Key Technical Terms & Materials in Tin-Plate Lids: BPA-Free, TPE Seals, Internal Coatings, and What They Mean

Term

Definition / Material

Why It Matters in Food / Beverage / Packaging

Tinplate (马口铁 / ETP)

Steel sheet with a thin layer of tin (electro-tinplate) over the base, or similar protective metallic finish. Provides corrosion resistance, mechanical strength.

The base material for many food / beverage lids; its quality (tin coating thickness, steel quality, temper) affects durability, capacity to resist corrosion, and safety.

Internal Coating / Lining

A layer of organic material applied on the interior surface of the lid (side facing the contents), to prevent direct metal–content contact. Prevents corrosion, metallic taste, discoloration, migration of metal ions, or reaction with acidic, salty or oily contents.

Critical for preserving product quality, safety, shelf life. Choice of coating affects performance, flavor stability, regulatory compliance.

BPA (Bisphenol A)

A chemical used historically in many epoxy resin coatings. When in contact with food or beverages, under certain conditions, BPA or its degradation products can migrate from coating into the product.

Many markets have increasingly restricted or prohibited BPA in food contact materials. Having coatings free of BPA (or “non-intentional” BPA) helps meet regulatory requirements and customer expectations.

BPA-Free / BPA-NI (Non-Intentional)

  • BPA-Free means no BPA is intentionally used in the formulation.  • BPA-NI means BPA is not used on purpose; any residual trace should be at or below regulatory thresholds.

Ensures compliance with regulations in EU, USA, China etc., helps with consumer trust, often required by major brands.

PPG Innovel / PPG Innovel PRO / BPA-NI Coatings

A family of internal coatings produced by PPG (a major coatings company) designed to provide food-safe lining without BPA or bisphenol starting substances. The Innovel PRO / PRO 2489 etc., are engineered for high performance in demanding lid production (high stamping speed, high temperature, etc.). (PPG)

These coatings are examples of how modern internal linings can satisfy both regulatory safety (non-BPA) and performance (durability, resistance, flavor neutrality). They serve as benchmarks / references in many procurement specifications.

TPE (Thermoplastic Elastomer)

A rubber-like material that can be processed like plastic but exhibits elastomeric properties. Often used for sealing gaskets / liner rings / sealing edges inside lids.

Offers good sealing (prevents liquids/gases leaking), durability, ability to withstand temperature changes, good compatibility with contents; often more stable and cleaner (less leaching, odor) than cheaper alternatives.

Criteria

Traditional Epoxy Coatings (may contain BPA)

Non-BPA / BPA-Free or BPA-NI Internal Coatings (e.g. Innovel PRO, etc.)

Sealing Material: TPE vs Older Plastisol / PVC / Rubber

Regulatory Compliance / Food Safety

Risk of BPA or related compounds, may not meet newer regulations in certain markets.

Designed to comply with modern food contact laws (EU Food Contact Regulation EC 1935/2004, US FDA, China GB etc.), lower migration, flavor neutrality. For example, PPG Innovel internal coatings are non-BPA and approved in many markets. (PPG)

TPE formulations can be made to meet food contact safety, are often more stable, less prone to leaching vs PVC / plastisol; but must check the specific compound’s test data.

Chemical / Corrosion Resistance

Good in many cases, but may degrade under strong acid, high salt, high temperature; the epoxy layer can be attacked or degraded.

Improved resistance in modern non-BPA coatings; ability to withstand hot-fill, retort, pasteurization, etc. PPG’s BPA-NI coatings are tested for such uses. (PPG)

TPE seals tend to maintain integrity under temperature / chemical stress better than poorer quality seals; elastomeric recovery (after compression) is important.

Durability & Production Compatibility

Traditional epoxy / older coatings are well-understood, sometimes less expensive; may have limitations on stamping speed / heat / pressure.

Modern non-BPA coatings are engineered for high-speed stamping, high heat & pressure, and more consistent behavior in production. Example: PPG Innovel PRO PPG2489 is made for high-speed stamping lines, can withstand high temperatures and pressures. (PPG)

Seal material must survive not only the initial seal but also filling, sterilizing, transport, temperature cycling. TPE tends to perform well if properly specified.

Cost / Lifecycle Cost

Lower upfront cost sometimes; but potential costs in regulatory risk, flavor issues, spoilage.

Slightly higher material / coating cost, but lower risk, better for export, better shelf life, may reduce waste.

Good seal performance avoids leaks / spoilage / returns, so even if more expensive materials cost more initially, lifetime benefit often justifies cost.