Blister Aluminium Foil Base For Pharmaceutical Packaging

Every time you open a blister pack of tablets or capsules and press your fingertip against that thin yet strong aluminum foil, have you ever wondered—this "barrier" protecting drug safety originally started as a roll of uncoated, gleaming silver aluminum foil?

In the pharmaceutical packaging industry, PTP aluminum foil (pharmaceutical blister foil) is the "standard protective clothing" for oral solid dosage forms. Its creation began with a series of precise processing and rigorous refinement of large rolls of PTP aluminium foil uncoated. Today, we'll unlock how this "plain aluminum foil" transformed into a core material for pharmaceutical-grade blister packaging.

Large rolls of uncoated PTP aluminum foil cannot be used directly in pharmaceutical blister packaging. Like a rough, unpolished gem, it possesses the potential to become a "precious item," but requires multiple professional processes to meet the pharmaceutical industry's extreme requirements for safety, barrier properties, and ease of handling. And the foundation of all this lies in the stringent selection of materials for the uncoated aluminum foil rolls themselves.

Once qualified rolls of blister aluminium foil base enter the production workshop, the true "transformation journey" officially begins. Every process revolves around "pharmaceutical safety," allowing no room for carelessness. The core process can be divided into three key steps, progressively upgrading ordinary aluminum foil into pharmaceutical-grade material.

Step 1: Surface Pre-treatment

Although the surface of uncoated aluminum foil rolls is clean, its surface tension is low. Direct coating will lead to coating peeling and weak adhesion. Therefore, the aluminum foil surface first needs to undergo corona treatment. High-voltage discharge alters the molecular structure of the aluminum foil surface, increasing the surface tension to 32-38 dynes/cm, allowing the subsequent coating to adhere tightly to the aluminum foil surface and resist peeling.

Simultaneously, this step further removes residual rolling oil and impurities from the aluminum foil surface, ensuring the surface roughness is controlled within 0.2-0.4μm, fully preparing for subsequent processing. It is worth noting that the entire pretreatment process must be carried out in a Class 300,000 cleanroom to avoid contamination of the aluminum foil by environmental dust and impurities.

Step 2: Core Coating

This is a crucial step in the transformation from uncoated aluminum foil rolls to pharmaceutical blister foil, and it's also the stage that best reflects the stringent pharmaceutical standards. The coating process uses gravure printing, precisely applying two core coating layers to the pre-treated aluminum foil surface. Each layer has a clear function and is indispensable.

The inner layer is the heat-sealing layer, which directly adheres to the pharmaceutical blister (PVC or PVDC rigid sheet), using pharmaceutical-grade materials such as vinyl ester resin. Its core function is to achieve a tight heat seal between the aluminum foil and the blister, ensuring the packaging's airtightness and preventing the entry of external moisture, oxygen, and dust.

It must also possess good heat-sealing strength; it cannot easily detach, causing drug leakage, nor can it be too strong, hindering the consumer's ability to open the package. During the coating process, precise control of the coating thickness and uniformity is required to avoid uneven coating or missed areas, which would directly affect the sealing effect and threaten drug safety.

The outer layer is the protective layer (also known as the printed base layer), using environmentally friendly pharmaceutical materials such as acrylic-amino resin. Its main functions are twofold: first, to protect the aluminum foil itself, preventing oxidation and discoloration, and extending its shelf life; second, to serve as a printing base, carrying key information such as the drug name, specifications, production date, and expiration date.

Pharmaceutical-grade solvent-free ink is used for printing to ensure the ink does not peel off, migrate, or contaminate the drug. The printing process requires high precision and clear colors, and also needs to undergo drying treatment to ensure rapid ink curing and avoid residual solvents.

Step3: Post-processing and Testing

After coating, the aluminum foil still needs to undergo post-processing steps such as rolling and slitting. Based on the specifications of the downstream pharmaceutical companies' blister packaging equipment, the large rolls of aluminum foil are slit into smaller rolls of appropriate width to facilitate subsequent blister forming and drug packaging. However, this does not mean the end of the transformation; the most stringent test is yet to come—full-process quality testing.

Some may wonder why, instead of directly using coated aluminum foil, we start with uncoated large rolls? In fact, this is precisely where the professionalism of pharmaceutical blister aluminum foil lies. Using uncoated PTP aluminum foil rolls as the substrate ensures maximum purity and stability of the aluminum foil, avoiding problems such as impurity contamination and coating aging that can occur with pre-coating.

Furthermore, customized coating processes allow for adjustments to coating materials and thickness based on the characteristics of different pharmaceuticals (such as moisture absorption or photosensitivity), achieving targeted protection. For example, a light-shielding coating can be added for photosensitive drugs, while a stronger barrier coating can be used for moisture-absorbing drugs, ensuring that each drug receives its own specific protection.