| HS Code | 491197 |
| Brand | HIUV |
| Productname | BC Single-glass Transparent EVA Film |
| Material | Ethylene Vinyl Acetate (EVA) |
| Producttype | Transparent EVA encapsulant film |
| Application | Single-glass photovoltaic modules with back contact (BC) cells |
| Color | Transparent |
| Thickness | 0.35-0.50 mm |
| Width | 1000-1200 mm |
| Length | 100-200 m/roll |
| Specificgravity | 0.94-0.96 g/cm³ |
| Lighttransmittance | ≥91% |
| Haze | ≤2% |
| Gelcontent | ≥75% |
| Crosslinkingdegree | ≥75% |
| Adhesiontoglass | ≥60 N/cm |
| Adhesiontobacksheet | ≥40 N/cm |
| Tensilestrength | ≥16 MPa |
| Elongationatbreak | ≥500% |
| Volumeresistivity | ≥1.0×10^15 Ω·cm |
| Dielectricstrength | ≥20 kV/mm |
| Uvcutoffwavelength | ≤360 nm |
| Thermalshrinkage | ≤3% |
| Waterabsorption | ≤0.1% |
| Meltingpoint | 70°C |
| Shelflife | 12 months |
| Storagetemperature | ≤30°C |
| Storagehumidity | ≤60% RH |
| Certification | TUV, UL, IEC, RoHS, REACH |
As an accredited HIUV BC Single-glass Transparent EVA Film factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
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Utility-scale monofacial single-glass crystalline silicon module lines specify front-side encapsulant film with a narrow crosslinking window because the lamination step must simultaneously fill cell gaps, wet the glass surface, and avoid peroxide gas entrapment before gelation. For HIUV BC single-glass transparent EVA film, the layup mass is controlled at 450 g/m² ± 3% per unit glass area, corresponding to a nominal thickness of 0.46 mm at a melt density of 0.95–0.97 g/cm³. A 1.72 m × 1.13 m glass sheet therefore consumes approximately 1.16 kg of film per module. Compliance at module level is demonstrated through IEC 61215-2:2021 qualification sequences, specifically MQT 12 humidity-freeze cycling and MQT 13 damp heat at 85 °C and 85% RH, with insulation resistance verified under IEC 61730-1:2023. The downstream production sequence begins with hot DI water glass washing at 45–55 °C, followed by automatic EVA sheet cutting and layup, string placement with a ±0.5 mm cell positioning tolerance, and final layup of the backsheet. Lamination occurs in a dual-chamber laminator with platen set at 145–148 °C, upper chamber vacuum at -100 to -60 kPa, and a total cycle of 16–18 min including 300–360 s pre-vacuum. Crosslinking is terminated at 75–85% gel content measured by solvent extraction according to ASTM D2765-16; below 70% gel content adhesion failure after damp heat is observed, while above 88% gel content backsheet peel strength decreases due to reduced macromolecular interdiffusion. Terminal modules are 540–620 W utility-scale panels for fixed-tilt and single-axis tracker arrays.
Interdigitated back-contact and metal-wrap-through cell architectures remove front busbars, placing all current collection behind the cell; this forces the front encapsulant to act as an optical medium over the full illuminated surface while also withstanding localized pressure differences around rear pads and vias. The film is laid up at 430–470 g/m² on the front side and 380–420 g/m² on the rear side, with the front-to-rear mass ratio held near 1.10–1.25 to avoid asymmetric shrinkage after curing. Optical transmittance is referenced to ASTM E903-20 over 380–1100 nm, and volume resistivity is verified by ASTM D257-14 at >1.0×10^14 Ω·cm to limit shunt leakage across rear soldering pads. Industry compliance uses IEC 61215-2:2021 MQT 10 UV preconditioning at 15 kWh/m² and MQT 14 mechanical load with 5400 Pa on the front surface. The downstream line differs from conventional H-pattern modules in three stages: flux-free or low-flux soldering of back-contact pads, automated optical inspection of pad coplanarity at ±0.15 mm, and lamination with a low-pressure dwell plateau to avoid microvoids around pads. A typical three-stage laminator profile is provided in Table 1. The critical process window is 142–148 °C platen setpoint; excursions above 150 °C accelerate peroxide decomposition before sufficient bubble nucleation has escaped, producing edge voids in 2–5 mm band widths. Terminal products are 370–450 W single-glass back-contact modules for residential and commercial rooftops.
