Design And Preparation Of LDHs Containing Rare Earth Elements And Their Properties Study For Intumescent Flame Retardant Poly (Butylene Succinate) Composites

Poly(butylene succinate)(PBS) has great potential for itsbiodegradable property among numerous polyester materials. However,like other aliphatic polyesters, PBS is highly combustible, which limits itsapplication in automotive components, electronics, or the electricalindustry. It is therefore necessary to provide fire resistance to PBSmaterials. In this thesis, we proposed a way to design and prepare novellayered double hydroxides (LDHs), and the idea was put forward accordingto the flammability of PBS and special construction of LDHs. A series ofsynergistic agents were thus designed and prepared, and their synergisticflame retardance were explored systemically as well as the mechanicalproperties of intumescent flame retardant PBS (IFR-PBS) composites. Themain contents are summarized as follows:Based on synergies of metal elements, a series of MgAlZnFe-CO3LDHs and LDHs containing La element (MgAlZnLa-CO3LDHs) wereprepared by the constant pH coprecipitation method. The results revealedthat these synthesized LDHs had regular and orderly crystal structures, andgood thermal stability.The flame retardant effects on PBS were studied with chosingdifferent intumescent flame retardants (mulriple IFR containing ammoniumpolyphosphate (APP) and melamine (MA), Melamine Pyrophosphate(MPP), melamine cyanurate (MCA), and so on). IFR-PBS composites,which was prepared by using APP as the acid source, MAas the gas source,and PBS itself as macromolecular carbon source, showed better flameresistance.MgAlZnFe-CO3LDHs chosen as a synergistic agent, mulriple IFRcombined by APP and MA was incorporated into PBS to prepare IFR-PBScomposites, and its dispersibility, rheological property, crystallizationproperty, thermal property, flame retardance, mechanical property wereadequately investigated. Compared to those of IFR-PBS compositeswithout MgAlZnFe-CO3LDHs, the LOI values of the novel IFR-PBScomposites increased from30to35and vertical flammability (UL-94)results reached V-0rate. Moreover, MgAlZnFe-CO3LDHs could refine thecrystalline structure, and improve some mechanical properties. LDHs containing rare earth element was also chosen as a synergisticagent, and the synergistic effect between IFR and LDHs containing rareearth element was investigated. The LOI of IFR-PBS composites dependednot only on the amount of the char, but also on the structure of the charlayer. The addition of LDHs containing rare earth element could promotethe formation of graphite structures on the outer surface of the char layer toimprove its strength and compactness markedly. It was revealed that thecarbon layer of high density due to combustion can effectively reduce therelease of flammable small molecules.In order to compare the difference between LDHs and other layeredmaterials as synergistic flame retardance of IFR-PBS composites,Montmorillonite (MMT) was introduced into IFR-PBS composites. Theresults indicated that the synergistic effects of MMT was not as noticeableas those of LDHs. It was revealed that MMT did not promote the moreformation of graphite structure on the outer surface, and show littlecatalysis on IFR-PBS composites. MMT also was not as good as LDHs assynergistic agent in the static combustion tests and dynamic combustiontests. But we could not deny that MMT also showed synergistic effects tosome extent.