Views: 111 Author: Site Editor Publish Time: 2026-09-29 Origin: Site
A TPE molded bottle cap liner is a thermoplastic elastomer component positioned between a bottle and its cap to provide sealing and cushioning. TPE combines rubber-like elasticity with thermoplastic processing, making it suitable for injection molding and customized closure designs.
For pharmaceutical packaging, USP recognizes that elastomeric components may be manufactured from either thermoset or thermoplastic elastomers and emphasizes protection, compatibility, safety and performance for the intended application. 美洲病理学会
Unlike a rigid plastic cap, the TPE liner can deform under compression and recover its shape, helping maintain contact pressure around the bottle opening.
Recommended visual:
Bottle → TPE Liner → Cap cross-section showing compression and sealing area.
For many flexible sealing applications, 40–80 Shore A can be used as a practical initial development window. However, there is no universal hardness specification.
A 50 Shore A liner and a 70 Shore A liner can behave very differently depending on:
Liner thickness: approximately 0.5–2.0 mm
Bottle-neck geometry
Cap torque
Compression ratio
Required sealing force
Operating temperature
Therefore, hardness should be selected together with the closure geometry and compression design, not independently.
Compression set measures how well an elastomer retains its elastic recovery after prolonged compression. ASTM D395 specifically covers compression-set testing for elastomeric materials used in compressive applications such as seals. ASTM Store
For TPE development, a useful screening target can be ≤25–35% compression set, with more demanding sealing applications often targeting ≤20–25%, depending on the formulation and test conditions.
Typical development tests may evaluate:
Property | Example Development Range |
|---|---|
Hardness | 40–80 Shore A |
Liner thickness | 0.5–2.0 mm |
Compression set screening | ≤20–35% |
Tensile strength | ≥5–15 MPa* |
Elongation | ≥300–600%* |
Service temperature | Approx. −30 to 100°C* |
*These are development reference ranges rather than universal specifications. Actual values depend strongly on TPE chemistry and grade.
A practical development process is:
TPE Granules → Injection Molding → Dimensional Inspection → Cap Assembly → Leak Test → Aging Test → Validation
For an initial trial, manufacturers should provide the TPE supplier with:
Bottle-neck drawing
Cap drawing
Liner dimensions
Target hardness
Cap torque range
Product composition
Filling temperature
Storage temperature
Sterilization conditions, if applicable
This information allows the material supplier to select a formulation based on the actual sealing conditions.
Possible causes include excessive compression set, insufficient compression, dimensional variation or inappropriate cap torque.
Recommended solution: test the complete closure system rather than changing TPE hardness alone.
If the liner generates excessive friction, consumers may experience difficulty opening the bottle.
Recommended solution: optimize hardness + liner thickness + compression + surface characteristics + cap torque.
TPE may be exposed to oils, alcohols, acids, pharmaceutical formulations or other chemicals.
A material that performs well with water may behave differently with an oil-based or solvent-containing formulation. Therefore, compatibility should be tested using the actual product whenever possible.
For pharmaceutical packaging, elastomeric components can potentially affect product quality or patient safety through chemical interactions. USP specifically identifies extractables and leachables as considerations beyond baseline requirements. 美洲病理学会
A practical validation program can include:
Shore hardness: initial material screening
Compression set: long-term deformation evaluation
Tensile/elongation: mechanical integrity
Chemical resistance: actual product exposure
Thermal aging: typically application-specific, e.g. 70°C / 168 h as a screening condition
Leak testing: finished bottle-cap assembly
Torque testing: opening and closing performance
Aging: accelerated and real-time conditions
For pharmaceutical applications, functional suitability should be assessed as part of the complete packaging system. USP <382> specifically addresses functional suitability of elastomeric components in parenteral packaging systems. USP
Yes, in suitable applications. The specific TPE grade must be validated for sealing, compression set, chemical compatibility, temperature and regulatory requirements.
40–80 Shore A can be used as an initial development range for many flexible sealing applications, but the final hardness depends on the bottle, cap and compression design.
There is no universal value. As an engineering screening target, ≤20–35% may be considered depending on the application, test method and service conditions. The final requirement should be established through actual seal testing.
Yes. Many TPE grades are designed for injection molding, allowing automated production of customized bottle liners and sealing components.
Some TPE formulations may be suitable, but pharmaceutical applications require application-specific qualification. USP guidance addresses elastomeric components, functional suitability and potential extractables/leachables. 美洲病理学会
Shandong Taierifeng New Material Co., Ltd. (TERRIFIC) is a TPE granules manufacturer specializing in customized thermoplastic elastomer materials.
For molded bottle cap liner applications, material selection can be based on hardness, compression set, sealing force, chemical resistance, processing requirements and end-use conditions.
If you are developing a new TPE bottle cap liner or TPE sealing gasket, providing the bottle drawing, cap drawing and application conditions can significantly improve the accuracy of material selection and sample development.
TERRIFIC — Customized TPE Materials for Reliable Sealing Applications.
