KENGO WHITE EVA Film 40E Sandblasting white translucent

KENGO WHITE EVA Film 40E Sandblasting white translucent is a crosslinkable ethylene-vinyl acetate copolymer interlayer supplied in roll form for glass lamination and photovoltaic module construction. The 40E designation is interpreted as a nominal caliper of 0.40 mm. Because manufacturer-published data for this specific sandblasting white translucent configuration is limited, lot-level thickness, melt flow, and optical values should be confirmed against the certificate of analysis before line introduction. The product is positioned for use in glass-to-glass photovoltaic module encapsulation behind the cell plane, frosted architectural laminated glass, and light-diffusing panels in which high diffuse transmittance, visual masking of underlying layers, and controlled vacuum deairing are required. The sandblasting surface texture distinguishes this film from clear EVA and from smooth or embossed white EVA grades; the stochastic micro-roughness lowers the initial contact area between the film and rigid substrates during layup and assists the removal of air at the start of the lamination cycle. Rolls should be stored in sealed polyethylene bags at 20–25 °C and 45–55 % RH until staging, with direct UV exposure minimized to avoid premature consumption of the peroxide curing species.

What Optical Changes Are Introduced by the Sandblasting White Translucent Surface?

The sandblasted matte interface modifies the angular distribution and total intensity of transmitted light. In a clear EVA interlayer, specular transmittance dominates and haze remains low; in the 40E grade, a dispersed inorganic opacifier—typically rutile titanium dioxide—introduces volume scattering, while the stochastic surface micro-roughness adds interfacial scattering. Total luminous transmittance and haze should be measured on cured laminates using ASTM D1003 or ISO 13468-2, with yellowness index checked under ASTM E313. Because sandblasting surface texture interacts with optical measurement geometry, values obtained from this film may show greater instrument-to-instrument variability than values obtained from polished clear films. Optical acceptance should therefore be defined on the completed laminate, not on the as-rolled film alone.

Compared with standard white EVA without a sandblasting finish, the 40E surface reduces the tendency for air pockets to be trapped between the film and glass, but the bulk optical performance remains governed primarily by the titanium dioxide loading. If the TiO₂ volume fraction is too low, the material appears milky rather than sufficiently opaque to mask cell ribbon patterns; if the loading is too high, melt rheology becomes strongly shear-sensitive and the film may lose flexibility at low ambient temperatures. Typical white translucent EVA films in the 0.40 mm caliper class exhibit total luminous transmittance between 60 % and 85 %, with haze above 90 %. The KENGO 40E configuration should be expected to operate within this class; published data for the specific product is limited, and incoming lots must be verified. A comparative matrix for clear EVA, standard white EVA, and sandblasting white translucent EVA is provided below.

The sandblasting texture should not be confused with a simple embossed deairing pattern. Embossed films use repeating geometric cells that can generate visible pattern transfer after cure if the pattern is not fully flattened; sandblasting produces a non-repeating roughness that is less likely to create periodic optical artifacts in the laminate. This is one of the primary differences when selecting between embossed white EVA and KENGO 40E for light-diffusing architectural glass. Surface roughness can be checked by profilometry per ISO 21920-2; because measurement of stochastic matte surfaces is sensitive to filter cutoff, the same scanning length and cutoff should be used for batch comparisons.

Lamination Processing Window, Melt Flow, and Cure Kinetics Boundaries

For a crosslinkable EVA interlayer with nominal caliper 0.40 mm, the lamination window is determined by the peroxide decomposition profile and the melt viscosity required for void-free gap filling. The melt flow index of this film class measured per ISO 1133-1:2022 at 190 °C and 2.16 kg typically falls between 20 g/10 min and 30 g/10 min. Higher titania loading tends to reduce MFI by increasing filler-filler interaction and shear thinning sensitivity. Batch-to-batch MFI variation should be monitored because a change of more than 3 g/10 min can alter edge bleed width and thickness uniformity over cell strings.

Cure progression can be tracked by differential scanning calorimetry under nitrogen using ASTM E2041. In this class of EVA, the cure exotherm commonly begins near 110–130 °C and peaks near 150–170 °C, depending on peroxide type, antioxidant package, and titania surface chemistry. The target glass surface temperature during lamination should be maintained between 145 °C and 155 °C for 8–12 min to achieve gel content above 75 % when measured by ASTM D2765 or an agreed xylene extraction method. At glass temperatures below 135 °C, crosslink density remains insufficient and the interlayer may show low peel adhesion to glass. Above 165 °C, rapid peroxide decomposition can generate gaseous byproducts that form edge bubbles, and titania-filled EVA may undergo local discoloration. The sandblasting texture does not widen the chemical cure window; its function is restricted to improving air removal during the vacuum stage.

The vacuum stage must be extended until the chamber pressure is below 20 mbar before membrane pressure is applied. Single-chamber laminators with silicone rubber membranes and platen temperature uniformity better than ±2 °C are commonly used for such films. The stochastic surface micro-roughness reduces the contact area and lowers the pressure differential needed to evacuate interlayer air, but it can also trap air if the matte side is placed against an untextured glass surface without an adequate vacuum hold. Layup orientation should be fixed for each glazing stack and validated by cross-section or ultrasonic inspection of first articles. Thickness variation outside ±0.03 mm can cause localized differences in glue-line thickness, altering the optical path length and creating visible mura or Newton rings when the film is laminated between two glass sheets. On automated layup lines, static cling and air flotation behavior differ between clear EVA and sandblasting white EVA; pick-and-place vacuum cups must be tuned to avoid double-sheet pickup because the rough surface can reduce the contact seal between the cup and the film.

