Study On The Preparation And Properties Of Polymer/Oligomer-modified LDHs Nanocomposites

LDHs are widely used in the preparation of naocomposites due to their special structure and properties. The aim of this thesis is to study the synthesis of oligomer modified LDHs and their applications in the preparation of nanocomposits by melt blending with polymers, investigate their structures, properties, and establish an important method for oligomerically modified LDHs.In this thesis, the oligomeric P(SSS-co-St)s have been synthesized by free-racical polymerization of a mixture of SSS and St, and the oligomeric P(SSS-co-MA)s have been synthesized by free-racical polymerization of a mixture of SSS and MA. Then the oligomer modified LDHs have been prepared via anion exchange of the nitrates in LDHs with the corresponding oligomers and co-precipitation of oligomers with metal nitrates. Their structures and properties have been investigated. The study indicates that the coprecipitation is better than ion exchange for the preparation of oligomer modified LDHs with a well-intercalated or exfoliated structure. TGA analysis demonstrates that the oligomer modified LDHs have higher thermal stability than the corresponding oligomers. Furthermore, we investigate the effect of the composition of oligomers on the properties of oligomers and the oligomer modified LDHs.The PP nanocomposites are achieved by melt blending PP with LDH and OLDH respectively with or without PP-g-MAH-St. Their structures and properties have been investigated. The study has indicated that the added OLDH causes PP producingβcrystal and a small amount of OLDH improves the comprehensive properties of PP, especially in the presence of PP-g-MAH-St. When LDH content is only 0.5% the degraded temperatures of the PP/MOLDH0.5 nanocomposite are 73℃and 40℃ higher than that of pure PP respectively at 5% and 10% mass loss. When LDH content is 4% the thermal stability of the PP/MOLDH4 nanocomposite enhances no longer, but the OI data increases 4 unit comparing with pure PP and it is fire retardant in air. Hot deformation temperature and mechanical property of PP nanocomposites are also improved obviously.The HDPE nanocomposites are achieved by melt blending HDPE with LDH and OLDH respectively with or without PP-g-MAH-St. The thermal stability, hot deformation temperature and mechanical property of HDPE nanocomposites are also investigated. The experimental results indicate that a small amount of OLDH could significantly improve the comprehensive properties of HDPE. The degradation temperature of HDPE/OLDH0.5 and HDPE/OLDH2 samples are 22℃, 33℃higher than that of pure HDPE at 5% mass loss. The hot deformation temperatures of HDPE/MOLDH4 and HDPE/OLDH4 samples are advanced 16℃and 14℃relative to HDPE, respectively. The flexural strength and flexural modulus of HDPE/MOLDH4 sample are improved 24% and 30% relative to HDPE.The PVC nanocomposites are prepared by melt blending PVC with OHT in the presence of other reagents. The experimental results indicate that a small amount of OHT could significantly improve the mechanical property and fire retardancy of PVC. The tensile strength datas of PVC/OHT1 and PVC/OHT3 are increased 0.52 MPa and 0.99 MPa relative to PVC, respectively. The tensile modulus datas of PVC/OHT1 and PVC/OHT3 are 0.49 GPa and 0.60 Gpa higher than that of PVC. The OI datas of PVC/OHT3 and PVC/OHT5 are increased 2 units and 4 units relative to PVC, respectively.