| HS Code | 186275 |
| Brand | Betterial |
| Product Name | Transparent EVA SolarFilm B601P |
| Model | B601P |
| Material | Ethylene-vinyl acetate (EVA) |
| Product Type | Solar encapsulant film |
| Appearance | Transparent film |
| Thickness | 0.45 mm |
| Width | 1000-2200 mm |
| Density | 0.94 g/cm³ |
| Transmittance | ≥91% |
| Haze | ≤1.5% |
| Melting Point | 65-75 °C |
| Softening Point | 50-60 °C |
| Crosslinking Degree | ≥75% |
| Peel Strength To Glass | ≥70 N/cm |
| Peel Strength To Backsheet | ≥40 N/cm |
| Volume Resistivity | ≥1×10^15 Ω·cm |
| Dielectric Constant | 2.8 at 1 kHz |
| Breakdown Voltage | ≥30 kV/mm |
| Tensile Strength | ≥18 MPa |
| Elongation At Break | ≥500% |
| Water Absorption | ≤0.1% |
| Uv Cut Off Wavelength | ≤360 nm |
| Thermal Shrinkage | ≤3% |
| Storage Temperature | 5-30 °C |
| Shelf Life | 12 months |
| Pid Resistance | Pass |
As an accredited Betterial Transparent EVA SolarFilm B601P factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
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Standard monofacial glass-backsheet modules position Betterial Transparent EVA SolarFilm B601P between low-iron patterned solar glass and the interconnected cell string. The as-received film is a thermosetting ethylene-vinyl acetate copolymer with a vinyl acetate fraction of 28–32 wt% and a melt flow rate measured according to ISO 1133-1:2022 at 190 °C under 2.16 kg in the range of 20–30 g/10 min. A peroxide-initiated cure system and a silane coupling agent are compounded into the film. The silane coupling agent forms siloxane bridges to the glass surface during lamination. The peroxide decomposes at the platen temperature to crosslink the vinyl acetate domains.
Production-scale lamination is executed on a three-chamber vacuum laminator. The layup is transferred at 18–25 °C laminate inlet temperature. The first chamber removes entrapped air to an absolute pressure below 0.1 kPa. The second chamber applies mechanical diaphragm pressure at 80–100 kPa while heated platens transfer thermal energy through the glass. The third chamber cures the film to a final gel fraction of 80–88 % determined by solvent extraction according to ASTM D2765. Platen set points of 148–152 °C with a total cycle of 16–18 min are typical for 3.2 mm glass / B601P / cells / B601P / backsheet stacks. Residual peroxide is monitored by differential scanning calorimetry; incomplete cure is indicated by an exotherm above 120 °C on first heating. Qualification of the finished panel is carried out against IEC 61215-2:2021, with the encapsulant influencing MQT 11 thermal cycling (200 cycles from -40 °C to 85 °C), MQT 12 humidity freeze, and MQT 13 damp heat (1000 h at 85 °C/85 % RH). Safety evaluation follows IEC 61730-2:2016. Peel adhesion of the cured film to patterned solar glass is verified at 40–70 N/cm using ASTM D903. The terminal product is a conventional monofacial module with a black or white backsheet, aluminum frame, and sealed junction box. Lamination failures on production lines typically present as edge voiding when platens remain below 145 °C or as trapped air marks when the first-stage vacuum time is reduced below 3 min. At relative humidity above 60 %, rolls are pre-conditioned at 25 °C and 30 % RH for 24 h before use to prevent bubble formation.
Bifacial glass-glass stacks replace the polymer backsheet with a second glass sheet. This changes the moisture ingress path. The front and rear layers are both 0.45–0.50 mm B601P. The laminate is assembled in the order glass / B601P / bifacial cell string / B601P / glass. The glass thickness is usually 2.0 mm or 2.5 mm on each side. Thermal mass increases compared with a single-glass backsheet module. Therefore the lamination cycle is extended to 20–22 min with platen set points at 150–155 °C. The first-stage vacuum is held for 4–5 min before diaphragm pressure is applied at 90–100 kPa. Cure is controlled to a final gel content of 82–90 % per ASTM D2765.
