塑料含有各种添加剂，例如填充剂，阻燃剂或颜料。因此，很少有塑料可以回收，而不会造成性能或美学损失。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
作者皮特r Christensen, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry says “We have discovered a new way to assemble plastics that takes recycling into consideration from a molecular perspective.”
Christensen was part of a multidisciplinary team led by Brett Helms, a staff scientist in Berkeley Lab’s Molecular Foundry.
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。
According to the researchers, the problem with many plastics is that the chemicals added to make them useful – such as fillers that make a plastic tough, or plasticizers that make a plastic flexible – are tightly bound to the monomers and stay in the plastic even after it’s been processed at a recycling plant.
在与不同化学成分的回收混合塑料中，很难预测其将从原始塑料中继承的哪些特性。
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。（信用：彼得·克里斯滕森（Peter Christensen）等人/伯克利实验室）
在回收混合塑料消费者废物的挑战中，对未知和不可预测的属性的继承是一个挑战。很难升级，制造一种新的，更高质量的产品。
一次回收塑料一个单体
This time-lapse video shows a piece of PDK plastic in acid as it degrades to its molecular building blocks – monomers. The acid helps to break the bonds between the monomers and separate them from the chemical additives that give plastic its look and feel. (Credit: Peter Christensen/ Berkeley Lab)
研究人员希望通过激励塑料的恢复和再利用来使塑料从垃圾填埋场和海洋中转移，这可能是通过PDK形成的聚合物的。赫尔姆斯说：“使用PDK，传统塑料的不变键被可逆键取代，允许塑料更有效地回收塑料。”
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。The acid helps to break the bonds between the monomers and separate them from the chemical additives that give plastic its look and feel.
“We’re interested in the chemistry that redirects plastic lifecycles from linear to circular,” said Helms. “We see an opportunity to make a difference for where there are no recycling options.” That includes adhesives, phone cases, watch bands, shoes, computer cables, and hard thermosets that are created by molding hot plastic material.
当克里斯滕森（Christensen）将各种酸应用于用于制造PDK粘合剂的玻璃器皿时，研究人员首先发现了基于PDK的塑料的令人兴奋的圆形特性，并注意到粘合剂的成分发生了变化。克里斯滕森（Christensen）用NMR（核磁共振）光谱仪器仪器分析了样品的分子结构。赫尔姆斯说：“令我们惊讶的是，它们是原始的单体。”
After testing various formulations at the Molecular Foundry, they demonstrated that not only does acid break down PDK polymers into monomers, but the process also allows the monomers to be separated from entwined additives.
Next, they proved that the recovered PDK monomers 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.
走向圆形塑料未来
PDK塑料是一种“圆形”材料，可以尽可能长时间地回收原始单体以重复使用，或“升级”以制造一种新的，更高质量的产品。（信用：彼得·克里斯滕森（Peter Christensen）等人/伯克利实验室）
研究人员认为，他们的新可回收塑料可能是当今使用许多不可回收塑料的好替代方法。
“We’re at a critical point where we need to think about the infrastructure needed to modernize recycling facilities for future waste sorting and processing,” said Helms. “If these facilities were designed to recycle or upcycle PDK and related plastics, then we would be able to more effectively divert plastic from landfills and the oceans. This is an exciting time to start thinking about how to design both materials and recycling facilities to enable circular plastics,” said Helms.
研究人员的下一个计划计划开发具有多种热和机械性能的PDK塑料，用于像纺织品，3D打印和泡沫一样多样化。此外，他们希望通过合并植物性材料和其他可持续资源来扩展配方。
资料来源：劳伦斯伯克利实验室
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