Synthesis and characterization of polybenzoxazine containing phosphorus

Nacre-Mimetic Green Flame Retardant: Ultra-High Nanofiller Content, Thin Nanocomposite as an Effective Flame Retardant

A nacre-mimetic brick-and-mortar structure was used to develop a new flame-retardant technology. A second biomimetic approach was utilized to develop a non-flammable elastomeric benzoxazine for use as a polymer matrix that effectively adheres to the hydrophilic laponite nanofiller. A combination of laponite and benzoxazine is used to apply an ultra-high nanofiller content, thin nanocomposite coating on a polyurethane foam. The technology used is made environmentally friendly by eliminating the need to add any undesirable flame retardants, such as phosphorus additives or halogenated compounds. The very-thin coating on the polyurethane foam (PUF) is obtained through a single dip-coating. The structure of the polymer has been confirmed by proton nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The flammability of the polymer and nanocomposite was evaluated by heat release capacity using microscale combustion calorimetry (MCC). A material with heat release capacity (HRC) lower than 100 J/Kg is considered non-ignitable. The nanocomposite developed exhibits HRC of 22 J/Kg, which is well within the classification of a non-ignitable material. The cone calorimeter test was also used to investigate the flame retardancy of the nanocomposite's thin film on polyurethane foam. This test confirms that the second peak of the heat release rate (HRR) decreased 62% or completely disappeared for the coated PUF with different loadings. Compression tests show an increase in the modulus of the PUF by 88% for the 4 wt% coating concentration. Upon repeated modulus tests, the rigidity decreases, approaching the modulus of the uncoated PUF. However, the effect of this repeated mechanical loading does not significantly affect the flame retarding performance.

Flame–retarded epoxy resin with high glass transition temperature cured by DOPO-containing H-benzimidazole

A halogen-free flame retardant of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-containing H-benzimidazole (DHBI) was synthesized and subsequently used as co-curing agent of 4,4′-diamino-diphenylmethane for diglycidyl ether of bisphenol-A. The structure of DHBI was characterized by Fourier transform infrared (FTIR) spectroscopy, proton, carbon 13 and phosphorus-31 nuclear magnetic resonance, and mass spectroscopy. A series of cured epoxy resins (EPs) were prepared and their flame retardancy, thermal stability, flexibility, and dielectric properties were investigated. The resulting cured EP (EP-10) with 7.45 wt% of DHBI successfully achieved UL 94 V-0 rate with limited oxygen index of 35.6% and without dropping phenomenon. Compared with the cured pristine EP (EP-00), the glass transition temperature of EP-10 was increased by 6.9°C, accompanied with an enhancement of flexible strength by 13.1 MPa and a decrement of dielectric constant by 0.3 at the testing frequency of 1 MHz.