The effect of Machine Direction Orientation (MDO) processing on the photostabilization of LLDPE samples containing Tinuvin® 770 was studied. The amount of Tinuvin® 770 in the processed samples was deliberately chosen at a level higher than the reported solubility at ambient temperature for two main reasons: the first reason was to assess the equilibrium between the soluble and nonsoluble forms of this additive and the impact of the MDO process, and the second was to demonstrate the role of a higher temperature in accelerated artificial photoaging on the protective role played by the nonsoluble part. The results reported in this article show that at room temperature, a nonnegligible amount of Tinuvin® 770 precipitates at the surface, which is commonly termed blooming. However, the additive that bloomed at the surface can be dissolved within the polymer with increasing temperature, which is the case in the conditions of accelerated artificial photoaging but not the case of natural outdoor weathering. Such physical phenomena are responsible for a possible bias brought by temperature during accelerated photoaging, which can affect aging tests. This questions the representativeness of accelerated aging at higher temperatures for polymers containing a blooming stabilizer.

研究了机器方向取向 (MDO) 处理对含有 Tinuvin® 770 的 LLDPE 样品的光稳定性的影响。加工样品中 Tinuvin® 770 的量被故意选择为高于在环境温度下报告的溶解度的水平，主要有两个原因：第一个原因是评估该添加剂的可溶和不可溶形式之间的平衡以及MDO 过程，其次是为了证明更高的温度在加速人工光老化中对不溶性部分起到的保护作用的作用。本文报告的结果表明，在室温下，表面有不可忽略的 Tinuvin® 770 沉淀，这通常称为起霜。然而，在表面起霜的添加剂可以随着温度的升高而溶解在聚合物中，这在加速人工光老化的情况下是这种情况，但在自然室外风化的情况下则不然。这种物理现象是加速光老化过程中温度可能带来的偏差的原因，这会影响老化测试。这对含有起霜稳定剂的聚合物在较高温度下加速老化的代表性提出了质疑。