Simi Schauer

From Waste to Paste

April 12, 2021

A new development makes it possible to convert discarded plastic bags left to pollute into strong, adhesive glue substances. Will this succeed in reducing the ongoing environmental damage perpetrated by disposable plastic?

In cooperation with the Nature and Parks Authority, the Ministry of Environmental Protection announced that it was promoting a ban on bringing disposables, including utensils, into nature reserve areas and national parks this past January.  Around the same time coincidentally, Coca-Cola issued a statement stating that by 2030, it would stop using plastic for their beverage bottles and transition to paper-based bottles, which are currently undergoing a series of tests and trials.

If both the Israeli government and one of the largest companies in the world (one of the top-ranking plastic polluters) understand that the use of disposable plastic is one of the most significant environmental challenges, then it is probably time to act. According to expert estimates, the weight of plastic in the oceans is on track to exceed the weight of all oceanic fish by 2050 if no significant changes are applied to plastic production and treatment policies.

Luckily, a new American development proposes to convert plastic bags into sticky adhesives as a creative way to upcycle plastic and slash the egregious amounts plastic waste buildup.

Not as Recyclable as You Think

According to expert estimates, the weight of plastic in the oceans is on track to exceed the weight of all oceanic fish by 2050 if no significant changes are applied to plastic production and treatment policies. Photo by Nick Fewings on Unsplash.

One of the major problems in the field of plastic waste treatment is that the plastic recycling process is expensive, requires lots of energy, uses water, heavily relies on transportation, all of which come at a significant environmental cost. But on the other hand, the production of new plastic from oil remains cheap and available.

“There are products, such as plastic beams used for camping, that can be made from different types of plastic that are melted together whether its the packaging for cleaning materials, cups, or pipe parts,” explains Prof. Ofira Ayalon of the Samuel Neaman Institute at the University of Haifa. 

“However, for the production of many other products, such as recycled ketchup bottles, only a uniform raw material can be used. As a result, it is necessary to separate the waste according to plastic type, which complicates the recycling process, making it more expensive.”

Plastic bags are usually made of polyethylene, a type of plastic that makes up about a third of all plastic produced in the world. According to Ayalon, the process of recycling polyethylene is not economically viable.

“Bags made of polyethylene are inferior raw materials, which will make the recycling process even more cumbersome,” she says. “Therefore, almost no bags are recycled today.”

From Hard Plastic to Adhesive Material

Polyethylene used as an adhesive. Figure from the study.

In a new study, the researchers propose to turn plastic waste into a high strength glue through a specially developed chemical process, which enables polyethylene to function as an adhesive that binds to metal.

As part of the process, the researchers added hydroxyl groups to the polyethylene: an oxygen atom covalently bonded to a hydrogen atom that can bond to other atoms like carbon, for example, whose thousands of atoms are connected in a chain of polymer components similar to polyethylene. To do this, they used a catalyst, a substance capable of accelerating chemical reactions, based on ruthenium (a hard metal that withstands high temperatures).

The researchers also discovered during the development of the method that adding a small amount of alcohol to the material increases its stickiness by a factor of 20. The researchers made chemical changes in less than 10% of the polyethylene polymer, but that was enough to turn it from hard plastic into an adhesive material

According to the researchers, turning polyethylene into a sticky material does not impair its other properties that are useful in industry, such as its ability to process, its thermal stability, and its mechanical properties. Unlike regular polyethylene, the upgraded material can even be painted, using a water-based latex paint.

Alternative Uses

According to the researchers, turning polyethylene into a sticky material does not impair its other properties that are useful in industry. Gif by Kleber.

Admittedly, the process of turning plastic bags into glue has not yet been proven to be profitable on an industrial scale, but researchers believe it can be and that it can be a starting point for adding other useful properties to polyethylene besides adhesiveness. The researchers’ success may indicate that other catalysts may change the properties of other types of plastics such as polypropylene, which is used to make recycled plastic bottles. In the future, this may allow other useful materials with economic value to be produced from used and discarded plastics.

According to the researchers, adhesive polyethylene can also be useful for many other purposes including the improvement of artificial knee implants and hip sockets, which are often made of polyethylene combined with metallic components. Additionally, it can be used in the production of electrical wiring and can be utilized to manufacture more durable toys made from plastic and metal compounds.

Tackle the Problem at its Source

If and when it becomes commercial, the new development may help solve the problem of plastic bag waste buildup, at the very least partially. However, according to Ayalon, in order to properly understand the scope of its environmental contribution, a life cycle analysis (LCA) must be performed. That is, a comprehensive assessment of the product’s environmental impact throughout its life (from the raw material stage, to production and use, to the end of its life as waste).

“If all of this impact is taken into account and the process is found to be environmentally worthwhile, it may be a good solution,” she says.

This new development joins with several other recent creative ideas designed to reduce the amount of plastic waste we as a society generate. For example, a study currently being conducted at Ben-Gurion University, in collaboration with the Portuguese recycling company ECOIBÉRIA, found bacteria capable of breaking down PET (polyethylene terephthalate) into monomers, its subunits, in order to reuse them as a raw material for other plastic products. At the same time, researchers in Sweden are currently developing an industrial process through which it will be possible to turn plastic waste into raw material for new plastic products.

However, Ayalon emphasizes that in the end, the best solution to the plastic waste problem is to simply produce less of it.

“Many times, thanks to the recycling bin, people who dispose of their plastic waste there feel that they are ‘allowed’ to waste plastic,” she says. “However, it is always better to tackle the problem at its source. In this case, manufacturing and using fewer plastic bags and other plastic products should be our primary objective.”

This ZAVIT Article was also published in The Jewish Journal on 6 Apr. 2021