Isherwood: A brief history of plastic
By Justin Isherwood
The first synthesis of “plastic” occurred in 1907, a period rich with chemical innovation and invention: explosives, gas warfare, synthetic nitrates, stainless steel, vulcanized rubber. Since, plastics have taken on industrial and cultural roles once fulfilled by native material; wood, steel, paper. Plastics what made cars 25% lighter, same for airplanes. Plastics package what once came in paper, cloth or wood.
Plastics have added an efficiency to human culture previously absent, plastic has reduced fabrication time and cost, plastic has vastly expanded the consumer economy and choice. We drive plastic, dress in plastic, watch movies on plastic, our homes sheathed in plastic, carpeted in plastic, varnished with plastic. Global production of plastics is in the range of 500 million metric tons, annually. At current production rates it is expected there will be more plastic in the world’s oceans than fish by 2050.
The essential problem is plastic’s lack of recyclability. Never mind to most consumers plastic seems the most recyclable of industrial components, the ugly truth is only about 5% of manufactured plastic is recycled, never mind that recycling symbol on the bottle. Recycled plastics are destined for low-value secondary plastics that are not in turn recycled but meet their fate in the local landfill.
The most recyclable of plastics are polylactides, but these lack the mechanical and thermal properties needed to manufacture stable long term products such as appliances, auto components, household furniture. The world basically needs a new form of plastic. Enter task-directed research. Recycling plastic is referred to as depolymerization, in essence to take the plastic back to its parent form and start over. Hendricks and partners have successfully depolymerized aromatic polycarbonates/polyesters, that can be returned to production.
The problem, the kinds of plastics that can be depolymerized do not have mechanical or thermal properties useful for industry. The recyclable plastics are not robust enough for the broad range of consumer products.
The search then is for a plastic that can be returned to its virgin state economically and have at the same time availability to a broad range of use for society and industry.
In the 27 April issue of Science was a story on Zhu et.al., a research group that has designed a fully recyclable polymer by means of what they call stereochemistry. The resulting polymer has a semi-crystalline state with superior thermal and mechanical characteristics. The recyclable nature of this plastic is due to (the reader can skip this part if they want) “the retention of a five-membered y-lactone core, that ensures thermal recyclability is preserved.” In English this “monomer plastic” with its chemical positions filled (fused) retains a position “unfused”, allowing it to be readily polymerized.
Depending on the catalyst used, the resulting plastic is highly aligned, meaning mechanically stable and so useful for durable consumer products. The inventors/authors (Zhu et.al) found that blending these plastics resulted in superior materials including a melting point 75°C. higher than the parent material. So that warped dashboard on your car just got fixed. Same for the patio furniture.
Plastic research may not sound like a critical science, but in our polymer world the reinvention of plastics is now critical to planetary health, human wellbeing and our attached economies. The plastic pollution of the world’s oceans continues to escalate, much of it one-way packaging material. Whether that ubiquitous water bottle, the hot dog wrapper, that package of screws from Fleet Farm and a candy wrapper.
That the paper industry of Central Wisconsin has taken a hit on its industrial worth is in part due to the loss of paper for industrial product packaging. A loss made up for in part by shipping container paper, the trade word is corrugated. Only to wonder if the paper industry or environmental science might have intercepted this industrial sift with better planning, better research. Yet to wonder if for much of consumer packaging whether paper products might yet be an option. Something compostable. Because plastic recycling, even with complete recyclability, is still a highly industrial process and in the near term beyond the ability of local waste management. This prospect does present an intriguing local potential when fully recyclable plastics can be accomplished at the municipal level, with a product that can be returned to local industry.
Not to forget, or hope, for our paper industry, because of its potential recycling ease, its use as a soil amendment, might yet reclaim a new place in consumer products. Imagine, a paper bag of peanuts. Same for Fleet Farm wing nuts. Why not a water bottle?