phosphors by coating with either organic or inorganic shells is an effective way to improve waterproof stability. However, the coating procedure usually has a negative impact on the luminous efficacy due to the increased passivation shell thickness. In this work, Mn4+-activated oxyfluoroniobate (Cs2NbOF5), a highly efficient phosphor with internal quantum efficiency of ca. 82%, has been successfully synthesized and it is interesting to note that Cs2NbOF5:Mn4+ can exhibit remarkably improved waterproof stability even without surface coating compared to well-accepted commercial fluoride red-emitting phosphor, K2SiF6:Mn4+. The results obtained indicate that Nb5+ ions inside red phosphor play a crucial role in improving the water-resistant performance of Mn4+, which provides a new concept for overcoming the downside of their waterproof in humid conditions and maintaining the luminescence efficiency. In the final phase white LEDs with a high luminous efficacy of 174 lm/W (higher than commercial fluoride red phosphors), low correlated color temperature (3164 K) and high color rendering index (Ra = 90 and R9 = 85) have been fabricated using Cs2NbOF5:Mn4+.

Fluorescence enhancement and encapsulation of quantum dots via a novel crosslinked vinyl-ether liquid crystals/polymer composite film

Fluorescence efficiency and stability of quantum dots (QDs) film, which are both key for optoelectronic device, are relatively difficult to be improved simultaneously. Herein, the facile synthesis of vinyl-ether terminated liquid crystals was reported. Based on the host vinyl-ether liquid crystals, the polymer dispersed vinyl-ether liquid crystals (PDVLC), polymer dispersed crosslinked vinyl-ether liquid crystals (PDCVLC) and fluorine-containing polymer dispersed crosslinked vinyl-ether liquid crystals (F-PDCVLC) QDs films were fabricated in succession by dual-step polymerization. As a result, the PDVLC film can realize fluorescence enhancement and tuning, whereas the PDCVLC film not only maintain fluorescence enhancement of PDVLC film but also improve the water-resistant performance. More importantly, the formation of crosslinked film makes it convenient to fabricate QDs film. Subsequently, the F-PDCVLC film can further improve the water-resistant properties by introducing fluorine-containing monomers to enhance the hydrophobic performance. This free-standing (F-) PDCVLC film may offer a new avenue to realize the optimization of QDs film performance.

Experimental and theoretical studies on formaldehyde catalytic combustion over Cu–Fe spinel-type catalyst

A series of Cu–Fe spinel-type catalysts were synthesized by sol–gel auto-combustion method for the catalytic combustion of HCHO. A combined experimental and theoretical investigation based on in situ FT-IR and density functional theory (DFT) was performed to uncover the reaction process of HCHO catalytic combustion on Cu–Fe spinel-type catalysts. The results show that CuxFe(3-x)O4 catalysts display the typical pattern of spinel structure. The chemical states of Cu and Fe cations on the catalyst surface include Cu+, Cu2+, Fe2+ and Fe3+. Cu0.5Fe2.5O4 exhibits excellent HCHO oxidation efficiency and good water-resistance performance. The superior catalytic performance of Cu0.5Fe2.5O4 catalyst is closely associated with the high crystalline degree of spinel. The flexible valences of metal cations in spinel-type catalysts are beneficial for electron transfer, thus facilitates HCHO adsorption and oxidation. Formate species (HCO2) is the major reaction intermediate during HCHO combustion. The reaction pathway of HCHO catalytic combustion contains eight elementary steps: HCHO adsorption, H2CO2 dehydrogenation, HCO2 dehydrogenation, CO2 desorption, O2 adsorption, OOH formation, H2O formation and desorption. HCO2 dehydrogenation is identified as the rate-determining step because of the highest energy barrier of 254.80 kJ/mol.

Preparation and Properties of Cyanobacteria-Based Carbon Quantum Dots/Polyvinyl Alcohol/ Nanocellulose Composite.

