DWK 240408 WHEATON Black Phenolic Screw Cap, PTFE-Faced Rubber Liner, 13-425

The WHEATON® 240408 is a black phenolic solid-top screw cap with a 13-425 thread finish and a PTFE-faced 14B styrene-butadiene rubber liner. The liner combines a chemically resistant PTFE sample-contact surface with a compressible rubber backing.

The cap, liner, and container form one functional sealing assembly. A matching thread finish is essential, but chemical compatibility, liner compression, and seal performance must also be considered.

The reviewed product-specific data do not establish a cap-height tolerance, exact external diameter, liner-compression target, prescribed application torque, or quantified leak-rate specification.

DWK's Closure Liner Guide describes a 0.005-inch virgin PTFE layer bonded to a white sulfur-cured styrene-butadiene rubber backing. The two materials perform different functions.

The PTFE facing is the primary intended sample-contact surface. The rubber backing provides mechanical compliance. Performance depends on the complete closure design and how the cap is applied.

PTFE is widely selected for its chemical resistance and low chemical reactivity. DWK describes the PTFE facing as providing an inert surface toward the sample in its intended liner construction.

However, the chemical resistance of a facing material should not be treated as an unrestricted compatibility rating for the entire cap, liner edge, backing, and container assembly.

• Sample chemistry: Evaluate the actual solvent, reagent, concentration, and mixture.
• Contact duration: Consider short-term handling separately from prolonged storage.
• Temperature: Evaluate chemical and material behavior under the actual storage and processing conditions.
• Seal interface: Confirm the PTFE-facing and liner assembly function with the selected container rim.
• Analytical sensitivity: Evaluate extractables, leachables, or sample interactions when the method requires them.
• Containment: Test for acceptable evaporation, leakage, or sample loss when relevant to the application.

The manufacturer does not provide a universal chemical-compatibility guarantee for every assembled container using this cap. Specific sample suitability must be established independently.

The 13-425 designation describes the nominal screw-thread finish used to pair the cap with a compatible container. The numerical designation identifies the nominal closure diameter and a particular thread style.

DWK's closure-size guidance explains that the container and closure thread finishes must correspond. A cap with a different finish, such as 13-415, should not be assumed interchangeable with a 13-425 container.

The thread finish also does not establish the container's clear internal mouth diameter. Verify the actual vial or bottle dimensions for filling or equipment-clearance requirements.

Plain 14B rubber offers useful resilience, but DWK identifies limitations with oils, strong acids, and hydrocarbons. The PTFE facing on 240408 provides a different intended sample-contact surface.

Neither cap should be substituted for the other without reviewing compatibility, the analytical method, and the required finished-container performance.

PTFE-faced closures are not all constructed in the same way. WHEATON offers different backing materials and cap styles. Those differences can be important in specialized analytical and storage applications.

These liners are different material constructions. Do not assign the temperature performance, chemical resistance, or puncture characteristics of one design to another.

The cap forms part of a mechanical sealing system. The rubber-backed liner must be compressed against the container mouth under appropriate conditions.

Proper seal performance depends on the cap threads, vial or bottle finish, rim geometry, liner condition, and application procedure. The reviewed manufacturer specifications do not publish a single torque value or leak-rate limit for all uses of 240408.

• Confirm compatibility: Use a matching 13-425 container finish.
• Inspect the liner: Reject caps with visible liner damage or separation.
• Inspect the rim: Keep the contact surface free from chips, defects, and residue.
• Use an approved application method: Apply and tighten the cap according to the laboratory's procedure.
• Qualify the final seal: Test leakage, evaporation, or sample loss when required.

DWK lists WHEATON 240408 as autoclavable. Its technical reference also describes PTFE/14B rubber as an autoclavable liner material.

Autoclavability is a material and product capability designation, not a validated procedure for every possible filled or capped assembly.

Thermal exposure may affect a particular sample, the container, or subsequent sealing performance. The entire process should be qualified according to facility requirements.

DWK's technical liner guide references U.S. FDA material regulations for components of its liner constructions, including PTFE and rubber materials.

These are manufacturer material-level statements. They should not be interpreted automatically as approval of a finished WHEATON 240408 closure assembly for a specific pharmaceutical, medical, food-contact, or sterile use.

When documentation is required for a regulated application, contact SOSCleanroom to request the relevant manufacturer information and evaluate its scope against the intended process.

PTFE-faced closures may be considered for sensitive laboratory samples where the sample-contact material is an important selection factor. However, no general liner construction automatically qualifies a product for a specific controlled environment.

The reviewed 240408 data do not establish supplied sterility, a sterility assurance level, a cleanroom ISO classification, an endotoxin specification, or quantitative extractables and particle limits. Additional qualification is required when such controls are necessary.

These are separate manufacturer catalog numbers. Verify the required liner construction, supplied quantity, and any approved product-specific substitution requirements before changing SKUs.

Contact SOSCleanroom for pricing, availability, and alternative case-quantity options.

• Verify product identity: Confirm WHEATON 240408 and 200 caps per case.
• Check finish: Confirm the required 13-425 screw-thread configuration.
• Inspect the cap: Check for cracks, damaged threads, or visible contamination.
• Verify liner material: Confirm PTFE-faced 14B rubber rather than plain 14B rubber.
• Inspect liner condition: Check for delamination, damage, poor seating, or contamination.
• Review the container: Confirm a matching neck finish and suitable sealing rim.
• Qualify processing: Follow the laboratory's approved cleaning, autoclaving, and closure-application requirements.
• Maintain traceability: Apply the facility's receiving and material-control procedures.

The following DWK technical reference explains screw-thread identification, PTFE/14B liner construction, chemical compatibility considerations, and alternative liner materials.

Documentation note: General material information does not constitute a product-specific leakproof certificate, sterility certification, or universal chemical-compatibility approval. Contact SOSCleanroom for additional available manufacturer documentation.

SOSCleanroom can assist with selecting WHEATON screw caps, confirming 13-425 container compatibility, comparing rubber and PTFE-faced liner constructions, and obtaining additional technical information.