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Home > Industry Information > Differences between PVB and EVA and differences in lamination process

Differences between PVB and EVA and differences in lamination process

2021-05-17

1.0 Introduction

Crystalline silicon solar cell industry uses adhesive bonding materials. Before the 1980s, liquid silicone resin and polyvinyl butyral resin sheet (PVB) were tried at home and abroad, but they were eliminated due to high prices, harsh construction conditions, and poor physical properties. In the 80s, foreign countries began to develop EVA film, which is a kind of hot-melt adhesive film. It is non-adhesive and anti-blocking at room temperature. After certain conditions, it will be melt-bonded and cross-linked and cured. It has achieved satisfactory results in solar cell packaging and outdoor use.

2.0 EVA (Ethylene Vinyl Acetate: Ethylene-Vinyl Acetate)

Ethylene-vinyl acetate copolymer (also known as ethylene-vinyl acetate copolymer) is obtained by copolymerization of ethylene (E) and vinyl acetate (VA). The English name is: Ethylene Vinyl Acetate, abbreviated as EVA, or E/VAC.

EVA is a kind of hot melt adhesive, that is, at normal temperature, EVA is a solid, non-viscous, poor light transmission. When EVA is heated to a certain temperature, EVA will melt and stick to the objects it comes into contact with. The EVA for solar cell packaging is a specially designed thermosetting hot melt adhesive, that is, a cross-linking reaction occurs at the same time of heating and melting. When the temperature is low, the cross-linking reaction takes place very slowly, and the time required to complete the curing is longer, whereas the time required is shorter. Therefore, it is necessary to select a suitable lamination temperature so that the EVA can obtain fluidity in the melt while curing reaction occurs. As the reaction progresses, the degree of crosslinking increases, and EVA loses its fluidity and functions as a package. The performance at temperature is:

Melt temperature (70-80°C). At this point, EVA is melted by heat and has good fluidity. It is the best time for vacuuming.

• At the curing temperature. At this point, the cross-linking agent contained in EVA generates free radicals, cross-linking occurs between EVA molecules, resulting in a three-dimensional network structure, poor fluidity, and high viscosity. This temperature is suitable for laminating components to make them more compact and have higher adhesion to glass and backsheets.

• Greater than cure temperature. At this point, the cross-linking agent decomposes the gas and easily causes bubbles in the module. At the same time, the degree of cross-linking of EVA decreases, and the yellowing tends to occur and shrinkage occurs.

3.0 PVB (Poly vinyl butyral)

Polymer material, white powder. The formula is H2(C8H14O2)n

Density: 1.07 g/cm3.

Molecular weight from 30-45k.

The refractive index is 1.488 (20°C).

The water absorption is not more than 4%.

Softening temperature 60-65°C.

The glass transition temperature is 66-84 degrees (varies with the degree of polymerization).

Solubility: It can be dissolved in most alcohols/ketones/ethers/esters organic solvents, insoluble in carbon hydroxy solvents, such as petroleum solvents such as gasoline.

In 1935, American scientists invented a polymer material, polyvinyl butyral, sandwiched between two layers of ordinary glass. The English name is POLYVINLBUTARAL, abbreviated as PVB. It is a polymer formed by the condensation reaction of high-molecular polyvinyl alcohol and butyraldehyde, and has nearly 23% by weight of vinyl alcohol groups in the final polymer. This polyvinyl butyral is plasticized with a special plasticizer (generally triethylene glycol esters), a continuous 0.38 to 1.52 formed by an extruder system and precise thickness control. Mm thick film.

4.0 The difference between the two

1, application area

EVA is mainly used for the encapsulation of crystalline silicon cells, and a small part of the membrane is also used, which mainly serves to protect the battery and to closely fit the cell sheet with the cover glass. The products currently used in the market are best known as DuPont's Tedlar, but there are also many other international companies producing various products such as 3M, and there are also several domestic manufacturers that can be used for solar energy, such as Foster and Sweeney. Ke et al.

PVB is currently mainly used in thin-film batteries, double glass components, building integration (BIPV) and other fields, with fewer production companies and product models, currently mainly Dupont, Kuraray, etc., some domestic companies are also trying to produce, such as Xinfu Pharmaceuticals and so on.

2, lamination process

The temperature requirements of PVB and EVA are different. EVA has good thermoplasticity and does not require high PVB for the equipment. PVB has a relatively high temperature requirement (around 155°C) and requires a higher laminator.

3. Others

PVB is a building material that has excellent gas barrier properties, good adhesion properties, and much better weather resistance. The disadvantage is that the barrier properties against moisture are poor, which is unacceptable for solar cells. And it's too soft to handle. The price is also more than three times that of EVA.

5.0 Summary

Both EVA and PVB are hot-melt adhesive films, which are mature products, each with its own advantages and disadvantages, and are applied in different fields. The trend of the packaging of crystalline silicon solar modules is to use EVA. Its excellent performance and affordable price are the products favored by many component manufacturers; PVB is very suitable for use in the fields of double glass components, thin film battery components and building integration, etc. The status of PVB is irreplaceable.


PVB is a multi-functional Polyvinyl Butyral resin by a chemical reaction and synthesis.

With high transparency, good toughness, flexibility, low temperature to fight resistance, and resistance to ultraviolet radiation, water, oil, anti-aging. PVB has very strong adhesiion to many kinds of materials such as: glass, metal, plastic, wood, leather and other materials, also has pigment dispersion and the excellent solubility of the resin.

PVB has been very widely used in the automotive and architecture safety glass interlayer , paint, ink, resistors, batteries, circuit boards, hot melt adhesive, the modified agent in the processing of textile fiber, etc.


Pvb Resin, Polyvinyl Butyral Resin, Recycled Pvb Resin, Polyvinyl Butyral Properties
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