Preparation And Modification Of ZnAlLa-CO₃-LDHs With Its Application In PVC

Layered Double Hydroxides will replace traditional lead salt stabilizer to become a new kind of PVC stabilizer for their unique chemical composition and layer structure. Rare earth stabilizer is another hot spot of PVC stabilizers. It has the advantage of coupling effect and non-toxic or low toxic. In this thesis, La3+was brought into layer board of LDHs to prepare ZnAlLa-CO3-LDHs. The main contents can be summaried as follows:Firstly, the traditional coprecipitation method was compared to coprecipitation-ion exchange method. The slurry before ion exchange and surface modification was considered if it needed to be washed. And the feasibility of ion exchange and surface modification performing at the same time was also discussed. According to FT-IR, XRD and laser particle size analyzer, ZnAlLa-CO3-LDHs of high crystallinity, small particle size, uniform particle size and high purity can be successfully obtained by coprecipitation-ion exchange method, which increased the productive efficiency and simplified the preparation process.Secondly, the relevant conditions of preparing ZnAlLa-CO3-LDHs were explored in details, the surface modification of ZnAlLa-CO3-LDHs was also carried out to improve the compatibility with PVC. The results showed that the optimal conditions of synthetizing precursor ZnAlLa-NO3-LDHs were:the molar ration of n(La3+)/n(Al3+) was1/8, the reaction pH was8.0and the aging time was24h; and the optimum conditions of ion exchange were:the dosage of sodium carbonate was1-2times of theoretical required, the reaction temperature was60～80℃and the reaction time was1.0-2.0h. The effects of treatment agent kinds and its quantity on surface modification were studied by grading analysis and activation degrees test, which revealed that the compatibility of ZnAlLa-CO3-LDHs with PVC was significantly improved when ZnAlLa-CO3-LDHs were modified by6%oleic acid sodium.Besides, composite ZnAlLa-CO3-LDHs and other heat stabilizers were explored by congo red test and thermal aging oven method. It increased thermal stability of PVC when adding1.5phr ZnAlLa-CO3-LDHs alone. Composite ZnAlLa-CO3-LDHs and MgAl-CO3-LDHs at the ratio of1:4in quality, dosage of3.0phr, increased thermal stability time of PVC significantly. When PVC:DOP: ZnAlLa-CO3-LDHs:MgAl-CO3-LDHs:Cast2was equal to100:40:0.6:2.4:0.4, the initial stability and long-term stability of PVC improved further.