What Is Laminated Glass?

Laminated glass is a type of safety glass produced by bonding two or more glass layers together under heat and pressure using a polymeric interlayer material placed between them. Thanks to this structure, when the glass breaks, the fragments remain adhered to each other, preventing large and sharp glass shards from scattering. The most commonly used interlayer material in laminated glass production is Polyvinyl Butyral (PVB) film. PVB creates an elastic bond between the glass layers, making the glass more durable. Additionally, PVB's ultraviolet filtration properties protect interior spaces from the harmful effects of UV radiation.

With these properties, laminated glass has become an indispensable component of modern architecture, automotive, defense, and maritime industries. The glass lamination process, which is one of the keys to producing durable, safe, and aesthetically pleasing glass products, is actually a process that appears simple but requires attention to many sensitive parameters. Among these parameters, humidity-controlled lamination room design stands at the forefront.

Today's Application Areas

The global laminated glass market is valued at approximately USD 26 billion as of 2024 and is expected to exceed USD 36 billion by 2030 with an average annual growth rate of 5.8%. The rise of electric vehicles, smart building regulations, and ballistic security demands are playing a decisive role in this growth.

Lamination Materials and Moisture Sensitivity

Interlayer selection directly determines the mechanical, optical, and safety properties of laminated glass. Each material has a different relationship with moisture; therefore, production environment conditions must be optimized according to the material type.

PVB: Polyvinyl Butyral

PVB is the most widely used interlayer material in the glass lamination industry with a market share exceeding 80%. Chemically, it is obtained from the reaction of polyvinyl alcohol with butyraldehyde. The hydroxyl (-OH) groups of PVB have a strong hydrophilic character; free hydroxyl groups bind to water molecules, increasing the moisture content of the material. PVB film absorbs approximately 0.4–0.5% water by weight under standard atmospheric conditions (50% RH, 23°C); however, this value can exceed 1.2% in an 80% RH environment.

Ideal Storage and Processing Conditions

Parameter	Storage	Processing (Clean Room)
Temperature	4–20°C	18–22°C
Relative Humidity (%RH)	<30%	20%–35%
Packaging Condition	Vacuum-sealed PE bag	Controlled opening
Sunlight	Dark	UV filtered

Once PVB rolls are removed from their original vacuum packaging, a race against time begins. Depending on ambient humidity levels, moisture-induced degradation can start within a short period. Therefore, opened rolls should be immediately processed or stored in humidity-controlled sealed containers.

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EVA: Ethylene-Vinyl Acetate

EVA is an alternative interlayer material used particularly in solar panel encapsulation applications and architectural laminated glass. Due to its chemical structure, it is less hydrophilic compared to PVB, and its moisture absorption rate is significantly lower. During the EVA lamination process, ambient humidity should be kept below 55% RH. However, ideal production conditions are still below 40% RH, because moisture negatively affects EVA's cross-linking process, reducing optical clarity.

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SGP: SentryGlas Plus (Ionomer)

SGP (SentryGlas Plus) is an ionomer-based interlayer material with approximately 5 times higher stiffness compared to standard PVB. It is preferred in high-rise building facades, bridge railings, and structural glass applications. SGP has the lowest moisture sensitivity among interlayer materials compared to PVB and EVA; short-term processing can be performed in environments up to 60% RH.

As NKT – Nem Kontrol Teknolojileri, we design specialized climate-controlled cabinets and dry cabinets for SGP interlayer processing. These special cabinets, equipped with TFT – İtalya industrial dehumidifiers, provide a controlled humidity environment during the opening, cutting, and placement of SGP material, maintaining production quality at the highest level.

Material Comparison

Material	Moisture Sensitivity	Processing Humidity Limit	Exposure Time	Cost (relative)
PVB	High	≤ 35% RH	≤ 4 hours	1× (base)
EVA	Medium	≤ 55% RH	≤ 8 hours	1.1×
SGP	Low	≤ 60% RH	≤ 24 hours	3–5×

Why Is Humidity Control Mandatory?

Neglecting humidity control leads to both short-term and long-term serious quality issues in laminated glass production.

Aesthetic Defects

Mechanical Property Loss

Processing moisture-laden PVB in the autoclave not only reduces adhesion strength but also negatively affects impact resistance. In EN 356 impact tests, glass produced in humidity-controlled environments using TFT – İtalya industrial dehumidifiers demonstrates 15–30% higher performance compared to products from uncontrolled environments.

Production Efficiency

Moisture problems dramatically increase scrap rates and rework costs. In facilities producing in uncontrolled environments, scrap rates can reach 8–15%, while in well-designed environments equipped with TFT – İtalya dehumidifiers, this rate can be kept below 1%.

Humidity-Controlled Clean Room Design

A clean room optimized for laminated glass production is formed by the integrated operation of dehumidification, filtration, ventilation, and pressure management systems.

