Delamination of laminated glass: its causes and how to prevent it
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Glass delamination is the result of poor processing and installation. Find out how we can help you avoid it.
Laminated glass is built to last. But that doesn't mean it lasts forever. Sometimes, homeowners and business owners will spot a defect in their laminated glass: a stain caused by the wearing away of the glass's plastic interlayer.
This is a defect specific to laminated glass and the way it's manufactured. Most types of glass consist of a single layer. Laminated glass, however, consists of two (or more) sheets of glass sandwiching a plastic interlayer.
It's this method of construction that gives laminated glass its extraordinary robustness. It's also the reason it breaks the way it does. Rather than shattering, the impacted surface cracks but stays in place. This qualifies it as a form of safety glass, meaning it can be used in applications where safety is paramount.
Robust, however, doesn't mean indestructible. Delamination occurs when the adhesive bond between the glass and the interlayer is reduced or perished altogether. It most often occurs in sheets of laminated glass with a PVB interlayer (a particular type of plastic).
So, what are the causes of delamination – and how can it be avoided? It's mainly a result of inadequate installation. It can also, however, be the result of poor-quality products. This is one reason why it's so important to work with a reputable glass processor.
What are the causes of delamination?
There are four main causes of delamination. Two stem from poor installation and two from poor processing.
1. Excess moisture
The first – and most common – cause of delamination is the exposure of laminated glass to excess moisture. PVB (the material used for many interlayers) is hygroscopic. This means it takes up and retains moisture.
If the panes of glass are exposed to excessive moisture, the bond can be reduced and delamination can occur.
This is usually a direct result of poor installation. The edge of an interlayer should "breathe". If it doesn't, delamination is all too possible.
2. Incompatible silicone
Secondly, there's the question of structural silicone. This should be compatible with the interlayer. Cut corners on this compatibility and delamination could occur.
3. Poor glass processing
Thirdly, there's poor processing. A glass processor will use cleaners and primers to prepare the glass before it's bonded with structural silicone. If these aren't fully removed, they can begin to wear away the adhesive layer and contribute to delamination.
4. Roller wave distortion
Finally, there's something called
"roller wave distortion". This isn't something that glass processors can eliminate entirely – but a good processor will make sure it's kept to a minimum.
It occurs when the rollers used in the manufacturing process distort the glass unevenly. These distortions can apply stress to the interlayer, especially at the edges where delamination is most likely to occur.
What can we learn from this? Perhaps the key takeaway is that you need to choose your processors and installers with care. Otherwise, you run the risk of letting other people let you down.
Which interlayers are most susceptible?
Different laminated glass products use different plastic interlayers. Here at ToughGlaze, for instance, we most often use PVB (polyvinyl butyral). This is the most common type of interlayer – and also the one most susceptible to delamination.
This is only a problem, however, if you get laminated glass from a substandard processor or get good-quality laminated glass badly installed. In the right hands, however, PVB is the most common interlayer for a reason.
Resin interlayers are also susceptible to delamination. They can also deteriorate under UV radiation.
Polyurethanes and ionoplasts, such as Sentry Glass and EVA (ethylene-vinyl acetate), are all less susceptible to delamination than PVB. Polyurethanes, however, can expand under heat and EVA performs less well than PVB under blast loading.
Why does it matter?
The obvious reason why delamination matters is that it looks ugly. Your mileage may vary, of course – some people like a lived-in look. But for most homeowners and business owners, delamination is something to be avoided purely for aesthetic reasons.
There is, however, a still more important reason to ensure you get good-quality laminated glass installed to a high level. This is because delamination weakens the glass. Given that one of the main purposes of laminated glass is to provide extra safety, this is clearly something to be avoided where possible.
The UK's
National Protective Security Authority (NPSA), for instance, conducted an experiment where it subjected four laminated windows to a TNT-strength blast load. Three of the panes had different depths of delamination, while the fourth was as good as new.
The NPSA found that "the glass will pull out of the frame and travel into the building (test cubicle) when there is 12-15mm or more linear edge delamination on all four sides".
In other words, delamination can compromise the robustness of laminated glass and make it vulnerable to blast impacts. For this reason alone, it's worth investing in high-quality laminated glass and working with high-quality installers.
How can you prevent delamination?
Your best bet is to work with a glass processor that has high levels of quality control during the manufacturing process. Look for ISO 9001:2015 – the international gold standard for industrial quality assurance.
Next, you should work with a trusted installer. This will ensure that the structural silicone and gaskets are compatible, that the edges are ventilated and that the interlayer isn't compressed by its frame or fittings.
Finally, you can mention delamination when specifying glass. The NPSA recommends stipulating acceptable levels of delamination and even offers a template you can use when communicating with a glass processor.
What is the life expectancy of laminated glass?
When properly maintained, laminated glass can last anywhere between 25 and 50 years. But it's less likely to have such a strong innings if you work with a subpar processor or installer.
So, if you're in the market for high-quality
laminated glass products, don't hesitate to
contact ToughGlaze. We'll fix you up with best-in-class materials that are built to last, not to delaminate.
