Layered double hydroxides (LDHs) are emerging as a new and green high‐efficient flame retardant. But LDHs aggregate seriously because of their hydrophilicity, which affect deeply the mechanical and flame retardant properties of their composites. For the first time in this paper, microencapsulated LDHs (MCLDHs) with melamine‐formaldehyde (MF) resin were prepared by microencapsulation technology to enhance their compatibility and dispersion within epoxy resin (EP). The mechanical and flame retardant performances of EP/MCLDH composite were studied by comparing with EP/LDH composite. Results showed that the water contact angle of MCLDHs increased from 8.9° to 122.1°, which indicated good compatibility. The particle size of MCLDHs decreased sharply, and more than one‐third were up to submicron scale, which can be conducive to dispersion. Moreover, the tensile strength and elongation at break of EP/MCLDHs with different flame retardant contents were higher than those of EP/LDHs. And the addition of MCLDHs increased the glass transition temperature (Tg) of EP/MCLDHs, which meant a strong interfacial interaction. Besides, compared with EP/LDHs, the limiting oxygen index values of EP/MCLDHs were higher, and its peak of heat release rate and total heat release decreased by 16.3% and 5.5% respectively. EP/MCLDHs achieved from V‐1 to V‐0 rate with the increasing content of MCLDHs from 20% to 30%, while LDHs/EP never passed tests. In the process of heating, H2O, CO2, and NH3 released from MCLDHs formed gaseous phase, and the remaining dense char layers and oxides produced condensed phase, which played an important role in inhibiting combustion.
Phenol formaldehyde (PF) resin is a well-tried adhesive for manufacturing laminated veneer lumber (LVL). PF has a high bonding strength, good cold pressing property and contributes a lot to the high production efficiency of LVL. In the present paper, PFs were synthesized at three different alkaline condition levels with a molar formaldehyde to phenol (F/P) ratio of 2.25. The bonding strength of PFs was not influenced by the alkalinity. Compared with PFs synthesized under alkalinity of 1 and 4%, PF with 8% alkalinity formed a resin with a high mole mass (MM), uniform mole mass distribution (MMD) and a high cross-linking density. With PF8%, the cold pressing property could be shortened from 30 to 12 min in the winter time. Cured PF8%had a higher cross-linking density than PF1%and PF4%. PF8%has a high potential for industrial production of LVL.
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