Adding value to polystyrene waste by chemically transforming it into sulfonated polystyrene

ABSTRACT Polystyrene (PS), one of the most used polymers in everyday life, has a low recycling rate due to its inexpensive virgin resin. In order to make polystyrene waste (WPS) recycling advantageous, it is possible to change it chemically, introducing heteroatoms in the polymer chain thus transforming the waste into a material with more added value. In this work, sulfonation reactions of polystyrene waste (disposable cups and expanded polystyrene -EPS) with different degrees of sulfonation were carried out by homogeneous sulfonation using acetylsulfate as a sulfonating agent, originating polystyrene sulfonate (PSS). The characterization of the products was done using Fourier Transformed Infrared Spectroscopy (FTIR), solubility tests and inductively coupled plasma optical emission spectroscopy (ICP-OES). Infrared spectroscopy revealed that the reaction was efficient and all the starting materials tested were successfully sulfonated and transformed into PSS. There was no distinction between the residues tested, revealing that it's possible to carry the reaction without sorting the waste. EPS was chosen as the substrate for further reactions varying the degree of sulfonation. Solubility and ICP-OES tests have shown that, by changing the synthesis conditions, it is possible to achieve different degrees of products sulfonation. As a result of the studied reactions it was found that varying the degree of sufonation it is possible to use polystyrene residues to produce PSS for different applications.

摘要 聚苯乙烯（Polystyrene, PS）是日常生活中应用最广泛的聚合物之一，因其原生树脂价格低廉，回收利用率偏低。为提升聚苯乙烯废弃物（Waste Polystyrene, WPS）的回收经济性，可通过化学改性手段在聚合物链中引入杂原子，将该废弃物转化为附加值更高的材料。本研究以乙酰硫酸酯作为磺化剂，通过均相磺化反应对两类聚苯乙烯废弃物——一次性餐杯与发泡聚苯乙烯（Expanded Polystyrene, EPS）——开展了不同磺化程度的改性实验，成功制备得到聚苯乙烯磺酸盐（Polystyrene Sulfonate, PSS）。采用傅里叶变换红外光谱（Fourier Transformed Infrared Spectroscopy, FTIR）、溶解度测试与电感耦合等离子体光学发射光谱（Inductively Coupled Plasma Optical Emission Spectroscopy, ICP-OES）对产物进行表征。红外光谱分析结果证实，该磺化反应效率优异，所有受试原料均成功完成磺化并转化为聚苯乙烯磺酸盐。两类受试废弃物未表现出反应性能差异，表明无需对聚苯乙烯废弃物进行分类即可开展该反应。后续实验选取发泡聚苯乙烯作为底物，调控其磺化程度。溶解度测试与电感耦合等离子体光学发射光谱分析结果显示，通过调整合成工艺参数，可获得不同磺化度的产物。本研究结果表明，通过调控磺化程度，可利用聚苯乙烯废弃物制备得到适用于不同应用场景的聚苯乙烯磺酸盐。