The Interlayer That Holds Glass Together

This year's American Chemical Society National Chemistry Week's theme, “Chemistry Under Construction,” brings attention to the role chemistry plays in the materials that shape our built environment. While concrete, steel, and stone may come to mind first, glass also plays an important role in modern construction.

If you drove to work this morning, you likely spent your commute looking through laminated safety glass. A typical windshield consists of two sheets of glass bonded together by a thin polymer interlayer, such as TROSIFOL® polyvinyl butyral (PVB) film. When a rock strikes the windshield, the glass may crack, but the interlayer helps hold the broken pieces together.

The same principle extends to buildings, where laminated glass is used in windows, façades, railings, and hurricane-resistant glazing.

Different Chemistries. Different Possibilities.

Not all laminated glass interlayers are made from the same chemistry.

Kuraray America's Advanced Interlayer Solutions (AIS) business offers two interlayer technologies,

1. TROSIFOL® PVB and
2. SENTRYGLAS® ionoplast,

each with distinct properties suited to different applications.

TROSIFOL® PVB: Flexibility and Protection

Polyvinyl butyral (PVB) has been used in laminated safety glass for nearly a century.

Known for its optical clarity, flexibility, toughness, and adhesion to glass, PVB remains a widely used interlayer material in automotive and architectural applications.

The chemistry begins with polyvinyl alcohol (PVA), which reacts with butyraldehyde to produce PVB resin. The resulting polymer retains chemical groups that help it bond to glass. When formulated with other additives and processed into film, it creates a flexible interlayer capable of absorbing impact energy and holding broken glass fragments together.

In construction, TROSIFOL® PVB interlayers are used in windows, façades, and other architectural glazing applications. Specialized formulations can also provide additional benefits, including improved acoustic comfort and enhanced stiffness for certain applications.

Kuraray America's integrated manufacturing capabilities span several stages of the process, from vinyl acetate monomer (VAM) and PVA to PVB resin and finished interlayer film.

SENTRYGLAS®: Strength That Expands Design Possibilities

As architectural designs evolve, glass is increasingly expected to do more than provide visibility and protection. Applications such as expansive façades, glass railings, overhead glazing, and transparent structural elements place greater demands on the materials holding laminated glass together.

Unlike conventional PVB, SENTRYGLAS® uses ionoplast technology. Its polymer chemistry incorporates ionic interactions that help hold molecular chains together, creating a material with exceptional strength and stiffness.

The result is an interlayer that is about five times stronger and up to 100 times stiffer than conventional PVB. These properties help laminated glass retain structural integrity after breakage and can enable thinner, lighter glass constructions, depending on the application and design requirements.

Originally developed for hurricane-resistant glazing, SENTRYGLAS® has expanded into a broad range of architectural applications, including building façades, balustrades, glass floors, staircases, and overhead glazing.

By combining structural performance with the transparency of glass, SENTRYGLAS® gives architects and engineers greater flexibility to create designs that balance aesthetics, safety, and performance.

Engineered for Impact: The Hurricane Connection

Hurricane Andrew's devastation in 1992 marked a turning point in how Florida approached building protection. In the years that followed, stricter building requirements increased the importance of impact-resistant glazing in hurricane-prone regions.

SENTRYGLAS® was originally developed for hurricane-resistant glazing and introduced in the late 1990s. Its strength and stiffness help laminated glass withstand demanding impact conditions, including those designed to simulate windborne debris during severe storms.

One example is the large missile impact test, in which a 9-pound, 2×4 piece of lumber is propelled toward a glazing system at approximately 34 mph. While the glass may break on impact, the interlayer helps retain the fragments and resist penetration by the wooden projectile. The glazing assembly must also withstand subsequent pressure cycling to demonstrate its performance under simulated storm conditions.

Performance also depends on how the interlayer bonds to glass and maintains its properties over time. Kuraray America evaluates adhesion, durability, and resistance to environmental exposure through laboratory testing and natural weathering studies. These assessments help support long-term performance in conditions involving temperature changes, humidity, and sunlight.

Kuraray America's technical expertise also contributes to the development of industry guidance and standards. Vaughn Schauss, who manages technical services for the Americas, serves as technical liaison to the National Glass Association's Protective Glazing Committee. In 2026, the association recognized him as Volunteer of the Year for his contributions to industry manuals, standards, and codes.

When Glass Becomes Part of the Structure

Beyond protecting buildings from severe weather, advanced interlayer technology has expanded how architects and engineers use glass in structural applications.

SENTRYGLAS® provides the stiffness and strength needed for demanding applications where laminated glass must support loads and retain residual strength following breakage, subject to the design of the complete glazing system.

• At Chicago's Willis Tower, visitors to The Ledge step into transparent glass boxes extending approximately four feet beyond the building's 103rd floor. Introduced in 2009, the attraction uses laminated glass incorporating SENTRYGLAS® interlayers, allowing visitors to experience the city from a perspective once difficult to imagine.

• In Paris, a glass floor installed on the Eiffel Tower's first level in 2014 allows visitors to look approximately 187 feet toward the ground below. The laminated glass incorporates SENTRYGLAS® interlayers to support structural performance and help maintain integrity if the glass breaks.
  
  
• At the Grand Canyon Skywalk in Arizona, visitors can walk approximately 70 feet beyond the canyon rim on a horseshoe-shaped glass walkway suspended high above the Colorado River. The structure uses multiple layers of glass and SENTRYGLAS® interlayers, demonstrating how laminated glass can be engineered for demanding load-bearing applications.
   

These projects demonstrate how polymer chemistry, combined with engineering and structural design, can transform glass from a conventional building material into an integral architectural element.

Sustainable Glazing: Reducing Environmental Impact

In October 2024, Kuraray introduced TROSIFOL® R3, a new line of PVB interlayers designed to support more sustainable glazing. The product range incorporates approaches such as recycled materials, more efficient manufacturing processes, and cleaner energy sources.

Depending on the product grade, TROSIFOL® R3 can potentially deliver up to a 90% reduction in cradle-to-gate carbon emissions compared with a standard clear PVB interlayer. This comparison addresses the interlayer material rather than the entire laminated glass assembly.

To help customers evaluate these differences, Kuraray also introduced an Interlayer CO₂ Classification system, providing a consistent way to compare the carbon footprint of different interlayer options.

Sustainability in glazing extends beyond material selection. Durability, service life, resource efficiency, and opportunities for material recovery all contribute to the industry's efforts to reduce environmental impact.

Chemistry That Shapes What's Possible

From hurricane-resistant windows to glass walkways high above the ground, laminated safety glass demonstrates how chemistry contributes to modern construction.

The polymer interlayer may be nearly invisible, but its role is significant. Through continued development of TROSIFOL® PVB and SENTRYGLAS® ionoplast technologies, Kuraray America is helping architects and engineers balance safety, structural performance, design flexibility, and sustainability.

As construction continues to evolve, so will the chemistry behind the materials that make it possible.