PVB vs SGP vs EVA: Choosing the Right Interlayer for Laminated Glass

Overview

The choice of interlayer is one of the most consequential decisions in laminated glass design. It determines structural capacity, post-breakage behaviour, durability, acoustic performance, and cost. Yet many engineers default to standard PVB without considering whether it is the right material for the application.

This guide compares the three most common interlayer families: PVB (polyvinyl butyral), ionomer (marketed as SentryGlas/SGP by Kuraray, or equivalent products), and EVA (ethylene-vinyl acetate). Each has distinct strengths and limitations.

PVB (Polyvinyl Butyral)

What it is

PVB is the most widely used interlayer worldwide, accounting for over 80% of the architectural laminated glass market. It is an amorphous thermoplastic polymer produced as a sheet typically 0.38 mm or 0.76 mm thick. Major manufacturers include Eastman (Saflex), Kuraray (Trosifol), and Sekisui (S-LEC).

Strengths

• Excellent optical clarity with low haze and high light transmission
• Good adhesion to glass with controllable adhesion grades (low, medium, high) for different safety requirements
• Wide availability and competitive pricing due to market dominance
• Acoustic variants available (tri-layer PVB with a soft core) for sound insulation
• Well-characterised with extensive published material data and regulatory acceptance

Limitations

• Highly temperature-sensitive: PVB stiffness drops dramatically above 25-30°C. Standard PVB Clear provides almost no shear transfer at elevated temperatures.
• Moisture sensitivity: PVB absorbs moisture at exposed edges, which can cause delamination and whitening over time if edges are not properly sealed.
• Limited structural capacity for long-duration loads at elevated temperatures (EN 16613 Family 0 for standard grades).

PVB grades

Structural PVB grades (marketed as "Extra Stiff" or "Structural" by manufacturers) offer significantly higher stiffness than standard PVB Clear. However, even the stiffest PVB grades cannot match ionomer performance under long-term elevated-temperature conditions.

Ionomer (SGP / SentryGlas)

What it is

Ionomer interlayers are semi-crystalline thermoplastic polymers with significantly higher stiffness and strength than PVB. The most well-known product is SentryGlas Plus (SGP) by Kuraray (originally developed by DuPont). Ionomer interlayers are typically 0.89 mm or 1.52 mm thick.

Strengths

• Exceptional stiffness: 50-200x stiffer than standard PVB under short-term loading. Maintains meaningful structural contribution even under permanent loads at 60°C.
• EN 16613 Family 2: The only interlayer type that consistently achieves the highest stiffness family classification.
• Excellent moisture resistance: Low moisture absorption makes it suitable for exposed-edge applications (structural glass fins, canopies).
• Superior post-breakage performance: Broken glass fragments remain firmly bonded, maintaining residual load-carrying capacity.
• High tensile strength (34.5 MPa) and elongation at break (400%), providing excellent energy absorption.

Limitations

• Higher cost: Typically 3-5x more expensive than PVB per square metre.
• Processing complexity: Requires higher autoclave temperatures and pressures for lamination. Not all processors are equipped.
• Adhesion considerations: Standard ionomer requires an adhesion promoter on the tin-side of float glass. Newer products (e.g., Ionomer Xtra) have been developed to address this.
• Limited acoustic performance: Stiffer materials generally transmit more sound than soft PVB acoustic interlayers.

EVA (Ethylene-Vinyl Acetate)

What it is

EVA is a semi-crystalline copolymer interlayer gaining market share for decorative and photovoltaic (PV) laminated glass. It is typically processed at lower temperatures than PVB and does not require an autoclave, making it attractive for smaller fabricators.

Strengths

• Low processing temperature: Can be laminated in a vacuum bag oven (no autoclave needed), reducing capital investment.
• Excellent moisture resistance: Very low water absorption, making it suitable for humid climates and exterior applications with exposed edges.
• Good UV resistance: Better long-term clarity than PVB in some applications.
• Decorative versatility: Available in colours and textures for decorative laminated glass applications.
• High elongation at break (800%), providing good impact energy absorption.

Limitations

• Very low stiffness: EVA is significantly softer than structural PVB, providing minimal shear transfer. Not suitable for structural applications where interlayer coupling is needed.
• Limited high-temperature data: Less published characterisation data compared to PVB and ionomer.
• Lower tensile strength (12 MPa) compared to PVB and ionomer.

Head-to-Head Comparison

How to Choose

The right interlayer depends on the application, the governing load case, and the project constraints: