Synthesese And Applications Of Intumescent Flame Retardants For Polyvinyl Alcohol And Their Action Mechanism

Polyvinyl alcohol (PVA), with characteristics of easy-filmability, well- adhesive, excellent spining and mechanical durability, has been widely applied in many fields such as building, transport, furniture and industrial materials. However, it has a low limiting oxygen index (LOI) value and is flammable. The fateful drawback of polyvinyl alcohol restricts its wider application. Therefore, how to improve its flame retardancy becomes a must for addressing the issue.This problem can be solved by adding flame-retardant additives to PVA. However, the existing flame retardants for PVA either contain halogen, some of which have seriously environmental problem, or have poor flame-retardant efficiency. In this thesis, a series of highly efficient halogen-free flame retardants for PVA have been designed and synthesized, and their applications and flame retardant mechanism have also been investigated.Two novel intumescent flame retardants, the ammonium salt of 2-hydroxyl -5, 5-dimethyl -2-2oxo- 1, 3, 2- dioxapho sphoriate(PNOH) and the sulfanilamide of salt of 2-hydroxyl -5, 5-dimethyl -2-2oxo- 1, 3, 2- dioxapho sphoriate(PSOH), were synthesized. Their structures were characterized by 1H NMR and FT-IR spectra, which confirmed the formation of the object compounds. PNOH was used together with ammonium polyphosphate (APP) to prepare a novel intumescent flame retardant (IFR) for PVA. When a few amounts (0.5%) of NiSAO were added, the flame retardancy of the IFR-PVA1799 systems was significantly improved, having a high LOI value of 34.2. At the same time when PSOH/APP/CoSA in a total IFR loading of 14 wt%, the IFR-PVA1788 systems got LOI value of 37.1.A large mount of flame retardant PVA formulations based on PNOH, PSOH, APP and metal chelates have been studied. Based on the results of LOI and UL-94 tests, two formulations with best flame retardancy were obtained: PVA1799+14.5%IFR + 0.5% NiSAO and PVA1788+113.5%IFR + 0.5% CoSA, whose LOI values are 34.2 and 37.1, respectively. The results indicated that the IFR was very efficient for the flame retardancy of PVA, and that there existed a synergistic effect between IFR and metal chelates.The results of TGA proved that the thermal degradation behavior of PVA had been improved due to the addition of IFR and metal chelates. The final residue of IFR-PVA/NiSAO system and IFR-PVA1788 system are much higher than that of neat PVA and IFRs, which means that there is a synergism between them. The result of TGA shows that both PSOH and APP have good thermal stability and high residue.The higher tensile strength and elongation at break can be obtained without an obvious change in the flame retardancy when NiSAO was added. IFR had no effect on the crystalline structure of PVA, and the tensile strength and elongation at break decreased. However, the addition of NiSAO can improve the mechanical properties and flame retardancy of IFR-PVA systems.