In impact windows, the PVB interlayer that adheres to the safety glass is a critical part of what makes these windows so durable against severe weather and even break-in attempts. But, what is PVB? How does it work? What are the alternatives to it?
To help you get to know impact windows a little better, here’s a quick explanation of PVB, its properties, and why it’s so widely used in impact windows (and glass doors).
What Is PVB?
PVB is an acronym for Polyvinyl Butyral. This is a resin material that is available as a powdered substance which is commonly used in the manufacture of impact-resistant and “bulletproof” glass. According to Elephchem, it’s also used in “wood coatings, metal coatings, metal primers, metal inks, foil coatings,” among many other applications to provide “glossy surface protective coatings.”
When sandwiched between two panes of glass and melted, then cooled, the resin forms a clear layer that adheres to both panes of glass to form a single, thick layer of material that is much more resistant to impacts and shattering than the base glass alone would be.
You can often identify an impact window by the fact that at least one of the glass panes is thicker than the others. If you look at a cutout, you’ll see the three distinct layers in the pane: glass, PVB, and more glass.
Some of the characteristics of PVB according to iSuoChem include:
- Good water and oil resistance.
- Strong adhesion to glass, metal, plastic, leather, and wood. (which is why it’s often used as a coating for these materials).
- Alcohol-soluble (alcohols can dissolve it).
On its own, as a layer of loose material, PVB is semi-flexible and not especially firm… so how does it improve a window’s impact resistance?
By providing shock absorption (which also has the benefit of improving soundproofing) and by letting the broken pieces of glass adhere to the semi-flexible laminate, maintaining the seal of the home. While the hardness of PVB isn’t high, it is resistant to tearing.
You can see this in action in videos of impact windows being struck with flying objects or, in the case of in Karoly’s Tampa Showroom location, baseball bats:
Even when the glass cracks, the underlying PVB remains in place and adheres to the broken pieces. This minimizes glass spalling, which helps protect you from having small pieces of glass all over your floor even when the window does break.
Because PVB is hydrophobic, it keeps the water from a hurricane or other storm out of your home despite cracks or breaks in the glass.
How Is PVB Made?
PVB is made through, as noted by Elephchem, “three main synthesis methods… in the industry: one-step method, dissolution method, and precipitation method.”
The one-step method involves taking polyvinyl acetate (PVAC) and subjecting it to hydrolysis (bonding water with the PVAC to break its chemical bonds). Hydrogen chloride (HCl) is added to the solution, resulting in polyvinyl alcohol (PVA), which is then further treated until a uniform layer of PVB is formed.
The ‘one-step’ name sounds like a bit of a misnomer when you lay out the multiple steps to the 8+ hour process, even when massively simplifying it and leaving out details.
The dissolution method takes the PVA and dissolves it using HCl and butyraldehyde for a condensation reaction. Meanwhile, the precipitation method dissolves PVA in water, filters the resulting solution, then adding HCl and butyraldehyde before suspending the PVB particles in the base liquor, washing it, adding alkali, then filtering the resultant powder.
What Is the Alternative to PVB?
PVB isn’t the only material that gets used for laminate interlayers in impact windows. Another popular, high-end alternative is SentryGlas, or SGP.
SGP is a much harder material than PVB. It has a tensile strength of roughly 34.5 Megapascals (MPa) (Source: Curbell Plastics) compared to PVB’s tensile strength of 25 MPa (Source: MatWeb).
This makes SGP much more rigid to the touch than PVB, making for an even tougher interlayer that further enhances the durability of the impact window or door the laminate is used in.
SGP is much stronger and results in a harder-to-break insulated glass unit than PVB, but that rigidity also means that sound transfers through the glass a bit more easily than it does with PVB.
Other potential alternatives include ethylene vinyl acetate (EVA) and thermoplastic polyurethane (TPU). However, EVA is less rigid than even PVB, while TPU is noted for enhanced flexibility, but also a high cost.
So, most exterior-mounted impact windows tend to use either PVB or SGP.
Get PVB Impact Windows Installed Expertly!
Thanks to its comparative affordability, inherent soundproofing enhancement, and ability to stand up to extreme punishment, PVB-laminated impact windows are a great option for homeowners throughout Tampa Bay!
However, even the best impact windows still need expert installation to ensure that they will be able to withstand actual hurricane conditions and other hazards. A great window can’t make up for a bad installation. When a window isn’t properly installed, that can be worse than just a failed inspection: it can mean leaks, poorer energy efficiency, and even total failure as the window falls out of the window at the first sign of a stiff breeze.
That’s why you need to make sure that, when you order new impact windows, they come with expert installation from a team of experienced professionals who know what they’re doing!
Karoly Windows and Doors, unlike many other window companies, does not outsource installation work to a third party subcontractor. Ever. We use our own team of experts to handle every installation from start to finish. That way, you never have to worry about whether the installers putting your windows in know what they’re doing.
Reach out today to get started on an expert impact window installation service that comes backed by a 25-year labor warranty! That’s how confident we are in the quality of our work!
