In the global supply chain for pharmaceuticals, nutraceuticals, and premium cosmetics, the sealing liner is not merely a component; it is the final barrier ensuring product integrity. A high-quality sealing liner performs four critical functions: moisture protection, oxidation prevention, leak-proofing, and tamper-evidency. Without a robust seal, active ingredients in pharmaceutical formulations can degrade, food products can lose their nutritional profile, and liquid cosmetics can leak during trans-Atlantic shipping. At Uniseel, we view the liner as a critical extension of our Unishell caps, providing a 'Unified Quality' that guarantees the contents are 'Sealed for Safety' from the cleanroom to the consumer's hand.
For brands exporting to the USA and European markets, the liner also serves as a legal and reputational safeguard. It provides consumers with a visible assurance that the product has not been tampered with, which is a mandatory requirement for many OTC (Over-the-Counter) healthcare products. Our liners are engineered to withstand the rigors of high-altitude air freight and the temperature fluctuations of sea freight, ensuring that your brand reputation remains intact globally.
Understanding the technical nuances of different liner materials is essential for choosing the right sealing strategy for your specific container and contents.
IHS Liner (Induction Heat Seal): The Gold Standard for Protection
The Induction Heat Seal (IHS) liner is a multi-layered aluminum foil structure that utilizes electromagnetic induction to create a hermetic seal. When the capped container passes under an induction sealing machine, a current heats the aluminum foil, melting a polymer coating that bonds the foil permanently to the rim of the bottle (PET, Glass, or HDPE).
• Features: Provides a 100% airtight and moisture-proof barrier. It is the only solution that offers true tamper-evidency (the foil must be destroyed to access the product).
• Applications: Essential for pharmaceutical powders, liquid supplements, premium olive oils, and industrial chemicals.
Pressure Sensitive Liner (PS): Tool-Free Convenience
Often referred to as foam pressure seals, these liners do not require specialized machinery. The seal is activated solely by the torque applied when the cap is tightened onto the container. The liner features a pressure-activated adhesive on the underside that bonds to the bottle rim.
• Features: Cost-effective and simple to implement for small to medium-scale production. It provides a 'Sealed for Protection' message upon opening.
• Applications: Primarily used for dry products such as vitamins, capsules, and dry food ingredients (spices, nuts).
PE/EPE Foam Liner: Durable & Reusable Sealing
The Expanded Polyethylene (EPE) foam liner is the most widely used general-purpose sealing material. It is a resilient, white foam disc that compresses against the bottle rim to form a physical seal.
• Features: Unlike IHS or PS liners, the foam liner stays inside the cap throughout the product's life. It is highly resistant to chemicals and provides excellent recovery after compression, allowing for multiple resealing cycles.
• Applications: Standard for cosmetic creams, shampoos, and household cleaning products.
PS22 Liner: The Industry Standard for Dry Goods
PS22 is a specific, high-performance grade of pressure-sensitive liner. It is designed with a thicker foam base and a specialized adhesive layer to provide superior adhesion to wide-mouth containers (up to 89mm). It is the preferred choice for professional nutraceutical brands looking for a reliable, machine-free sealing option.
Safety and compliance are non-negotiable at Uniseel. Our core sealing products, including the IHS for PET and our Pressure Sensitive liners, have undergone rigorous testing by SGS to ensure they meet the highest international standards. We provide full documentation for FDA 21 CFR 175.300 (Food Contact Safety), REACH SVHC, and RoHS compliance. This ensures that our liners do not leach harmful chemicals or heavy metals into your product, maintaining the purity of your formulations. Our production is carried out in an ISO Class 7 Cleanroom, preventing microbial and particulate contamination at the source.
Q1: Can I use an IHS liner for a glass jar?
A1: Yes, but you must specify 'IHS for Glass' at the time of order. The heat-seal polymer layer is chemically formulated differently for glass compared to PET or HDPE to ensure a permanent bond.
Q2: Why is my induction liner not sealing properly?
A2: Sealing failure is usually caused by three factors: incorrect induction machine settings (power/speed), contamination on the bottle rim (oil or powder), or insufficient cap torque.
Q3: Do pressure-sensitive (PS) liners provide an airtight seal?
A3: While PS liners are excellent for keeping dry products fresh, they do not provide a 100% hermetic (airtight) seal like IHS liners. For liquid products or high-moisture sensitivity, IHS is always recommended.
Q4: How do I determine the correct liner size?
A4: The liner diameter should match the inner diameter of the cap. For our 38/400 to 89/400 Unishell series, we provide pre-cut liners with ± 0.1mm tolerance to ensure a perfect friction fit inside the cap shell.
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