PTP Aluminum Foil: Specifications, Structure & Selection Guide
PTP (Press-Through-Pack) aluminum foil is the lidding material that seals a formed blister cavity and lets the patient push a tablet or capsule straight through it. It looks like a simple roll of silver foil, but in pharmaceutical packaging it is a regulated primary packaging component — and getting the specification wrong means failed seal integrity tests, rejected batches, or a stability failure twelve months down the line.
This guide covers what PTP foil actually is, how it is built, which parameters matter, and how to specify it correctly in an RFQ.
What PTP aluminum foil is
PTP foil is a multi-layer laminate built on an aluminum foil base. The aluminum provides an absolute barrier against moisture, oxygen and light; the coatings on either side make it printable and heat-sealable.
It is used with a forming film (PVC, PVC/PVDC, or cold-form alu-alu) on a blister packaging line. The forming film creates the cavity; the PTP foil seals it. When the patient presses the cavity, the foil ruptures cleanly and the dose is released — hence “press-through”.
Two properties are in permanent tension with each other, and this is the central engineering challenge of PTP foil:
- It must seal strongly — strong enough to protect the drug through its full shelf life.
- It must rupture cleanly — weak enough for an elderly patient to push a tablet through without the foil delaminating or tearing into shreds.
Almost every specification decision below is a balancing act between these two requirements.
Layer structure
A standard PTP foil has four functional layers, from the outside in:
| Layer | Full name | Function | Typical coating weight |
| OP | Over-print lacquer / protective primer | Protects the printed ink, provides heat resistance during sealing, gives a printable surface | 1.0 ± 0.5 g/m² |
| Printing | Ink layer | Branding, drug name, dosage, batch coding | As required |
| AL | Aluminum foil substrate | The actual barrier — blocks moisture, oxygen, liwanag | 20–30 μm typical |
| HSL | Heat seal lacquer (also called VC adhesive) | Bonds the foil to the forming film under heat and pressure | 3–8 g/m² |
The HSL is the layer that determines seal performance. It must be matched to the forming film — an HSL formulated for PVC will not reliably seal to PVDC-coated PVC or to PP. Specify your forming film when you request a quote. This is the single most common cause of “the foil doesn’t seal” complaints.
Alloy and temper selection
Alloys
| haluang metal | Series | Why it is used | Typical PTP use |
| 8011 | Al-Fe-Si | The industry default. Excellent balance of strength, formability and pinhole resistance. Fe and Si additions raise strength over pure aluminum without hurting elongation much. | Most common choice — standard tablets and capsules |
| 8021 | Al-Fe-Si (low Si) | Higher purity, better ductility and deep-draw performance | Cold-form and high-barrier applications |
| 8079 | Al-Fe-Si | Very low pinhole count, excellent barrier consistency | Moisture-sensitive drugs, high-value formulations |
Tempers
PTP foil is almost always supplied in H18 (full hard). The hard temper gives the foil the stiffness it needs to rupture cleanly on press-through, and it resists wrinkling on high-speed rotary blister lines.
- H18 — standard for PTP. Higher tensile strength, lower elongation.
- H16 / H14 — occasionally used where slightly more formability is needed.
- O (annealed / soft) — not used for PTP lidding. Soft foil stretches rather than ruptures. O temper is used for cold-form alu-alu, which is a completely different product.
Common confusion: buyers sometimes request “8011-O” for PTP because they have seen O temper on a cold-form specification. If you want press-through performance, you need H18. If you want deep-draw cold forming, you want O temper on 8021 o 8079 — and that is a different material.
Key specifications
Ang kapal
| Ang kapal | Typical use | Notes |
| 0.016 mm (16 M) | Light-duty, cost-sensitive | Thinner foil is harder to handle; higher pinhole risk |
| 0.020 mm (20 M) | Standard commercial PTP | The most widely used gauge |
| 0.025 mm (25 M) | Standard for most tablet/capsule packs | Good balance of barrier and press-through |
| 0.030 mm (30 M) | Larger cavities, heavier tablets | Stiffer, requires more force to push through |
| 0.040 mm (40 M) | Child-resistant and tropical blister formats | Significantly harder to rupture — intentional |
If you are developing a child-resistant pack, thickness is one of several levers; the others are the forming film structure and the HSL formulation. Do not simply thicken the foil and assume the pack will pass — CR certification is tested on the finished pack, not the foil alone.
