Preparation and characterization of microencapsulated LDHs with melamine‐formaldehyde resin and its flame retardant application in epoxy resin

Abstract

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.

A High-Performance and Low-Cost Soy Flour Adhesive with a Hydroxymethyl Melamine Prepolymer

“…Compared with the FTIR spectra of M, that of HMP showed a new absorption at 2934 cm −1 , which was attributable to the –CH 2 stretching vibrations [22,23]. In addition, the new peak observed at 1338 cm −1 correspond to the C–N stretching of CH 2 –N [24]. Both of them indicated that the –NH 2 of the M reacted with formaldehyde to generate prepolymers.…”

A flame‐retardant DOPO‐MgAl‐LDH was prepared and applied in poly (methyl methacrylate) resin

“…Meanwhile, Wang et al prepared super hydrophobic Mg/Al‐LDH by gradual deposition of poly (dimethyl siloxane) (PDMS) and 1H, 1H, 2H, 2H‐perfluorododecyl trichlorosilane (FDTS), showing self‐cleaning characteristics and flame retardancy. It is worth mentioning that melamine formaldehyde (MF) resin microencapsulated LDHs was first prepared by microencapsulation technology and displayed good compatibility and dispersion in epoxy resin . However, these modifications only improve the compatibility of the LDH by surface or intercalation treatment, and the synergistic flame‐retardant effect on the polymer is inconspicuous.…”

Synthesis of a novel DPPA‐containing benzoxazine to flame‐retard epoxy resin with maintained thermal properties

“…The higher cross‐linking density and hydrogen bonding result in tighter chain packing. The tighter chain packing and the rigid structure of DHA‐B are good for increasing E′ …”