Fundamentals
What is PVB film?
PVB film is a polyvinyl butyral sheet used as the interlayer in laminated safety glass. Bonded between glass plies under heat and pressure, it holds fragments in place after breakage, blocks over 99% of ultraviolet light, and damps sound. Standard thicknesses run from 0.38 mm to 1.52 mm.
ImageMacro cross-section of laminated safety glass with the amber PVB interlayer visible between two glass plies
What PVB actually does
Polyvinyl butyral is a thermoplastic resin. On its own it is a flexible, slightly tacky sheet with no particular structural value. Its usefulness comes from what happens when it is placed between two panes of glass and processed under heat and pressure: it bonds to the glass surface strongly enough to stay attached through fracture, while remaining tough enough to stretch rather than tear.
That combination is what makes laminated safety glass behave the way it does. Ordinary annealed glass fractures into sharp shards that fall. Toughened glass fractures into blunt granules that also fall. Laminated glass fractures — and stays where it is, because every fragment is still adhered to the interlayer.
The four properties PVB delivers
Every one of these comes from the same interlayer, which is why laminated glass replaced separate solutions.
- Post-breakage retention — fragments stay bonded to the film instead of falling, which is the safety case for overhead glazing, balustrades and windscreens.
- UV blocking — PVB absorbs more than 99% of ultraviolet below 380 nm, protecting interior finishes, fabrics and displays without a coating or a tint.
- Acoustic damping — the interlayer damps vibration across the glass, reducing sound transmission relative to monolithic glass of the same total thickness.
- Impact and penetration resistance — the film stretches and absorbs energy, which is why security and bullet-resistant glazing is built from multiple PVB plies.
Why adhesion is the specification that matters
The single most misunderstood property of PVB is adhesion. It is intuitive to assume more adhesion is better — the fragments stick harder, so the glass must be safer. The opposite is true beyond a point.
A laminate with excessive adhesion behaves brittlely. The interlayer cannot stretch and dissipate impact energy because it is locked to the glass, so the energy goes into the laminate instead and the panel fails at lower impact. A laminate with insufficient adhesion releases fragments, which defeats the purpose entirely.
Interlayer is therefore supplied in controlled adhesion grades, and the target is a middle band rather than a maximum. This is measured by the pummel test, where a chilled laminate is struck and the amount of glass remaining bonded to the interlayer is rated on a scale.
Where each PVB type is used
| Interlayer type | Primary purpose | Typical application |
|---|---|---|
| Clear | Structural safety, clarity, UV blocking | Facades, balustrades, overhead glazing, windscreens |
| Coloured | Solar control, privacy, design intent | Coloured facades, spandrels, interior partitions |
| Printed / decorative | Pattern and artwork inside a safety laminate | Feature glazing, branded entrances, patterned privacy glass |
| Acoustic | Sound reduction across the glazing line | Airport, hotel and highway-facing facades |
Frequently asked questions
Is PVB the same as EVA?
No. Both are laminating interlayers, but PVB requires an autoclave and delivers higher structural strength and better long-term clarity. EVA cures with heat and vacuum without an autoclave, tolerates moisture better, and bonds to a wider range of inserts — but is weaker structurally and can yellow over time in lower grades.
How thick is PVB film?
The standard ladder is 0.38 mm, 0.76 mm, 1.14 mm and 1.52 mm — multiples of a single 0.38 mm ply. Architectural glazing typically uses 0.76 mm; balustrades, overhead glazing and walkable floors generally move to 1.52 mm.
Does PVB yellow over time?
Quality PVB does not yellow meaningfully in service, because it is protected from direct UV by the outer glass ply and by its own UV absorption. Yellowing is a sign of either a low-grade interlayer or moisture ingress at exposed laminate edges.
Can laminated glass made with PVB be cut after lamination?
Not conventionally. The laminate must be scored on both faces, broken, and the interlayer then separated — a process that leaves a poor edge and is unsuitable for finished work. Laminated glass is cut to size before lamination, not after.