Performance of alkaline activation for the consolidation of earthen architecture

Preparation and improving mechanism of PBAT/PPC-based micro-layer biodegradable mulch film with excellent water resistance and mechanical properties

A porous GO/PI coating prepared via breath figure method: Low dielectric constant with improved mechanical and water resistance properties

Outdoor bamboo-fiber-reinforced composite: Influence of resin content on water resistance and mechanical properties

Traditional waterborne polyurethane (WPU) has poor water resistance because of the incorporation of permanent hydrophilic groups, such as carboxyl group or ammonium salt, into polymer chains. Therefore, developing WPU with excellent water resistance and mechanical properties is highly desirable for industrial applications. In this study, CO2-triggered hydrophobic/hydrophilic switchable waterborne polyurethane–acrylate (WPUA) containing methyl methacrylate (MMA) units were designed and synthesized. The molecular structure, hydrophobic/hydrophilic switchable behavior, water resistance, and mechanical properties were systematically investigated and characterized. The WPUA with 10 wt% MMA exhibited a low water uptake (2.15 wt%) and linear swelling ratio (0.17 L%), as well as a high tensile strength (16.7 MPa) and modulus (85.9 MPa), which were much higher than those of the pristine WPU. This study indicated that the CO2-triggered WPUA dispersed stably as latex particles in water and possessed excellent water resistance and mechanical properties after the film formation.

Improving water resistance and mechanical properties of waterborne acrylic resin modified by 3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl ether

Effects of wheat gluten protein on the properties of starch based sustainable wood polymer nanocomposites

Waterborne polyurethane (WPU) often suffers from poor water resistance and mechanical properties due to hydrophilic emulsifiers. To address these issues, this study introduces glycidyl carbamate (GC) as a crosslinker to improve WPU performance. Three types of GC were synthesized using aliphatic, cycloaliphatic, and aromatic isocyanates, respectively. The crosslinked network was established through a reaction between the epoxide group of GC and the carboxylic acid and amine groups of WPU. Among these, the WPU film utilizing aromatic isocyanate-based GC exhibited the highest crosslink density, modulus, hardness, and water resistance, due to the rigidity of the aromatic molecular structure. However, the film displayed excessive brittleness, resulting in reduced tensile strength, along with yellowing typically associated with aromatic compounds. The WPU crosslinked with cycloaliphatic GC demonstrated the next best mechanical properties and water resistance, with a 2.7-fold increase in tensile strength, a 1.5-fold increase in hardness, and a 66% reduction in the water swelling ratio compared to neat WPU. This study presents a novel and effective strategy to enhance the water resistance and mechanical properties of WPU films, making them suitable for advanced coating applications.

An important principle in rational manufacturing design is matching the properties of composites to their intended uses. Herein, six laminated composites (LCs) were manufactured using fibrous moso bamboo and poplar veneer units, and their pore structure, water resistance, and mechanical properties were evaluated. The LC density (640-1290 kg/m3) increased significantly with increasing bamboo veneer unit content. The LC surface texture and roughness depended on the density and type of surface layer. With increasing LC density, the water absorption rate (WAR), width swelling rate (WSR), and thickness swelling rate (TSR) decreased exponentially and the mechanical properties increased linearly. This behavior was closely related to the changes in pore structure caused by density. Notably, the water resistance and mechanical properties of the LCs with densities higher than 910 kg/m3 were superior to the highest levels specified in GB/T 20241-2006 for ''laminated veneer lumber'' and GB/T 30364-2013 for "bamboo scrimber flooring". Thus, these engineered materials are promising for outdoor structures and flooring.

Advances in transglutaminase cross-linked protein-based food packaging films; a review

Study on properties of untreated FGD gypsum-based high-strength building materials

Waterborne polyurethane (WPU) is an environmentally friendly product that can replace organic solvents with water. Still, its linear molecular chain structure and the presence of hydrophilic groups greatly affect water resistance and mechanical properties, limiting its wide application in the field of coatings. Herein, a series of fluorosilicone modified waterborne polyurethanes (FSiWPUs) were prepared by introducing tridecafluoro‐nonanol (TFN) and (3‐aminopropyl) triethoxysilane (APTES) into the ends of molecular chains of WPUs. These chains were constituted by different soft segments, including polybutylene adipate glycol, polycarbonate diol, or polytetramethylene ether glycol. Then fluorine element in TFN migrates and aggregates onto the surface during FSiWPU film‐forming to reduce the surface energy. Meanwhile, the hydrolytic condensation of APTES forms a Si–O–Si micro‐crosslinking structure. As a result, the two capping agents enable the modified FSiWPU to have better hydrophobicity, water resistance, and mechanical properties. The research results show that when the TFN:APTES molar ratio of capping agents introduced is 8:2, the static water contact angles of FSiWPUs with different soft sections reach 161.4°–165.3° and the maximum water absorption rate reduce to 8.9%–13.78%. Due to the simultaneous improvement of hydrophobic, water resistance, and mechanical properties, the modified FSiWPUs become the most promising candidates for superhydrophobic coatings.

