JA EVA adhesive Film

JA EVA adhesive Film is supplied as a thermoplastic ethylene-vinyl acetate copolymer sheet in model designations JA-18, JA-28, and JA-33, corresponding to nominal vinyl acetate mass fractions of 18 %, 28 %, and 33 %. The film is manufactured in thicknesses from 0.25 mm to 0.80 mm with a thickness tolerance of ±0.02 mm, in widths from 200 mm to 2,400 mm, and in roll lengths of 50 m or 150 m. The product is intended for flat-bed vacuum lamination of glass, polycarbonate, and photovoltaic cell arrays, with processing temperatures between 130 °C and 160 °C. The low-temperature thermoplastic behaviour is governed by vinyl acetate content; higher vinyl acetate content reduces crystalline melt peak and increases optical clarity but also raises equilibrium moisture uptake and creep compliance. JA-18 is specified when higher modulus and lower room-temperature tack are required for rigid flat laminates. JA-28 is specified for photovoltaic encapsulation because of the balance between adhesion and flow. JA-33 is specified for high-flow gap filling in curved glass assemblies. The embossed surface on one side reduces roll blocking and permits air evacuation during vacuum bag processing.

Vinyl Acetate Content, Melt Flow Index, and Thickness Tolerance

The specification matrix in Table 1 summarises representative values obtained from conditioned film with residual moisture below 0.2 %. Melt flow index is measured according to ISO 1133-1:2022 at 190 °C with a 2.16 kg load. Tensile properties are determined on die-cut specimens under ASTM D638-14 at a crosshead speed of 500 mm/min. Peel adhesion to glass is measured after lamination and cure by the 180° peel method according to ISO 8510-2:2006. Melting peak is recorded by differential scanning calorimetry at 10 K/min. Thickness profile is measured continuously by beta transmission gauging across the web; the ±0.02 mm tolerance is expressed as a total indicator run at any point over a 1 m length. Published data for this specific JA product configuration is limited outside the manufacturer's technical bulletin; the values shown are representative ranges for equivalent EVA copolymer films and should be verified for each roll lot.

During photovoltaic module lamination on a two-chamber laminator with oil-heated platens, the JA-28 grade is typically processed with a three-step thermal profile: chamber vacuum at 100 Pa for 5 min at 145 °C, then a pressing stage at 0.08 MPa to 0.10 MPa for 8 min to 12 min, followed by cooling to 60 °C before demolding. The EVA melt under these conditions has a complex viscosity between 2×10³ Pa·s and 5×10³ Pa·s at 150 °C and 1 rad/s as measured by parallel-plate rheometry; this viscosity range is low enough to fill 0.2 mm busbar gaps but high enough to prevent excessive cell displacement under 0.10 MPa diaphragm pressure. The peroxide cure system is activated above 135 °C; gel content after lamination is controlled between 75 % and 90 % as measured by solvent extraction in boiling xylene for 12 h. Insufficient cure is detectable as creep or delamination after thermal cycling per IEC 61215-2:2021, MQT 11, from -40 °C to 85 °C for 200 cycles. A pre-lamination moisture content above 0.2 wt% generates cavities at cell busbar edges during vacuum removal; rolls should be re-dried at 40 °C for 4 h in a desiccant dryer if exposed to 60 % RH for more than 8 h. The lamination window is narrow because a 10 °C increase from 145 °C to 155 °C can reduce crosslinking time by approximately 50 %, while a drop to 135 °C can leave gel content below 70 %. Bladder pressure uniformity across the platen should be held within ±0.005 MPa to prevent wedge-shaped encapsulant flow in modules wider than 1.6 m.

How Does JA EVA Adhesive Film Compare with PVB and POE Interlayers?

