What Limits Seal Integrity in Pharmaceutical Unit-Dose Strip Pack Converting?

The use of DuPont™ Sclairfilm® BL-1 in pharmaceutical unit-dose strip packaging places the 51 µm PVDC-coated LLDPE web into high-speed vertical form-fill-seal equipment in which the uncoated LLDPE side is sealed against itself at jaw temperatures between 120°C and 150°C and dwell times of 0.3–0.8 s. In this converting arrangement the PVDC side is positioned on the outside of the formed packet and is never in direct contact with heated jaw faces; this positional constraint is necessary because sustained contact between PVDC and sealing tooling above 125°C can initiate dehydrochlorination, producing visible discoloration and corrosive trace gas release. Regulatory compliance for this application is evaluated under FDA 21 CFR 177.1520(c) for the LLDPE substrate and FDA 21 CFR 177.1630 for the PVDC coating layer, supplemented by Regulation (EU) No 10/2011 as amended, which requires overall migration below 10 mg/dm² and specific migration assessment for vinylidene chloride monomer. Pharmacopoeial suitability is additionally assessed through USP <661.1> plastic material screening and USP <671> container performance testing for moisture vapor transmission where the dosage form is hygroscopic. The formulation addition ratio in pharmaceutical converting is not a blending operation but a fixed web-to-product ratio: the film is run at 100% as received, with the PVDC coating already applied to the LLDPE substrate at a dry coating weight reported for transparent barrier films of this class between 2.0 g/m² and 4.0 g/m², corresponding to approximately 2.4–4.7% of total film thickness; converters should verify the exact lot-specific coating weight from the certificate of analysis because public data for the specific BL-1 configuration is limited. In production, strip-pack equipment typically uses flat sealing jaws with serrated profiles, hydraulic or pneumatic pressure of 0.35–0.70 MPa, and chilled release zones immediately downstream of the seal die to prevent blocked winding. Terminal finished product types include aluminum-free solid-dose strip packs for effervescent tablets, single-dose powder sachets for oral rehydration salts, and overwrapped transdermal patch pouches where moisture ingress below 1.0 g/(m²·day) is a critical stability requirement.

In single-serve instant coffee and dry beverage lines, the PVDC-coated LLDPE web is laminated to an outer 12 µm AlOx-coated PET film using a solventless polyurethane adhesive applied at 1.8–2.4 g/m²; the structure places the PVDC layer between the outer barrier film and the LLDPE sealant layer, which protects the PVDC from mechanical abrasion and prevents direct food contact with the coating. The laminated web is cured at 35–40°C for 24–48 h before slitting and is then converted on multi-lane stick-pack machines at sealing jaw temperatures of 115–135°C, where the uncoated LLDPE surface seals to itself at each longitudinal and transverse crimp zone. Regulatory compliance for food-contact use is assessed under FDA 21 CFR 177.1520(c) for the polyethylene substrate, FDA 21 CFR 175.105 for the laminating adhesive, and Regulation (EU) No 10/2011 for the finished structure, with organoleptic testing performed according to ISO 13301 for taint and odour transfer. The formulation addition ratio at the converting stage is the adhesive laydown of 1.8–2.4 g/m²; no dilution of the PVDC barrier layer occurs because the film is supplied as a finished barrier web, but converters must monitor the uncoated LLDPE side for seal contamination from mineral oil in slitting lubricants. Production bottlenecks on high-speed stick-pack lines occur when residual solvent or moisture is trapped between the PVDC layer and the outer PET film, producing tunnel defects that reduce oxygen barrier below the target of 5–15 cm³/(m²·day·atm) at 23°C and 0% RH. Terminal finished goods include instant coffee stick packs, powdered milk-based beverage sachets, and protein powder single-serve pouches requiring aroma retention without foil laminates.

Medical Device Sterile Barrier Systems — Sealing Envelope Conditions

Validation of sterile barrier packaging built on 51 µm PVDC-coated LLDPE starts with the constraint that the PVDC layer is never presented to the sealing die; the uncoated LLDPE side is heat-sealed to uncoated Tyvek® 1073B or medical-grade paper at sealing temperatures between 125°C and 145°C, dwell times of 0.5–1.0 s, and jaw pressure of 0.40–0.70 MPa. The seal strength after conditioning is verified under ASTM F88/F88M and is typically specified at a minimum of 1.5 N/15 mm for pouches intended for ethylene oxide sterilization, while whole-package integrity is challenged using ASTM F1929 dye penetration and ASTM F2096 bubble emission tests. Conformance to ISO 11607-1:2019 requires documentation of the sealing process window through installation, operational, and performance qualification, while ISO 11607-2:2019 governs the controlled environment and process validation for the converter; additionally, the film is typically tested for cytotoxicity and irritation potential under ISO 10993-5 and ISO 10993-10 when used in Class II and Class III device packaging. The formulation addition ratio is fixed at the film stage: the PVDC coating weight is applied to one side of the LLDPE substrate at a typical dry add-on of 2.0–4.0 g/m², and the converter consumes the web at 100% without blending, mixing, or reactive dilution. Downstream production uses rotary pouch machines with notched sealing jaws and silicone rubber backing pads to maintain uniform pressure across the seal area; web tension is normally controlled at 0.4–0.8 N/mm of film width to avoid tunnel formation over Tyvek seals. Terminal finished product types include pre-formed chevron pouches for surgical instruments, form-fill-seal pouches for syringes and catheters, and header bags for wound care dressings where the PVDC layer contributes to the post-sterilization gas barrier.

