Abstract
Phosphated cellulose (PCF) was synthesized based on urea, phosphated acid and cellulose. The structure of the PCF was confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy coupled with the Energy Dispersive Spectrometer (SEM-EDS). Benzoxazine (Ba)/PCF hybrid materials were fabricated and thermally cured to prepare polybenzoxazine composites (PBa/PCF). The effects of PCF on the curing temperature of Ba were analyzed through differential scanning calorimetry (DSC). The thermogravimetric (TGA) results demonstrated an increased char residue of 50% for the PBa composites incorporating PCF-5% compared with the pure PBa. The peak heat release rate (PHRR) and total heat release (THR) values of the PBa/PCF-5% composites clearly decreased by 58.1% and 16.5% compared to those of the pristine PBa. The smoke released from the PBa/PCF system significantly reduced with the loading of PCF. Moreover, the limited oxygen index (LOI) and vertical burning test level (UL-94) of PBa/PCF-5% reached up to 31 and V0. The flame retardant mechanism of the PCF in the PBa matrix was investigated TG-FTIR and char residues analysis. Finally, the dynamical mechanical analysis (DMA) results demonstrated that the Tg of the PBa/PCF composites was approximately 230 °C, which does not affect further applications of PBa composites.
Highlights
Polybenzoxazine (PBa) is a new type phenolic resin, which can be synthesized by formaldehyde, primary amines and phenols through Mannch reaction [1,2,3]
Cellulose macromolecule belongs to polysaccharide, which is composed of D-glucose with β-1, 4 glycosidic bonds [34]
The significance of PCF in enhancing the flame retardancy of PBa was demonstrated through the results presented above
Summary
Polybenzoxazine (PBa) is a new type phenolic resin, which can be synthesized by formaldehyde, primary amines and phenols through Mannch reaction [1,2,3]. PBa offers outstanding performance in comparison to traditional phenolic resin, such as its flexible molecular design, near-zero shrinkage behavior during polymerization, low water absorption, low dielectric constant, low coefficient of thermal expansion and so on [4,5,6,7,8]. These characteristics make it possible to broaden the application prospects of PBa beyond aerospace, electronics and automobile manufacturing [9,10,11,12,13]. The flame retardant mechanism of the composite was investigated by analyzing char residues and gas phase products
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