From an ecological point of view, plastics are not without their problems: although they consist of elements that occur in nature, they form very stable compounds during the manufacturing process. However, they form very stable compounds in the manufacturing process. Natural decomposition is therefore impossible. Nevertheless, there are enormous differences between the various plastics. In this article, we will look at polyethylene (PE). Due to its unique properties, PE film is used in many ways - but what about sustainability?
Polyethylene (PE) - The environmentally friendly all-rounder
PE films and objects are used everywhere on a daily basis and as a matter of course. The use of the plastic is hardly ever questioned. The discovery of its industrial synthesis in 1933 was rather accidental. However, it took some time and, above all, technical progress before its production became profitable.
Karl Ziegler, a German chemist, and his Italian partner Giulio Natta identified the catalysts needed for simpler and faster production. Ziegler provided the basis for this in 1953: While working at the Max Planck Institute for Coal Research, he discovered that ethene can be polymerized into polyethylene with titanium catalysts, even at low pressures.
The triumphant advance of the new material thus took its course. It is no coincidence that PE is now the world's leading plastic due to the impressive variety of its applications.
As a thermoplastic, PE is more environmentally friendly than conventional plastics: it can be recycled and incinerated without leaving any residues. The starting point for its production is a gas - ethene. It is extracted from natural gas and crude oil. Longer hydrocarbon chains are split into shorter ones. This produces a plastic mass that is sieved and crushed. This produces the white PE granules that can be further processed.
For the production of films, for example, extrusion is used: Under pressure, the deformable mass is continuously pressed through a special opening so that high hose bubbles are created. This PE hose is cooled step by step and stored on rolls so that it can then be made up as desired.
 In addition to extrusion, other processing methods include injection molding, blow molding, compression molding, foaming and fiber spinning. |
Polyethylene: Excellent technical properties
PE can be divided into different classes - depending on the density produced:
Low Density Material (LDPE)
Relatively low density - more elastic and softer compared to High Density material, but shrinkable - most packaging is made of LDPE - resistant at a continuous temperature between -50 °C to +80 °C
Middle Density Material (MDPE)
Medium density - combines advantages of LDPE and HDPE - resistant at continuous temperature between -50 °C and +90 °C
High Density Material (HDPE)
Relatively high density - compared to LDPE more resilient, non-shrinkable and can be converted into very low thicknesses - resistant at a continuous temperature between -50 °C and +100 °C
These special properties indicate that PE films can be used for a variety of purposes due to their different textures.
 You can find even more information about sustainable packaging in our blog! We use sustainable plastics for our pouch packaging, for example. |
PE: Costs and benefits - An interesting relationship
With the development of modern manufacturing processes, PE began a veritable triumphant advance: Polyethylene can be produced in large quantities at extremely low cost and in a relatively resource-friendly manner. Only around 1 percent of the annual consumption of crude oil is accounted for by the production of this plastic. In addition, there have long been alternative methods based on coal or renewable raw materials, for example.
The enormous potential of polyethylene is already indicated at this point. A look at its versatility completes the picture: PE is used not only to produce high-quality films with a wide variety of properties, but also extremely hard and, above all, durable items such as various containers, pipes and even furniture.
Another aspect - not to be underestimated - is that PE is harmless to human health. The North Rhine-Westphalia Consumer Center certified that the plastic does not contain any harmful plasticizers.
It is precisely these plasticizers and other additives that make other plastics significantly more problematic. It is not for nothing that PE films and packaging are preferred in the food industry.
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No plasticizers or other harmful additives are processed in polyethylene - the plastic is harmless to health. |
Big topic: PE and environmental protection
However, the positive properties of PE are countered by criticism in terms of environmental protection: The enormous problems caused by pollution with PE waste have certainly not escaped your attention; huge amounts of plastic waste are floating in the world's oceans in particular. The consequences are manifold and affect flora and fauna both directly and indirectly.
Although PE and other plastics decompose very slowly, mechanical influences cause the formation of microplastics. The occurrence of microplastics can now even be detected in the food chains. The health consequences for humans and animals cannot yet be assessed.
Here the question arises: Is plastic itself considered the cause of these developments? The answer is: Not at all. Rather, it is the consumers who do not handle PE waste properly.
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PE recycling - What is currently possible?
Currently, PE plastics are preferably recycled mechanically: they are cleaned, shredded and remelted so that new granulate can be obtained from them - the so-called recyclate. However, a prerequisite is that thorough pre-sorting is carried out to ensure grade purity and achieve a homogeneous result.
In contrast, chemical recycling is much more complex: in this process, the waste is transformed into a state reminiscent of crude oil, and pre-sorting is not absolutely necessary.
Status quo: recyclate - description and differentiation
This recycled plastic can easily be reintroduced into a product cycle: The recovered granulate is melted down for further processing by injection molding, blow molding or another extrusion process. However, there are differences between household plastic waste and industrial waste, which have improved enormously in quality over time.
The recyclates from private plastic waste can therefore only be used in certain proportions in the production of shrink or fine shrink films.
The special thing about high-quality recyclates is that they can be reprocessed and reused almost as often as required without any loss of quality - quite unlike other raw materials such as paper.
 From a sustainability perspective, precisely configured packaging is always better. Small start-ups benefit from this just as much as large companies. |
Exciting prospects: New recycling processes open up enormous potential
An interesting prospect is emerging for polyethylene - a new recycling process has been developed: In several reaction steps, polyethylene can be turned into the extremely high-quality propylene, which in turn is used to produce polypropylene (PP). This plastic can not only be used in a variety of ways, but is also very easy to recycle.
In view of the enormous spread of plastics, their inherent mechanical resistance is just as big a problem as their chemical inertia: Reaction inertia inhibits the chemical breakup of the long polymer chains.
This is where the new process comes in: To solve the problem of the previously inefficient chemical separation of the single bonds of carbon atoms, the scientists led by John Hartwig of the University of California at Berkeley took a roundabout route. They used platinum-tin and platinum-zinc catalysts to separate some of the hydrogen from the carbon atoms.
The result: The PE chain now contains a series of more reactive carbon double bonds. The ethylene molecules in the reaction vessel can dock onto these. The propylene molecules then split off with the addition of an additional catalyst.
After the discovery of this process, even better efficiency was to be achieved - this is where isomerization came into play. The result was convincing, as more than 80 percent of the PE plastic could be converted into propylene in this way. This is all the more significant because up to now polypropylene has often been produced from shale gas. This is extracted in the course of the controversial fracking process.
Conclusion: PE film and environmental protection - a good match (soon)
The fact is: polyethylene is the most widely used plastic globally. This is due not only to its outstanding properties, from which PE films benefit, but also to its good recyclability compared to PET, PS, PVC or PA. However, this potential has so far been insufficiently exploited, even though pure recycling produces a recyclate that can be used as often as desired.
In fact, it is not the mechanical resistance and chemical inertness of the plastic, which are essential for many products, that are problematic, but the human handling of the plastic waste. Up to now, far too little of the waste has been specifically recycled, so that plastics end up in the environment - especially in the oceans - where they slowly decompose into microplastics.
However, new developments can make the recycling of polyethylene much more attractive, because the result is either adhesives or propylene. This manufacturing base for the high-quality and versatile polypropylene has so far been obtained from shale gas.
However, the fracking process is necessary for its extraction. As soon as the new methods are ready for the market, enormous quantities of PE waste can be recycled, thus conserving natural resources and, above all, reducing the burden on the environment.