On multi-lane vertical form-fill-seal lines running at speeds above 40 packs/min, dehydrated seasoning and dry sauce mix packaging subjects the barrier web to a cyclic thermal load because the sealing jaws must reach 120–150°C repeatedly without transferring excessive heat through the LLDPE layer into the PVDC coating. In this application the PVDC-coated LLDPE serves as the entire barrier web for sachets that contain salt, sugar, hydrolyzed vegetable protein, spices, and fat-containing flavour encapsulates, where oxygen ingress above 10–20 cm³/(m²·day·atm) would accelerate rancidity. Food-contact compliance is established under FDA 21 CFR 177.1520(c) for the polyethylene substrate and FDA 21 CFR 177.1630 for the PVDC coating, with the finished sachet evaluated for overall migration under Regulation (EU) No 10/2011 and for specific migration of vinylidene chloride monomer in accordance with Annex I; where the films are printed before slitting, the printing ink must comply with Regulation (EC) No 1935/2004 and applicable national printing ink ordinances. The formulation addition ratio in this converting process is the ratio of printed ink coverage to film surface area, which is maintained between 5% and 30% for registered designs, and the film itself is consumed at 100% web width without dilution; if a cold-seal coating is applied to the uncoated LLDPE side, the nominal add-on is typically 0.8–1.2 g/m² dry weight. On multi-lane machines, longitudinal seal rollers preheat the web to 60–80°C before transverse jaws close, and the PVDC side is positioned away from the product so that any incidental jaw contact is limited to the uncoated surface. Terminal finished product types include seasoning powder sachets for instant noodles, dry soup mixes, and sauce granules packaged in pillow pouches with serrated tear notches.

PVDC-Coated LLDPE as the Sealant Web in Aroma-Sensitive Snack Laminates

Aroma-sensitive snack laminates incorporating 51 µm PVDC-coated LLDPE as the sealant web are typically structured as reverse-printed BOPP or PET outer layer / adhesive / PVDC-coated LLDPE, and the PVDC layer is positioned on the adhesive side while the uncoated LLDPE forms the food-contact and heat-seal surface. Compliance for such structures is assessed under FDA 21 CFR 177.1520(c) for the LLDPE substrate, FDA 21 CFR 177.1630 for the PVDC coating, and FDA 21 CFR 175.105 for the laminating adhesive, alongside Regulation (EU) No 10/2011 for the finished package; if the target market includes shelf-stable snacks with fat content above 20%, overall migration testing under simulated fatty food conditions is conducted according to the EN 1186 series methods. The formulation addition ratio at the laminating stage is the adhesive dry weight of 2.0–3.0 g/m², which is used to bond the outer printed web to the PVDC surface; no additional PVDC coating is applied by the converter, and the film is used at 100% as received, though the supplier’s lot certificate should be consulted for the exact PVDC coating weight because public data for the specific BL-1 configuration is limited. Downstream production uses horizontal form-fill-seal machines with flat heated jaws set between 115°C and 140°C, and the PVDC layer is protected from direct heat by the LLDPE layer; long dwell times above 1.0 s are avoided because heat conduction through the LLDPE can raise the PVDC interfacial temperature above 125°C, leading to localised dehydrochlorination and pinhole formation. Terminal finished product types include flavoured potato chip pillow pouches, dry-roasted nut packages, and ready-to-eat popcorn bags where aroma retention and prevention of oxidative rancidity are the main technical requirements.

When Probiotic Sachets Require Low Oxygen Ingress Without Desiccant Overpack

When probiotic powders containing freeze-dried Lactobacillus or Bifidobacterium strains are packaged without desiccant overpack, the stability of the sachet format is governed by the ingress of molecular oxygen through the seal area and the non-seal panel; for such products the 51 µm PVDC-coated LLDPE web provides an oxygen barrier in the range of 5–20 cm³/(m²·day·atm) at 23°C and 0% RH, though the converter must verify lot-specific oxygen transmission because published data for the BL-1 configuration is limited. Food-supplement packaging compliance is assessed under FDA 21 CFR 177.1520(c) and FDA 21 CFR 177.1630 for the polymer components, Regulation (EU) No 10/2011 for food-contact plastics, and Directive 2002/46/EC for the labelling and composition of food supplements where relevant; where the product is marketed in the United States, 21 CFR 111 cGMP requirements impose batch-level packaging process controls. The formulation addition ratio at the packaging stage is a web-to-fill-weight ratio rather than a polymer compounding step: sachet fill weights typically range from 1.0 g to 5.0 g, and the film-to-product mass ratio is between 0.05 and 0.15 for single-dose formats, while the PVDC coating remains a fixed supplier-applied dry add-on of 2.0–4.0 g/m². Downstream converting is performed on small-format vertical fill-seal machines with heated sealing jaws set to 110–135°C, and the uncoated LLDPE side is sealed to itself while the PVDC layer is oriented to the outside; the sealing jaw profile uses a diamond knurl pattern with 0.5 mm pitch to reduce seal thinning at the pouch edges. Terminal finished product types include probiotic stick packs, enzyme supplement sachets, and effervescent vitamin powders where the PVDC layer also restricts moisture-driven degradation of reactive actives.