Glass-glass stacks are sensitive to edge bleed into the module edge gap. B601P melt flow under heat causes a bleed front that can reach 2–4 mm beyond the cell edge. The laminator’s edge pin system must be adjusted to avoid contact marks. If the edge bleed is not controlled, the resulting thermoplastic-rich vitreous edge can act as a moisture wicking path. Because EVA has higher water vapor transmission than polyolefin encapsulants, the glass-edge seal region is critical. Water vapor entering through the edge can hydrolyze the vinyl acetate groups, releasing acetic acid. This acid can catalyze further hydrolysis and raise the risk of potential-induced degradation in the finished bifacial module. To limit edge moisture ingress, some production lines combine B601P with a POE strip at the perimeter; however, B601P remains used across the active cell area for its optical and adhesion profile. Compatibility between the EVA and POE strip is controlled by melt viscosity overlap; the two films must exhibit similar flow fronts at the lamination plateau temperature. If the POE strip has a lower melt viscosity than B601P, it can penetrate into the active area and create an irregular skin layer under the glass.
Finished bifacial modules are qualified to IEC 61215-2:2021. The encapsulant is particularly monitored during MQT 13 damp heat and MQT 11 thermal cycling. Bifacial electrical performance is measured according to IEC 60904-1-2:2019 with front and rear irradiance. Safety testing uses IEC 61730-2:2016. Insulation resistance measured after damp heat is verified according to IEC 61215-2:2021 MQT 14, with wet leakage current limits defined by the module insulation class. The terminal product is a frameless dual-glass bifacial module with short-edge rail clamp mounting or adhesive-bonded mounting. The edge is sealed with butyl tape or structural silicone after lamination. The junction box is potted with a low-acetic-acid silicone adhesive to avoid interaction with the EVA edge.
Thin-film CdTe and a-Si modules with front transparent conductive oxide substrates use B601P as a backside encapsulant rather than as an optical window. The film is placed between the back of the coated glass and a moisture barrier backsheet or second glass sheet. In this stack the front interface remains the TCO glass. The encapsulant must not exude vinyl acetate oligomers that reduce optical transmission at the cell edge. Curing temperature is intentionally lowered to 138–143 °C to avoid thermal damage to sputter-deposited TCO layers. Vacuum lamination cycle is prolonged to 22–25 min to compensate for the lower platen temperature. Gel content after cure is checked at 75–82 % according to ASTM D2765. Because the cure temperature is lower than the standard EVA cure window, the residual peroxide level should be verified by differential scanning calorimetry before series production. Published data for this specific B601P low-temperature cure configuration is limited. Finished thin-film modules follow IEC 61215-2:2021 and IEC 61730-2:2016. Damp heat and thermal cycling failures caused by edge ingress are a known failure mode. The terminal product is a frameless utility-scale thin-film laminate with butyl edge tape and a sealed junction box. B601P thickness of 0.45–0.50 mm is typical for this stack. At relative humidity above 60 %, the film is pre-conditioned to avoid bubble formation in the lower-temperature cycle.
Building-integrated photovoltaic glazing uses B601P as both a cell encapsulant and a glass interlayer. The stack is glass / B601P / cell string / B601P / glass. Sometimes a third glass layer or a rear polymer backing is added to meet building energy codes. The cured interlayer must tolerate building-grade static load, but EVA is not a structural interlayer in the same sense as PVB or ionoplast. Its storage modulus declines at elevated temperature, which means the glass unit must not rely on the EVA to transfer shear between glass plies under sustained load. The framing system isolates the laminated unit from continuous tensile stress.
European BIPV installation is governed by EN 50583-1:2016 for building integration. Fire performance is classified under EN 13501-1. Mechanical resistance of the glazing is tested according to the applicable EN 12600 or ISO 12543 series, depending on the member state. PV performance is qualified under IEC 61215-2:2021 and safety under IEC 61730-2:2016. The fire classification depends on the whole glazing build, not on B601P alone; the film contributes organic mass and can affect the burning droplet classification.
Formulation for BIPV stacks uses B601P with a silane coupling agent targeted to both glass and backside cell busbar coatings. The film’s peroxide package should be selected for longer gelation time because the thick glass slows heat transfer. A higher initial gel time allows the film to fill the cavity around the cells without forming flow lines. Flow lines located at the cell edges reduce the aesthetic quality of semi-transparent BIPV units and create optical distortion.
Lamination is performed in a vacuum bag or membrane press. For large curtain wall panels, platen temperature is maintained between 145–152 °C. The thicker glass assemblies, often 5–8 mm outer lite and 4–6 mm inner lite, require plateau hold times of 25–35 min. First-stage vacuum must be extended to 6–8 min to evacuate air from the deep cavity around the busbar and edge wiring. Pressure is applied at 80–100 kPa only after the glass surface reaches 120 °C. Premature pressurization traps air near the cell tabs. Terminal product is a custom-sized semi-transparent BIPV spandrel panel or roof panel with a structural sealant frame and a concealed junction box. Edge bleed must not exceed the black ceramic frit boundary; excess bleed can interfere with the structural silicone bond. Rolls should not be stored with amine-containing polyamide films in direct contact, because amine migration can deactivate the silane coupling agent and lower glass adhesion.
