Converters running EMS-Grivory Grilamid® L 25 G nat 6011 on five-layer cast coextrusion lines commonly position the polyamide 12 as a thermoformable food-contact stress-crack barrier in retortable lidding for hot-fill sauces, dressings, and ready-meals. The resin is predried in a desiccant-bed dryer to a residual moisture level below 0.10%, typically at 80°C for 4 h to 6 h, because PA12 is hygroscopic enough to generate hydrolysis gels at film-die temperatures. The main extruder uses a barrier screw with an L/D ratio of 30:1 to 40:1 and a barrel profile of 230°C to 265°C; the die body is held at 250°C to 260°C. In the final film, the PA12 layer is typically 15 µm to 35 µm thick and is tied to LLDPE or metallocene plastomer sealants with anhydride-grafted tie resins at 3 µm to 6 µm. The selection of PA12 rather than PA6 for this position is driven by the lower equilibrated moisture uptake of PA12, which reduces water plasticisation and interlayer undulation during retort cycling at 121°C. Food-contact compliance must be established on the finished laminate under Regulation (EU) No 10/2011, including specific migration testing for laurolactam into food simulants D2 or 95% ethanol depending on the intended food category; where North American clearance is required, the film must fall within the applicable nylon resin listing in 21 CFR 177.1500 or a suitable Food Contact Notification. The PA12 layer is not selected for primary oxygen barrier, because its oxygen transmission rate measured by ASTM D3985 at 23°C and 0% RH is higher than PA6 or EVOH alternatives; the critical contribution is flex-crack resistance after repeated transport flexing, determined by ASTM F392/F392M Gelbo flex testing with subsequent pinhole detection. On the cast-film line, chill-roll settings control PA12 crystallinity and blocking: a first roll temperature above 90°C produces tackiness and reel blocking, while a first roll below 60°C quenches the PA12 into a low-crystallinity state that later distorts during thermoforming.

What Limits Interlaminar Peel Strength on PA12/Tie/LLDPE Cast Film Lines?

The interfacial bond between Grilamid® L 25 G nat 6011 and an anhydride-grafted linear low-density polyethylene tie layer is limited by the lower amide-group density of PA12 relative to PA6, so a tie resin and thermal profile that produce acceptable peel strength on PA6 often yield adhesive failure at the PA12/tie interface. On production-scale lines, the signature of adhesive failure is a glossy PA12 surface with minimal tie resin transfer after peel testing under ASTM F904-23. The corrective sequence begins with increasing the tie-layer barrel temperature from 200°C to 230°C while holding the PA12 melt at 245°C to 255°C; the adapter and die temperatures should not exceed 260°C because thermal degradation of PA12 forms gel specks and angel hair at the die lip. If peel strength remains below specification, the converter either raises tie-layer thickness by 2 µm to 4 µm or selects a higher maleic anhydride graft level within the tie resin. However, higher anhydride content increases the risk of crosslinking reactions at the interface if moisture exceeds 0.10% or if the tie resin is held in a hot runner above 240°C. Chill-roll temperature also controls interfacial wetting: a first roll below 65°C quenches the PA12 before chain entanglement with the tie layer, while a first roll above 90°C causes uneven sticking and transverse thickness bands. A three-roll cooling configuration with set points of 70–80°C, 60–70°C, and 45–55°C is commonly used. Edge bead must be held within ±5% of the mean thickness because slit rolls with thick edges exhibit locally elevated peel force that masks true interfacial adhesion. Published data for this exact grade in five-layer cast-film peel testing remains limited, so each converter must generate a response curve of tie-layer temperature and thickness against peel strength rather than importing a PA6 baseline.

Form-fill-seal lines running medical pouch stock convert Grilamid® L 25 G nat 6011 as a sealant web against flash-spun high-density polyethylene nonwoven or extrusion-coated PET lidding. The PA12 layer is used because its low water absorption reduces seal perimeter distortion after steam sterilisation at 121°C to 134°C and after ethylene oxide exposure at 50°C to 55°C with high relative humidity. Seal jaws on multi-lane FFS equipment are held at 135°C to 165°C, with dwell times of 0.4 s to 1.2 s and jaw pressures of 0.3 MPa to 0.6 MPa. Because the natural 6011 grade is unpigmented, optical inspection at 400 nm LED illumination can detect gel specks and carbonised particles, but slip-additive bloom from erucamide or oleamide can reduce seal strength after gamma irradiation at 25 kGy to 40 kGy. Sterile barrier performance is assessed according to ISO 11607-1:2019, seal strength according to ASTM F88/F88M-21, and seal integrity by visible and pressure-decay methods. A critical limitation is that the raw polymer specification alone does not establish biocompatibility; converters must obtain cytotoxicity data under ISO 10993-5 and sensitisation data under ISO 10993-10 on the finished film, including any adhesive and ink layers.