| Laminator stage | Platen setpoint (°C) | Chamber pressure (kPa) | Dwell time (s) |
|---|---|---|---|
| Pre-vacuum | ambient | -90 to -100 | 300–360 |
| Pressure ramp | 142–148 | -60 to -80 | 180–240 |
| Cure plateau | 145–148 | -40 to -60 | 900–1080 |
| Cooling | ≤110 | -80 | 180–300 |
Residential rooftops with string inverter systems commonly operate at system voltages near 1000 V, making potential-induced degradation a major screening criterion for front encapsulant films. The film is applied at 0.44 kg/m² on the front side and 0.36 kg/m² on the rear side, with a total film mass of approximately 1.08 kg for a 1.70 m × 1.13 m module. Compliance is verified under IEC TS 62804-1:2015 using 85 °C, 85% RH, -1500 V bias for 96 h, with maximum power loss <5% after test. The encapsulation process on a residential module line typically includes pre-lamination annealing of glass at 60–70 °C for 20 min to reduce moisture condensation in high-humidity workshops. Lamination is completed in a single-chamber laminator at 145 ± 2 °C platen setpoint, 17 min total cycle, and -80 kPa chamber vacuum. Terminal product types are 400–450 W all-black or white-backsheet residential modules. The EVA film should be stored at 25 ± 5 °C and RH <60%; if opened at RH >60%, pre-drying at 40 °C for 4–6 h is required to prevent micro-bubble formation. No amine-based curing additives should be introduced because premature crosslinking leads to incomplete cell gap filling and lamination voids.
Building-integrated photovoltaic façade elements require the encapsulant to function simultaneously as an optical coupling layer and as a structural interlayer under continuous wind and thermal movement. When the film is used as a PV interlayer in single-glass BIPV curtain wall cassettes, the specified addition is typically 0.76 mm nominal thickness, corresponding to 730 g/m², and may be installed as a double layer on either side of the cell string to achieve the required post-lamination interlayer thickness. Compliance is assessed through ISO 12543-1:2021 for laminated safety glass, EN 50583-1:2016 for building-applied photovoltaics, and IEC 61730-1:2023 for electrical safety. The downstream process includes cutting cells into shingled or half-cell formats, laying the EVA film onto a low-iron front glass substrate, placing the cell matrix with 10–20 mm edge clearances, applying the second EVA layer, and sealing with a polymer backsheet or a second glass pane. Lamination is performed in a vacuum bag laminator at 135–140 °C for 30–35 min, followed by a cooling press at 15–20 kPa to minimize optical distortion. Terminal products include semi-transparent façade spandrels, skylight strips, and curtain wall units with power densities of 140–180 W/m² at cell coverage ratios between 30% and 60%. Published data for this specific single-glass BIPV configuration is limited; therefore, interlayer thickness and lamination cure must be validated by cross-sectional adhesion peel specimens according to ASTM D903-20 on a batch basis.