Target Conditions

Filtration Cascade

Stage	Filter Class	Captured Particles	Efficiency	Replacement Period
1st Stage (Pre)	G4 / ISO Coarse 60%	>10 µm	60–65%	1–3 months
2nd Stage (Medium)	F7 / ISO ePM1 60%	>1 µm	80–90%	6–12 months
3rd Stage (Fine)	F9 / ISO ePM1 80%	>0.5 µm	90–95%	12–18 months
4th Stage (Final – optional)	H13 HEPA	>0.3 µm	≥99.95%	2–4 years

The filters in the ventilation system supplying air to the lamination room ensure the air remains clean. G4–F7 range filters capture larger particles and improve overall air quality. H13–H14 HEPA filters capture 99.95% of particles 0.3 micrometers and larger, minimizing contamination during the lamination process.

Positive Pressure System

Maintaining air pressure inside the clean room +10 to +25 Pa higher than the external environment prevents humid and contaminated air from entering even during door openings. For this principle to work effectively:

• Room airtightness (including roof, wall penetrations, cable ducts) must be regularly verified with smoke tests
• Doors should have double sealants, with slow-closing mechanisms for sudden openings
• Personnel transitions should be made through airlocks (airlock/gowning room)
• Pressure differential must be continuously monitored, with alarms triggered when it drops below 8 Pa

Equipment Selection: TFT – İtalya Dehumidifiers

For PVB processing environments, silica gel rotor (desiccant) dehumidifier technology should be preferred. TFT – İtalya industrial dehumidifiers meet the low dew point requirement and can achieve very low humidity levels of 10–15% RH.

Technology Comparison

Technology	Operating Principle	Min. RH	Energy	Recommended Use
Condensation Dehumidifier	Cooling below dew point	35–40%	Medium	EVA line
Silica Gel Rotor (Desiccant)	Silica gel rotor adsorption	10–15%	Medium-high	PVB line
Combined System	Condensation + rotor	15–20%	Optimized	Preferred

NKT – Nem Kontrol Teknolojileri recommends TFT – İtalya AD and ADP series industrial dehumidifiers for glass lamination facilities. These units are sized according to the lamination room volume and moisture load to provide the most efficient solution.

Capacity Calculation Principles

The capacity determination of TFT – İtalya dehumidifiers is calculated based on three moisture load components:

1. Building infiltration load: Humid air leaking through walls, ceiling, floor, and door edges (depends on room size and insulation quality)
2. Personnel load: Each active worker produces approximately 50–80 g of moisture per hour
3. Fresh air load: Moisture carried by fresh air taken from outside

Equipment capacity is determined by adding a 20–30% safety margin to the total moisture load. Dehumidification systems of critical importance for production continuity should be designed with an N+1 redundancy principle: when one unit is under maintenance or has failed, the other unit must be able to handle the entire load.

Maintenance and Monitoring Protocols

Continuous Monitoring System

IoT-based continuous monitoring systems are critically important in modern laminated glass facilities:

• Humidity and temperature recording every 10 minutes (data logger)
• Alarm thresholds: critical alert for above 38% RH and below 18°C
• 30-day data archiving (for production quality records)
• Calibration: Sensors must be verified every 6 months with NIST/DKD traceable references

Periodic Maintenance Schedule

Task	Frequency	Responsible
G4 pre-filter inspection/replacement	Monthly	Maintenance
F7 filter pressure differential measurement	Monthly	Maintenance
F9 filter pressure differential measurement	Monthly	Maintenance
Humidity sensor calibration	Every 6 months	Quality
TFT – İtalya rotor dehumidifier maintenance	Every 6 months	NKT service
Room airtightness (smoke test)	Annual	Quality/External audit
H13 HEPA replacement	Every 2–4 years	Specialist service

Common Production Issues and Solutions

Issue	Symptoms	Root Cause	Solution / Prevention
Delamination	Loss of transparency, visible separation	PVB moisture >0.5%	Moisture monitoring, control with TFT – İtalya dehumidifier
Bulging / Flowering	Regional swelling	Trapped air or moisture	Autoclave parameter revision
Haze (cloudiness)	Loss of optical clarity	Micro moisture entrapment	Target ambient humidity <20%
Edge yellowing	Yellow/brown band from edge	Long-term moisture diffusion	Edge sealant protection
Optical distortion	Light diffraction, reflection errors	Temperature non-uniformity	Autoclave profile verification
Inconsistent adhesion	Punch test variations	Humidity variation	Consistent clean room protocol

Cost Analysis: ROI of Humidity Control

For a typical mid-sized laminated glass facility (daily production capacity of 500–1,000 m²), the humidity control system investment based on TFT – İtalya industrial dehumidifiers pays for itself in 18–30 months through annual scrap reduction and energy savings.

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