Plastics contain various additives, like fillers, flame retardants or pigments. Hence few plastics can be recycled without loss in performance or aesthetics. A team of researchers at the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) has designed a recyclable plastic that, like a Lego playset, can be disassembled into its constituent parts at the molecular level, and then reassembled into a different shape, texture, and color again and again without loss of performance or quality. The new material, called poly(diketoenamine), or PDK, was reported in the journal Nature Chemistry
伯克利实验室分子铸造厂的博士后研究员彼得·克里斯滕森（Peter Christensen）说：“我们发现了一种组装塑料的新方法，从分子角度考虑回收。”
克里斯滕森（Christensen）是由伯克利实验室（Berkeley Lab）分子铸造厂的一名工作人员布雷特·赫尔姆斯（Brett Helms）领导的跨学科团队的成员。
从水瓶到汽车零件，所有塑料均由称为聚合物的大分子组成，这些分子由称为单体的较短含碳化合物的重复单位组成。
根据研究人员的说法，许多塑料的问题是，添加的化学物质使它们有用，例如使塑料坚硬或使塑料柔性的塑料变质的填充剂紧密地绑定到单体并在塑料中固定在塑料中it’s been processed at a recycling plant.
During recycling mixed plastics with different chemical compositions, it’s hard to predict which properties it will inherit from the original plastics.
与常规塑料不同，可以通过将材料浸入高度酸性溶液中，从而从任何复合添加剂中回收并从任何复合添加剂中释放出来。(Credit: Peter Christensen et al./Berkeley Lab)
This inheritance of unknown and therefore unpredictable properties is a challenge in recycling mixed plastic consumer waste. It is difficult to upcycle, to make a new, higher quality product.
Recycling plastic one monomer at a time
该延时视频显示了一块酸中的PDK塑料，因为它降解为分子构建块 - 单体。酸有助于打破单体之间的键，并将其与化学添加剂分开，从而使塑料看起来和感觉。（信用：彼得·克里斯滕森/伯克利实验室）
The researchers want to divert plastics from landfills and the oceans by incentivizing the recovery and reuse of plastics, which could be possible with polymers formed from PDKs. “With PDKs, the immutable bonds of conventional plastics are replaced with reversible bonds that allow the plastic to be recycled more effectively,” Helms said.
与常规塑料不同，可以通过将材料浸入高度酸性溶液中，从而从任何复合添加剂中回收并从任何复合添加剂中释放出来。酸有助于打破单体之间的键，并将其与化学添加剂分开，从而使塑料看起来和感觉。
赫尔姆斯说：“我们对将塑料生命周期从线性重定向到圆形的化学感兴趣。”“我们看到了没有回收选择的机会。”其中包括胶粘剂，手机盒，手表，鞋子，计算机电缆以及通过成型热塑料材料而创建的硬汉。
The researchers first discovered the exciting circular property of PDK-based plastics when Christensen was applying various acids to glassware used to make PDK adhesives, and noticed that the adhesive’s composition had changed. Curious as to how the adhesive might have been transformed, Christensen analyzed the sample’s molecular structure with an NMR (nuclear magnetic resonance) spectroscopy instrument. “To our surprise, they were the original monomers,” Helms said.
在测试了分子铸造厂的各种配方后，他们证明了酸不仅会将PDK聚合物分解为单体，而且该过程还可以使单体与缠绕的添加剂分离。
接下来,他们证明了此后单体中恢复过来can be remade into polymers, and those recycled polymers can form new plastic materials without inheriting the color or other features of the original material – so that broken black watchband you tossed in the trash could find new life as a computer keyboard if it’s made with PDK plastic. They could also upcycle the plastic by adding additional features, such as flexibility.
朝着一个圆形塑料的未来
PDK plastics are a “circular” material whose original monomers can be recovered for reuse for as long as possible, or “upcycled” to make a new, higher quality product. (Credit: Peter Christensen et al./Berkeley Lab)
The researchers believe that their new recyclable plastic could be a good alternative to many nonrecyclable plastics in use today.
赫尔姆斯说：“我们正处于一个关键时刻，我们需要考虑现代化回收设施所需的基础设施，以实现未来的废物分类和处理。”“如果这些设施被设计为回收或升级PDK及相关塑料，那么我们将能够更有效地从垃圾填埋场和海洋中转移塑料。这是一个激动人心的时刻，开始思考如何设计材料和回收设施以实现圆形塑料。”赫尔姆斯说。
The researchers next plan to develop PDK plastics with a wide range of thermal and mechanical properties for applications as diverse as textiles, 3D printing, and foams. In addition, they are looking to expand the formulations by incorporating plant-based materials and other sustainable sources.
Source: LawrenceBerkeleyLaboratory
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