Agrivoltaic canopies over lettuce and berry cultivation expose modules to elevated albedo, high UV load, and prolonged near-horizon irradiation; the front encapsulant must maintain transmittance without yellowing under cumulative UV doses exceeding standard test levels. The layup for a bifacial single-glass module uses 450 g/m² front-side EVA film and 380 g/m² rear-side EVA film over a UV-stable transparent backsheet. Compliance at module level follows IEC 61215-2:2021 MQT 10 UV preconditioning at 15 kWh/m², while spectral transmission is measured by ASTM E903-20 at 380–1100 nm, with initial hemispherical transmittance not less than 91% after glass and film lamination. The downstream process integrates bifacial stringing with transparent backsheet layup, and lamination uses a three-step profile: 8 min vacuum at -90 kPa, 6 min pressure ramp, and 12 min cure at 145–147 °C. Because agrivoltaic arrays often use bifacial modules, the rear-side EVA must not be replaced with a white reflective film; terminal product types are 400–550 W transparent-backsheet bifacial modules for elevated canopy structures with 3.5–4.5 m clearance heights. Residual peroxide after cure is monitored by DSC to ensure no secondary crosslinking; gel content is held at 72–80% by solvent extraction.
Floating photovoltaic installations on brackish water impose sustained high humidity, salt spray, and partial shading from wave action on single-glass module front encapsulants. The film is laid at 460 g/m² front and 400 g/m² rear, with a total mass of 2.35 kg for a 2.28 m × 1.13 m large-format module. Compliance requires IEC 61215-2:2021 MQT 13 damp heat extended to 2000 h at 85 °C/85% RH plus IEC 61730-1:2023 wet leakage testing with ≥40 MΩ·m² insulation resistance. The production process includes edge-tape application before lamination to prevent EVA bleed into frame drainage slots, a 1550 mm wide laminator with 2.0 m effective chamber depth, and a cure cycle of 18 min at 146 °C platen setpoint. Terminal products are 420–600 W floating solar modules with corrosion-resistant frames. Salt mist exposure of cured film edges indicates that gel content below 75% accelerates delamination at the glass-EVA interface after 1000 h damp heat; therefore, the lower gel content limit for floating modules is set at 78%. Pre-lamination film conditioning at 40 °C for 6 h is mandatory when storage RH exceeds 60%.
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HIUV BC Single-glass Transparent EVA Film is supplied as a peroxide-curable ethylene-vinyl acetate encapsulant film for lamination of single-glass photovoltaic modules. The film is applied as either front-side or rear-side transparent encapsulation in glass-backsheet, transparent-backsheet, and back-contact cell constructions where optical coupling and adhesion are process-critical. The BC suffix is the manufacturer’s commercial grade identifier. Because batch-specific datasheet values for this configuration are not uniformly published, the property envelope described in this document is derived from transparent EVA encapsulant data of equivalent class and from production-lot certificates of analysis, not from a guaranteed HIUV BC datasheet. In a single-glass stack, the film is positioned between the cover glass and the active cell layer, or between the cell layer and a transparent backsheet, where it must retain low haze, specified light transmittance, and dimensional stability through lamination and field exposure.
The primary technical differentiation is chemical composition and optical path. Unlike pigmented white EVA, which incorporates TiO₂ for rear-side reflectance, the BC transparent grade is formulated without reflective pigment and therefore preserves a broad transmittance window for front-side or transparent rear-side use. Compared with polyolefin elastomer (POE) encapsulants, an EVA matrix generally develops greater glass adhesion at lower lamination temperature, often exceeding 50 N/cm at 145 °C on clean glass, but has lower volume resistivity and a documented tendency to release acetic acid during damp-heat aging. Compared with EPE co-extruded films, which place a POE core between EVA skins, the BC film is a single-layer EVA and eliminates the additional skin-core interfaces that can act as moisture transport paths if edge sealing is incomplete. The substitution decision depends on system voltage, PID sensitivity, backsheet permeability, and required insulation resistance.
Typical uncured film is supplied in roll widths from 985 mm to 2200 mm and thicknesses of 0.45 mm, 0.50 mm, or 0.60 mm with a thickness tolerance commonly specified at ±0.05 mm. Roll lengths for EVA encapsulants of this class are frequently 150 m to 300 m, depending on thickness and core diameter. Density is typically 0.95 g/cm³ to 0.96 g/cm³ when measured per ISO 1183-1:2019. Melt flow index before cure is commonly reported between 20 g/10 min and 40 g/10 min at 190 °C under 2.16 kg load per ISO 1133-1:2022. Vinyl acetate content is controlled between 28 wt% and 33 wt% to balance optical clarity, adhesion, and crosslink density. These values are batch-dependent and the HIUV BC certificate of analysis remains the controlling document for incoming acceptance.
