For moisture-sensitive oral solid dose formats packaged in aluminium-free blister constructions, the use of Aclar polychlorotrifluoroethylene (PCTFE) Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable is specified when a transparent thermoformable film must maintain a water vapour transmission rate below that of monolayer PVC or PVdC-coated PVC at equivalent wall thickness. The film is supplied as a homopolymer fluoropolymer in cast and oriented grades; commercial designations include Aclar Rx 20, Aclar Rx 22, Aclar Rx 160, UltRx 2000, and UltRx 3000, with nominal thicknesses from 15 µm to 152 µm. Because PCTFE does not self-seal at standard lidding temperatures, laminates incorporate a heat-sealable polyolefin or vinyl sealant as the innermost layer. Regulatory assessment for pharmaceutical packaging qualification is dosage-form specific and commonly references USP <661.1>, USP <661.2>, USP <671>, 21 CFR 177.1380, and ISO 15378:2017; the film is intended only as a packaging component and is not a drug substance or excipient.

Incoming roll-stock specifications for pharma grade Aclar PCTFE typically include a thickness tolerance of ±5 % for films 15 µm to 51 µm and ±4 % for films 76 µm to 152 µm. Density is 2.10 g/cm³ to 2.15 g/cm³ per ASTM D792; tensile strength in the machine direction is reported in supplier technical bulletins as 30 MPa to 40 MPa, with elongation at break from 50 % to 150 % depending on grade and thickness per ASTM D882. Water absorption remains below 0.01 % after 24 h immersion per ASTM D570. Optical haze for cast grades is typically below 5 %, and gel or black speck counts are controlled by supplier sampling plans referenced to ANSI/ASQ Z1.4. These incoming specifications are not sufficient for final package release; formed cavity WVTR and seal strength are revalidated after each thermoforming tooling change.

What Limits Moisture Ingress in Solid Oral Dose Packaging?

Moisture flux through a blister cavity is dominated by the film permeability coefficient, thickness distribution after thermoforming, and seal continuity at the lidding interface. Aclar PCTFE contains alternating carbon-fluorine and carbon-chlorine backbone substituents that reduce free-volume transport and produce a normalised water vapour transmission rate typically between 0.010 g/m²·day and 0.040 g/m²·day at 25 µm, 38 °C, and 90 % RH when measured according to ASTM F1249 or USP <671>. Oxygen transmission is not the primary selection criterion for blister packaging but remains relevant for oxidation-prone actives; published supplier data place the oxygen transmission rate of 25 µm PCTFE film in the range of 10 cm³/m²·day·atm to 60 cm³/m²·day·atm under 23 °C, 0 % RH per ASTM D3985. Because the barrier is not dependent on a water-absorbing polymer matrix, performance is stable across ambient humidity, unlike EVOH layers that lose oxygen barrier at relative humidity above 60 %. Corner thinning in deep thermoformed cavities increases local moisture ingress; therefore, the nominal flat-film WVTR is not a sufficient release criterion for formed packages.

Tablet and capsule blister lines configured for transparent films process Aclar PCTFE through plug-assisted forming tools at preheat temperatures near 110 °C to 130 °C on the laminate surface. The thermoplastic layer is typically laminated to 200 µm to 250 µm PVC or 250 µm PP support layers; adhesive tie layers must withstand the draw ratio without delamination at cavity depths of 4 mm to 12 mm or beyond. For granule sachets, a 23 µm to 51 µm Aclar barrier layer is inserted between polyethylene sealant films, and the converting process is run on horizontal form-fill-seal machines with jaw temperatures ranging from 160 °C to 200 °C depending on sealant grade and dwell time. Feedstock spools should be stored below 30 °C and at relative humidity below 60 % to avoid blocking or electrostatic discharge; PCTFE itself has a water absorption below 0.01 % per ASTM D570, so moisture conditioning is not required before thermoforming.

