What is polystyrene film and what properties characterise this plastic?
Polystyrene (PS) is a thermoplastic produced by the polymerisation of styrene, an aromatic monomer. In film form, PS shows its best properties: it is crystal-clear, has high stiffness and is relatively easy to process. Polystyrene film can be easily printed and bonded, properties that make it particularly attractive for technical, industrial and creative applications.
Basic properties of polystyrene as a thermoplastic
As a thermoplastic, polystyrene can be heated at temperatures around 100 °C, formed and then solidified again. PS is hard, dimensionally stable, has a closed surface and is well resistant to many acids, alkalis and alcohol, but less so against solvents such as petrol or acetone. PS films have low thermal conductivity, are translucent (except in coloured variants) and offer good dimensional stability.
The difference between PS film and other plastic films such as polyethylene (PE)
In contrast to PE film, polystyrene film is stiffer, harder and optically more brilliant. PE is more flexible, tougher and better suited for stretchable applications. PS film, by contrast, is particularly suitable when dimensional stability, clarity and a smooth surface are important, for example in packaging, displays or thermoformed parts.
Polystyrene film: crystal-clear with higher hardness and stiffness
The high stiffness and hardness of polystyrene film make it the ideal choice for many specialist applications in display construction, printing, medical technology or blister packaging. Because polystyrene can be supplied crystal-clear or white coloured, the film can be tailored exactly to the visual requirements.
What types of polystyrene films exist and how do they differ?
Unmodified polystyrene vs. expanded polystyrene (EPS)
Unmodified PS is hard and clear, ideal for smooth, thin films. In contrast, expanded polystyrene (EPS) is produced by blowing a propellant into polystyrene granulate. This creates gas-filled foam beads that are expanded into a closed-cell insulating material. EPS is lightweight, insulating and excellent as insulation material in construction.
Extruded polystyrene and its special properties
XPS (extruded polystyrene), for example brands such as Styrodur, Austrotherm XPS or Jackodur, is produced in a continuous extrusion process. The closed cell structure offers not only good insulation values but also low water absorption and high compressive strength. This makes XPS the first choice for perimeter insulation and under floor slabs.
The importance of tacticity: atactic polystyrene and its applications
Atactic polystyrene has no regular molecular structure, making it soft and rubber-like, in contrast to isotactic PS, which is more crystalline and firmer. Due to the low crystallisation speed, atactic PS usually remains a residual product in practice or is used as a plasticiser in compounds.
In which application areas are polystyrene films mainly used?
Applications in construction as insulation material and rigid foam
PS films and their foamed variants (EPS and XPS) are popular in the construction industry due to their insulating properties and cost-efficiency. They are used as rigid foam boards in facades, roofs or under screeds, often with graphite-based additives for improved insulation value even in humid environments.
Versatile applications of foamed polystyrene
From food packaging through insulating boxes, ski helmets, to decorations and displays, foamed polystyrene is a true all-rounder thanks to its formability and light weight. It is excellent for:
- Food packaging
- Thermal insulation
- Shock protection packaging
- Model making
- Technical moulded parts in electrical devices and mechanical engineering
Polystyrene films for packaging and displays: printability and processing
Polystyrene film can be printed, thermoformed and bonded without difficulty, making it a standard material for blister packaging, visor films, transparencies, signs and displays.
How are polystyrene and its films manufactured?
The polymerisation process: from the aromatic base material to the finished plastic
The manufacturing of polystyrene begins with styrene, which is obtained from ethylbenzene by chain polymerisation. In a controlled reaction, a plastic with phenyl groups is created, which enables the characteristic stiffness and transparency.
Extrusion and other processes for film production
For polystyrene films the extrusion process is mostly used: the polystyrene granulate is heated, melted, pressed through a die and wound up as a smooth film. Alternatively, the film can be stretched to produce thinner, firmer variants.
What temperature properties and limits does polystyrene film have?
Polystyrene is dimensionally stable up to approximately 90 to 100 °C, after which it begins to soften and deform. PS is therefore not suitable for high-temperature applications. Prolonged exposure to light can also cause embrittlement, which can be prevented through additives such as UV stabilisers.
How can polystyrene films be processed and joined?
Suitable adhesives for bonding PS films
Polystyrene can be bonded very well with solvent-based adhesives, heat-sealing processes or specialised dispersion adhesives. Important: a clean surface and avoiding excessive temperature to prevent deformation.
Options for printing and surface treatment
Polystyrene films can be printed very well using screen printing, offset printing as well as digital printing. Depending on the application, the surface can also be antistatic, matte, glossy or scratch-resistant coated.
Is EPS (expanded polystyrene) the right choice for your project?
Advantages of expandable polystyrene over other materials
EPS scores with low weight, insulating effect, formability and cost savings. It is easy to process, can be supplied with flame retardants and offers a wide range of density classes, from lightweight packaging material to firm XPS rigid foam for construction purposes.
GOBA Takeaway
Polystyrene films are a true engineering multi-talent: cost-effective, dimensionally stable, crystal-clear and versatile, from display to insulation board. Their simple processing, printable surface and high stiffness make them a standard material in many industries. Whether extruded, foamed or thermoformed, PS remains a plastic classic with a future.