High-Consistency Silicone Rubber with Superior Fatigue Resistance in Heat and Cold - Silastic®

Silastic® HCM 60-1225-GRAY is a fully formulated silicone rubber with high fatigue resistance. The peroxide-cured high-consistency rubber (HCR) is a ready-to-use material with a peroxide-curing system. Tighter-fitting underhood content, increased operating temperatures, extended vehicle service life, and lightweight for fuel efficiency are the key challenges of automotive design.

Silastic® HCM 60-1225-GRAY is specially designed to address these challenges by providing heat-aging stability, low compression set, high tear strength and high fatigue life. It facilitates improved component durability over a broad operating temperature range. The HCR rubber delivers good cured properties and processing stability for high-performance fabricated components.

Applications

Silastic® HCM 60-1225-GRAY, a high-performance silicone rubber offered by Dow Corning, is specially formulated for production of automotive parts demanding high fatigue resistance for extended service life in extreme conditions. The following are the potential applications of Silastic® HCM 60-1225-GRAY:

  • Mounts for NVH control
  • Steering system boots
  • Engine mounts
  • Exhaust hangers
  • Constant-velocity joints (CVJ) boots

Silastic® HCM 60-1225-GRAY can help to avoid the use of heat shields on driveline inboard joints for highly durable, heat-resistant CVJ boots. In other fabricated components, the elastomer is formulated to resist cracking and tearing with repeated flexing or stretching, endure high engine and exhaust operating temperatures, and deliver effective vibration damping and isolation on components to facilitate NVH control.

Typical Properties

Silastic® HCM 60-1225-GRAY silicone rubber has a broad service temperature range from -40°C to 200°C, outperforming other elastomer or thermoplastic materials. It neither softens in heat nor becomes brittle in cold. With unprecedented fatigue resistance, Silastic® HCM 60-1225-GRAY enables making components with improved service life in extreme heat and cold. The following table presents the typical properties of Silastic® HCM 60-1225-GRAY silicone rubber:

Test Method(1)

Property

Unit

Value

AS MOLDED(2)
ASTM D792 Specific Gravity 1.12
ASTM D2240 Hardness Shore A 61
ASTM D412 Die C Tensile Strength MPa (psi) 7.6 (1,102)
ASTM D412 Die C Elongation % 410
ASTM D624 Tear Strength, Die C kN/m (ppi) 34 (194)
ASTM D624 Tear Strength, Die B kN/m (ppi) 42 (240)
ASTM D430 Method B Extensional Fatigue Life Cycles 3 x 106
ASTM D430 Method B Bend-Flex Fatigue Life, Cycles to Grade 1 Cycles 3 x 106
HEAT-AGED 70 HOURS AT 225°C (437°F)(2)
ASTM D573 Hardness Change % -2.6
ASTM D573 Tensile Change % -21
ASTM D573 Elongation Change % -39
ASTM D395 Method B Compression Set After 22 Hours at 175°C (347°F), Plied % 15

(1) ASTM: American Society for Testing and Materials.
(2) Properties obtained on 2 mm thick slab, press-cured 10 minutes at 177°C (350°F).

In automotive component fabrication, Silastic® HCM 60-1225-GRAY exhibits significant improvement in flexural fatigue life when compared to two common HCR elastomers (Figure 1).

Compared to two common HCR elastomers for fabricated automotive components, Silastic® HCM 60-1225-GRAY silicone rubber shows substantial improvement in flexural fatigue life.

Figure 1. Compared to two common HCR elastomers for fabricated automotive components, Silastic® HCM 60-1225-GRAY silicone rubber shows substantial improvement in flexural fatigue life.

Key Features and Advantages

Silastic® HCM 60-1225-GRAY provides several advantages over common engineering elastomers used in challenging automotive applications.

Figure 2. Silastic® HCM 60-1225-GRAY provides several advantages over common engineering elastomers used in challenging automotive applications.

The following are the key features and advantages of Silastic® HCM 60-1225-GRAY over common engineering elastomers used in challenging automotive applications (Figure 2):

  • Fast cure times at elevated temperatures
  • Custom compounding for special colors or properties
  • Versatility in processing and cure-rate
  • Higher throughput without post-curing required
  • Easy mold release
  • Wider service temperature range to endure extreme heat and cold
  • Unprecedented fatigue life with improved durability
  • Stable processing

This information has been sourced, reviewed and adapted from materials provided by Dow Corning Automotive.

For more information on this source, please visit Dow Corning Automotive.

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