Blue luminescent carbon quantum dots (CQDs) were prepared from cyanobacteria by a hydrothermal method. The PL quantum yields of the obtained CQDs was 5.30%. Cyanobacteria-based carbon quantum dots/polyvinyl alcohol/nanocellulose composite films were prepared, which could emit bright blue under UV light. FTIR characterization showed that the composite films had hydroxyl groups on the surface and no new groups were formed after combining the three materials. The photoluminescence (PL) spectra revealed that the emission of the prepared CQDs was excitation dependent. Studies on the water resistance performance and light barrier properties of the composite films showed that they possessed higher water resistance properties and better UV/infrared light barrier properties. Therefore, we report the cyanobacteria-based carbon quantum dots/polyvinyl alcohol/nanocellulose composite films have the potential to be applied in flexible packaging materials, anti-fake materials, UV/infrared light barrier materials and so on.

Assembly of graphene oxide into the hyperbranched frameworks for the fabrication of flexible protein-based films with enhanced conductivities

Development of strong and tough biopolymer materials with favorable conductive properties is highly desirable and remains a great challenge in current scientific research. In this study, a novel strategy is designed to prepare a conductive plant protein-based films through the integration of functional graphene oxide (GO) into a hyperbranched network. The process was based on the Fe(III) ion-triggered simultaneous polymerization of dopamine and pyrrole. The incorporation of conductive GO nanosheets with the in situ formed polypyrrole nanoparticles could uniquely act as cross-linking sites to make the nanocomposites highly conductive. As a result, strong sacrificial metal-ligand bonds and covalent bonds would be confined within the network. The toughness and strength of the nanocomposite film increased by 428.5% and 324.1%, respectively. In addition, this hybrid film showed significant improvement in electrical and thermal conductivities owing to the contribution of the highly conductive hyperbranched structures in the polymer matrix. Furthermore, this renewable and biodegradable film had superior water resistance and ultraviolet-barrier performance, which are of great importance to the practical applications.

Ferric Ions Modified Polyvinyl Alcohol for Enhanced Molecular Structure and Mechanical Performance.

The highly crystallized molecular structure of polyvinyl alcohol (PVA) makes the polymer with poor performance in mechanical strength and water resistance. To modify the molecular structure of PVA and to diminish the complicated procedures and environmental impacts, ferric ions (in ion composite form) have been used to set the interactions with the molecule chains of PVA. The crystallinity, chemical groups change, and mechanical performance of the polymer has been confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), and the bonding/membrane tensile strength test. The crystallinity of PVA is reduced from 41.6% to 7.7% with the addition of 2.0% of ferric ions. The tensile strength of the modified PVA membrane is increased by 240%. Moreover, with tougher structure and improved fluidity, the strength of ferric ions modified PVA bonded wood samples is increased by 157%. The modification of PVA with ion composite may have vast applications in many fields, such as paper industry, wood adhesives, functional materials, and polymer structure design.

Performance of cellulose acetate propionate in polycaprolactone and starch composites: biodegradation and water resistance properties

Introducing starch into some polymers such as polycaprolactone (PCL) has been used to produce biodegradable plastics. The existance of a derivative of cellulose such as cellulose acetate propionate (CAP) with starch and PCL combinations might affect the degradation rate of starch when only mixed with PCL. To check whether this was the case, different investigations such as enzymatic degradation, composting trial and water resistance performance over a wide range of different compositions of such composites were studied. It is deducible that the use of cellulose acetate propionate can improve the performance of such composites without a big significantly changing their whole biodegradability. It was found that the presence of cellulose acetate propionate improved the water resistance properties which enable such composites to be used in the packaging industry.

