We investigated the influence of multiple extrusions of poly-(ethylene terephthalate) (PET) blended with a polymer-based oxygen scavenger. PET and PET blended with an oxygen scavenger additive were extruded up to four times to polymer strands. They were chilled in a water bath and cut to granules. Between the extrusions, the granules were dried at (only) 60°C to avoid the oxygen scavenger losing its reactivity. The water content was up to 0.5 wt.-% and therefore up to factor 100 higher than the recommended water content for PET extrusion. For further analysis, films were extruded and bottles were stretch-blow-molded. Due to polymer degradation and the recycled PET blend viscosity being too low, this material had to be blended with virgin PET in order to be processable. We used 33 wt.-% recycled PET and 66 wt.-% virgin PET ratio. The impact of the thermomechanical stress by multiple extrusions was investigated by several test methods: analysis of the melt pressure in the extruder barrel during extrusion, intrinsic viscosity and melt flow rate, microscopy, differential scanning calorimetry, color value measurements (L*a*b* values), tensile testing, compression testing, and oxygen absorption measurements. The intrinsic viscosity reduced after four re-extrusions in a compounder from 0.82 dl/g to 0.35 dl/g for PET with scavenger and to 0.41 dl/g for pure PET. This, even though low, difference can be explained by the slightly higher PET degradation due to the oxygen scavenger. We found slightly better mechanical properties (yield stress, Young’s modulus) for pure PET films compared to PET blended with an oxygen scavenger. At up to three extrusions, there was little influence on these properties. The extruded material with 3 wt.-% oxygen scavenger additive has an oxygen absorption capacity of 9.5 mg oxygen per 1 g of granules, i.e., the scavenger additive absorbed about 300 mg oxygen per 1 g of additive. Our results are relevant for in-house recycling processes of PET with oxygen scavenger.

中文翻译：

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由聚对苯二甲酸乙二醇酯和除氧剂制成的共混物的多次挤出对加工和包装相关性能的影响

我们研究了聚对苯二甲酸乙二醇酯 (PET) 与聚合物除氧剂混合多次挤出的影响。PET 和与除氧剂添加剂混合的 PET 最多被挤出四次，形成聚合物线材。它们在水浴中冷却并切成颗粒。在挤出之间，颗粒在（仅）60°C 下干燥以避免除氧剂失去其反应性。水含量高达 0.5 wt.-%，因此比 PET 挤出的推荐水含量高 100 倍。为了进一步分析，挤出薄膜并拉伸吹塑瓶。由于聚合物降解和回收的 PET 混合物粘度太低，这种材料必须与原始 PET 混合才能进行加工。我们使用了 33 wt.-% 的再生 PET 和 66 wt.-% 的原生 PET 比例。通过多种测试方法研究了多次挤出对热机械应力的影响：挤出过程中挤出机机筒中的熔体压力分析、特性粘度和熔体流动速率、显微镜、差示扫描量热法、色值测量 (L*a*b * 值）、拉伸测试、压缩测试和氧吸收测量。在复合机中四次再挤出后，特性粘度从 0.82 dl/g 降低到 0.35 dl/g（对于带清除剂的 PET）和 0.41 dl/g（对于纯 PET）。尽管这种差异很小，但可以通过除氧剂导致的 PET 降解率略高来解释。我们发现纯 PET 薄膜的机械性能（屈服应力、杨氏模量）比与除氧剂混合的 PET 略好。在多达三个挤压，对这些属性几乎没有影响。具有3wt.-％氧清除剂添加剂的挤出材料具有每1g颗粒9.5mg氧的氧吸收能力，即每1g添加剂吸收约300mg氧的清除剂添加剂。我们的结果与带有除氧剂的 PET 的内部回收过程相关。