KENGO ET LOW EVA Film (for special inserts material lamination,PMMA glass )

KENGO ET LOW is an ethylene-vinyl acetate film grade formulated for flatbed lamination of poly(methyl methacrylate) sheet, frequently specified as PMMA or acrylic glass, and for encapsulation of special insert materials such as printed decorative films, textiles, paper and wood veneer, metal mesh, mineral composites, and selected functional coatings. The product is supplied as a peroxide-curable, silane-grafted thermoplastic film in thicknesses of 0.38 mm, 0.50 mm, and 0.76 mm, with thickness tolerance normally held within ±0.03 mm. Vinyl acetate content is controlled between 28 wt% and 33 wt% to lower lamination temperature while maintaining post-crosslink cohesive strength. Density measured according to ISO 1183-1 is typically 0.95–0.97 g/cm³. Melt flow rate before cure, determined by ISO 1133-1 at 190 °C and 2.16 kg, is typically 15–35 g/10 min. The grade does not require plasticizer addition, differentiating it from PVB interlayers that depend on formulated plasticizer systems.

In flatbed laminating lines with vacuum-bag or diaphragm presses, the material is used when PMMA and inserts are heat-sensitive or when standard EVA cure temperatures above 145 °C cause warpage, bubble formation, or insert damage. The melt rheology is designed for high-shear wetting at low pressure. A typical cycle uses initial vacuum of ≤30 kPa absolute, followed by a positive pressure ramp to 0.5–1.0 MPa at platen set points between 115 °C and 125 °C. At these temperatures, PMMA remains below its thermoforming window but still requires cooling under pressure to 60 °C or lower to prevent surface marking and edge squeeze-out. The low-temperature cure profile is achieved by peroxide selection with a 10 h half-life below 100 °C, allowing gel content development within 15–25 min.

Why Does Lamination Temperature Dictate PMMA Insert Compatibility?

PMMA sheet has a glass transition near 105 °C and begins to soften measurably above 115 °C. Each additional degree of platen setpoint therefore increases edge deformation and surface transfer from press pads or textured films. Standard EVA and PVB interlayers typically require lamination temperatures from 135 °C to 160 °C, forcing PMMA to remain near or above its distortion threshold for extended periods. KENGO ET LOW shifts the cure exotherm into the 115–125 °C region, reducing cumulative thermal exposure. Lamination pressure must still be controlled below 1.0 MPa because PMMA compressive yield strength declines with temperature; at 120 °C, sustained pressure above 1.2 MPa can produce visible thickness variation across the sheet. The low-temperature cure also permits low-glass-transition insert films that would shrink or delaminate at PVB-grade temperatures.

Adhesion and Mechanical Integrity at the PMMA–EVA Interface

Adhesion to PMMA and non-glass inserts is developed through silane grafting, polar vinyl acetate groups, and free-radical grafting reactions initiated by peroxide decomposition. T-peel adhesion measured according to ASTM D1876 at a crosshead speed of 300 mm/min typically falls between 30 N/cm and 55 N/cm on clean PMMA, with cohesive failure within the EVA layer rather than adhesive failure at the interface. Tensile strength and elongation at break are evaluated according to ISO 527-3 using type 5 specimens; post-laminated film typically exhibits tensile strength 8–14 MPa and elongation at break 400–600% before crosslinking, reducing to 150–300% after cure because of the three-dimensional network. The gel content after lamination determined by ASTM D2765 in boiling xylene is normally 75–85%, providing creep resistance at service temperatures up to 70 °C when the laminate is not load-bearing. For insert materials with low surface energy, such as untreated PET or printed UV-cured coatings, corona or plasma pretreatment to a surface energy of 42–48 mN/m is generally required to achieve reproducible peel strength. Without pretreatment, published data for low-energy insert surfaces is limited, and peel strength can fall below 15 N/cm.

Production-scale laminating lines using 2.4 m × 1.2 m diaphragm presses have shown that platen temperature nonuniformity exceeding ±2 °C across the short axis can generate gel-content variation between 65% at edges and 85% in the center. This variation produces localized low-peel zones and edge haze when the laminate is later cut. Temperature mapping with contact thermocouples embedded in a sacrificial PMMA stack is therefore recommended before processing critical orders. The same mapping identifies hot spots above 130 °C that can mark PMMA and create optical distortion.

