I. Detailed Comparison of Main Materials
1. Conductive Silicone Rubber
Base Material: Methyl Vinyl Silicone Rubber (VMQ). Platinum curing is preferred; common hardness ranges from 30~50 Shore A.
Advantages
Excellent temperature resistance: -60～180℃. No hardening under thermal cycling, suitable for vehicle-mounted equipment, coffee machines and industrial devices.
Inherent sealing performance, easily achieving IP65~IP67 water and dust resistance.
Silent pressing with soft tactile feel; elasticity and travel can be freely adjusted.
Resistant to ozone, UV radiation, oil stains, weak acids and weak alkalis, and resistant to aging during long-term outdoor service.
Conductive carbon particles can be integrally molded to form an integrated keypad panel with high mold versatility.
Supports laser etching for backlighting, multi-color molding and anti-slip textures.
Disadvantages
Silicone rubber cured via conventional bis-2,4 vulcanization produces precipitated small molecules. Platinum secondary vulcanization is mandatory for coffee machines and food-contact equipment.
Applications: Vehicle-mounted equipment, construction machinery, instrument control panels, coffee machines, outdoor handheld terminals, and equipment operating in humid and dusty environments.2. Engineering Plastic Keycaps
ABS
Easy injection molding, simple coloring and low cost.
Temperature resistance ≤80℃; prone to surface glossing after long-term friction; poor resistance to chemicals and weathering.
Indoor home appliances, remote controllers and general consumer electronics.
PC
High impact resistance, high transparency, heat resistance up to 110℃, ideal for backlit keys.
Susceptible to cracking when exposed to solvents such as alcohol and cleaning agents.
Backlit panels and transparent keys for high-end equipment.
PBT
Excellent wear resistance, resistant to surface glossing from oil contact, heat stable, dimensionally stable and resistant to cleaning agents.
Relatively high cost and difficult coloring.
Frequently operated control panels, industrial keyboards and equipment with long-duration operation.
Plastic key structure: PC/PBT keycap + PCB + Metal Dome
Features: Distinct crisp “click” tactile feedback, service life over 1 million presses and stable contact resistance.
Drawback: Poor water resistance; an additional sealing ring is required.
3. TPU Thermoplastic Polyurethane
Good wear resistance and elasticity; compatible with two-color injection molding together with PC/ABS.
Low maximum service temperature (-20～85℃); prone to oil bleeding and aging under prolonged high temperature.
Small handheld devices, anti-slip composite keys. Not suitable for high-temperature environments (forbidden around coffee machines and boilers).
4. Membrane Keypads
Ultra-thin, integrated flat structure with neat appearance.
Poor scratch resistance, moderate temperature resistance; cannot withstand pressing by sharp hard objects.
Meters and slim control panels; not applicable for heavy-duty or outdoor use.
II. Quick Material Selection Guide
Scenario 1: Coffee machines, food equipment and high-temperature humid equipment
【First Choice: Platinum-cured food-grade silicone keys】
Reason: Resistant to high-temperature steam, free of odor-causing precipitates, waterproof and compliant with safety standards, matching silicone tubing product lines for coffee machines.
Scenario 2: Truck on-board terminals, construction machinery and outdoor controllers
【Preferred: Platinum-cured conductive silicone rubber】
It copes with wide temperature fluctuations, dust and rain, and silicone delivers irreplaceable sealing advantages.
Scenario 3: Indoor instruments and control cabinets requiring crisp key feedback
【PBT keycaps + metal dome structure】
Scenario 4: Low-cost indoor home appliances and remote controllers
【General conductive silicone rubber / ABS keycaps】
III. Critical Purchase Notes for Silicone Keys (Key Points)
- Platinum curing is mandatory for equipment contacting food or hot water; bis-2,4 vulcanization is prohibited to prevent migration of small molecules and odor generation.
- Recommended hardness: 40~45A, balancing rebound feel and tear resistance.
- Spray PU hand-feel coating on the surface to reduce fingerprint marks and improve wear resistance.
- Adopt heat-resistant modified VMQ formulation for long-term high-temperature working conditions.
- For long service life requirements: thicken silicone bridge sections and optimize the ratio of conductive carbon particles.
IV. Summary
High-temperature, humid, outdoor applications requiring waterproof sealing → Platinum-cured conductive silicone rubber.
Indoor normal-temperature applications requiring crisp tactile feedback and frequent operation → PBT + PC with metal dome structure.
Low-budget indoor general home appliances → ABS / general conductive silicone rubber.