The principal alternative to EVA in laminated safety glass is plasticized PVB, which typically requires autoclave pressures of 1.0 MPa to 1.4 MPa at 130 °C to 140 °C to achieve bubble-free lamination. JA EVA adhesive Film can be processed in a vacuum bag or vacuum press without autoclave consolidation. However, PVB exhibits higher shear modulus at room temperature and is preferred in safety glazing where edge adhesion after water immersion is specified by ISO 12543-2; published data for this specific configuration is limited, but EVA interlayers are generally not specified where the glazing must retain impact resistance after extended water exposure. Compared with POE encapsulation films, JA EVA adhesive Film has a higher water vapour transmission measured by ASTM F1249-20 and a lower volume resistivity, typically 1×10¹⁴ Ω·cm versus 1×10¹⁵ Ω·cm for POE at 23 °C and 50 % RH. Acetic acid evolution potential during damp heat exposure is also higher for EVA; POE is generally selected where IEC 61215-2:2021, MQT 13 damp heat at 85 °C and 85 % RH for 1,000 h must produce less than 5 % power loss. Compared with TPU interlayer films, EVA offers lower melt viscosity and lower processing temperature but is not selected where continuous immersion hydrolysis resistance is required. Compared with reactive polyurethane hot-melt films, EVA does not require moisture-cure storage and can be exposed briefly at ambient conditions without viscosity drift.

Unconditioned rolls exposed to ambient air at greater than 60 % RH should be considered moisture-compromised for photovoltaic encapsulation because the EVA copolymer absorbs water at approximately 0.1 % to 0.3 % mass fraction under equilibrium at 23 °C and 50 % RH. The recommended storage condition is 20 °C to 25 °C in sealed aluminium-barrier packaging, with the roll stored horizontally on the original core to prevent telescoping and edge deformation. If the packaging is opened in a cold warehouse and transferred to a warmer laminating area, condensation on the film surface occurs when the film temperature is below the dew point of the surrounding air; a 2 h conditioning period with unopened packaging is recommended for a temperature differential of 10 °C or more. The film is incompatible with amine-based silane coupling agents added in bulk, because alkaline conditions accelerate ester hydrolysis and can reduce adhesion to glass after damp heat aging. It should also be isolated from open containers of peroxide initiators during handling, as localised peroxide contamination can create non-uniform crosslink density in the laminated sheet.

When Vacuum Lamination Dwell Time Falls Below Cure-Onset Requirements

If the dwell time above 140 °C is less than 6 min, the peroxide decomposition responsible for crosslinking remains incomplete, and the laminated assembly may exhibit low gel content, high creep under continuous load, and delamination at frame edges after 50 thermal cycles per IEC 61215-2:2021, MQT 11. Oil-heated platens at a setpoint of 150 °C do not guarantee that the glass surface reaches 145 °C within 5 min when high-loading laminates with 6 mm glass and thick backsheets are processed. Thermocouple mapping of the lamination stack is therefore required to set the dwell time for each module configuration. The silicone diaphragm hardness and platen flatness also influence local pressure transfer: a Shore A hardness of 55 to 60 and a platen flatness within 0.1 mm/m are commonly used in production lines for laminates up to 2 m wide. A minimum gel content of 70 % after solvent extraction is commonly specified for photovoltaic modules, and crosslink density below this value correlates with failure of the adhesion test after damp heat 1,000 h. Lamination profiles should be validated by differential scanning calorimetry and peel adhesion coupons before full production. When laminated at maximum thickness 0.80 mm, the cure-time correction should be confirmed by measuring core temperature at the thickest busbar crossing, not by platen setpoint alone.

After lamination over low-iron float glass with a clear JA-28 interlayer of 0.38 mm, visible transmittance is typically above 90 % and haze is below 2 % when measured according to ISO 13468-2:2021 and ASTM D1003-21. Yellowness index after damp heat at 85 °C and 85 % RH for 1,000 h should remain below a change of 2 units when the crosslinking reaction is complete and residual peroxide content is low. The compliance matrix in Table 2 lists the minimum acceptance criteria used for release testing of JA EVA adhesive Film in photovoltaic and glass lamination applications. Specific clauses are current at the time of publication; exact editions should be verified against the purchaser's specifications.