Lamination of the BC transparent EVA film is ordinarily performed on a flatbed vacuum laminator with heated platens and a silicone membrane or equivalent pressure-transfer mechanism. Typical chamber setpoints for EVA cure fall between 145 °C and 165 °C, with vacuum drawn in two or three stages before membrane pressurization. The peroxide cure package used in this encapsulant class has a one-hour half-life temperature in the range of 135 °C to 145 °C; therefore, platen temperature drift greater than ±3 °C across the module area can create measurable gel-content variation. A target gel content after lamination of not less than 80% is standard for EVA encapsulants, but actual cycle time must be validated by solvent extraction or differential scanning calorimetry on the completed module stack. Insufficient first-stage vacuum produces air entrapment at cell edges, while excessive early membrane pressure can displace cells before the film reaches full melt flow. Large-format laminators with platen dimensions of 2.2 m by 4.4 m generally require zone-controlled heating to maintain cross-machine temperature uniformity.
Adhesion is evaluated after lamination by 90° or 180° peel test on glass and backsheet coupons. Transparent EVA of this class typically develops glass adhesion above 50 N/cm when cured within the specified temperature window; values below 30 N/cm are associated with silane adhesion promoter migration, under-cure, or contamination on the glass receiving surface. Damp-heat aging at 85 °C and 85% RH for 1000 h to 2000 h per IEC 61215-1:2021 is used to assess adhesion retention and yellowing. Transparent EVA films with insufficient UV stabilizer loading may show yellowing before 1000 h, so UV preconditioning and damp-heat exposure should be reviewed for the specific module bill of materials.
Back-contact cell architectures remove front-side busbars and therefore increase the demand for consistent film thickness over the cell surface. A localized thickness reduction below 0.40 mm can create a shorter electrical insulation path between the cell and glass or backsheet. Volume resistivity of cured EVA is typically maintained above 1×1014 Ω·cm when tested per ASTM D257 or IEC 62631-3-1, but the value is temperature- and humidity-dependent. In single-glass modules, rear-side moisture ingress through a permeable backsheet can reduce insulation resistance faster than in double-glass construction because only one glass pane is present. Sodium ion migration from the cover glass remains a documented EVA-related failure pathway; POE-based encapsulants are generally specified for severe PID environments due to higher volume resistivity and the absence of vinyl acetate hydrolysis products. The BC transparent EVA film may be used where the bill of materials and system voltage fall within validated EVA limits, but it is not a direct substitution for POE in all PID-sensitive designs.
Rolls should be stored in a clean, dry environment at 0 °C to 30 °C, out of direct sunlight, with relative humidity below 60%. If storage RH exceeds 60%, pre-drying or dry-room conditioning is recommended before the film enters the layup station. Exposure to ambient moisture before lamination can produce bubble defects at cell edges and reduce silane coupling efficiency. Uncured EVA film has finite peroxide stability; elevated storage temperature accelerates peroxide decomposition and shifts melt flow index. Rolls should not be stacked more than three high if core deformation is to be avoided. When moving rolls from cold storage to a warm production floor, condensation risk is managed by a staged temperature ramp over 12 h to 24 h in the original protective packaging.
Optical performance of the transparent EVA film is typically characterized by total luminous transmittance, haze, and solar-weighted transmittance. Using ASTM D1003, haze after lamination is generally below 3%; values above this threshold may indicate additive phase separation, insufficient mixing, or contamination. Solar-weighted transmittance in the 380 nm to 1100 nm range is typically above 91% after correction for reflection losses. Shrinkage of the film is critical: machine-direction shrinkage above 3% at 120 °C for 3 min can pull busbars or create cell-to-cell misalignment during lamination. Refractive index of EVA at 589 nm is approximately 1.48 to 1.50, sufficiently matched to glass to minimize interfacial reflection when no air gap remains. Cure nonuniformity can generate local refractive index variation and low-intensity internal haze that is not detected by handheld gloss meters.