Roll dimensions
| Parameter | Common range |
| Lapad ng katawan | Up to 600 mm (specify to your machine) |
| Core inner diameter | 76 mm (3″) standard; 152 mm (6″) available |
| Roll outer diameter | 240–280 mm typical |
| Roll length | 1,000–4,000 m depending on gauge and OD |
Roll OD is constrained by your blister machine’s unwind capacity, not by the mill. Check it before confirming an order.
Performance criteria that actually get tested
When a pharmaceutical buyer qualifies a PTP foil, these are the parameters that end up on the COA.
1. Pinhole count
Pinholes are the enemy — a single through-hole destroys the moisture barrier. Pharmaceutical foil is held to a far tighter standard than household or industrial foil.
- Test method: transmitted-light pinhole inspection (commonly referenced to ASTM B479 for annealed aluminum foil, or equivalent national standards)
- Requirement for pharma-grade lidding: effectively zero pinholes at 20 μm and above; where a limit is specified it is typically on the order of ≤1 per square metre
Ask your supplier what inspection method and sampling rate they use, and whether pinhole detection is inline or offline. Inline detection at production speed is materially better than sampling after the fact.
2. Heat seal strength
The seal must hold for the product’s shelf life and must not leak.
- Measured as peel strength, typically in N/15 mm
- Test conditions (temperature, dwell time, pressure) must match your sealing line — a number quoted without conditions is meaningless
- Seal to PVC and seal to PVDC-coated PVC will give different values
Always specify: seal strength tested against [your forming film] at [temperature / dwell / pressure].
3. HSL coating weight and consistency
Under-applied HSL gives weak, leaking seals. Over-applied HSL causes stringing, blocking (layers sticking together in the roll), and messy press-through.
- Typical HSL: 3–8 g/m²
- Consistency across the roll width matters more than the absolute figure
4. Adhesion of OP and HSL
Coating adhesion is checked by tape test (a 3M tape pull is the common industry shorthand) and by solvent rub. Poor adhesion shows up as ink or lacquer transfer during sealing.
5. Barrier performance
The aluminum layer itself provides essentially complete barrier. In practice, barrier performance of the finished pack is dominated by:
- The forming film (PVC alone is a poor moisture barrier; PVDC coating improves it substantially)
- Seal integrity
- Pinholes in the foil
Aluminum foil at 20 μm has a water vapour transmission rate effectively at zero. If a pack is failing stability, look at the forming film and the seal before blaming the foil.
6. Surface wetting tension
Relevant if the foil is being laminated or printed further. Expressed in dyne/cm; a common minimum for reliable print and coat adhesion is in the low-to-mid 30s, with higher values for demanding processes.
PTP vs cold-form alu-alu vs tropical blister
These three are continually confused. The choice is driven by how moisture-sensitive your drug is.
| Format | Structure | Materyal | Use case |
| PTP (press-through) | OP / Al / HSL over a PVC or PVC/PVDC cavity | 8011-H18, 20–25 μm | Standard tablets and capsules. Transparent pack, drug is visible. |
| Cold-form alu-alu | OPA / Al / PVC, drawn into a cavity without heat | 8021-O or 8079-O, 45–65 μm | Highly moisture- or light-sensitive drugs. Fully opaque, near-absolute barrier. Larger and slower to produce. |
| Tropical blister | Alu-alu cavity + PTP lidding + outer PTP sachet | Combination | Maximum protection plus desiccant option, used in hot/humid climates (Zone III/IV markets). |
Rule of thumb: if your product passes stability in a PVC/PVDC blister, use PTP. If it does not, move to cold-form. Cold-form blisters cost more per cavity, run slower, and the pack is roughly double the size — do not upgrade to it unless stability data requires it.
How to specify PTP foil in an RFQ
A quotation request that only says “PTP foil, 0.02 mm” will come back with a wide price range and may not match your line. Include these eight items and you will get an accurate, comparable quote:
- Alloy and temper — e.g. 8011-H18
- Thickness and tolerance — e.g. 0.025 mm, ±5%
- Lapad ng katawan, core ID, and maximum roll OD — e.g. 250 mm / 76 mm / 280 mm
- Structure — plain, or OP/print/HSL
- HSL type and target coating weight — e.g. PVC-compatible HSL, 5 g/m²
- Forming film you will seal to — PVC, PVC/PVDC (state the PVDC coating weight), PP, alu-alu
- Printing requirement — unprinted, one colour, or full print with artwork
- Regulatory documents required — COA, DMF reference, ISO 15378, FDA food-contact statement, REACH/RoHS
Also state your monthly volume at target delivery schedule. Processing fees for pharmaceutical foil scale with volume, and lead times for printed foil are longer than for plain.
