For laminated glass specifications, PVB offers cost-effective performance for standard vertical glazing ($15-25/m²), SGP delivers superior structural strength and edge stability for overhead/floor applications ($80-150/m²), and EVA provides moderate performance for decorative applications ($25-40/m²). The interlayer choice determines post-breakage strength, deflection control, and service life.
This guide compares PVB, SGP, and EVA across structural performance, environmental durability, and cost to help architects make specification decisions backed by engineering data.
What Are Laminated Glass Interlayers?
Laminated glass consists of two or more glass plies bonded with a polymer interlayer through autoclave processing. The interlayer holds glass fragments after breakage, provides structural coupling for load distribution, and blocks 99% of UV radiation.
According to ISO 12543 and ASTM C1172, the interlayer must maintain adhesion and mechanical properties across the design temperature range. PVB, SGP, and EVA represent different polymer chemistries optimized for distinct performance requirements.
PVB (Polyvinyl Butyral): Industry Standard
Composition and Properties
PVB is a thermoplastic resin ranging from 0.38mm to 2.28mm thickness. At 20°C, PVB exhibits shear modulus of 0.5-1.5 MPa. At 50°C (typical in facades under solar load), shear modulus drops to 0.1-0.2 MPa, reducing laminate bending stiffness.
Specify PVB where deflection limits are generous and long-term creep is acceptable. For high-stress structural applications, PVB’s thermal softening limits suitability.
Edge Durability and Cost
PVB is hygroscopic, absorbing moisture at exposed edges. Without edge sealing, moisture causes delamination visible as white haze. This requires structural silicone edge sealing or capped framing.
PVB represents the most economical interlayer at $15-$25 per square meter with wide global availability.
SGP (SentryGlas Plus): High-Performance Structural Interlayer
Superior Structural Performance
SGP offers shear modulus 50-100 times higher than PVB. SGP maintains 100-150 MPa at 20°C and retains 50-80 MPa at 50°C. This enables structural laminated glass to function nearly as monolithic glass.
Specify SGP when post-breakage load-bearing capacity is required per ASTM E1300 for overhead glazing or when deflection must be minimized.
Edge Stability
SGP is hydrophobic with minimal moisture absorption. Edge delamination is virtually eliminated even without edge sealing, making it preferred for glass railings, glass floors, and fin-supported facades.
SGP resists yellowing and maintains clarity after decades of UV exposure. Testing shows less than 2% change in visible light transmission after 5,000 hours of accelerated weathering.
Cost and Value
SGP costs $80-$150 per square meter, approximately 4-6 times PVB pricing. This premium is justified where thinner glass sections reduce overall system cost or where PVB edge delamination would require expensive maintenance.
EVA (Ethylene-Vinyl Acetate): Emerging Alternative
Properties and Applications
EVA is a thermoplastic copolymer ranging from 0.38mm to 1.52mm, processing at lower temperatures than PVB (120-140°C vs 140-150°C). EVA offers shear modulus of 2-5 MPa at 20°C.
The lower processing temperature enables bonding of heat-sensitive interlayers like decorative films or LED arrays, making EVA attractive for decorative glass and smart glass applications.
Limitations
EVA exhibits higher creep under sustained load compared to SGP and greater susceptibility to edge yellowing. Limit EVA to non-structural or interior applications. EVA costs $25-$40 per square meter.
Performance Comparison
| Parameter | PVB | SGP | EVA |
|---|---|---|---|
| Shear Modulus (20°C) | 0.5-1.5 MPa | 100-150 MPa | 2-5 MPa |
| Shear Modulus (50°C) | 0.1-0.2 MPa | 50-80 MPa | 0.5-2 MPa |
| Post-Breakage Strength | Moderate | Excellent | Moderate |
| Edge Delamination Risk | High (requires sealing) | Very low | Moderate |
| Temperature Range | -20°C to 60°C | -40°C to 80°C | -10°C to 70°C |
| Relative Cost | 1× (baseline) | 4-6× | 1.5-2× |
Application-Specific Recommendations
| Application | Recommended Interlayer | Justification |
|---|---|---|
| Curtain Wall (Vertical) | PVB or SGP | PVB adequate for standard; SGP for high wind loads |
| Overhead Glazing | SGP required | Post-breakage load bearing per ASTM E1300 |
| Glass Floors | SGP required | Sustained load + minimal deflection + edge exposure |
| Glass Railings | SGP preferred | Exposed edges + impact + deflection limits |
| Acoustic Glazing | PVB (thick/multi-ply) | Superior damping properties |
| Interior Partitions | PVB or EVA | Cost-effective; minimal environmental exposure |
| Decorative Glass | EVA or PVB | Lower processing temps preserve features |
Structural Design Considerations
When calculating laminated glass bending strength, the interlayer shear modulus influences effective thickness. The shear transfer coefficient (Γ) ranges from 0 (no coupling) to 1 (full monolithic behavior).
For PVB at elevated temperature, Γ approaches 0.2-0.3. For SGP, Γ reaches 0.8-0.9. This means a 12mm+1.52SGP+12mm laminate performs structurally similar to a thicker PVB configuration.
Account for long-term creep when specifying PVB for sustained loads. SGP’s high modulus remains stable under decades of constant stress, while PVB deflection increases 30-50% over time.
Environmental Durability
Per EN 1279-2 accelerated aging, PVB laminates without edge sealing show delamination after 500 hours at 58°C / 100% RH. SGP laminates pass 2,000+ hours without edge degradation.
Both PVB and SGP block >99% of UV below 380nm. However, PVB can yellow slightly over decades. SGP maintains optical neutrality.
FAQ
Can I use PVB for overhead glazing?
PVB can be used if calculations per ASTM E1300 demonstrate adequate post-breakage capacity. However, SGP is preferred due to superior post-breakage performance.
Does SGP improve impact resistance?
Both provide similar sudden impact performance. The key difference is post-breakage behavior: SGP laminates retain stiffness and load-bearing capacity after glass fracture.
Why does PVB delaminate at edges?
PVB absorbs moisture at exposed edges, causing loss of adhesion visible as white haze. Structural silicone edge sealing prevents moisture ingress.
How does interlayer thickness affect performance?
Thicker interlayers improve post-breakage strength and acoustic damping but do not significantly increase stiffness. For structural performance, material type matters more than thickness.
Conclusion
PVB remains cost-effective for vertical glazing with edge sealing. SGP commands structural applications—overhead, floor, railing—where exceptional stiffness and edge stability justify the cost premium. EVA occupies specialty niches requiring lower processing temperatures.
Zhongbo Glass manufactures laminated glass up to 4200mm × 28000mm using PVB, SGP, and EVA interlayers. Contact us for technical specifications and factory-direct pricing.
