Nonflammable cellulosic substrates by application of novel radiation-curable flame retardant monomers derived from cyclotriphosphazene
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Three novel phosphorus-based flame retardant monomers were successfully prepared by reacting 1-(acryloyloxy)-3-(methacryloyloxy)-2-propanol (AHM) with hexachlorocyclotriphosphazene and characterized by FT-IR, 1H-NMR, 13C-NMR, 31P-NMR and 2D 1H-31P NMR correlation experiments. With the aid of a photoinitiator and a UV flood curing system, these monomers were cured onto cellulosic substrates to generate flame retardant coatings. An experiment was designed through SAS JMP® Pro 10 to investigate the influences of monomer concentration, photoinitiator concentration and UV exposure time on coating yield. All three monomers formed coatings under UV conditions in the presence of the photoinitiator that were durable to extraction. Burn testing showed that a loading of only 15 % of these monomers was required to prevent the substrates from combusting in the horizontal, 45° and vertical orientations. The regions of the fabric that were exposed to the flame were converted to char; a characteristic of flame retardant chemicals that function through the condensed phased. The ability of these monomers to encourage the formation of non-flammable char was further revealed by thermogravimetric analysis. Treated fabrics gave significantly elevated char yields at 600 °C. Finally, the grafted polymeric layers that were produced on the substrates were observed using scanning electron microscopy.
KeywordsFlame retardant Graft polymerization Radiation curing Cellulose
The authors wish to express gratitude to Dr. Hanna Gracz of the NCSU BIO-NMR Facility for her help with NMR studies. We are also grateful to the National Textile Center for funding this research through project number C10-NS03.
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