Automotive photovoltaic roof laminates impose a forming requirement that differs from flat plate module processing. Curved glass roof profiles with radii below 1.5 m require the encapsulant to flow into the three-dimensional mold cavity before crosslinking. B601P is laid over the cell string at 18–22 °C room temperature. Preforming is performed at 80–100 °C under vacuum to conform the film to the curved glass surface. Full cure then occurs at 150–160 °C in a silicone vacuum membrane press with a surface pressure of 0.7–0.9 bar gauge. The final gel content is set at 80–88 % by ASTM D2765. Because the substrate is a shaded automotive glass, the stack includes a backsheet with high-temperature polyamide or PET-GL. Compliance for the photoelectric part is often based on IEC 61215-2:2021 thermal cycling and IEC 61730-2:2016, while vehicle-level environmental testing follows ISO 16750-4:2010 for temperature and humidity. Terminal product is a curved glass roof with embedded heterojunction cells and an automotive-grade connector. Batch-to-batch adhesion to curved glass must be monitored; edge bleed beyond 3 mm interferes with the black ceramic frit. B601P is not a windshield safety interlayer. The laminated glass assembly must be validated separately by the vehicle manufacturer for roof glazing safety. Amine-containing surface primers should be avoided because they can shift the crosslinking kinetics and reduce adhesion reproducibility.
Greenhouse and agricultural photovoltaic applications place the encapsulant in high-humidity and high-UV environments. B601P is paired with low-iron glass that has an anti-reflective coating. The film must maintain photosynthetically active radiation transmission between 400 nm and 700 nm. Optical transmittance of the laminated stack is measured according to ASTM D1003. Yellowness index is measured according to ASTM E313. Xenon arc exposure according to ISO 4892-2 is used to compare photochemical stability. A change in yellowness index over 1000 h of xenon exposure is generally held below 4 for qualified greenhouse module stacks, but published data for B601P in this specific configuration is limited.
The film contains a hindered amine light stabilizer and a UV absorber. The UV absorber shifts the cut-off near 360–380 nm. That makes the film suitable for glassed PV greenhouse modules but not for horticultural films where UV-A is used. Lamination for agricultural modules uses the standard glass-backsheet cycle. Platens are set to 148–152 °C. The cycle is 16–18 min for 3.2 mm textured glass. The edge seal requires additional attention because greenhouse modules are exposed to irrigation water and fertilizer mist. A watertight junction box and silicone edge seal are used. The terminal product is a semi-transparent or opaque PV greenhouse panel with tempered glass and an aluminum frame. B601P is not recommended as the direct covering film without glass, because its UV absorber package reduces the part of the solar spectrum that some greenhouse crops use for photomorphogenesis.
Flexible photovoltaic charging laminates require the encapsulant to exhibit sufficient initial tack to hold the cell strings in place before cure. B601P is used between an ETFE frontsheet and a reinforced PET or aluminum-laminated backsheet. The low thermal mass of the stack permits platen temperatures of 135–140 °C with a cycle of 12–15 min. The silicone membrane pressure is reduced to 30–50 kPa to avoid cell cracking in the bendable stack. Cure completeness is checked by ASTM D2765 with a minimum gel content of 75 %. Optical transmission of the completed flexible laminate is measured according to ASTM D1003, and yellowness index according to ASTM E313 after UV preconditioning. Compliance for portable modules is generally traceable to IEC 61215-2:2021 for thermal cycling and bypass diode thermal test, though flexible module qualification requires additional bend cycle validation. Published data for B601P in this specific flexible configuration is limited. The terminal product is a rollable or foldable solar charger with a form factor below 3.5 kg/m². Process limitations include edge delamination when the ETFE frontsheet is not surface-activated and bubble formation when the backsheet adhesive releases gas during cure.
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Betterial Transparent EVA SolarFilm B601P is supplied as a peroxide-cure ethylene-vinyl acetate encapsulant film for crystalline-silicon photovoltaic module lamination. The product is produced in a transparent, UV-stabilized formulation with a nominal thickness of 0.45 mm, slit widths from 1000 mm to 1300 mm, and roll lengths up to 150 m. The vinyl acetate content is in the 28–33 wt% range, giving melt-flow index values between 25 g/10 min and 35 g/10 min at 190 °C/2.16 kg when measured according to ISO 1133-1:2022. The material is intended for both glass/cell/backsheet and glass/glass stacks and is positioned for fast-cure lamination cycles used in high-volume module production. Published data for this specific B601P configuration is limited; the performance envelopes below therefore reference the transparent fast-cure EVA class covered by IEC 62788-1-2 and the lamination parameters required to reach those values.
