Full Circle Recycling of Polysiloxanes via Room-Temperature Fluoride-Catalyzed Depolymerization to Repolymerizable Cyclics
Full Circle Recycling of Polysiloxanes via Room-Temperature Fluoride-Catalyzed Depolymerization to Repolymerizable Cyclics
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DOI：
10.1021/acsapm.0c01406
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发表时间：
2021-03-10
影响因子：
5
通讯作者：
Furgal, Joseph C.
中科院分区：
文献类型：
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作者：
Rupasinghe, Buddhima;Furgal, Joseph C.
硅氧烷基聚合物材料因其化学、机械和热稳定性以及低毒性而在世界各地得到广泛应用。尽管它们很有用，但当它们被丢弃时，用于制造它们的高能源成本就会消失，浪费资源和能源。因此，需要实用且简单的方法来回收这些材料。然而，这些方法的简化还不够完善。目前用于回收有机硅基材料（例如聚二甲基硅氧烷）的技术通常涉及高温/高压和复杂的装置。为了解决这个问题，我们建立了一种有效的室温技术，用于在特定的高溶胀有机溶剂中，在低催化量的氟化物存在下，对有机硅基聚合物、弹性体和树脂进行解聚。经GCMS和Si-29核磁共振验证，该产品主要含有环状硅氧烷单元（D-4、D-5和D-6）。几乎任何有机硅树脂都可以使用这些方法快速解聚。富含有机硅的系统可实现最佳的转化率和最高数量的可识别环状化合物，而复杂的树脂则可产生复杂的产品以及可识别的环状化合物。我们还通过酸、碱和氟化物催化重新聚合该工艺的产品，以重整有机硅。该工艺由于使用条件温和且溶剂回收能力强，具有大规模工业加工的潜力。
Siloxane-based polymeric materials are widely used all over the world because of their chemical, mechanical, and thermal stability and due to their low toxicity. Despite their usefulness, the high energy cost used to make them is lost when they are discarded, wasting resources and energy. Practical and simple methods of recycling these materials are therefore required. However, the simplification of these methods is underdeveloped. The present techniques used to recycle silicone-based materials, such as polydimethylsiloxanes, often involve high temperatures/pressures and complicated setups. To address this issue, we have established an efficient room-temperature technique for the depolymerization of silicone-based polymers, elastomers, and resins in the presence of low catalytic amounts of fluoride in specific high swell organic solvents. The products primarily contain cyclic siloxane units (D-4, D-5, and D-6) as verified by GCMS and Si-29 nuclear magnetic resonance. Nearly any silicone resin can be depolymerized rapidly using these methods. Silicone-rich systems result in the best conversions and the highest quantity of identifiable cyclics, while complex resins resulted in complicated products alongside discernible cyclics. We have also repolymerized the products from this process to reform silicones via acid, base, and fluoride catalysis. This process has the potential for large-scale industrial processing because of the use of mild conditions and solvent recycling ability.