At nominal thickness 38.1 μm, DuPont Sclairfilm MDPE LWS-2 is specified by film basis weight rather than gauge alone because the medium-density polyethylene density range 0.932–0.940 g/cm³ yields a basis weight of 35.5–35.8 g/m². This value governs layer-ratio calculations in the downstream converting routes below. The film functions as a heat-sealable web or direct food-contact liner; it does not provide oxygen-barrier functionality and must not be specified as a replacement for aluminium foil, EVOH, or metallized polyester in high-oxygen-barrier structures.

What Changes in Seal Strength When the Sealant Web Drops to 35.5 g/m²?

In dried beverage powder, seasoning, and dehydrated fruit sachets, the converting line places 38.1 μm MDPE LWS-2 as the innermost sealant web in a three-component laminate consisting of 12 μm biaxially oriented polyester, 9 μm aluminium foil, and the MDPE sealant web. The sealant layer contributes 35.5–35.8 g/m² at a nominal density of 0.932–0.940 g/cm³, representing 42.8–44.4 wt% of an 80.6–82.9 g/m² finished laminate before printed ink and adhesive variation. Food-contact status is documented under FDA 21 CFR 177.1520 for olefin polymers and under EU Regulation (EU) No 10/2011 Annex I, with overall migration testing performed according to EN 1186-1. The film is unwound on a duplex or triplex solventless laminator with closed-loop tension maintained at 80–120 N/m and corona-treated in-line to 38–42 mN/m; a solventless polyurethane adhesive is applied at 2.0–3.0 g/m² through a four-roller coating head. After lamination, the reel is cured for 48–72 h at 25–35 °C under FIFO rotation before slitting. Heat-seal validation on finished stand-up pouches is performed according to ASTM F88-21 with a jaw pressure of 0.3–0.6 MPa and dwell of 0.3–0.8 s; the exact seal-temperature set point must be profile-mapped against film surface thermocouple data because medium-density polyethylene seal initiation is sensitive to polyethylene density and additive bloom. Terminal formats include quad-seal stand-up pouches and strip-packs for dry beverage mixes, protein powders, and dried fruit pieces, where the sealant film must survive drop-load flexural fatigue after filling. Published data for this specific laminate structure are limited; seal strength should be recertified after any change in adhesive supplier or lamination speed above 300 m/min.

38.1 μm MDPE LWS-2 in mono-web vertical form-fill-seal applications enters the packaging cell as a direct food-contact film for individually quick-frozen vegetables, frozen fruit pieces, and free-flowing frozen bakery shapes. Because no secondary substrate dilutes the sealant, the fill weight is the full basis weight of 35.5–35.8 g/m² at a density characterization of 0.932–0.940 g/cm³; in reverse-printed BOPP/MDPE duplex structures the same layer remains at 35.5–35.8 g/m² while the total basis weight increases to 51.1–56.9 g/m², with the MDPE sealant web representing 62.4–70.1 wt% of the laminated web excluding ink. Food-contact compliance is assessed under FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011, with specific migration testing executed under EN 1186-1 and EN 13130-1. On a vertical form-fill-seal line, the film is threaded over a polished forming collar with a servo-driven draw-off belt; the jaw sealer is configured with an interrupted transverse sealing profile to clear frozen product dust and condensation frost. Surface slip behavior, measured with ASTM D1894-14, dictates draw-belt tension and jaw release; converters must avoid external silicone-oil lubricants that can depress seal strength below the validated minimum. Flex-crack resistance is screened using ASTM F392 with a 4 °C to −25 °C test profile, while seal force is verified with ASTM F88-21 at 180° peel. Film rolls must be conditioned to 20–25 °C before payout; condensation from cold storage causes web wandering and slugging at the former. Terminal package types include pillow pouches and gusseted freezer bags in the 300 g to 2.5 kg fill-weight range, where sealing through minute surface ice contamination is the primary production bottleneck.

When 38.1 μm MDPE Sealant Web Is Laminated to Medical-Grade Porous Substrates

In sterile barrier packaging for terminally sterilized devices, 38.1 μm MDPE LWS-2 is laminated to medical-grade paper or Tyvek porous webs to produce peel-open pouches and header bags. The sealant layer contributes 35.5–35.8 g/m², which corresponds to 32.3–36.5 wt% of a finished paper/PE laminate when the paper substrate is 60–70 g/m² and the reactive polyurethane adhesive is applied at 2.5–4.0 g/m². Compliance is controlled under ISO 11607-1:2019 and ISO 11607-2:2019 for terminal sterile barrier systems, EN 868-5:2018 for paper/plastic pouch materials, and ISO 10993-1 for biological evaluation of the finished pouch material. Converting is performed on rotogravure adhesive lamination equipment with a gravure cylinder delivering 2.5–4.0 g/m² of reactive polyurethane; the laminating nip is maintained at 50–70 °C with 3–5 bar pneumatic pressure, and the reel is cured for 72 h at 25–35 °C. Pouch cutting and sealing are validated as an installation and operational qualification package under ISO 11607-2:2019, with seal peel force measured on ASTM F88-21 and seal leakage screened with ASTM F1929. The MDPE layer functions only as the heat-seal interface; it is not a microbial barrier alone, and the porous paper or Tyvek substrate provides sterilant ingress. Gamma irradiation tolerance must be validated for the complete device-pouch system; oxidative embrittlement of unstabilized polyolefin under irradiation is a known failure mode. Terminal packages include peel-open pouches and header bags for catheters, syringes, and single-use surgical kits. Published data for seal-strength stability after ethylene oxide sterilization of this exact 38.1 μm MDPE/paper configuration are limited; validations are material-lot-specific.

For flexible intermediate bulk container liners, 38.1 μm MDPE LWS-2 is slit and heat-sealed into tubular inner bags that are inserted into coated woven polypropylene outer sacks of 180–240 g/m². The liner film contributes 35.5–35.8 g/m², or 12.9–16.6 wt% of the empty bag mass excluding lifting loops, fill spouts, and discharge spouts. Compliance for bulk packaging is assessed under ISO 21898:2004; when the liner is used for food ingredients, food-contact status is documented under FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011. Liner fabrication begins with slit-edge rewinding at 20–25 °C to avoid blocking, followed by tube forming with gusset bars, bottom impulse heat sealing, top hemming, and insertion into the outer woven sack. Seam strength is tested on ISO 527-3:2018 strip specimens cut transverse to the weld, and impact toughness of the liner web is screened with ASTM D1709. The liner is not independently suitable for direct lifting; it relies on the outer woven polypropylene for structural load transfer. The 38.1 μm MDPE liner is used in 500–1200 kg FIBCs for hygroscopic calcium chloride, sodium benzoate, titanium dioxide, and food-grade starches, where the film reduces moisture ingress into the bulk solid during storage and transport. Published data for liner weld strength after hot-filled product discharge is limited; converters should qualify seams after a full thermal cycle at the maximum fill temperature claimed on the bag label.