Table 1 summarizes the class-typical property envelope for transparent single-glass EVA encapsulants. Published data for the HIUV BC-specific configuration are limited; the values below do not substitute for the manufacturer lot certificate.
| Parameter | Typical range | Test method |
|---|---|---|
| Thickness tolerance | ±0.05 mm | ISO 4593 |
| Width tolerance | ±2 mm | manufacturer internal |
| Density | 0.95–0.96 g/cm³ | ISO 1183-1:2019 |
| Melt flow index before cure | 20–40 g/10 min at 190 °C, 2.16 kg | ISO 1133-1:2022 |
| Vinyl acetate content | 28–33 wt% | manufacturer internal |
| Gel content after cure | ≥80% | ASTM D2765-16 |
| Total luminous transmittance after lamination | ≥91% | ASTM D1003 |
| Haze after lamination | ≤3% | ASTM D1003 |
| Volume resistivity | ≥1×1014 Ω·cm | ASTM D257 |
| Adhesion to glass | ≥50 N/cm | IEC 61215-1:2021 coupon peel method |
| Shrinkage at 120 °C, 3 min | ≤3% | ASTM D1204 |
Regulatory status for EVA encapsulant films in photovoltaic modules is typically assessed under RoHS 2011/65/EU and REACH 1907/2006/EC. No intentionally added cadmium, lead, mercury, hexavalent chromium, polybrominated biphenyls, or polybrominated diphenyl ethers are declared. Specific compliance for the HIUV BC lot should be confirmed by supplier declaration because additive packages can vary by production campaign.
Material substitution in single-glass encapsulation is evaluated through electrical resistivity, damp-heat adhesion, and optical transmittance data. Table 2 compares class-level differences among transparent EVA, pigmented white EVA, POE, and EPE co-extruded films; actual HIUV BC values are lot-dependent.
| Property | HIUV BC transparent EVA | Pigmented white EVA | POE | EPE co-extruded |
|---|---|---|---|---|
| Base resin | EVA | EVA with TiO₂ filler | polyolefin elastomer | EVA skins / POE core |
| Rear-side reflectance | low | high | low | low to moderate depending core |
| Front-side solar-weighted transmittance | ≥91% | reduced by pigment | ≥91% | ≥91% |
| Glass adhesion at 145 °C | ≥50 N/cm | ≥50 N/cm | moderate | high via EVA skins |
| Volume resistivity | 1014–1015 Ω·cm | 1014–1015 Ω·cm | ≥1015 Ω·cm | ≥1015 Ω·cm core |
| Acetic acid generation under damp heat | possible | possible | not expected | reduced due POE core |
| Typical use | front or transparent rear encapsulation | rear reflective encapsulation | PID-sensitive single-glass or bifacial | cost-balanced PID improvement |
On production-scale laminators, three recurring failure modes are observed with transparent single-glass EVA films: edge bubble formation, cell displacement, and post-cure gel-content variation. Edge bubble formation is typically traced to moisture uptake above 60% RH or insufficient vacuum dwell. Cell displacement often arises when the film’s melt flow index at platen temperature is higher than specified because of incorrect preheat or peroxide degradation; this appears as shifted cells and busbar misalignment after cycle completion. Gel-content variation across a module is frequently a symptom of platen temperature drift exceeding ±3 °C. Incoming film should be sampled per roll for thickness, moisture, shrinkage, and melt flow index before release to the layup station. When a new lot exhibits higher shrinkage at the edge-seal step, vacuum profile adjustment and reduced preheat time are required rather than increasing process temperature, which may accelerate peroxide consumption and reduce final adhesion.
