Search

• Simultaneously flame retarded, high bonding strength and formaldehyde-free adhesive was fabricated. • A stable system of organic–inorganic hybridization was constructed. • The wet shear bond strength of lap plate increased by 53.5%. • Inorganic adhesive greatly reduced total heat release and total smoke production rate of wood-based composites. Developing high performance and non-toxic adhesives to replace the petroleum-based adhesives are highly desirable for wood industry. The use of magnesium oxychloride cement (MOC) inorganic adhesive is beneficial for the protection of human health and conservation of fossil resources. However, the low initial viscosity and poor water resistance have limited their application in plywood fabrication. In this study, polyacrylamide (PAM) and sodium polyacrylate (PAAS) were added to the adhesive as organic agents to construct wood-based composites by the organic–inorganic hybrid strategy. The MOC would be solidified by a cold-pressing method, forming a formaldehyde-free wood adhesive with high bonding performance. The addition of PAM efficiently improved the stability and processability of MOC, while PAAS improved the water resistance of MOC by inducing Mg2+ chelation and transforming the phase 5 structure. This adhesive exhibited a 53.5% increase in wet shear strength in contrast with the unmodified MOC adhesive. In addition, the MOC adhesive bonded wood-based composites showed high flame-retardant properties. [ABSTRACT FROM AUTHOR]

Large span bamboo bundle laminated veneer lumbers (BLVLs) were prepared by combining the prepress densification process and the intermittent hot press process. Their mechanical performances of the intermittent hot joints and adjacent positions were also investigated. Based on this, a new type of BLVL double-beam members was developed and their bending properties including ultimate load, static bending strength and strain distribution were systematically analyzed by comparing with other double beams with different members. The results showed that large span BLVLs could be well prepared by intermittent hot press process and its mechanical properties could meet the requirements of 160-E superior products according to Chinese national standard GB/T 17657-2013. Besides, the values for the cross-section flexural rigidity and bending modulus of BLVL double beams were extremely high. Bamboo-wood composites (BWC) double beams with more ductility coefficient had a great ability of plastic deformation. For these double beams, the cross-section stiffness was the first factor which to be considered and optimized and the change of the strain along thickness direction was linear, which was in line with the hypothesis theory of bending plane of materials. This study was finally beneficial to design, manufacture, and application of bamboo-based structural engineering materials with lightweight, low cost, and excellent mechanical performances by supplying financial data support. [ABSTRACT FROM AUTHOR]

• A stable system of nanoparticles-enhanced organic–inorganic hybrid network was constructed. • Inorganic nanoparticles were uniformly dispersed in the cement system. • The effect of HAPE on crystallization of hydrated products is studied. • The modified MOC possessed integrated water resistance and compressive strength. It is a big challenge to improve both water resistance and mechanical properties for magnesium oxychloride cement (MOC). In this paper, hydroxyapatite (HA)/polyester (PEs) was introduced to improve both properties of MOC. The HA was evenly dispersed and had a good interfacial compatibility with the polyester, forming a stable nanoparticle reinforced organic–inorganic hybrid network (HAPEs). By introducing the organic–inorganic hybrid structure into MOC, the adverse effects caused by the uneven dispersion of nanoparticles can be avoided. The softening coefficient of the obtained MOC-HAPEs1.2% was 0.98, increasing by 206% compared to unmodified MOC. The enhanced water resistance was associated with the molecular network structure and abundant cross-linking points of the HAPEs. In the meantime, the mechanical properties of MOC were slightly improved. Moreover, the setting time of MOC was prolonged, which was conducive to the operability of its construction. [ABSTRACT FROM AUTHOR]

• A stable system of nanoparticles-enhanced organic–inorganic hybrid network was constructed. • Inorganic nanoparticles were uniformly dispersed in the cement system. • The effect of HAPE on crystallization of hydrated products is studied. • The modified MOC possessed integrated water resistance and compressive strength. It is a big challenge to improve both water resistance and mechanical properties for magnesium oxychloride cement (MOC). In this paper, hydroxyapatite (HA)/polyester (PEs) was introduced to improve both properties of MOC. The HA was evenly dispersed and had a good interfacial compatibility with the polyester, forming a stable nanoparticle reinforced organic–inorganic hybrid network (HAPEs). By introducing the organic–inorganic hybrid structure into MOC, the adverse effects caused by the uneven dispersion of nanoparticles can be avoided. The softening coefficient of the obtained MOC-HAPEs1.2% was 0.98, increasing by 206% compared to unmodified MOC. The enhanced water resistance was associated with the molecular network structure and abundant cross-linking points of the HAPEs. In the meantime, the mechanical properties of MOC were slightly improved. Moreover, the setting time of MOC was prolonged, which was conducive to the operability of its construction. [ABSTRACT FROM AUTHOR]

[Display omitted] • D-gluconic acid sodium salt delayed the curing rate of MOC. • Compressive strength of MOC was increased by gel-like structure filling in pores. • After water immersion, the gel-like structure hinders the penetration of moisture. • The water-resistance of MOC composites was significantly improved. • The composite improves the feasibility of utilizing MOC in summer. Magnesium oxychloride cement (MOC) has the advantages of low-carbon emission, reducing the magnesium chloride waste, and lack of humid curing. However, the MOC has not been widely utilized yet due to the poor water resistance and the short setting time at high ambient temperatures. Herein, a simple and low-cost approach was developed through incorporating D-gluconic acid sodium salt into the MOC. After adding 1.4 wt% D-gluconic acid sodium salt, the initial and final setting time were extended to 257 min and 421 min, respectively, compared to that of unmodified MOC (92 min and 192 min). Based on the X-ray photoelectron spectroscopy (XPS) analysis, the rod-like phase 5 (5 Mg(OH) 2 ·MgCl 2 ·8H 2 O) in the MOC was converted into the gel-like phase 5 through the chelation between D-gluconic acid sodium salt and phase 5. The gel-like structures were evidently observed in the MOC pores (especially after immersing in water), and they efficiently hinder the moisture penetrating into internal structure of the MOC. Subsequently, the softening coefficient was enhanced from 0.38 to 0.91 when the D-gluconic acid sodium salt content was increased from 0% to 1.4%. In comparison to the unmodified MOC, 0.6 wt% of D-gluconic acid sodium salt could enhance the compressive strength by 24.6% after curing for 7 days. When the D-gluconic acid sodium salt content increased to over 0.6%, the compressive strength decreased. Meanwhile, the analysis of phase components proved that the phase 5 content of the modified MOC specimens remained unchanged or even increased after immersing into the water, establishing protection of the gel-like structure on the phase 5. [ABSTRACT FROM AUTHOR]