Adhesive bonding has become a critical enabling technology in modern aerospace manufacturing
Adhesive bonding has become a critical enabling technology in modern aerospace manufacturing, supporting the industry’s push toward lightweighting, sustainability, automation, and high-rate production
Against this backdrop, Syensqo is advancing the role of paste adhesives as flexible, high-performance alternatives to traditional joining methods. According to Juan Abad Zapatero, customer engineer at Syensqo, these materials are designed not only to meet demanding structural requirements, but also to integrate seamlessly into evolving aerospace manufacturing ecosystems.
Syensqo was established in December 2023 following the separation of Solvay into two independent companies. While Solvay retained its essential chemicals business, Syensqo emerged as a science-driven materials specialist focused on high-performance polymers, composites, and specialty solutions. The company’s name deliberately references Solvay’s scientific heritage, including the historic Solvay Conferences of the early 20th century that brought together figures such as Albert Einstein and Marie Curie. Today, Syensqo employs around 13,000 people across 30 countries, with more than 16 industrial sites and major R&D centres supporting markets such as aerospace, mobility, energy, and electronics.
ADHESIVES IN THE AIR
From an aerospace perspective, Syensqo’s portfolio spans carbon fibres, prepregs, resins, primers, surface films, film adhesives, and paste adhesives. These materials are used across fixed-wing aircraft, rotorcraft, advanced air mobility platforms, propulsion systems, and space and launch applications. Adhesives, in particular, are increasingly central as aircraft structures evolve toward multi-material designs and higher levels of automation.
“Unlike mechanical fasteners or welds, adhesives distribute loads evenly across the joint area, avoiding local stress concentrations,” explains Zapatero. This improves fatigue resistance and long-term durability, while also enabling secondary functions such as sealing against moisture, air, and chemical ingress – critical for corrosion protection in metallic structures. Adhesives also dampen vibration and noise, a benefit that is especially relevant for emerging electric and advanced air mobility platforms.
Weight reduction is another key driver. Mechanical fasteners add mass and require overlapping structures, whereas adhesive bonding can reduce both thickness and part count. In addition, adhesives enable greater design freedom, allowing engineers to join dissimilar materials, bond thin or complex geometries, and achieve smooth, aerodynamically clean surfaces. From a manufacturing standpoint, adhesives are also well suited to high-rate and automated production, aligning with the aerospace industry’s push for cost efficiency.
FILM VS PASTE ADHESIVES
Within Syensqo’s adhesive offerings, two product forms dominate aerospace applications: film adhesives and paste adhesives. Film adhesives are well established in primary structures, offering excellent toughness, environmental resistance, and controlled bondline thickness. Paste adhesives, however, are gaining increasing attention due to their process flexibility and compatibility with automation.
Paste adhesives are designed to deliver film-adhesive-like performance in a paste format. “Paste adhesives combine high strength, high toughness, and excellent hot–wet performance for both bonding and repair of metallic and composite substrates,” Zapatero says. They can be cured in an autoclave, out of autoclave, or even at ambient conditions, with a wide range of cure temperatures and cycle times. This flexibility is particularly valuable for large structures, repairs, and rate-driven production environments.
Paste systems are available as one-component premixed formulations or two-component systems that are mixed at the point of use. The latter offer improved storage stability and do not require freezer storage. Despite their relatively high viscosity, these adhesives are thixotropic and slump-resistant, allowing application on non-horizontal surfaces while still flowing under shear during dispensing.
Crucially, Paste adhesives are well suited to automated application. They can be dispensed using pumping and metering equipment, placing precisely the required amount of material exactly where it is needed. “That capability has a very powerful impact in terms of cost efficiency,” Zapatero notes, citing reduced material waste, lower capital expenditure, elimination of autoclaves in some cases, and faster cycle times.
THE AEROPASTE PORTFOLIO
Building on this foundation, Syensqo has introduced Aeropaste, a new generation of epoxy-based structural paste adhesives tailored for aerospace applications. The Aeropaste portfolio is designed to address challenges including lightweighting, cost reduction, processing flexibility, and high-rate manufacturing. Available in both one- and two-component variants, Aeropaste products cover a broad range of cure temperatures and schedules.
Aeropaste systems are optimised for bonding and repair of metallic structures while maintaining film-adhesive-like mechanical performance. They offer a strong balance of shear and peel strength, are highly toughened, and retain performance in hot and wet service environments. Another key advantage is tolerance to bondline thickness variation, which simplifies manufacturing and supports automated deposition. Gap-filling capability further enhances design freedom for components with non-uniform bondlines.
Ease of use is also a defining feature. One-component systems can be dispensed directly from cartridges using standard electric guns, while two-component systems rely on integrated static mixers with fixed mix ratios, avoiding complex calculations. Shelf life typically ranges from six to twelve months, and open times can vary from minutes to several hours depending on formulation and conditions.
Beyond the adhesive itself, Zapatero emphasises that durable bonding depends fundamentally on surface quality: “Adhesion depends on something you can’t see – the chemical condition of the surface.” To address this, Syensqo has partnered with Brighton Science to apply surface intelligence tools based on precise measurement of surface energy via water contact angle analysis. Unlike traditional methods such as water-break tests, this approach provides quantitative, non-destructive, and repeatable data.
Using portable and automation-compatible equipment, manufacturers can assess surface cleanliness, activation, and aging in real time, directly on the production floor. This enables validation of surface readiness prior to bonding and tighter control over variability introduced by surface preparation methods such as abrasion, plasma, or flame treatment. Importantly, surface energy is not static; it degrades with time, humidity, temperature, and handling. By monitoring these effects, Syensqo aims to help customers define optimal processing windows and storage protocols.
The company’s Aeropaste adhesives, combined with data-driven surface intelligence, illustrate how adhesive bonding is evolving from a materials choice into an integrated engineering system. For aerospace engineers facing increasing pressure to deliver lighter, more sustainable, and more affordable aircraft, these innovations position paste adhesives as a cornerstone of next-generation structural design and manufacturing.
