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首页> 外文期刊>Journal of Macromolecular Science. Pure and Applied Chemistry >Thermal properties, degradation and stability of poly(vinyl chloride) predegraded thermooxidatively in the presence of dioctyl phthalate plasticizer
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Thermal properties, degradation and stability of poly(vinyl chloride) predegraded thermooxidatively in the presence of dioctyl phthalate plasticizer

机译：在邻苯二甲酸二辛酯增塑剂存在下热氧化预降解的聚氯乙烯的热性能，降解和稳定性

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摘要

Thermooxidative degradation of poly(vinyl chloride) (PVC) is inevitable during its processing. Recycling of this polymer requires reprocessing in most cases, and due to the low thermal stability of PVC, it is of paramount importance to reveal the effect of thermooxidation on the thermal stability of this commercially important polymer. However, detailed systematic investigations are lacking on this crucial problem. In this study, the thermal behavior of PVCs thermooxidized in dilute dioctyl phthalate (DOP) (di(2-ethylhexyl) phthalate, DEHP) plasticizer was investigated by DSC, thermal gravimetry and isothermal degradation under inert atmosphere. It was found that thermooxidation leads to PVCs with certain extent of internal plasticization by DOP chemically bound to the PVC chains and by the oxidized chain segments as well. Thermogravimetry and isothermal dehydrochlorination under inert atmosphere revealed that even low extent of thermooxidation of PVC (0.4 mol% of HCl loss in 30 min at 200°C) leads to dramatically decreased thermal stability of this polymer with 50-60°C lower onset decomposition temperature than that of the virgin resin. This unexpected finding means that at least part of the oxidized moieties formed during oxidation of the PVC chains acts as initiators for thermal dehydrochlorination at relatively low temperatures, resulting in significant decrease of the thermal stability of the polymer. These striking results also indicate that the decreased thermal stability caused by thermooxidation in the course of the primary processing of this polymer should be taken into account in order to efficiently stabilize PVC products for reprocessing and recycling.
机译：聚氯乙烯（PVC）在加工过程中不可避免地发生热氧化降解。回收这种聚合物在大多数情况下都需要进行后处理，并且由于PVC的热稳定性低，因此最重要的是揭示热氧化作用对这种商业上重要的聚合物的热稳定性的影响。但是，缺乏对该关键问题进行详细的系统研究。在这项研究中，通过DSC，热重分析和在惰性气氛下的等温降解研究了在邻苯二甲酸二辛酯（DOP）（邻苯二甲酸二（2-乙基己基）酯，DEHP）增塑剂中热氧化的聚氯乙烯的热行为。发现通过DOP化学结合到PVC链上以及通过氧化的链段，热氧化导致PVC具有一定程度的内部增塑。惰性气氛下的热重分析和等温脱氯化氢表明，即使PVC的热氧化程度较低（200°C下30分钟内HCl损失0.4 mol％）也会导致该聚合物的热稳定性急剧降低，起始分解温度降低50-60°C比原始树脂要高。这一出乎意料的发现意味着在PVC链氧化过程中形成的至少一部分氧化部分在相对较低的温度下充当热脱氯化氢的引发剂，导致聚合物的热稳定性显着降低。这些惊人的结果还表明，应考虑到在该聚合物的初加工过程中因热氧化而导致的热稳定性下降，以便有效地稳定PVC产品进行再加工和回收。

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