After cure, tensile properties measured according to ASTM D638-14 or ISO 527-1:2019 should be recorded, with elongation at break monitored as a more sensitive indicator of crosslink density than tensile strength. For 0.40 mm white EVA interlayers, elongation at break below 300 % after cure may indicate either overcure or poor dispersion of the titania masterbatch. Adhesion to glass can be evaluated by ASTM D903 or ISO 813 using a peel test method agreed between film supplier and laminator. Minimum peel strength values are application-specific; no universal acceptance value should be applied to all glass types and cleaning processes.

Production-scale vacuum bag laminators with platen dimensions of 2.2 m × 1.4 m or larger may exhibit edge-to-center pressure variation during membrane transfer. For the 40E film, this variation can produce edge over-bleed of 1–3 mm and slight thinning over solder ribbons. A controlled membrane pressure ramp of 0.3 bar/s or less after the vacuum hold is preferable to immediate full membrane pressure. Tooling changeover from clear EVA to sandblasting white EVA often requires extension of the vacuum hold by 60–120 s, not because the material is more difficult to deair, but because the rough surface changes the initial gas flow geometry between the film and the glass. Production sites at altitudes above 1500 m should verify that vacuum pump capacity can still reach the required chamber pressure; otherwise edge bubble occurrence increases. Films should not be cold-stretched during roll handling, because localized tensile strain can reduce the surface roughness pattern and create optical streaks after cure. Film blocking can occur if rolls are stored at ambient temperatures above 30 °C or under high stack pressure. Interleaving or release liners are generally not used with sandblasting white EVA; the stochastic texture itself acts as an anti-blocking surface. However, if the film is wound too tightly, the surface roughness can be compressed over time and become glossy at the outer wraps. Outer wraps should be checked before use and discarded or conditioned if the matte appearance is no longer uniform. At start-up, the first 3 laminates from a new roll should be destructively inspected by peel test and cross-section microscopy because the outer wraps may have reduced surface roughness due to winding compression.

When Moisture Uptake or Chemical Incompatibilities Become Limiting Factors

Rolls exposed to relative humidity above 60 % during storage or staging should be treated as moisture-contaminated until reconditioned. Ethylene-vinyl acetate copolymer absorbs water at the film surface; water reacts with residual acetic acid or peroxide decomposition products during cure and increases the probability of haze, interfacial voids, and reduced adhesion. Pre-drying should be performed in a desiccated cabinet at 25–30 °C for 2–4 h with a dew point below -20 °C. Direct infrared preheating of the film surface above 40 °C is not recommended because selective softening of the sandblasting texture can reduce its deairing benefit.

Chemical incompatibilities include amine-based silane additives and strongly alkaline glass-cleaning residues. Amine species can react with vinyl acetate repeat units or accelerate peroxide decomposition, leading to premature crosslinking in the roll or yellowing after cure. Glass surfaces should be cleaned with neutral pH detergents and rinsed to conductivity below 10 µS/cm before layup. The film should not be combined with acid-catalyzed silicone sealants that release acetic acid during the same thermal cycle, because the combination may increase corrosion risk at module edges. Because EVA can generate acetic acid under damp heat aging, glass-to-glass modules using this white translucent EVA require low-MVTR edge sealants—typically below 0.1 g/m²·day—when long-term outdoor exposure is specified.

Compared with polyolefin elastomer encapsulants, this EVA grade has lower volume resistivity and may not be appropriate for high-efficiency cell architectures that are highly sensitive to potential-induced degradation. The white translucent optical design is a light-management layer, not a PID suppression layer. Qualification under damp heat 85 °C / 85 % RH for 1000 h per IEC 61215-2:2021 should be performed on the complete laminate, because film-level optical data cannot predict interfacial adhesion, discoloration, or edge seal compatibility. Ultraviolet stabilizer package compatibility should be confirmed with the supplier when the laminate is intended for unframed or high-altitude installations. Outdoor UV exposure can degrade the EVA backbone and produce yellow chromophores if the UV absorber and hindered amine light stabilizer system is insufficient. Xenon arc testing per ISO 4892-2 or ASTM G155 may be specified for architectural applications, with yellowness index change tracked under ASTM E313. Since the sandblasting white surface scatters UV in addition to visible light, UV absorption measurements made on polished clear EVA are not transferable to this product.

Incoming quality control for each lot should verify nominal caliper per ASTM D374 or ISO 4593, melt flow index per ISO 1133-1:2022, and gel content after a standardized lamination cycle per ASTM D2765 or an agreed xylene extraction method. A complete compliance matrix should include the following minimum verifications.

For photovoltaic applications, the film should be accepted only after the downstream module laminate passes the stress-test sequence defined in IEC 61215-2:2021, since film-level optical data cannot predict interfacial adhesion or long-term discoloration. This is particularly relevant for white translucent interlayers, where minor formulation changes in the titania masterbatch can shift reflectance, melt flow, and long-term yellowness without affecting film thickness.