乙二胺双马来酰胺酸根合镧(Ⅲ)-层状矿物复合热稳定剂对聚氯乙烯的热稳定作用

Effects of Composite Heat Stabilizer of Layered Minerals and Complexes of Ethylenediamine Double Maleamic Acid Radical with Lanthanum(Ⅲ) on Thermal Stability of PVC

利用稀土配合物具有较强协同作用的优点,将自身对聚氯乙烯(PVC)具有一定热稳定作用的乙二胺双马来酰胺酸根合镧(Ⅲ)配合物(LaL)与层状矿物,如高岭土、蒙脱土、水滑石和水镁石进行复配,通过热重分析、刚果红试验和静态烘箱老化法研究了乙二胺双马来酰胺酸根合镧(Ⅲ)与高岭土、蒙脱土、水滑石和水镁石复合物对PVC热稳定性的影响。结果表明,乙二胺双马来酰胺酸根合镧(Ⅲ)与层状矿物具有良好的协同效应,且与水镁石效果最为显著,当二者质量比为1∶1时,PVC热稳定时间由2 min提升至70 min,且能有效地抑制单一稀土热稳定剂使用时的初期着色能力。复合热稳定剂的添加大幅度提高了PVC热降解的活化能,尤其是LaL-水镁石复合物(LaL-Brucite)的添加,N_2气氛下的活化能相对于纯PVC样品,由123.5 kJ/mol提升至234.7 kJ/mol,提高了111.2 kJ/mol;空气气氛下的活化能相对于纯PVC样品,由115.9 kJ/mol提升至133.0 kJ/mol,提高了17.1 kJ/mol;有效地提高了PVC的热稳定性。

The strong synergy function of the rare earth complexes and the layered minerals was used to improve the thermal stability of PVC. The complex of ethylenediamine double maleamic acid radical and lanthanum （Ⅲ） （LaL） was compounded with layered minerals, such as kaolinite, montmorillonite （MMT）, hydrotalcite （LDHs） and brucite （Bru） etc. The stabilization effects of complexes of LaL-kaolin, LaL-MMT, LaL-LDHs, LaL-Bru on PVC were investigated by thermal gravity analysis, Congo red test and discoloration test. The results show that the complexes of ethylenediamine double maleamic acid radical with lanthanum （Ⅲ） and the layered minerals present excellent synergistic effects on the thermal stability of PVC. When the mass ratio of LaL-Bru is 1：1, the stability time is increased from 2min to 70 min, attributing to the most significant synergistic effect of LaL-Bru system and exhibiting remarkable initial color of PVC. Composite heat stabilizers greatly enhance the activation energy of PVC thermal degradation. Compared with the pure PVC sample, the activation energy of LaL-Bru in N2 increases from 123.5 kJ/mol to 234.7 kJ/mol, and the activation energy of LaL-Bru in air increases from 115.9 kJ/mol to 133.0 kJ/mol.