Synthesis Of Rare Earth Accelerant And Its Application In Rubber Composites

As rare earth elements have the special structure of 4f empty electron orbits, they can have 6～12 coordination bonds when forming rare earth complexes with other elements. From the view of hard-soft acid-base, rare earth elements are apt to forming complexes with hard base, for example, Re-O and Re-N bonds.A rare earth accelerant called DLa which had been never reported up to now was synthesized in this dissertation. The optimum reactant molar ratio of D and La(NO3)3·6H2O was defined as 1.7 when the reaction yield was 82.7%. The product DLa was characterized by FT-IR, UV, TG, Element analysis and 1H-NMR. The structural formula of DLa was defined as LaD2(NO3)·H2O. Compared with accelerant D, DLa had better thermal stability.The rubber composites were prepared by mechanical mixing method. The properties of NR, NR/SiO₂ and SBR/SiO₂ composites with different accelerant systems were investigated.The properties of NR and NR/SiO₂ composites were studied at first.The effect of D and DLa amount on vulcanization behavior, mechanical properties and aging properties of NR were researched. D and DLa could accelerate vulcanization significantly, and compared to D, DLa had lower vulcanization speed, however, DLa had longer scorch time which meant DLa had good processing security. Tensile strength and modulus firstly increased and later decreased with increasing the amount of D and DLa, and the optimum amount of them was 1 phr.Four accelerant systems including CZ, D/CZ, DLa/CZ, DZn/CZ were investigated in NR/SiO₂ composites. The rheological behavior, filler network structure, vulcanization behavior, mechanical properties and aging properties were measured through RPA, curing analysis, TGA, SEM and DMA. Results showed that D/CZ had the optimum comprehensive propeties, DZn/CZ was worse than DLa/CZ and better than CZ.Then, properties of SBR/SiO₂ composites with different accelerant systems were investigated. Firstly, the effect of D and DLa amount on SBR/SiO₂ composites were studied, and the optimum amount was 2.8 phr. Properties of the composites with different accelerant system were measured by many test ways. The results showed that composites with D/CZ had the optimum vulcanization activity, and DLa/CZ was lower than D/CZ but higher than CZ, however, DLa/CZ had longer scorch time than D/CZ. Compared with D/CZ, DLa/CZ had better mechanical properties and aging properties. DLa/CZ had the optimum mechanical properties because it had higher cross-link density.According to the fitting results of dynamic vulcanization kinetics, the three accelerant systems were compared. D and DLa could accelerate the vulcanization of SBR/SiO₂ composites, and D was better than DLa. D/CZ was the best and DLa/CZ was worse than D/CZ but better than CZ. The results also showed that the higher the vulcanization speed, the quicker and easier the desulfuration. Though DLa/CZ had lower vulcanization speed, the anti-reversion was better.Properties of SBR/SiO₂ composites with different rare earth accelerants (DLa, DEr, DCe) were compared, it is showed that DLa had the best vulcanization and properties.In a word, in NR and SBR/SiO₂ composites, composites with DLa/CZ had the optimum properties; while in NR/SiO₂ composites, DLa/CZ was worse than D/CZ in mechanical properties, however, better in ozone aging and ultraviolet radiation aging.