Fabrication And Study On Structure And Properties Of Flame-Retardant PET/MWNTs Nanocomposites

In this study, multi-walled carbon nanotubes (MWNTs) treated respectively by HNO3, HNO3/H2SO4 mixture or ball-milling were dispersed in glycol in aid of ultrasonication, followed by adding terephthalate acid (TPA) powder to carry out the esterification. In the presence of phosphorus-containing reactive flame retardant (CEPPA-EG), the polycondensation was carried out to prepare in situ flame retardant poly(ethylene terephthalate) (FRPET)/MWNTs composites with different MWNTs loadings.Fourier transform infrared (FTIR) spectroscopy was utilized to confirm the esterification between the CEPPA and glycol. The thermal decomposition of flame retardant was effectively increased, demonstrated by thermogravimetrc analysis (TGA). The results of scanning electron microscopy (SEM) observation indicated that uniform dispersion of the ball-milled and oxidized MWNTs in FRPET matrix occurred, with the latter was more homogenous. Adding TPA powders further benefits the MWNTs'dispersion state.Differential scanning calorimery (DSC) and wide angle X-ray diffraction (WAXD) results showed that the crystallizability and degree of crystallization of FRPET were enhanced by incorporation of purified and ball-milled MWNTs. However, the reversed results were obtained when using oxidized MWNTs in preparation of nanocomposites. The physical strength and compactness of protected barrier layer were enhanced by adding MWNTs in FRPET. When the phosphorus content was kept constant, the flammability of the nanocomposites was further reduced probably due to the synergistic effects between flame retardant and MWNTs, as indicated by the increase of limited oxygen index (LOI) from 31% to 38% by adding 0.4wt% of O1h-MWNTs. Instron tensile tests indicated that, to some extent, the strength and modulus of FRPET increased with incorporation of 0.2 to 1.0wt% MWNTs.