Grade selection for a given dosage form is based on the required formed-cavity WVTR, draw ratio, and optical inspection requirement. Rx 20 and Rx 22 are typically specified for low-moisture-sensitivity oral solid products requiring a thin, easy-to-form barrier; UltRx 2000 and UltRx 3000 are specified where the package must deliver both low moisture and low oxygen transmission through a formed blister. Rx 160 is supplied in the 152 µm thickness and is used for high-barrier applications where transparent packaging must approach foil-like moisture protection without losing the ability to inspect the dose. The number following the grade designation is not a direct thickness specification in all cases; converter drawings should refer to the supplier technical datasheet for the exact gauge, roll length, and test certificate content.

The following comparison of transparent barrier materials is drawn from supplier technical bulletins and published standard permeability tables; values are for formed laminates under stated conditions.

When Injection and Oral Liquid Containers Require Fluoropolymer Barrier Layers

When the dosage form is an aqueous oral liquid or a parenteral injection, the primary package is usually glass or multilayer plastic; Aclar PCTFE enters as a secondary overwrap, lidding film, or component of an aluminium-free pouch. In injectable packaging, a 51 µm to 152 µm Aclar layer can reduce moisture ingress into lyophilised drug products stored in plastic vials or semipermeable overwrap pouches, provided that the seal is continuous and the pouch geometry does not introduce pinhole defects during folding. The film’s low extractables burden, low water absorption, and broad pH resistance are relevant to oral liquid packaging components such as induction seals and child-resistant closures, although direct contact with the liquid should be qualified under USP <661.1> and USP <661.2> with the specific drug product. Published data for Aclar PCTFE in direct parenteral contact is limited; qualification typically relies on extraction studies using ISO 10993-1:2018, USP <87>, and USP <88> biological reactivity evaluations when the film is intended as a primary contact layer.

Granule and sachet packaging lines use a different laminate structure because the film is not thermoformed into discrete cavities but is folded around free-flowing powder. The Aclar barrier layer is located between two polyethylene or polypropylene sealant layers, and the outer print web is usually reverse-printed PET or oriented polypropylene. A barrier layer of 23 µm Aclar reduces moisture ingress but increases laminate stiffness; a 51 µm layer is used for high-hygroscopicity granules that must remain below a defined water content over a 24-month shelf life. For oral liquids, Aclar is not used as a blow-fill-seal resin; instead, it appears as an induction seal liner or closure liner where transparency and chemical resistance are required. For injectables, the film is most often laminated to medical-grade paper or polyester as a vented pouch for syringes and cartridges, where the moisture barrier must prevent plunger stopper hydration and label adhesive degradation.

Aclar PCTFE is not typically used as the primary contact surface of a prefilled syringe or cartridge because the component geometry cannot be efficiently manufactured from multilayer film; the film functions as a pouch overwrap around filled syringes, vials, or combination products. In such pouches, the film is reverse-printed and laminated to a polyester outer layer, and the inner sealant layer is usually low-density polyethylene or cyclic olefin copolymer. Moisture ingress in these packages is controlled by the PCTFE layer, while oxygen ingress is controlled by the same PCTFE layer at a higher rate than foil. A typical syringe overwrap specification may require a formed pouch WVTR below 0.02 g/m²·day and seal strength above 2 N/15 mm when tested per ASTM F88/F88M-22. The package must also survive ethylene oxide or steam sterilisation without delamination; peelable chevron seals are preferred for aseptic opening in clinical settings.

PCTFE Film Thermoforming Window and Laminate Construction

Extrusion lamination of Aclar PCTFE to PVC or polyethylene requires a melt-extruded tie layer, typically EVA or acid-modified polyolefin, because the fluoropolymer surface energy is low and the film cannot be hot-tack sealed to itself. Converter specifications commonly require corona or plasma treatment at 40–50 mN/m dyne level prior to adhesive lamination; treatment decay after storage requires re-verification by contact-angle or dyne ink testing. Thermoforming lines should use heated plug assist and lower forming pressure than foil cold-forming, with film preheat controlled by infrared sensors to avoid local overheating beyond 210 °C. The forming window is narrow for PCTFE/PVC laminates because the PCTFE layer resists flow at the PVC-optimal temperature while PVC may degrade at higher temperature; surface temperature is often maintained at 120 °C ± 5 °C to avoid delamination and corner thinning. Blister sealing operations set seal temperature, pressure, and dwell time to the sealant layer rather than to the PCTFE layer; typical sealing temperatures for PE or EVA sealants range from 160 °C to 200 °C. Because PCTFE is not an elastomer, rapid draw rates and sharp corner radii can generate stress whitening and microcracks that compromise barrier properties; therefore, tooling radii below 2 mm should be avoided unless validated on the target line.

