Glass Laminated Structures with PVB & EVA – Making the Right Choice

Posted on Jul 18

Summary

EVA-Lam, the first EVA with better properties than PVB - such as better optics, better resistance to moisture, adhesion three times higher, excellent soundproofing, crosslink of 87 percent and high UV filtering.

At present, glass has become one major actor in modern architecture. We can find it in walling, in structures or as a decorative mode, surpassing any other material.

Its image of luminosity, cleanliness, and ease of use, added to its low cost, contribute to its great expansion. Furthermore, we do not see in the short or long term any material that can shade it.

In this great expansion, we find that glass laminated with EVA (Ethyl Vinyl Acetate) stands in a very representative position and a growing relevant place. It has become the architectural glass application with the highest increase in recent years and especially the one with the greatest expected growth globally for the next decades to come.

Thanks to its security and to its technical advantages in thermal isolation and soundproofing the glass manufactured with EVA laminates is the architectural application with the greater prospects.

EVA-Lam today

EVA was developed by NASA during the space race to bear extreme conditions. It is nowadays a product in expansion and in continuous development. It has no known roof as it guarantees stability, adherence, filtering and its thermal and mechanical properties. Under this high added value products and excellence prism, our manufacturers have developed the new EVA-Lam outdoor EVA that foregoes the architectural needs of the future. Our EVA-Lam is made in Europe in full-scale modern facilities along with other EVA products. The chemical processes allow us to guarantee all the product’s characteristics. The manufacturers laboratory, where all products are tested, is equipped with state of the art technology with the highest standards. This gives us an in-depth knowledge of the product to satisfy the ultimate needs of our customers. Thanks to those fixed quality standards, as well as with the production parameters we can say that “EVA-Lam is BETTER than PVB”.

BETTER THAN PVB

- Better optics: EVA-Lam is the only product in the market with transparency values close to the extra clear glass.
- Better resistance to moisture: EVA-Lam Visual is more resistant to moisture than PVB at open edge. PVB suffers a high degree of de-lamination at open edge, but EVA-Lam has far less of such negative behavior. 
- Adhesion is three times higher: it has an adhesion three times over PVB, which makes it ideal for the use with toughened glass submitted to heavy load or mechanical stress such as doors, stairs or external façades.  
- Excellent Soundproofing: Given its high degree of soundproofing this is the ideal product for noisy areas. 
- Crosslink of 87%: EVA-Lam is thermo-stable thermally and mechanically making it a material with a durability and stability well over any thermoplastic. 
- High UV filtering: The 99,8% of UV filtering at the 370nm wavelength is an indication of its suitability to protect from sunbeams.
- 3D Reticulation: EVA-Lam is able to laminate decorative insertion, but can also reduce the number of layers in a tempered glass reaching a 50% reduction in manufacturing costs vs an Autoclave.

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Glass laminate structures are manufactured using either one of two different polymer materials, namely EVA  (Ethylene Vinyl Acetate) or  PVB  (Polyvinyl Butyral) plastic films. In the past, PVB film has predominantly been used for glass lamination in the building & construction as well as transportation industries, however, over the last few years and currently, EVA film has been successfully challenging PVB material for laminated structures because of its added beneficial properties.

EVA is a good polymer material able to fulfill all the key requirements provided by PVB films, but over and above also has the ability to overcome some of the drawbacks of PVB films. Some of the advantageous properties of EVA have been already proven in the photo-voltaic industry.

laminated structures

EVA has shown to be the ideal material used for the construction and lamination of photovoltaic modules to produce energy for a long time, even under the extreme operating conditions. One more thing you should remember is that the photovoltaic modules are produced and sold with a 15 year warranty period.

Both EVA and PVB are thermoplastic polymers and have inherent elastic and natural adhesive properties, hence, they are quite different from the rigid thermoplastic materials and that is why they are known as soft-polymer materials.

Although both are thermoplastic materials, they are quite different in their chemical structures. From their chemical structures, you can see that PVB gets only a basic unit that repeats around 1 times in the polymer chains, while EVA gets 2.