Oil, Grease, and Alkaline Fluid Packaging with High Flex-Crack Thresholds

Industrial pouch packs for cutting-oil, lithium grease, and alkaline degreaser concentrates use Grilamid® L 25 G nat 6011 as a monolayer liner or laminated outer ply because PA12 resists swelling in long-chain hydrocarbons and retains low-temperature impact resistance. The film is processed as a cast monolayer at 50 µm to 150 µm, then slit to rewind lengths of 2,000 m to 6,000 m. Chemical resistance is screened by immersion testing under ISO 1817 or ASTM D543, with tensile and seal-strength retention measured after 7 days at 60°C in the specific packaged fluid. Flex-crack resistance is evaluated by ASTM F392/F392M Gelbo flex, with pinhole counts recorded after 300 cycles. PA12 is not suitable for packages containing strong mineral acids, phenols, cresols, or oxidising agents; these substances cause stress cracking and molecular weight loss. On the film line, melt filtration through a 40/80/100 mesh screen pack reduces gel-induced pinholes that would otherwise appear after flexing. The moisture uptake of PA12 after exposure to aqueous alkaline solutions at 60°C is lower than PA6, but the film still requires sealed barrier packaging for storage in tropical warehouses because moisture uptake above 0.3% can shift heat-seal performance.

When a PA12 Sealant Layer Is Selected for Low-Temperature Thermoforming on High-Speed Tray Lines

Tray lidding applications that run on thermoform-fill-seal machines at 40 cycles/min to 60 cycles/min choose Grilamid® L 25 G nat 6011 when the lidding film must follow a shallow tray radius without stress whitening and must retain seal integrity under condensation. The PA12 film is laminated to biaxially oriented PET or polyamide support films using a solventless two-component polyurethane adhesive, leaving the PA12 side exposed for heat sealing to APET or PP tray flanges. Low-temperature forming occurs at 85°C to 115°C, below the PA12 melting onset of approximately 174°C; deformation proceeds by lamellar slip rather than full melting, so preheating uniformity across the web width must be maintained within ±5°C. If the forming temperature exceeds 120°C, the PA12 surface can transfer to forming dies and micro-tears appear at corner radii. The seal initiation temperature of the PA12 layer is typically 120°C to 150°C under 0.4 MPa jaw pressure, but the precise value must be established on the finished laminate because outer layers alter heat transfer. Dwell-time variations of ±0.2 s produce measurable changes in seal strength, which complicates multi-lane tooling because jaw temperature uniformity across the width must be held within ±5°C. Amide oligomer bloom on the forming dies is controlled by weekly cleaning with a 1% citric acid solution or an alkaline detergent compatible with PA12. The film is corona-treated to 42–48 mN/m on the adhesive side before lamination, but the seal side must not be corona-treated above 36 mN/m because excessive oxidation can increase seal initiation temperature and reduce hot-tack.

Pharmaceutical blister base-web extrusion lamination with aluminium foil uses Grilamid® L 25 G nat 6011 as a flexible support and heat-seal layer in PVC-free or PVDC-free structures. The PA12 film is corona-treated to 42–48 mN/m and laminated to foil with a solvent-free two-component polyurethane adhesive at 1.8 g/m² to 2.8 g/m² coat weight. Peel strength is measured by ISO 8510-2, and formed cavities are inspected for stress cracks by 0.1% methylene blue penetration. Because PA12 has a lower bending modulus than PET, formed corner zones show fewer stress cracks, but published data for this exact grade in pharmaceutical blister base-web laminates is limited; the converter must establish the maximum draw ratio and minimum corner radius on the forming line before release to production. The PA12 side of the base web seals against coated or uncoated lidding foils, and seal strength must be re-verified with each lot of adhesive because solvent-free systems can exhibit batch-to-batch variation in crosslink density that shifts the heat-seal curve by 3°C to 5°C.