Intermetallic compound PtMny-derived Pt−MnOx supported on mesoporous CeO2: Highly efficient catalysts for the combustion of toluene

Intermetallic compounds are a kind of important materials in heterogeneous catalysis. In this work, we first synthesized the PtMny intermetallic nanocrystals using the polyvinyl pyrrolidone-assisted ethylene glycol reduction method, and then loaded them on the surface of mesoporous CeO2 (meso-CeO2) derived from a KIT-6-templating route, generating the mPt−nMnOx/meso-CeO2 (m = 0−0.39 wt%, n = 0−1.21 wt%) catalysts after calcination at 500 °C in air. It is found that the as-obtained catalysts displayed an ordered mesoporous architecture with surface areas of 95−108 m2/g. The 0.37Pt−0.16MnOx/meso-CeO2 sample exhibited the best catalytic performance for toluene combustion (T50 % =162 °C and T90 % =171 °C at space velocity = 40,000 mL/(g h)). Kinetic analysis reveals that the apparent activation energy (57 kJ/mol) obtained over the best-performing 0.37Pt−0.16MnOx/meso-CeO2 sample was lower than those (63−75 kJ/mol) obtained over the other samples. Furthermore, the 0.37Pt−0.16MnOx/meso-CeO2 sample possessed good thermal stability and water-resistant performance. Benzyl alcohol, benzoic acid, and maleic anhydride were proven to be the main intermediates of toluene combustion, hence, toluene combustion might take place through a sequence of toluene → benzyl alcohol and benzoic acid → maleic anhydride → carbon dioxide and water, which might obey the Eley−Rideal reaction mechanism. It is concluded that loading of Pt and MnOx enhanced the adsorbed oxygen and Mn2+ species concentration and low-temperature reducibility, thus promoting toluene combustion over 0.37Pt−0.16MnOx/meso-CeO2.

Characterisation of a multilayer external wall thermal insulation system. Application in a Mediterranean climate

In recent years, the materials applied to buildings' envelopes have been studied in-depth to improve their thermal insulation properties, enabling significant energy savings. This led to the development of new thermal insulation renders with lower thermal conductivities (λ) (λ < 0.040 W m−1 K−1). However, their mechanical and water resistance performance has also decreased. In this context, this research discusses the performance of a multilayer thermal insulation system with a super-insulating thermal render (λ < 0.030 W m−1 K−1), to be applied on the exterior, subjected to a Mediterranean climate. A set of mechanical, physical, and microstructural tests were conducted. Within the scope of this study, it was possible to improve the render's mechanical performance and water resistance, when protective layers were applied in a multilayer system. When its performance is compared with other multilayer products currently in the market, this new solution presents competitive results, which further encourage the tests in real operative conditions.

The Application of Nanostructured Modifier Additives Based on Zeolite-Bearing Tuffs in Asphalt

Often, the quality of contemporary bitumen binders cannot meet the performance requirements for hot mixed asphalt (HMA) concrete intended for severe application conditions. Therefore, the companies involved in the road construction and HMA producers use various chemical admixtures and modifiers to enhance the characteristics of bitumen. These materials are capable to enhance the adhesion between the binder and aggregates, reduce water saturation, as well as increase water and freeze-thaw resistance of HMA. For example, water resistance is considered to be one of the controlling parameters for high-quality asphalt applications. The use of these admixtures has little effect on the rheological characteristics and the temperature range of the binders. As a result, in the regions with hot summers and hot climate zones asphalt pavements are subjected to significant permanent deformations such as rutting. In the regions with cold winters, asphalt pavements can develop a critical fragility resulting in the crack propagation and failure of asphalt pavement. This research reports on the use of nanomodified hybrid additive with zeolite-bearing tuffs used as a mineral filler to control the HMA performance. An effective technology that includes the modification of zeolite-bearing precursor and manufacturing of the hybridized material with nanocarbon was developed. This research demonstrates the effects of carbon nanomaterials on pore structure and surface morphology of the modified hybrid additive. Few methods of the additive incorporation into asphalt mix was proposed. The results of the reported study confirm an improvement of the strength and water resistance performance of asphalt with developed nanohybrid additive.