Modern aircraft rely on sophisticated glazing systems for cockpit windshields, cabin windows, and observation panels. These transparent structures must provide exceptional optical clarity and have properties that can withstand extreme mechanical loads, pressure cycles, temperature fluctuations, and the impact of bird strikes or debris.
One of the key materials that can help enable the creation of these high-performance glazing systems is thermoplastic polyurethane (TPU), which is widely used as an interlayer laminating film in safety glass manufactured for aerospace applications.
Aircraft glazing is typically constructed as a multi-layer laminate, combining glass and / or engineering plastics such as polycarbonate. Between these layers sits an interlayer film, which bonds the materials together to form a single structural composite. The interlayer plays a crucial role in both performance and safety: it helps to distribute load, absorb impact energy, and retain fragments if outer glass layers are damaged.
In cockpit windows and passenger cabin glazing, this laminated architecture ensures the window can withstand the demanding aerospace environment while maintaining excellent visibility for pilots and passengers.
Why TPU interlayers are used
TPU films offer a combination of mechanical and optical properties that make them particularly well suited to aerospace glazing. TPU interlayers tend to exhibit high tensile strength, strong adhesion to both glass and plastics, and excellent elongation, enabling them to absorb impact energy and reduce the risk of catastrophic failure of the laminate.
Equally important is their optical performance. TPU interlayers – such as Huntsman’s KRYSTALFLEX® films – can typically provide very high light transmission (around 90% or greater) with extremely low haze, ensuring minimal distortion and clear visibility for cockpit operations.
TPU films can also remain stable across the wide temperature ranges encountered during air travel, with some formulations capable of maintaining performance down to approximately −60 °C. This resistance to temperature extremes is critical for aircraft windows exposed to high-altitude conditions.
Enhancing safety and impact resistance
One of the primary functions of a TPU interlayer is to improve the impact and damage tolerance potential of laminated glazing. The elastomeric nature of TPU means it has the potential to absorb and dissipate kinetic energy during events such as bird strikes or debris impact. In the event of glass breakage, the interlayer can hold fractured pieces in place, preventing dangerous shards from entering the cockpit or passenger cabin.
This energy-absorbing capability also makes TPU suitable for ballistic-resistant or blast-resistant glazing, which is used in certain military aircraft and high-security aviation applications.
Compatibility with hybrid glazing structures
Another advantage of TPU interlayers is their ability to bond dissimilar materials together, such as glass, polycarbonate, acrylic (PMMA), and PET. This capability enables the development of hybrid glazing systems that combine the hardness and scratch resistance of glass with the lightweight impact resistance of plastics.
Such hybrid laminates are particularly valuable in aerospace design, where reducing weight is a priority alongside maintaining structural integrity.
Processing and Manufacturing
TPU interlayers such as those in the KRYSTALFLEX® TPU range are typically incorporated into glazing systems through lamination processes such as autoclave bonding. During lamination, heat and pressure activate the thermoplastic film, allowing it to bond tightly to the surrounding layers and form a clear, void-free composite structure.
Because TPU interlayers do not require plasticizers and generally do not need refrigerated storage, they can also help simplify material handling and improve long-term durability compared with some alternative interlayer materials.
Supporting the future of aerospace glazing
As aircraft glazing systems continue to evolve to incorporate features such as lightweight composites, embedded sensors, or smart transparency technologies, interlayer materials will continue to play a critical role. TPU interlayer films offer a unique balance of clarity, toughness, flexibility, and compatibility with multiple substrates, making them an important enabling material for advanced safety glazing.
In both cockpit and passenger windows, these films can help ensure that aircraft glazing remains lightweight, durable, and capable of protecting occupants under some of the most demanding conditions in transportation engineering.
Disclaimer
While all the information in this publication is to the best of our knowledge and belief accurate at the date of publication, NOTHING HEREIN IS TO BE CONSTRUCTED AS A WARRANTY, EXPRESS OR OTHERWISE. Huntsman warrants only that its products meet the agreed specifications. Typical properties, where stated, are to be considered as representative of current production and should not be treated as specifications. In all cases, it is the responsibility of the user to determine the applicability of such information and the suitability of any product for its own particular purpose. The sale of products referred to in this publication is subject to the general terms and conditions of sale of Huntsman International LLC or of its affiliated companies.
KRYSTALFLEX® is a registered trademark of Huntsman International LLC or an affiliate thereof in one or more, but not all, countries. © 2026. Huntsman Corporation or an affiliate thereof. All rights reserved.