Special inserts such as printed decorative films, mineral-based paper, anodized aluminum mesh, and natural textiles present uneven surface topography. The film fills gaps of up to 0.15 mm because of its pre-cure melt flow. For thicker inserts above 0.25 mm, a secondary prelamination pass using the same EVA film is often necessary to avoid trapped air. The prelamination pass is typically run at 105–110 °C with vacuum pressure only, softening the film without fully activating the peroxide. This intermediate step creates a conformal adhesive layer that later bonds to the second outer sheet without bubble formation.

When Low-Temperature Processing Replaces PVB in Insert Lamination

PVB is commonly selected for safety glass because of established impact performance, but its lamination requires controlled moisture content generally below 0.5 wt% and often autoclave processing. PVB also contains plasticizer that can migrate into decorative insert layers, soften printing inks, and cause delamination around cutouts or textured surfaces. The low-temperature EVA grade eliminates autoclave processing and plasticizer-related migration; the film is peroxide-crosslinked after lamination, producing a thermoset interlayer with higher dimensional stability at elevated temperatures. The replacement is appropriate for interior partitions, signage, furniture panels, and decorative safety glazing where PMMA or special inserts are primary substrates and where the final composite does not require PVB-specific impact certification. For external load-bearing glazing, the laminate must be tested to the relevant impact and durability standard, such as EN ISO 12543-4, because the low-temperature EVA grade has not been independently certified for all safety-glazing classes.

In continuous lamination lines, edge sealing is rarely required for EVA because the cured network resists plastic flow. However, oxygen at the laminate edge can inhibit cure and produce a tacky border layer if the vacuum cycle is interrupted or if platen temperature uniformity exceeds ±3 °C. Manufacturing lines with silicone vacuum bags should verify that silicone oil release agents are completely removed before loading PMMA, because residual silicone lowers peel strength to 10–15 N/cm. When laminating hygroscopic inserts such as paper and wood veneer, insert moisture content should be stabilized at 6–8%. Higher moisture levels release steam above 100 °C and form bubbles, while lower moisture can cause brittle insert fracture and edge cracking during cutting.

Comparative behavior of KENGO ET LOW against standard EVA, PVB, and TPU interlayers in PMMA/insert laminations is summarized below. Values are typical ranges from producer datasheets and independent laminate testing; batch-level verification is required for certification.

Compared with standard EVA formulations used in photovoltaic encapsulation, KENGO ET LOW is not formulated with the same UV-blocking package. Standard PV-grade EVA may contain UV absorbers that reduce transmittance and shift color when laminated over printed inserts. The low-temperature grade uses a lower vinyl acetate content than elastomeric hot-melt EVA, which increases stiffness and reduces cold flow at ambient storage. Compared with PVB, the material does not require controlled moisture conditioning before lamination; however, it also does not exhibit the same well-characterized post-breakage adhesion profile under impact. TPU interlayers typically provide higher elongation and low-temperature toughness, but they require drying to 0.02 wt% moisture or less and are more sensitive to high platen temperatures above 150 °C; KENGO ET LOW is therefore selected for nonstructural lamination where process simplicity and PMMA compatibility dominate.

Optical and Crosslinking Benchmarks for KENGO ET LOW

Optical laminates made with PMMA and 0.76 mm KENGO ET LOW are evaluated by ISO 13468-2 total luminous transmittance using D65 illuminant and ASTM D1003 haze. Typical values are 90–92% transmittance and 1.8–2.5% haze for a 3 mm PMMA / 0.76 mm film / 3 mm PMMA stack. For thinner gauges such as 0.38 mm, haze may decrease to 1.5–2.0%, but edge flow and gap-filling capacity are reduced. Yellowing under accelerated weathering is measured according to ISO 4892-2 method A; low-iron PMMA and UV-stabilized EVA grades typically show ΔYI below 1.5 after 1000 h. Crosslinking is monitored in production by gel content and residual peroxide analysis. Undercure below 65% gel content indicates insufficient thermal history and can lead to creep in vertical laminates at temperatures above 50 °C. Overcure above 90% gel content may increase brittleness and reduce elongation to break below 100%.

Compliance testing for the grade is structured around the following matrix of standards. The supplier’s batch certificate may not include every listed test; missing PMMA-specific peel values should be confirmed on the target substrate.

Storage of unopened rolls should be maintained at 20–25 °C and 30–50% RH. If rolls are exposed to relative humidity above 60% for more than 6 h, pre-drying at 40–45 °C in a desiccant dryer for 4–6 h is advised before lamination. The film must not be combined with amine-based additives or cleaning agents that can decompose the peroxide catalyst; premature crosslinking in storage has been observed when such chemicals are present as residual film on rolls. For cold storage below 5 °C, the roll should be allowed to acclimatize in unopened packaging for 12 h to prevent condensation on the film surface.