This paper is aimed at procurement, structural engineers and project managers to systematically sort out material routes, key specifications, structural tolerances and validation logic, and to provide a validation checklist that can be directly used for project evaluation.
1. Industry Drivers: Why "More Temperature Resistance + Lower Compression Set" is the Main Thread
- New energy, charging/energy storage, automotive electronics and outdoor equipment have shifted upward in operating temperatures and are placing more emphasis on long life.
- Miniaturization of equipment results in smaller seal contact areas and narrower preload windows, placing higher demands on material resilience retention.
- Reliability audits are more stringent: material consistency, lot traceability, and validation reports have become the "ticket to entry".
2. Key indicators: translating needs into testable data
- Hardness (Shore A): Affects assembly force, compression window and feel (e.g. key type).
- Tensile Strength/Elongation: Focus on the risk of tearing during assembly and use.
- Compression Set (CS): the core indicator of long-term seal retention (defined by temperature/time/compression rate).
- Temperature resistance and low-temperature resilience: seal retention and risk of cracking under high and low temperature cycling.
- Media compatibility: oil, coolant, cleaning agents, ozone/UV and other environmental factors.
3. Material routes: common formulation choices and applicable boundaries
3.1 HTV (solid silica gel) vs LSR (liquid silica gel)
- HTV: Cost-controlled, compression molding/extrusion compatible, suitable for medium to large size seals and strips.
- LSR: Dimensionally stable and automation friendly, suitable for precision small parts and projects with high consistency requirements.
3.2 "Low CS" is not as low as it should be: matching to the assembly structure is more critical.
- CS Too low but too hard may result in difficult assembly and understressed sealing surfaces.
- It is recommended to evaluate CS, hardness, compression, and groove tolerances in conjunction.
4. Structure and tolerances: material upgrades must be coordinated with design controls
- Pre-compression: Finding the balance between assemblable and sealable (test fitting + leakage verification is recommended).
- Chamfering/rounding of grooves: Reduces cuts and assembly scratches and significantly improves yields.
- Critical dimensions CPK: Prioritize process capability control for dimensions related to "sealing lines".
5. Validation recommendations: the 6 most overlooked items
- CS Test: Specify temperature, time, compression rate and sample morphology (pieces/test pieces).
- High and low temperature cycle: combined with the actual working conditions (including humidity and heat / salt spray depending on the industry).
- Media immersion: Record volume changes and hardness changes according to the real media and cycle.
- Leak testing: consistent differential pressure, time, assembly status, preferably including batch sampling.
- Appearance and burr standards: Define more stringent appearance requirements for assembled sealing surface areas.
- Lot traceability: material lot number, ingredients, vulcanization conditions, and inspection records close the loop.
6. Vendor communication checklist (can be forwarded directly)
- Usage scenarios: temperature range, media, lifetime, assembly method, compression window
- Drawings: critical dimensions and tolerances, groove structure, surface roughness requirements
- Validation: CS/Circulation/Media/Leakage Objectives and Reporting Formats
- Delivery: incoming material inspection standards, lot traceability requirements, change management mechanisms
Frequently Asked Questions (FAQ)
1. Is it feasible to just change the material without changing the structure?
The risk is usually higher. Variations in material hardness, springback and coefficient of friction can magnify structural tolerance issues and at a minimum, test fit and leakage verification is recommended.
2. What about the "temperature resistance" indicator?
Priority is given to looking at long-term operating temperatures with retention of performance after thermal aging, rather than short-term limiting temperatures.
3.CS What conditions should I choose?
The temperature of the working condition is the main focus, and at the same time do 10-20 ℃ higher than the working condition of the tightened conditions, for life margin assessment.