EVA comprises of two different repetitive units depending on the number and depending on how they are scattered into the molecular chains so that they could give EVA different properties and performance. Therefore, EVA is used for an extensive range of application because it is more functional thermoplastic than PVB.

Due to their molecular arrangements and structures, they are well-known as amorphous polymer materials. This is the reason why both of them have excellent optical properties and they have been used in laminate glasses for architectural applications.

laminated structure rsg

Apart from the optical properties, they have mechanical properties so that they can be used for architectural applications. The existence of elastic modulus properties helps them dilute the glass-glass dimensional and thermal dilatation tensions when in operation under different weathering conditions.

When there are any architectural constructions going on, security is the key parameter that should be guaranteed regardless of the type of glass laminate that is used. For instance, to build balustrade walls, it’s not allowed to be constructed with just a single pane of glass.

Legislations enforce the use of laminated glass structures to ensure that when there is a breakage in any one of the glass panels for whatever reason, the other one will be capable of sustaining the small glass pieces adhered to its surface. Safety is paramount and legislations to protect users by requiring the use of laminated glass panels.

The lamination process is adapting to the implementation of the security elements between glass panels. The main aim of the non-glass element is to deliver flexibility to the structure as well as a good adhesion to the glass during a glass breakage.

The difference between PVB and EVA is in terms of their processing ability or the final mechanical properties (dilation, coefficients, elastic modulus, and young modulus) of the product depending on their use and final application.

laminated structure chat

The chemical and physical properties are important. The differences in chemical composition and structure between EVA and PVB allow the chemists, polymer scientists, and chemical engineers to play with the raw materials to convert and transform them into certain products with differential and preferred performance.
Another important property that requires to be fulfilled for these products is the adhesion to glass. Both the polymer materials have intrinsic adhesive properties and can be increased by the use of special additives to the respective polymer material.

As per the principle, EVA is a better adhesive material as compared to PVB. PVB has an acceptable to less adhesiveness to glass and has a high level of hygroscopicity. When it comes to adhesion apart from EVA and PVB, other materials can be used in the lamination process. But most of them are liquid products that need to mix up at least two different solutions to react. This is not an easy task for the lamination manufacturing purposes.

Moreover, you might end up with a glass adhesion interlayer with multiple degrees of elasticity that might not be able to fulfill the needed mechanical properties for a glass interlayer element. Intrinsically, the EVA and PVB are supplied as films and are easy to handle as well as manipulate while preparing glass laminates before transforming and integrating to a flexible element of the structured product.

Another main difference between PVB and EVA is their rate of water vapor transmission that comes from natural water or weather humidity. However, PVB has around 8-9 times higher tendency to permeate water than the EVA material. This property offers a great advantage to EVA as compared to PVB in terms of storage, use, and transportation, as well as product resistance against weathering conditions.

For the capillarity, PVB laminates suffer from water penetration throughout the edges and glass lamination pieces angles that affect the durability and mechanical resistance of the laminate negatively.

One of the most important differences between these materials is that EVA can be converted to a thermoset product during the lamination process. The process converts the free and sound flowing of molecules in the mass into a chemically cross-linked EVA molecule. In fact, the lamination process aims to convert the interlayer material into a flexible, elastic, structured, and no longer a temperature melted product. The laminated structure becomes a new elastic and stable interlayer between the glass panels and offers the global structure with the needed mechanical properties.

The chemical transformation of EVA polymer materials may take place in small ovens while handling vacuum and temperature control. However, the cost of the required equipment is substantially less than the one that is used generally for PVB, namely with an Autoclave system.

One of the great benefits of EVA is its lower water absorbing ability in comparison with the PVB. As a result, it stores and manipulates the film out of the climatic chamber whereas PVB requires it to be manipulated before the lamination process.

Due to the lower adhesiveness, PVB film requires to be processed in autoclaves. It is a procedure whereby high pressure is applied to the lamination structure in order to improve the limited adhesive properties.

When it comes to the lamination of PVB polymer, there’s no chemical crosslinking process between the molecules like the way it happens with EVA polymer lamination process.

Now you might have got the idea between the EVA and PVB glass laminated structures. If you’re interested to get more info, just get in touch with RSG Glass Products as soon as possible, and we’ll gladly get right back to you!

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