Preparation And Stability Of Rare Earth Stabilizer For PVC Containing Benzophenone Structure

In this thesis,two rare earth stabilizers,lanthanum 2,4-dihydroxybenzophenone（LBP）and lanthanum 2-benzoylbenzoate（LBA）,were synthesized,and the complexes were characterized and the molecular formula was determined.The effects of complexes and their complex with Zinc stearate（Zn St₂）,Calcium stearate（Ca St₂）and Pentaerythritol（PE）on the thermal stability of PVC were studied by Congo red test paper method and high temperature thermal aging box.The results show that when LBP and LBA are added to PVC alone,the thermal stability time is 37 min and 16 min respectively,which is not ideal to improve the initial discoloration resistance and thermal stability time of PVC.In binary compounding,the synergistic effect of the two rare earth stabilizers and pentaerythritol is the best.When the compounding ratio of LBP and LBA to Pentaerythritol is 3:2（mass ratio,the same below）,The thermal stability time is 64 min and 37 min respectively.In ternary compounding,when the compounding ratio of LBP to Zn St₂ and PE is 2:1:2,the thermal stability time is 81 min,and when the compounding ratio of LBA to Zn St₂ and PE is 1:1:3,the thermal stability time is 58 min,The two ternary composite stabilizers have the best effect on the thermal stability of PVC.Then,the artificial accelerated UV aging experiment and outdoor natural light aging experiment were used to test the changes of weight loss rate,color difference value and mechanical properties of PVC sheets with different samples during light aging,so as to measure the influence of samples on the light stability of PVC.The results show that the weight loss rate of PVC sheet without sample is 8.1%after artificial accelerated UV aging for 10 days,and the weight loss is the most obvious.The weight loss rate of PVC sheet with LBP and LBA containing ternary composite stabilizer（LBP:Zn St₂:PE=2:1:2,LBA:Zn St₂:PE=1:1:3）is 2.7%and 6.2%respectively after aging for 10 days,which shows that the two ternary composite stabilizers have stronger ability to improve the UV resistance of PVC sheet,Good light stability,through the color difference valueΔE also reflects that two ternary composite stabilizers have the best effect on improving the light aging resistance of PVC.In the test of mechanical properties,after 35 days of aging,the retention rate of tensile strength of pure PVC is 52.7%,while the retention rates of tensile strength of PVC with two ternary composite stabilizers of LBP and LBA are 87.6%and 81.8%respectively.The two ternary composite stabilizers are the best to improve the light stability of PVC.The results show that the rare earth stabilizer can absorb the hydrogen chloride produced by PVC degradation and reduce the concentration of hydrogen chloride,so as to weaken the catalytic effect of hydrogen chloride on PVC degradation,inhibit the formation of double bond,prevent the formation of peroxide and carbonyl compounds under the action of oxygen.