During aging of polymers, oxidized species on macromolecular chains in solid state, volatile degradation products in liquid state and gaseous degradation products in gaseous state are often investigated separately. The conversion among these products is not especially concerned and biased results may be obtained based on the products in a single state. In this paper, photo-oxidative products of commercial polypropylene (PP) and unstabilized PP in solid, liquid and gaseous states were investigated by using Fourier transform infrared spectroscopy (FTIR), pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) and gas chromatography (GC). By comparing the formation profiles, conversion among the photo-oxidative products in three states was traced. During photo-oxidative aging, the main chains of PP were first oxidized to form carbonyl species in solid state, or fractured to form volatile alkenes as liquid. With the proceeding of aging, the oxidized main chains fractured to form small molecules, resulting in the conversion of oxidized species from solid state to liquid and gaseous states. When the aging degree was extremely high, the accumulation of liquid oxidized products was limited due to migration and condensation. Therefore, both the carbonyl index (CI) and the concentrations of volatile oxidized products were increased first and then decreased, while the concentrations of gaseous products kept increasing all along.

中文翻译：

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固态，液态和气态聚丙烯的光氧化产物之间的转化。

在聚合物老化期间，经常分别研究固态大分子链上的氧化物种，液态的挥发性降解产物和气态的气态降解产物。这些产品之间的转换并不特别在意，并且基于单一状态的产品可能会获得有偏差的结果。在本文中，使用傅立叶变换红外光谱（FTIR），热解-气相色谱/质谱（Py-GC / MS）研究了商用聚丙烯（PP）和不稳定的PP的固态，液态和气态的光氧化产物。和气相色谱仪（GC）。通过比较形成曲线，跟踪了三种状态下光氧化产物之间的转化。在光氧化老化过程中，PP的主链首先被氧化形成固态的羰基物种，或断裂形成液态的挥发性烯烃。随着老化的进行，被氧化的主链断裂形成小分子，导致被氧化的物种从固态转变为液态和气态。当老化度极高时，由于迁移和冷凝，液体氧化产物的积累受到限制。因此，羰基指数（CI）和挥发性氧化产物的浓度先升高然后降低，而气态产物的浓度一直保持增加。导致氧化物质从固态转变为液态和气态。当老化度极高时，由于迁移和冷凝，液体氧化产物的积累受到限制。因此，羰基指数（CI）和挥发性氧化产物的浓度先升高然后降低，而气态产物的浓度一直保持增加。导致氧化物质从固态转变为液态和气态。当老化度极高时，由于迁移和冷凝，液体氧化产物的积累受到限制。因此，羰基指数（CI）和挥发性氧化产物的浓度先升高然后降低，而气态产物的浓度一直保持增加。