The Controllable Preparation Of Rere Earth Nanomaterial And Its Fundamental Research In The PVC Modification

As a widely used polymer material,polyvinyl chloride(PVC)is subject to photo/thermal decomposition during thermal processing and outdoor use,causing the aging of PVC,which greatly limits the performances and fields in the application of PVC.Photo/thermal stabilizers can effectively improve the photostability and thermal-stability of PVC materials,but most of them have problems such as poor stability,bad compatibility,and high prices.The addition of multiple components often causes the aggravation of multiphase compatibility and the decline of mechanical properties.At present,the research and development of multifunctional additives are still in their infancy.How to overcome the defects of multi-functional additives and improve the photo/thermal-stability and lifespan of PVC has always been the research focus of researchers in this field.Cerium oxide(CeO2),As a typical rare earth material,has been extensively studied in the fields of catalysis,batteries,and fluorescence.At present,there are rare researches on the influence of CeO2 on the photostability/thermal-stability and ultraviolet shielding performance of PVC.It has important theoretical and applied value and is also a very challenging topic on how to achieve the highly dispersion of CeO2 on PVC substrate,improve the photothermal stability of PVC,endow PVC with excellent UV shielding ability,mechanical strength and other properties by constructing CeO2 nanomaterials with different morphology,particle size and surface/interface structure.In this thesis,the following work is carried out on the related research and application of controlled synthesis of CeO2 nanomaterials,construction and performance research of PVC-CeO2 composite materials:1.Based on the explosive nucleation environment provided by the nucleation-crystallization isolation method,The controllable preparation of Ce2(CO3)2O·H2O precursor and CeO2 with different morphology,particle size and surface defects has been achieved through the systematic modulation of preparation parameters such as precipitant concentration,crystallization time,crystallization temperature,baking temperature,colloid mill parameters,etc.The optimal conditions for the preparation of CeO2 nanomaterials with abundant defects were investigated,the controlled macro-quantitative preparation of CeO2 nanomaterials rich was realized,and the formation mechanism was preliminary discussed.The particle size of nano CeO2 is 22 nm,and the ratio of Ce3+ions is 18.54%,and the oxygen defect concentration is 3.94 × 1021 cm-3 with the absorbance of all UVC,more than 94%of UVB and more than 40%of UVA.The prepared CeO2 can be used as an ultraviolet shielding additive and is expected to play a role in improving the photostability/thermal stability of PVC.2.A series of PVC-CeO2 composite films with different compositions and contents were prepared by the casting method,and the photostability/thermal stability,UV shielding performance and mechanical properties of PVC-CeO2 films were systematically studied.The results show that the initial release temperature of HC1 of the films increased from 265? to 278?.and the residue quality of the composite films during the thermal decomposition at 275? was increased from 40.2%to 47.8%.The introduction of CeO2 endow the composite film material with excellent UV shielding performance and photostability.The performance and structure of composite film had no obvious changes under ultraviolet irradiation for 2000 h.Based on the above results and DFT calculations,the enhanced UV-shielding efficiency and photostability/thermal stability of PVC-CeO2 composite film are mainly attributed to the excellent UV absorption capacity of defect-rich CeO2 nanocrystals,the formation of coordinate complex between Ce atoms in CeO2 and labile Cl atoms in PVC main chains,the adsorption function of CeO2 nanocrystals to the HC1 released from PVC.Related research provides a new clue for the rational design and synthesis of rare earth based multifunctional additives,which are expected to be used as a multifunctional additive in polymers,especially as the functional materials in PVC.