Common defects and what causes them
| Defect | Likely cause | Direction of fix |
| Weak seal / leaking packs | HSL mismatch with forming film; HSL under-applied; sealing temperature too low | Match HSL to film; increase coating weight; raise seal temperature |
| Foil won’t push through cleanly | Foil too thick or too hard; cavity design too tight | Reduce gauge; review cavity draft angle |
| Foil shreds instead of rupturing | HSL too strong; foil too soft | Review HSL formulation; confirm H18 temper |
| Ink scuffing or transfer | OP layer insufficient or poorly cured | Increase OP coating weight; confirm cure |
| Black spots on foil surface | Rolling oil residue or annealing contamination | Requires mill-side correction — reject the batch |
| Coating brittleness / pag crack na | Over-cured lacquer; excessive coating weight | Reduce coating weight; adjust cure parameters |
| Blocking (roll layers stick) | HSL too heavy or insufficiently cured | Reduce HSL; review winding tension and storage temperature |
Regulatory and quality framework
Pharmaceutical packaging foil sits inside a regulated supply chain. The documents buyers most commonly ask for:
- ISO 15378 — the GMP standard specific to primary packaging materials for medicinal products
- FDA Drug Master File (DMF) — a confidential reference the foil supplier files, which the drug manufacturer references in its own submission
- USP <671> — US Pharmacopeia chapter on containers and moisture permeation
- YBB standards (Tsina) — e.g. YBB00152002 for medicinal aluminum foil
- EU GMP / EU GMP Annex requirements for packaging materials, plus EU food-contact framework where applicable
- REACH / RoHS — for heavy metal and substance restrictions
Ask a prospective supplier which of these they can actually support with documents, not which they claim to comply with. A supplier that cannot produce a DMF reference or ISO 15378 certificate on request will slow down your regulatory filing.
Storage and handling
Foil is more delicate than it looks:
- Store sealed, dry, and below roughly 40 °C, away from condensation and corrosive chemicals
- Keep rolls off the floor and in original packaging until use
- Allow rolls to acclimatise to the packing room before opening — cold foil attracts condensation, which damages coating adhesion
- Use on a first-in, first-out basis; HSL performance degrades slowly over long storage
- Typical practical shelf life is around 12 months under proper storage — confirm with your supplier and agree it contractually
Frequently asked questions
What thickness of PTP aluminum foil should I use? 20 μm and 25 μm are the commercial defaults. Choose 20 μm for standard cavities and cost sensitivity; 25 μm where you want more margin on barrier and handling. Move to 30 μm or above only for large cavities or child-resistant designs.
Why is 8011-H18 the standard alloy-temper for PTP foil? 8011 offers the best combination of tensile strength, pinhole resistance and cost. The H18 temper gives the stiffness needed for clean press-through and stable running on high-speed lines.
Can PTP foil be used for cold-form blister packaging? No. Cold forming requires a soft (O temper) papel de liha, typically 8021-O or 8079-O at 45–65 μm. PTP foil in H18 temper will crack when deep-drawn.
What is the difference between PTP foil and alu-alu foil? PTP is a hard-temper lidding foil that seals over a plastic-formed cavity and is designed to be pushed through. Alu-alu is a soft-temper laminate that is itself drawn into the cavity and provides near-absolute barrier. They are not interchangeable.
What heat seal strength should I specify? There is no universal number — it depends on your forming film and sealing conditions. Specify the target strength together with the film type and the test conditions (temperature, dwell, pressure). Your supplier should seal-test against your actual forming film before mass production.
Are pinholes really a problem at 20 M? At 20 μm and above, properly produced foil should have effectively none. Pinhole control is a primary differentiator between a mill with good melt filtration and inline inspection and one without — which is why price alone is a poor selection criterion for pharmaceutical foil.
Can you print on PTP foil? Oo nga. Printing goes between the OP layer and the aluminum, so it is protected from scuffing. Provide artwork and confirm colour count early — printing extends lead time.
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