Lamination of B601P on a three-chamber vacuum laminator requires a platen setpoint of 145–155 °C, with platen temperature uniformity better than ±2 °C across a 2.1 m × 4.0 m module format. The vacuum chamber should reach an absolute pressure below 1 mbar before the membrane applies a pressing force of 0.08–0.10 MPa. At these conditions, a total cycle of 8–12 min is typical for fast-cure EVA, but the exact dwell time depends on cell gap, ribbon layout, and backsheet shrinkage. Production lines with poor edge-bleed control retain gas in the busbar region; bubble defects are observed when vacuum dwell is shortened below 240 s on modules with cell spacing below 2 mm.
Pre-drying is required when storage humidity exceeds 60% RH or when the roll has been out of sealed packaging for more than 24 h at 25 °C. Moisture uptake above 0.05 wt% contributes to void formation during cure and lowers adhesion to the glass by reducing silane hydrolysis efficiency. During the heating ramp, the peroxide decomposition peak near 150 °C drives the crosslinking reaction; gel content below 75% after lamination indicates under-cure and is correlated with increased acetic acid generation after damp heat at 85 °C/85% RH per IEC 61215-1:2021, MQT 13.
On a production line with a 2.1 m wide roll and a 4.0 m long module, transverse thickness variation outside ±0.03 mm can cause local under-lamination at cell edges, particularly under the busbar. Edge bleed is controlled by the die-cut pattern and film overhang; typical overhang is 3–5 mm beyond the cell perimeter. Excessive overhang creates material loss into the chamber and may contaminate the membrane, while insufficient overhang produces unbonded cell edges. Bubbles at busbar crossings, creeping edge return of the film, and hazy spots after storage are commonly reported production defects associated with transparent EVA; such failures are typically process-induced and arise from platen temperature gradients, insufficient vacuum dwell, or moisture in the backsheet.
After lamination, the cured film is characterized on glass/EVA/glass laminates. Incoming quality control should compare the following class-level thresholds against the batch certificate. Published data for the specific B601P configuration is limited; values are class typical for transparent fast-cure EVA and should be confirmed per lot. Test laminates should be prepared using the production lamination recipe, not a laboratory hot press that cannot replicate vacuum and membrane pressure. A hot-press cure at 150 °C and 0.1 MPa for 12 min may produce artificially low gel content because volatiles are not evacuated. Optical and adhesion specimens should be taken from the center of a 300 mm × 300 mm glass/EVA/glass coupon prepared in a vacuum laminator with identical platen temperature and chamber vacuum.
| Property | Unit | Threshold or range | Test method |
|---|---|---|---|
| Total luminous transmittance after lamination | % | ≥ 91.0 | IEC 62788-1-4 / ASTM D1003-21 |
| Haze after lamination | % | ≤ 1.5 | ASTM D1003-21 |
| Gel content after cure | % | ≥ 80 | ASTM D2765-16, xylene extraction |
| Peel strength to glass, initial | N/cm | ≥ 80 | IEC 62788-1-6 / IEC 61215-1:2021 |
| Volume resistivity at 25 °C | Ω·cm | ≥ 1.0 × 1014 | IEC 62631-3-1 |
| Shrinkage at 120 °C, 30 min, MD/TD | % | ≤ 5.0 / ≤ 3.0 | ASTM D2732-20 |
| Water absorption, 24 h at 23 °C | wt% | ≤ 0.2 | ISO 62:2008 |
| Tensile strength at break after cure | MPa | 20–25 | ASTM D882-18 |
| Elongation at break after cure | % | ≥ 600 | ASTM D882-18 |
The volume resistivity threshold is an initial-value measurement. After 1000 h damp heat at 85 °C/85% RH, some EVA formulations drop by one to two orders of magnitude due to acetic acid formation; B601P-specific damp-heat aged resistivity data should be obtained from the manufacturer before use in PID-sensitive glass/glass modules. The crosslinked network is characterized by gel content rather than melt-flow behaviour because the cured film should not remelt; residual melt-flow after lamination indicates insufficient peroxide decomposition or non-uniform platen temperature. Acetic acid generation in EVA is a known failure mode because the vinyl acetate content of 28–33 wt% creates ester groups that hydrolyze under damp heat. The acid by-product lowers encapsulant volume resistivity and can corrode cell metallisation. For modules requiring high PID resistance, the manufacturer’s damp-heat aged data should be reviewed, or a POE front-side film should be considered.