Jose Tall Wheatgrass (JTW), Agropyron elongatum, is a salt resistant cropcurrently produced in California to help manage saline subsurface drainage water. There is aneed to find high value uses for such material. The objective of this study was tocharacterize the mechanical properties and water resistance of medium densityparticleboard made from saline JTW. A two- factor factorial experiment design was used todetermine the effects of NaOH treatment and type of adhesives, including polymericmethane diphenyl diisocyanate (PMDI) and Urea formaldehyde (UF) resin, on mechanicalproperties and water resistance of finished particleboards. To study the binding capability ofthe particles, NaOH treatment was used to wash the particles for removing the wax andinorganic silica on the surface of JTW. This study also characterized the effects of differentparticleboard densities (0.71, 0.72, 0.73, 0.74, and 0.75 g/cm3) and initial moisture contents(MC) of the particles (2%, 4%, 6%, 8%, and 10%) on mechanical properties and waterresistance of particleboards. Water resistance and mechanical properties of finishedparticleboard were measured. The water resistance properties included water absorption and thickness swell and mechanical properties included modulus of rupture (MOR), modulusof elasticity (MOE), internal bond strength (IB), and tensile strength (TS). The particleboardsmade with PMDI showed superior mechanical strength and water resistance compared withthose made with UF regardless of the use of NaOH treatment. The NaOH treatmentdeteriorated the mechanical strength and water resistance capability of the particleboards,but did not affect the contact angles between the adhesives and JTW. When the density ofthe particleboards increased, both mechanical strength and the water resistance wereimproved. Among the five MC tested, from the particles of 8% initial MC resulted in the bestmechanical properties and water resistance of the particleboard.

The goal of this study was two-fold. The first was to determine the comparative properties of dry-formed hardboard made from renewable biomass (wheat and soybean straws) and from conventional soft wood fiber. The second was to compare the adhesion properties of a soybean-based adhesive with a conventional urea-formaldehyde resin. The hardboard properties evaluated were thickness swell, modulus of rupture, modulus of elasticity, and internal bond strength. The soybean-based adhesive resulted in significantly better mechanical properties and better water resistance than the urea-formaldehyde resin. Wheat straw and soybean straw were comparable in their mechanical and water resistance properties for hardboard production. However, hardboard made from wheat straw fiber and soy straw fiber had comparable mechanical properties but inferior water resistance to hardboard made from wood fiber. Wheat straw fiber and soy straw fiber can be used as co-fibers without treatment to be competitive with pure wood fiber for both mechanical and water resistance properties. A 50%/50% agrifiber/wood fiber composition provided comparable mechanical and water resistance properties to pure wood fiber for hardboard production. The thickness swell of hardboard increased with increasing agrifiber composition. Fiber, rather than adhesive, was the major contributor to thickness swell. Wheat straw fiber and soy straw fiber should be physically or chemically treated to increase their water resistance.

In order to improve the comprehensive performance of cross‐linked carboxymethyl starch (CCMS)/polyvinyl alcohol (PVA) composite films, expand its application in the field of daily packaging. The CCMS/PVA blend films were prepared by solution casting method. The effect of environmentally friendly non‐toxic additives citric acid, urea, CaCl2, and nano‐SiO2 on the microscopic surface morphology, crystallization properties, thermal properties, mechanical properties, water resistance and optical properties of the CCMS/PVA composite films were investigated. The biocomposite films were characterized by SEM, FT‐IR, XRD, TGA, tensile testing, water absorption test, water vapor transmission test, and UV–visible spectrophotometer. The result indicates that the compound addition of citric acid and urea greatly increase the elongation at break of the composite films from 9.2% to 225.7%. With the composite addition of citric acid and nano‐SiO2, the composite film has the best water resistance and water vapor barrier properties. The composite films added with citric acid, urea and nano‐SiO2 can obtain the best thermal stability. Among these four additives, CaCl2 has the largest negative effect on the elongation at break and urea has the largest negative effect on water resistance properties of the CCMS/PVA composites. The CCMS/PVA composite films prepared by adding 30% citric acid and 6% nano‐SiO2 has the best comprehensive performance. The tensile strength, elongation at break, solubility, thermal decomposition temperature, water vapor permeability and light transmittance of the CCMS/PVA/CA/S composite films are 3.3 MPa, 168%, 34.6%, 293.2°C, 1.54 × 10−11 g s−1 m−1 Pa−1 and 22.47%, respectively. The biocomposite film has the potential to be applied in the field of packaging, and provides a reference for further research.

The functional properties of biopolymer-based film packaging materials are susceptible to external storage conditions. The effects of different storage temperature, relative humidity (RH) and duration on the apparent form, barrier properties, mechanical properties and microstructure of corn–wheat starch/zein bilayer films were studied. From 0 to 150 days, storage temperature and RH, but not storage time, affected the appearance and colour of the bilayer films. The increase in haze of the bilayer films stored at 25°C was much greater than that at low temperatures. With increased storage time, the moisture content first increased and then decreased, while the water resistance and oxygen barrier properties of the bilayer films worsened. After 150 days, the bilayer film stored at 25°C with 54% RH had better water resistance properties. The oxygen barrier properties of the bilayer film stored at 25°C with 43% RH were preferable to those of other groups because the peroxide value of vegetable oil packed in the former bilayer film was the lowest. The tensile strength of bilayer films stored at 25°C with RH of 43, 54 and 65% decreased, but was still better than those stored at low temperatures (−17°C, 4°C), which were tough due to their high elongation at break. Scanning electron microscopy results showed tight bonds between the bilayer films, and the network structure inside the films disappeared and reappeared during storage. The cross-sectional compactness changed, and there was no film separation after 150 days.