PVB (polyvinyl butyral) and EVA (ethylene vinyl acetate) can both be used in photovoltaic module encapsulation, but they differ in polymer structure, bonding behavior, thermal processing, and moisture management requirements. EVA has long been widely used in crystalline silicon modules, while PVB is used in selected double glass modules, thin film photovoltaic products, and building integrated photovoltaics (BIPV). Material selection depends on the module design, encapsulant specifications, operating environment, and manufacturing process.
Main Differences Between PVB and EVA
Applications and Module Structures
EVA encapsulant film
EVA is a widely used encapsulant in conventional crystalline silicon photovoltaic modules. During lamination, EVA softens and flows under heat, then crosslinks under the specified temperature and time conditions. The resulting encapsulant bonds the cell strings to the glass, backsheet, or rear glass.
The encapsulant provides mechanical protection for the cells and helps limit exposure to environmental factors. EVA is also used in some thin film photovoltaic modules. Different formulations can vary in optical transmittance, adhesion strength, crosslinking rate, UV resistance, and damp heat performance. The grade should therefore be selected according to the module design.
One terminology distinction is important: DuPont's Tedlar is a polyvinyl fluoride (PVF) film brand commonly associated with photovoltaic backsheets. It is not an EVA encapsulant film. Encapsulant films and backsheet materials should be evaluated separately.
PVB encapsulant film
PVB has traditionally been used in laminated architectural and safety glass. Specialized PVB interlayers have also been developed for certain photovoltaic applications, including selected double glass modules, thin film products, and building integrated photovoltaics.
PVB adhesion, optical properties, and processing behavior depend on the formulation and product design. Photovoltaic grade PVB should not be treated as interchangeable with standard architectural glass PVB. Its optical performance, weather resistance, damp heat behavior, compatibility with the cell structure, and recommended lamination conditions should be checked against the manufacturer's specifications.
Material Properties and Encapsulation Performance
The differences between EVA and PVB extend beyond processing temperature. Their behavior after lamination and their response to long term environmental exposure must also be considered.
Bonding and curing mechanism: Photovoltaic grade EVA typically crosslinks during lamination to form a cured encapsulant layer. PVB primarily softens and flows under heat and pressure, then solidifies as it cools. It does not use the same crosslinking process as EVA.
Optical performance: Both materials can be formulated for photovoltaic applications. Transmittance, UV transmission, and long term yellowing depend on the specific grade and formulation, not simply on the polymer name.
Weather resistance: EVA performance depends on its formulation, degree of crosslinking, and operating environment. PVB also requires evaluation for damp heat exposure, UV resistance, and long term adhesion stability. Neither material should be considered universally more durable under all conditions.
Moisture management: PVB's moisture absorption and sensitivity require attention. Uncontrolled moisture content may affect lamination quality and long term reliability. EVA also relies on the overall moisture protection provided by the module design. Actual moisture barrier performance should be assessed using product data and the complete module structure.
Handling and storage: Both materials should be stored and processed according to supplier instructions. For PVB, raw material moisture content and storage conditions are particularly important. For EVA, storage life, thermal history, and crosslinking performance also need to be controlled.
Lamination Process Differences Between PVB and EVA
EVA Lamination
EVA lamination typically includes vacuum evacuation, heating, pressing, and crosslinking. The equipment first removes air from the module stack. The EVA then softens and flows to improve contact with the glass, cell strings, and backsheet or rear glass. Crosslinking takes place under the specified temperature and time conditions.
For some commercial photovoltaic grade EVA products, manufacturer data specify lamination temperatures of approximately 145 to 150°C. Certain fast curing grades use conditions such as 150°C for 15 minutes. These figures apply to specific materials and processes and should not be treated as universal settings for all EVA films.
Production parameters must be adjusted according to film thickness, module structure, laminator temperature uniformity, evacuation time, and crosslinking requirements. Results should be verified through measurements such as gel content or degree of crosslinking, adhesion strength, and visual inspection.
PVB Lamination
PVB lamination mainly relies on heating to soften the material and allow it to flow under pressure, bringing adjacent layers into contact. The bonding layer then solidifies during cooling. Because this mechanism differs from EVA crosslinking, EVA cure times and process settings should not be transferred directly to PVB.
The actual lamination temperature, pressure, vacuum conditions, and cooling method depend on the specific PVB grade and equipment design. Some photovoltaic grade PVB products use processing temperatures in the approximate range of 130 to 155°C. This range is provided only as a general reference for understanding the process, not as a production setting. The material supplier's technical data and a validated process specification should determine the final parameters.
PVB processing also requires attention to incoming material moisture, storage conditions before lamination, air removal, interlayer adhesion, and dimensional stability after cooling. Excess moisture or unsuitable processing conditions may lead to bubbles, poor adhesion, or other lamination defects.
How to Choose Between PVB and EVA
Material selection should start with the module design and long term reliability requirements rather than price or lamination temperature alone.
Module structure: Identify whether the product uses crystalline silicon cells, thin film cells, or a building integrated design, and whether the construction uses glass on both sides or glass combined with a backsheet.
Encapsulation performance: Compare optical transmittance, adhesion strength, UV resistance, damp heat performance, and electrical insulation requirements.
Moisture and environmental conditions: Evaluate temperature, humidity, outdoor exposure, and the module's moisture protection design. Check material data for moisture absorption and water vapor transmission.
Manufacturing process: Confirm that the existing laminator can meet the selected material's heating, vacuum, pressure, and cooling requirements. Determine whether tooling or cycle time adjustments are necessary.
Quality validation: Use representative samples to evaluate bubbles, adhesion, optical performance, and relevant reliability indicators. Conduct further validation according to the applicable module requirements.
Overall, EVA has an established track record in photovoltaic module manufacturing and is compatible with a wide range of existing lamination processes. PVB is suitable for selected products requiring particular optical, bonding, or building integration characteristics. Neither material is universally superior for every photovoltaic module. The final choice should be based on the material specifications, module structure, and a validated manufacturing process.
In addition to supporting processes related to photovoltaic materials and equipment, Hansheng Automation provides precision machining based on customer supplied drawings for single piece and small batch orders. Our custom machining services cover yacht structural components, remote controlled racing car parts, functional components for tobacco packaging machinery, and parts for filling machinery. The machining process is determined by the part drawings, material, and technical requirements.
