You’ve seen it before: a solar panel that looks perfectly fine from a distance, but up close, something is wrong. Bubbles are forming under the surface, or the edges of the backsheet are starting to lift and peel away like old wallpaper. This isn’t just a cosmetic issue; it’s a critical failure known as delamination, and it can slash a module’s energy output and shorten its lifespan.
But what causes it? While many factors can contribute, one of the most common culprits is a silent, invisible chemical reaction happening right inside the panel. The very material meant to protect the solar cells—the EVA encapsulant—can begin to break down, releasing a familiar chemical: acetic acid.
That’s right. The main component of vinegar could be slowly eating away at the adhesive bonds holding your solar panel together. In this article, we’ll explore this process—known as EVA hydrolysis—and explain how measuring this chemical byproduct helps predict and prevent catastrophic delamination.
What is EVA Hydrolysis? The Chemistry Explained Simply
Most solar panels use Ethylene Vinyl Acetate (EVA) as an encapsulant. It’s a transparent polymer that cushions the fragile solar cells, protects them from moisture, and helps bond the glass front to the protective backsheet. It does its job remarkably well—most of the time.
However, when exposed to the two things a solar panel sees every day—heat and humidity—a slow chemical reaction called hydrolysis can begin.
Think of it like this:
EVA + Water (Humidity) + Heat → Acetic Acid + Other Byproducts
Over years of service in the field, moisture inevitably finds its way into the module. This water, energized by heat, starts to break the chemical bonds within the EVA polymer. A primary result of this breakdown is the release of acetic acid. The process is gradual, but it’s relentless.
The Domino Effect: From Acid to Adhesion Failure
So, the EVA creates a tiny amount of acid. Why is that such a big deal?
The problem is that this acid doesn’t just stay put; it migrates through the encapsulant and attacks the most vulnerable interface: the bond between the EVA and the backsheet. Most backsheets have a thin adhesive layer designed to create a permanent bond during lamination. Acetic acid is highly corrosive to these adhesives.
As the acid concentration increases, it chemically degrades this layer, causing the bond to weaken and eventually fail. This is where theory becomes a measurable reality.
Research has established a direct and alarming correlation between the acetic acid concentration within the EVA and the loss of adhesion strength.
- At 0.0 to 0.5 wt% acetic acid, the adhesion is strong, just as the manufacturer intended.
- As the concentration climbs to 1.0 wt%, adhesion strength can plummet by more than 50%.
- Once it exceeds 1.5 wt%, the bond can be almost completely gone. The backsheet is no longer truly bonded, leaving the solar cells critically exposed to the elements.
This relationship isn’t just a theory; it’s a predictable failure curve.
[Image: Graph showing the correlation between acetic acid concentration and the decrease in backsheet adhesion strength.]
The graph above clearly illustrates this inverse relationship. As the acetic acid concentration (the cause) rises, the peel strength (the effect) falls dramatically. This degradation is a key factor in solar module reliability and performance, as delamination is often a precursor to moisture ingress, short circuits, and total module failure.
How to Measure the Risk: A Protocol for Predicting Failure
You can’t see acetic acid forming inside a module, so how can you know if a new material or module design is at risk? You have to accelerate time in a controlled environment and measure the results.
At PVTestLab, our protocol for quantifying hydrolysis risk is a systematic, three-step process that translates chemical degradation into predictive mechanical data.
Step 1: Accelerated Aging with Damp Heat Testing
We start by placing laminate samples—composed of the client’s chosen glass, EVA, and backsheet—into a climatic chamber for a Damp Heat Test. The standard conditions are harsh: 85°C and 85% relative humidity. This environment rapidly accelerates the hydrolysis reaction that would normally take years to occur in the field. Samples are tested for extended durations, often 1000 or 2000 hours.
Step 2: Quantifying Acetic Acid Formation
After aging, samples of the EVA are carefully extracted. Using analytical chemistry techniques like titration, we precisely measure the weight percentage (wt%) of acetic acid that has formed within the encapsulant. This provides a hard number for the chemical degradation.
Step 3: Measuring Mechanical Adhesion Strength
Next, we determine the real-world consequence of that chemical breakdown. We perform a 90° or 180° peel test, where a machine pulls the backsheet away from the EVA at a constant speed. The force required to separate the layers is measured in Newtons per centimeter (N/cm).
[Image: A peel test being performed on a solar module laminate sample in a lab setting.]
A high peel strength indicates a robust, healthy bond. A low peel strength confirms that the acetic acid has done its damage, compromising the module’s structural integrity.
„The peel test gives us a hard number,“ notes Patrick Thoma, PV Process Specialist at PVTestLab. „It transforms a chemical theory into a mechanical failure point we can predict and prevent. When a material supplier sees the adhesion drop after 1000 hours of damp heat, they know they have a problem.“
This kind of detailed analysis is central to our material testing and lamination trials. It allows manufacturers to validate their products against known failure modes before they reach the market.
Why This Matters for Your Next Project
For material developers creating new encapsulants or module manufacturers designing next-generation panels, this test is more than an academic exercise—it’s a critical tool for risk management.
Choosing materials without understanding their long-term hydrolysis behavior is a gamble. It can lead to:
- Unexpected field failures years after installation.
- Costly warranty claims and product recalls.
- Damage to your brand’s reputation for quality and reliability.
By proactively quantifying the link between damp heat exposure, acetic acid formation, and adhesion loss, you can make informed decisions. This predictive testing is a crucial first step in the prototyping and module development cycle. It allows you to compare different EVA formulations, select backsheets with more resilient adhesive layers, and engineer a final product built to withstand the elements for 25 years or more.
Frequently Asked Questions About EVA Hydrolysis
What is EVA?
EVA stands for Ethylene Vinyl Acetate. It is a highly transparent and durable polymer thermoplastic used to encapsulate solar cells, protecting them from moisture, impact, and vibration while bonding the entire module sandwich together.
Is all EVA the same?
Absolutely not. EVA formulations vary significantly between manufacturers. They contain different additives, such as crosslinking agents, UV stabilizers, and antioxidants. These differences dramatically affect their resistance to hydrolysis and yellowing.
Does this only happen in hot, humid climates?
Hot and humid climates like those in Southeast Asia or the coastal United States will accelerate hydrolysis. However, the process can occur in any climate over the long term. Daily temperature cycles can pump moist air in and out of a module’s edge, providing the water needed for the reaction to proceed slowly.
Are there alternatives to EVA?
Yes. Polyolefin Elastomers (POE) are a popular alternative known for their excellent resistance to moisture and hydrolysis (they don’t produce acetic acid). However, POE can be more difficult to process during lamination and may have different adhesion characteristics, requiring its own set of validation tests.
Can you see delamination happening?
In the early stages, it’s impossible to see with the naked eye. The degradation is happening on a microscopic, chemical level. By the time you can visually identify bubbles, tunnels, or peeling edges, the structural integrity of the module has already been significantly compromised.
From Understanding to Action
EVA hydrolysis isn’t a random defect; it’s a predictable degradation mechanism rooted in basic chemistry. The key takeaway is that by systematically stressing materials in a controlled environment, we can measure the chemical byproducts and link them directly to a loss of mechanical strength.
This empowers us to move from guessing to knowing.
You no longer have to wonder if your chosen materials will last. With the right testing protocol, you can quantify their long-term stability and build solar modules that are not only efficient on day one but also resilient for decades to come. Understanding these fundamental failure modes is the first step toward greater innovation and reliability in the solar industry.