Presence of iron in polymers extruded with corrosive contaminants or abrasive fillers

Abstract Off-site measurements of the dimensions of extruder screws are used to monitor their wear. This wear causes the presence of metals in the processed polymer. We detected the presence of iron in polymers processed with corrosive contaminants or abrasive fillers. To this end we processed poly(ethylene terephthalate), PET, pure or contaminated with poly(vinyl chloride), PVC, and other thermoplastics reinforced with glass fibers, talc or vegetal fibers, and analyzed the metals in the processed materials by X-ray fluorescence spectroscopy. We show that iron dispersed in the polymer melt is generated by corrosion from the PET contaminated with PVC and by erosion from abrasive fillers. The contents of iron in the extruded polymers clearly indicate equipment wear. This contaminant acts as a polymer pro-degradant, decreasing its lifetime. Additionally, we show that the lower concentration of iron for composites with vegetal fibers indicates a lower abrasion in comparison to talc and glass fibers.

摘要 挤出机螺杆尺寸的离线测量可用于监测其磨损情况。螺杆磨损会导致加工后的聚合物中出现金属杂质。我们在含有腐蚀性污染物或磨蚀性填料的加工聚合物中检测到了铁元素。为此，我们分别加工了纯聚对苯二甲酸乙二酯（poly(ethylene terephthalate), PET）、受聚氯乙烯（poly(vinyl chloride), PVC）污染的聚对苯二甲酸乙二酯，以及添加玻璃纤维、滑石粉或植物纤维增强的其他热塑性塑料，并通过X射线荧光光谱法对加工后材料中的金属成分进行了分析。研究表明，分散在聚合物熔体中的铁元素来源于受PVC污染的PET的腐蚀作用，以及磨蚀性填料带来的冲蚀磨损。挤出聚合物中的铁元素含量可清晰反映设备的磨损情况。该铁杂质可作为聚合物的促降解剂，缩短聚合物的使用寿命。此外，我们还发现，与添加滑石粉和玻璃纤维的复合材料相比，植物纤维增强复合材料中的铁元素浓度更低，这意味着其冲蚀磨损程度更低。