硬脂酸稀土对PVC热稳定性的作用机理研究

Structural Characterization of Rare-Earth Stearate and It's Thermal Stability Mechanism for PVC

采用FTIR及XRD对硬脂酸稀土稳定剂进行结构表征 ,可知硬脂酸稀土中硬脂酸酸根与稀土离子间的作用主要是离子键性质的 ,且硬脂酸稀土具有层状晶体结构 ,晶层中稀土离子倾斜于基面。刚果红法测定结果表明 ,随着硬脂酸稀土用量增加 ,PVC的热稳定时间呈现增加的趋势 ,4种不同稀土硬脂酸盐稳定能力大小顺序为Last>Ndst>Yst>Dyst。通过FTIR对PVC稀土稳定体系稳定机理进行预测 ,结果表明Last和Ndst两种稀土稳定剂能取代不稳定的Cl原子 ,阻止PVC分子链上脱HCl反应 ,改变构象使其达到稳定的效果。Yst和Dyst在改变构象方面贡献较不明显。

Structural characterization of rare-earth stearate was conducted by FTIR and XRD. The results show that the bonds between the stearate and rare-earth metal ions in rare-earth stearate are main ionic character and have the stratified crystalline structure with the crystal layer formed from a plane layer of rare-earth ions combined with two layers of fully extended zigzag chains of stearic acid radicals arranged parallelly to each other on its both sides, and the rare-earth ions axes are inclined to the crystal layer planes in it. Congo red test showed that the stabilizing time increased when the stabilizers' concentration increased. The order of stability of this four rare-earth stearates is Last > Ndst > Yst > Dyst. Furthermore, the thermal stability mechanism of rare earth stearate for PVC has been presumed by FTIR. The results indicate that Last and Ndst can bate the chain reaction and exchange the labile functional groups in the backbone chains for other more stable substituents derived from the stabilizer and change the framwork, while Yst and Dyst's effect is not clear.