Catalysis for Compatibilizers: Upcycling Plastic Waste into Value-Added Materials

塑料对环境的影响是一个Jekyll-and-Hyde难题。虽然塑料污染构成了一个非常真实的环境危险，但塑料也将整个欧洲的二氧化碳排放量减少了5-9倍，部分原因是它们被用作运输车辆的轻质部件和建筑绝缘材料。塑料还通过减少20%的食物浪费来应对粮食安全的全球挑战。然而，目前的生产方法是不可持续的。到2015年，全球生产的8300公吨塑料中，有4900公吨被丢弃。从线性塑料生产模式向循环经济模式转变具有迫切的重要性，需要创新的科学技术。目前99%以上的塑料生产来自原油。到2050年，预计年产量将使用全球石油储量的20%，产生的二氧化碳是航空业的两倍。为了节约石油库存和避免能源密集型裂解过程，寻找替代原料至关重要。废弃的塑料废物提供了一种有吸引力的替代原料，通过将这种废物回收利用成有用的附加值产品。然而，目前只有10%的塑料被回收利用。这在一定程度上是因为“回收”材料通常是向下循环的，材料性能的降低，如强度和灵活性，导致应用价值逐渐降低，直到回收迅速不再具有成本效益。使这一复杂过程变得更加复杂的是，塑料产品往往含有多种类型的塑料。例如，牛奶盒是由聚乙烯(PE)制成的，但盖子和标签是由聚丙烯(PP)组成的；这些塑料需要分离，然后作为单独的成分进行回收。创造性的科学解决方案是解决这些问题的关键。在过去的两年里，出现了一种改变游戏规则的技术。“化学拉链”的发明使PE和PP的组合能够有效回收，避免了分离这两种材料的需要。“拉链”是一种具有不同的交替的“牙齿”的分子；一组牙齿与PE相互作用，另一组牙齿与PP相互作用，将这两种塑料缝合在一起。值得注意的是，由PE、PP和拉链组合而成的新型混合塑料提供了比任何单独组件都更坚固的可回收材料。这些“拉链”的工业化商业化将彻底改变PE和PP的临终处理方式。然而，到目前为止，开发的技术是有限的。虽然已经为PE和PP开发了化学拉链，但对于聚酯的类似系统仍未被探索。将这一概念转化为聚酯是一个令人兴奋的目标，因为可降解聚酯的使用在过去四年中翻了一番。解放军的商业产品包括一次性饮水杯、薄膜和食品包装，一些解放军产品涉及混合塑料系统，如带有PE膜的解放军食品托盘。回收公司报告称，聚乳酸对回收流的污染越来越严重，这是一个问题，因为目前的分离技术不如传统塑料那么发达，而且这一挑战将会越来越大。生产可以将聚乳酸与PE、PP或聚苯乙烯(PS)相结合的新化学拉链将彻底改变目前的回收工艺，并从废物中创造一系列新的可循环塑料材料，但这些系统的开发受到了生产此类拉链的巨大科学挑战的阻碍。该项目将通过设计一种催化剂，在两种不同的化学反应之间切换，一次一颗牙齿地制造这些拉链，从而为解放军生产定制的化学拉链。这些变革性的拉链将应用于聚乳酸与PE、PP和PS的组合，从塑料垃圾中创造出一种新的理想的、多样化的和有价值的材料，为社会带来重要的经济、环境和能源效益。

The environmental impact of plastics is a Jekyll-and-Hyde conundrum. While plastic pollution poses a very real environmental danger, plastics have also reduced CO2 emissions across Europe by a factor of 5-9, partly through their use as lightweight components in transport vehicles and as building insulation materials. Plastics also address the global challenge of food security by reducing food waste by 20%. However, current production methods are unsustainable. Of the 8300 Mt of plastic produced globally by 2015, 4900 Mt has been discarded. Moving from a linear plastic production model to a circular economy is of urgent importance and requires innovative scientific technologies.Over 99% of plastics are currently produced from crude oil. By 2050, annual production is predicted to use 20% of global oil reserves and generate twice as much CO2 as the aviation industry. To conserve oil stocks and avoid energy intensive cracking processes, it is essential to find alternative feedstocks. Discarded plastic waste offers an attractive alternative feedstock, by upcycling this waste material into useful value-added products. Yet only 10% of plastics are currently recycled. This is partly because "recycled" materials are generally downcycled, with a reduction in material properties such as strength and flexibility leading to progressively lower value applications until recycling is rapidly no longer cost effective. Further complicating this complex process, plastic products often contain multiple types of plastic. For example, milk cartons are made of polyethylene (PE) but the lids and labels consist of polypropylene (PP); these plastics require separation and subsequent recycling as individual components. Creative scientific solutions are crucial to address these problems.A game-changing technology has emerged in the past two years. The creation of "chemical zips" has enabled efficient recycling of a combination of PE and PP, avoiding the need for separation of these two materials. The "zip" is a molecule designed with different and alternating "teeth"; one set of teeth interacts with PE while the other set interacts with PP to stitch these two plastics together. Remarkably, the new hybrid plastics produced by combining PE, PP and the "zip" give upcycled materials that are stronger than any of the individual components. The industrial commercialisation of these "zips" is set to revolutionise the end-of-life treatment of PE and PP. However, the technology developed to date is limited.While chemical zips have been developed for PE and PP, analogous systems for polyesters remain unexplored. Translating this concept to polyesters is an exciting target, as the use of degradable polyesters such as polylactic acid (PLA) has doubled in the past four years. Commercial PLA products include disposable drinking cups, films and food packaging, and some PLA products involve mixed plastic systems such as PLA food trays with a PE film. Recycling companies have reported increasing contamination of recycling streams with PLA, which is problematic as the current separation technologies are less well developed than for conventional plastics, and this challenge is set to grow.The production of new chemical zips that could amalgamate PLA with PE, PP or polystyrene (PS) would revolutionise current recycling processes and create a range of new upcycled plastic materials from waste, yet the development of these systems has been hindered by the significant scientific challenge of producing such zips. This project will enable the production of bespoke chemical zips for PLA by designing a catalyst that can switch between two different chemical reactions to build up these zips one tooth at a time. These transformative zips will then be applied to the combination of PLA with PE, PP and PS to create a new class of desirable, diverse and valuable materials from plastic waste, with important economic, environmental and energy benefits for society.