Plastics in paper packaging

Part 2: Important coating polymers

In the first part of our series on plastic content in paper-based packaging for food and consumer goods, we focused on the reasons for using plastic layers and typical functional requirements – without going into specific types of polymers. In part 2, we now turn our attention to individual, sometimes specialised plastic materials and plastic substitutes that are used specifically to achieve certain functional properties. We look not only at conventional plastics, but also at bio-based and alternative materials that are important in terms of barrier effect, sealability and surface protection, as well as from an environmental and regulatory perspective. Our focus is on plastics in paper packaging: from PE to bio-based polyesters – an overview of functions, environmental aspects and regulatory requirements.

Polyethylene (PE) 

Polyethylene is the plastic most commonly used in paper-based packaging, usually applied as a thin coating on cardboard or paper. It primarily serves as a moisture and grease barrier, ensuring that liquids or oils do not penetrate the paper fibres. At the same time, PE’s thermoplastic properties enable reliable sealability, which is particularly important for bags, cups and food cartons. PE is chemically inert, food-safe and relatively inexpensive, which explains its widespread use. From an environmental point of view, however, it is problematic because it can only be separated from the fibre material in paper recycling through complex processes and remains persistent in nature. More recycling-friendly variants, such as thinner coatings or modified PE types, are currently being developed to improve the recyclability of paper-PE composites.

Styrene acrylate copolymers 

Styrene acrylate copolymers combine the properties of styrene and acrylic acid esters. In paper-based packaging, they are primarily used as binders in barrier or protective coatings, where they provide adhesion, mechanical stability and water resistance. They are also found in certain adhesives and printing inks, where they contribute to a robust, durable surface.

Acrylate polymers 

Acrylate polymers (pure acrylates) are frequently used in adhesives for labels and packaging tapes. They are characterised by strong adhesion, UV and moisture resistance, and temperature stability. In addition to adhesives, acrylates are also used as transparent coatings on films or paper to improve barrier properties against gases and aromas without compromising printability or optical quality.

Polysiloxanes

Polysiloxanes, also known as silicones, are primarily used in packaging as ultra-thin coatings or additives. For example, they serve as a non-stick or release layer on paper substrates, such as label backing papers, so that adhesive surfaces can be easily removed. When added in small quantities, polysiloxanes also improve the processability and lubricity of coatings, such as in the coating of paper. Due to their temperature and chemical resistance, they are suitable for many food contact applications.

Polyhydroxybutyrate (PHB) 

PHB belongs to the family of bio-based polyhydroxyalkanoates (PHA) and is produced by microorganisms from renewable raw materials. It is completely biodegradable and can replace polypropylene in certain applications. PHB is rigid, dimensionally stable and suitable for direct food contact, but it is more brittle and heat-sensitive than many conventional plastics. In paper composites, it can serve as a coating or film layer, especially in compostable disposable packaging.

Bio-based polyesters 

Bio-based polyesters comprise a range of materials that are made entirely or partially from renewable raw materials. A well-known example is polylactic acid (PLA), which is compostable under industrial conditions and is used in the form of films, trays or paper coatings. Other bio-based polyesters include PEF, which can replace PET, and PBS or PBAT, which are used for compostable films and bags. These materials offer potential for reducing fossil raw materials, but face challenges such as limited heat resistance or limited recycling infrastructure.

Conclusion 

The materials presented, which are not an exhaustive list, complement the range of functional plastics in paper-based packaging and demonstrate the wide variety of options available for achieving specific properties such as barrier effect, sealability or surface protection. Their choice depends heavily on technical requirements, regulatory compliance and environmental goals – an area that is likely to become even more dynamic in the coming years.

List of sources for research on the various coatings used on paper:

1. Packoi. “PE Coated Paper.” Access on 3 September 2025. [https://packoi.com/de/blog/pe-coated-paper/](https://packoi.com/de/blog/pe-coated-paper/). 

2. Siegwerk Druckfarben AG & Co. KGaA. “Paper Coating Guide.” Access on 3 September 2025. [https://www.siegwerk.com/fileadmin/Data/Documents/Publications/Flyer/210_297_4C_SW_Flyer_PaperCoatingGuide_DE_Final.pdf] (https://www.siegwerk.com/fileadmin/Data/Documents/Publications/Flyer/210_297_4C_SW_Flyer_PaperCoatingGuide_DE_Final.pdf).

3. Guyenne Paper. “Coating: What is it?” Access on 3 September 2025. [https://www.guyennepapier.com/de/blog/detail/beschichtung-was-ist-das/](https://www.guyennepapier.com/de/blog/detail/beschichtung-was-ist-das/).

Author: Dr. Daniel Wachtendorf, Innoform GmbH August 2025