吡嗪-2,3-二羧酸镧的合成及其对聚氯乙烯稳定性的作用

Synthesis of lanthanum 2,3-pyrazinedicarboxylic acid and its stabilizing effect on PVC

以吡嗪-2,3-二羧酸(2,3-PDA)为配体,用硝酸镧和氨水合成了吡嗪-2,3-二羧酸镧(2,3-LPDA)稀土热稳定剂,通过红外光谱分析、元素分析和热分析确定了其分子式;通过静态热稳定实验研究了2,3-LPDA、其他辅助热稳定剂以及2,3-LPDA与硬脂酸锌、硬脂酸钙、季戊四醇的二元和三元复配体系的热稳定性,并对其对聚氯乙烯(PVC)塑化性能和力学性能的影响进行了表征;最后,探究了2,3-LPDA的热稳定机理。结果表明,2,3-LPDA的分子式为La_(2)(C_(6)N_(2)O_(4))_(2)(NO_(3))_(2)·3H_(2)O;当2,3-LPDA∶硬脂酸锌∶季戊四醇的复配质量比为2∶1∶2时,PVC的热稳定时间可以达到44min,且复配体系对PVC的塑化性能有明显提高作用,使PVC的拉伸强度显著提升;2,3-LPDA能够减少PVC中的C—Cl的存在,并且可以吸收PVC降解产生的Cl^(-),与稀土离子结合生成LaCl_(3),从而抑制PVC的降解,达到热稳定效果。

A lanthanum 2,3-pyrazinedicarboxylic acid(2,3-LPDA)rare earth thermal stabilizer was synthesized using 2,3-pyrazinedicarboxylic acid as a ligand together with lanthanum nitrate and ammonia water,and its molecular formula was analyzed through infrared spectroscopic characterization and elemental and thermal analyses.The thermal stability of 2,3-LPDA and its compounding system with other auxiliary heat stabilizers like zinc stearate,calcium stearate,and pentaerythritol were investigated through a static thermal stabilization experiment.The effect of thermal stabilizers on the plasticization and mechanical properties of PVC were evaluated.The thermal stability mechanism of 2,3-LPDA was analyzed.The results indicated that the molecular formula of 2,3-LPDA was determined to be La_(2)(C_(6)N_(2)O_(4))_(2)(NO_(3))_(2)·3H_(2)O.When the compounding ratio of 2,3-LPDA to zinc stearate to pentaerythritol was set as 2∶1∶2,the thermal stabilization time of PVC reached 44 min and its processability and tensile strength was improved significantly.The presence of 2,3-LPDA could depressed the dissociation of the C—Cl bond in PVC and absorbed the Cl^(-)produced by the degradation of PVC through a combination with rare earth ions to form LaCl_(3).This effectively inhibited the degradation of PVC,resulting in a good thermal stability.