Fabrication of c-6 position carboxyl regenerated cotton cellulose by H2O2 and its promotion in flame retardency of epoxy resin

Hydrogen peroxide was adopted to oxidize alkali-pretreated regenerated cotton cellulose (RCC) with carboxylic content (CC) ranging from 3.2% to 15.6% depending on the H2O2/RCC molar ratios used, at the present of copper sulfate. FT-IR, 13C-NMR, SEM and BET were performed to characterize the oxidized RCC (ORCC) structure, respectively. The FT-IR and 13C-NMR results confirmed that the primary hydroxyl at C6 site in glucose units of RCC was selectively oxidized to carboxyl group by H2O2. SEM revealed that the pretreated regenerated cellulose by alkali solution would disentanglement the RCC fiber and increased its interface, resulting in promoting oxidation reaction. Additional evidence of reaction interfaces increment was provided by BET (BET), which presented the surface area increased from 10.12 to 17.92 m2/g by alkali-pretreated process, and ORCC15.6 achieved a significant increase value for 62.45 m2/g. TGA and TG-IR measurement illuminated that the content combustible gases such as methanol of ORCC released decrease, while the residual carbon increased with the increase of CC. Then, pentaerythritol (PER), RCC and ORCC were used as carbon sources (5 wt%) with microencapsulated ammonium polyphosphate (MFAPP, 5 wt%) in the epoxy resin (EP, 90 wt%). UL-94 testing, LOI and Cone calorimeter test (CCT) were characterized to evaluate the flame retardency of these EP-IFRs composites. Due to the introduction of carboxyl group into RCC improved the char amount of EP-IFRs (increased by 164.7% in comparison with PER), EP/MFAPP/ORCC15.6 was classified as V-0 with LOI of 29.5%. CCT evidenced excellent reaction of the EP/IFRs to fire since PHRR, THR and TSP was decreased by 42.4%, 47.6% and 50.5% in the presence of ORCC15.6 in comparison with PER, respectively. This study proposed a green and novel method to fabricate ORCC by H2O2 and demonstrated ORCC15.6 was an excellent carbon source for EP-IRFs composites.