Study On Intumescent Flame Retardant Polypropylene Composites Using Hindered Amine As Synergistic Agent

Polypropylene (PP) has been widely used in many fields due to its good comprehensive performance. But PP is very combustible and easy-dripping so the flame is easy to spread. Due to the advantage such as low smoke, low release of toxic gases during burning and anti-dripping, eco-friendly intumescent flame retardants (IFRs) have been well developed as the replacement of the halogen-containing flame retardants. However, it also has some disadvantages like weak water resistance, low compatibility with polymers and heavy loading, which deteriorates light stability and mechanical properties of PP greatly.In mis essay, a lot of literatures have been reviewed on the basis of intumescent flame retardants and N-alkoxyoxy hindered amine. For the sake of improving the flame retardancy of intumescent flame retardant PP (IFR-PP) composites as well as other performance, a novel and multifunctional flame retardant synergist, N-alkoxyoxy hindered amine containing silane (Si-NORs), was synthesized and applied to IFR-PP composites. Both the synergetic mechanism of Si-NORs and the effects of maleic anhydride grafted PP (PP-g-MAH) as a compatibilizer on the properties of IFR-PP containing Si-NORs were also discussed and investigated.Main research works are as follows:1. Based on the easy-controlled chloride displacement reaction of cyanuric chloride and eco-friendly sol-gel reaction of silane couplings, Si-NORs was synthesized by cyanuric chloride, reactive N-alkoxyoxy hindered amine (with a hydroxyl group) and silane coupling agents (with an amino group) by three steps. Then structure and composition of Si-NORs were characterized by FTIR and XPS and the thermal stability was investigated by TGA. The TGA results demonstrated that Si-NORs had high thermal stabilities and char forming properties. The initial decomposition temperature was 255.19℃ and the amount of char residue was 20.7 wt% at 800℃. Besides, the weight loss of Si-NORs during the process of thermal decomposition was slowed down obviously due to the sol-gel reaction of silane couplings.2. IFR-PP composites were prepared with different content of Si-NORs and characterized by limiting oxygen index (LOI), vertical burning tests (UL-94 tests), light stability tests, TGA, mechanical properties tests and SEM. The results indicated that with the addition of lwt% Si-NORs and 25wt% IFR, the LOI value of IFR-PP composites increased from 30 to 32 and the UL-94 tests showed that it could reach V-0 rating. Moreover, the light stability, thermal stability, mechanical properties, compatibility and char residues structure were improved greatly. Furthermore, the possible synergetic mechanism of Si-NORs was also discussed. The synergetic effect of Si-NORs was mainly due to the capture of active free radicals in the both gas and condensed phase by free radical scavengers generated from the thermal decomposition of Si-NORs. Besides, the formation of crosslinking structure with Si-O-C and Si-C further improved the thermal stability and obstructing effects of char residues.3. The effects of PP-g-MAH as a compatibilizer on the properties of IFR-PP containing Si-NORs was investigated. The results showed that PP-g-MAH could further improve the flame retardancy, light stability, thermal stability, mechanical properties (except for impact strength) and compatibility for IFR-PP composites in different extent, but the loading should be limited under 5wt%.