On-line barrier verification of formed cavities is difficult because WVTR test methods require flat samples or whole-package testing; therefore, production releases rely on statistical process control of forming temperature, plug depth, and film flatness plus periodic destructive permeability testing. Thickness mapping of formed blister cavities with a contact transducer or optical interferometer is more sensitive to barrier loss than visual inspection alone. The critical measurement points are the corner radius and the flange-to-wall transition, where wall thickness can fall to 40 % to 70 % of the original film thickness depending on draw ratio and plug temperature. A package with a measured minimum wall thickness below the supplier’s specified lower limit is rejected even if the average cavity thickness meets specification.

Thermal degradation of PCTFE is a process-boundary consideration because the homopolymer begins to undergo dehydrofluorination when exposed to sustained temperatures above 300 °C; the melting point is in the 210–215 °C range, and the continuous-use temperature in packaging is typically below 150 °C. In a thermoforming line, local barrel or die temperatures in adjacent extrusion coating units may exceed the film’s degradation threshold if the film is fed too close to a hot melt die; therefore, the lamination nip must be designed so that the PCTFE web does not contact the molten melt curtain for more than a few milliseconds. For parenteral packaging systems, terminal sterilisation by steam at 121 °C or 125 °C is below the thermal limit of the film, but the laminate’s sealant layer and adhesive system must be selected for autoclave exposure if the film is used in a primary pouch. Radiation sterilisation is not recommended for PCTFE-containing packaging because high-energy irradiation can induce fluorine radical chain scission; doses above 25 kGy have been associated with measurable loss of tensile elongation and barrier uniformity in published polymer studies, so gamma-sterilised pharmaceutical packages should use a validated lower dose or switch to steam or ethylene oxide where compatible.

Leachables assessment for Aclar PCTFE in oral and injectable applications is carried out under USP <661.1> and USP <661.2>, with extraction conditions selected according to the drug product administration route. The fluoropolymer is chemically resistant to hydrolysis, oxidising agents, and most acids at ambient temperature, but exposure to strong alkalis, elemental sodium, or certain amines at elevated temperatures can degrade the polymer surface. Packaging development records should therefore exclude contact with strong caustic cleaning agents and should evaluate sealant-layer adhesives separately. In stability protocols for film-packaged products, moisture-sensitive formulations are bracketed at 25 °C/60 % RH, 30 °C/65 % RH, or 40 °C/75 % RH according to ICH Q1A(R2); the measured WVTR of the formed cavity, not the flat film, is the release criterion for the packaging line.

The regulatory and test matrix below lists the standards most frequently cited in qualification of Aclar PCTFE pharmaceutical packaging.

Unlike aluminium foil, Aclar PCTFE does not create a complete inorganic moisture seal; foil remains specified for products needing WVTR below 0.005 g/m²·day or complete opacity. Unlike EVOH, the PCTFE barrier does not require internal desiccation to maintain performance under high external humidity. Unlike COC, Aclar PCTFE can be flexed and folded without the same brittle fracture tendency, and it is supplied in thinner barrier layers for low-profile blister cavities. Replacing PVdC-coated PVC with Aclar PCTFE changes the moisture barrier and the thermoforming line thermal profile: the Aclar laminate is thicker than an equivalent barrier coating and has a lower WVTR at equivalent gauges, but it also has a higher film cost and requires the same seal continuity control as any barrier blister. Those differences are evaluated through barrier testing on formed cavities, seal strength per ASTM F88/F88M-22, and package stability rather than from nominal film data alone.