Selection of B601P instead of a polyolefin elastomer (POE) or polyvinyl butyral (PVB) changes the moisture transport, lamination temperature, and adhesion balance of the module. POE is often specified for glass/glass bifacial modules because of its lower water vapour transmission and acetic acid-free formulation; however, POE generally requires longer vacuum dwell and higher pressing pressure, and its lower adhesion to glass before primer application can increase busbar delamination on textured glass. B601P, as an EVA class film, offers faster wetting and a broader adhesion window to standard low-iron solar glass at 145–155 °C, but its moisture barrier is lower. Published data for this specific B601P configuration is limited; typical EVA films exhibit water vapour transmission approximately two to three times higher than POE of equal thickness under 38 °C/90% RH. Modules with edge-shorted areas may therefore use POE as front-side encapsulant while retaining B601P on the rear side to reduce cost without sacrificing backsheet adhesion.
PVB offers strong glass adhesion and edge seal performance, but it typically laminates at 135–140 °C and requires plasticizer-controlled moisture. Its melt viscosity is higher than EVA, and its use in high-volume crystalline-silicon lines has been limited by lower throughput and greater sensitivity to ambient humidity. B601P is supplied as a thermoplastic film with pre-cure melt flow high enough to fill cell gaps, then thermoset by peroxide; PVB remains thermoplastic, so creep resistance above 80 °C is lower. This distinction matters for glass/glass modules that operate above 70 °C cell temperature in hot climate installations.
Compared with standard-cure transparent EVA, B601P is formulated for reduced cycle time; however, the increased peroxide decomposition rate can make the film more sensitive to platen temperature gradients and shorter vacuum dwell. White EVA is not a drop-in replacement because its reflective filler increases viscosity and reduces optical transmission. B601P transparent film may be used as a rear encapsulant only when rear-side reflection is not required, such as with a black backsheet or glass/glass bifacial stack that prioritizes rear-side light transmission.
Incoming quality-control sampling typically checks thickness across the web at 9 points, width, visible gel particles, and crosslinking after a standard lamination cycle. On a 2.1 m roll, thickness variation outside ±0.03 mm can cause local under-lamination at cell edges. Rolls with blocking, soft spots, or localized haze bands should be quarantined because these defects can propagate as bubble clusters after lamination. Incoming film with an irregular peroxide dispersion or high gel particle count may produce uneven cure and low peel force on the finished module.
Rolls should be stored in sealed polyethylene bags with desiccant at 15–25 °C, with a maximum shelf life of 12 months from production. Once opened, the film should be used within 24 h at relative humidity above 60%. Partial rolls returned to storage after exposure may absorb moisture unevenly, producing visible hazy patches after lamination. Before loading, the unwind tension should be set at 20–40 N per 1 m web width to prevent stretching and avoid transverse thickness variation. Films stored at temperatures above 30 °C for more than 7 days may exhibit partial pre-cure and should be tested for melt-flow index and gel particle count before use.
The film is supplied with compliance documentation for RoHS Directive 2011/65/EU and REACH EC 1907/2006 SVHC content. Module-level qualification is governed by IEC 61215-1:2021 and IEC 61730-2:2016, but these standards evaluate the assembled module rather than the film alone; pass/fail depends on glass, cell, and backsheet interactions. B601P-specific accelerated aging data, such as UV preconditioning, thermal cycling, and damp-heat adhesion retention, should be requested from the manufacturer for each stack configuration.
| Standard / regulation | Scope | Evaluation status |
|---|---|---|
| ISO 1133-1:2022 | Melt mass-flow rate | Incoming QC |
| ASTM D2765-16 | Gel content after crosslinking | Incoming QC after lamination |
| IEC 62788-1-4 / ASTM D1003-21 | Optical transmittance and haze | Incoming QC on glass laminate |
| IEC 62788-1-6 | EVA adhesion and cure | Batch release / module qualification |
| IEC 61215-1:2021 | Module design qualification | Module-level, not film-level |
| IEC 61730-2:2016 | Module safety qualification | Module-level, not film-level |
| RoHS 2011/65/EU | Hazardous substance restrictions | Supplier declaration |
| REACH EC 1907/2006 | SVHC reporting | Supplier declaration |
