Graphite-like carbon nitride and functionalized layered double hydroxide filled polypropylene-grafted maleic anhydride nanocomposites: Comparison in flame retardancy, and thermal, mechanical and UV-shielding properties

Graphite-like carbon nitride (g-C3N4) and borate modified layered double hydroxides (LDH-B) were successfully fabricated by thermal pyrolysis and modified aqueous miscible organic solvent treatment methods, respectively. Then these nano-additives were introduced to prepare polypropylene-grafted maleic anhydride (PP-g-MA)/g-C3N4 and PP-g-MA/LDH-B nanocomposites using a modified solvent mixing strategy. Several important parameters of the nanocomposites including thermal, mechanical and UV-blocking properties were investigated. Results indicated that pure g-C3N4 exhibited 347.6 and 427.2 °C increase in onset decomposition temperature under air and nitrogen conditions, respectively, compared with LDH-B. In case of PP-g-MA nanocomposites, both T-10 and T-50 (the temperature at 10% and 50% weight loss, respectively) were improved by 14.6 and 27.7 °C, respectively, by the addition of g-C3N4 while those only increased by 2.3 and 17.8 °C upon introducing LDH-B. Furthermore, PP-g-MA/g-C3N4 system showed a remarkable increment (9.8 °C) in crystallization temperature while an increase of 4.2 °C for PP-g-MA/LDH-B nanocomposite. Introducing g-C3N4 and LDH-B into PP-g-MA led to a reduction of 28% and 19% in pHRR, respectively. It was noted that the incorporation of g-C3N4 caused significant improvement in storage modulus from 2445.0 MPa for neat PP-g-MA to 2783.5 MPa for PP-g-MA/g-C3N4 while that of PP-g-MA/LDH-B was dramatically decreased by 27.3%. Optical results indicated that PP-g-MA/g-C3N4 was rendered fascinating UV adsorption ability relative to PP-g-MA/LDH-B. It is expected that the novel two-dimensional nanomaterial could bring new creativity into polymer composites.