Abstract
To derive P,N-doped cellulose fibrils, phosphoric acid and aqueous ammonia were placed in a one-pot reaction, and the phosphate groups and ammonium phosphates were successfully introduced into the cellulose surface. The obtained P,N-doped cellulose fibrils with high liberation were thereafter incorporated into a high-density polyethylene (HDPE) matrix to improve the flame retardancy of HDPE composites, and they had a significant improvement on flame retardancy of HDPE composites. In particular, 7 wt % P,N-doped cellulose fibrils considerably reduced the average and peak heat release rate (HRR) by 29.6% and 72.9%, respectively, and increased the limited oxygen index (LOI) by 30.5%. The presence of phosphate groups and ammonium phosphates within P,N-doped cellulose fibrils was found to promote the thermal degradation of HDPE composites at a lower temperature (i.e., 240 °C). The released acid catalyzed the dehydration of cellulose to form an aromatic carbonaceous structure with a higher crystalline orientation, which improves the flame retardancy of HDPE composites.
Highlights
Natural fiber reinforced polymer composites (NFRPCs) have been widely applied in fields of decking, railing, construction and packaging because they are biodegradable, renewable, and have excellent mechanical properties [1]
Quantities of highly fibrillated cellulose fibrils are further exposed as a result of a removal of phosphoric acid coating (Figure 1c)
The X-ray photoelectron spectroscopy (XPS) can provide information pertaining to the elemental composition and content of a characteristic crystal structure of cellulose I, that appears at 15.9◦, 22.3◦ and 33.7◦ according to Miller untreated and treated cellulose that supplements the Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM)-EDS results
Summary
Natural fiber reinforced polymer composites (NFRPCs) have been widely applied in fields of decking, railing, construction and packaging because they are biodegradable, renewable, and have excellent mechanical properties [1]. These materials, are highly flammable, limiting their applications in building, transportation, and furniture manufacturing industries. The combination of phosphoric acid derived by biomass hydrolysis and flame retardant polymer composites promotes the utilization of cellulose fibrils and affords a means to protect the environment. Cellulose is treated with phosphoric acid and aqueous ammonia in a one-pot reaction to produce P,N-doped cellulose fibrils These cellulose fibrils are subsequently introduced to high-density polyethylene (HDPE) to improve flame retardancy. The formation of P,N-doped cellulose fibril and its influence on thermal degradation, flammability properties, and mechanism of the resultant composites are systematically examined in this study
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