Is Sorbothane Waterproof? A Comprehensive Guide to Its Water Resistance and Practical Applications

Sorbothane is a unique viscoelastic material widely known for its exceptional shock-absorbing, vibration-damping, and energy-absorbing properties. Used across various industries—from footwear and sports equipment to industrial machinery and medical devices—Sorbothane has earned a solid reputation for outstanding performance under dynamic stress. But one common question continually surfaces among consumers and engineers alike: Is Sorbothane waterproof?

In this in-depth article, we will explore the water resistance capabilities of Sorbothane, examine its material composition, analyze real-world performance in wet environments, compare it to alternative dampening materials, and discuss best practices for its use where moisture is a concern. Whether you’re designing a high-performance running shoe, protecting delicate medical equipment, or using Sorbothane in industrial applications, this guide delivers the technical clarity and practical advice you need.

Understanding Sorbothane: What It Is and How It Works

Composition and Physical Properties

Sorbothane is a proprietary polymeric material derived from polyether-based polyurethane. Its unique molecular structure allows it to behave like both a solid and a liquid under varying conditions—a characteristic central to its viscoelastic nature. When a force is applied, Sorbothane deforms slowly to absorb the energy and then gradually returns to its original shape, minimizing stress on the connected components.

Key physical properties of Sorbothane include:

• High damping coefficient (can absorb up to 94.7% of shock energy)
• Excellent resilience and rebound control
• Good resistance to environmental aging when properly sealed
• Non-toxic and available in FDA-compliant grades

Its dual-phase behavior makes it ideal for applications requiring long-term durability and consistent performance under repeated impact or vibration.

How Sorbothane Differs from Other Elastomers

While many elastomers like silicone rubber, neoprene, or standard urethane exhibit some degree of flexibility and damping, Sorbothane stands apart. It offers a superior balance between elasticity and viscosity. Many rubber-like materials return energy quickly (high rebound), which can amplify vibrations. In contrast, Sorbothane converts kinetic energy into heat and dissipates it, offering quieter, smoother performance.

This makes Sorbothane especially useful in environments where mechanical noise or repetitive stress could damage sensitive systems.

Is Sorbothane Waterproof? Defining the Terminology

Waterproof vs. Water-Resistant: Clarifying the Terms

Before answering the question directly, it’s essential to clarify the difference between “waterproof” and “water-resistant,” as these terms are often misused.

• Waterproof: A material that completely prevents water from passing through or degrading it under prolonged or high-pressure exposure.
• Water-resistant: A material that resists water penetration to a certain degree but may degrade over time when exposed to moisture.

Sorbothane, while highly durable in many environments, falls into the water-resistant category rather than being fully waterproof.

Sorbothane’s Reaction to Moisture and Water Exposure

Extensive testing has demonstrated that Sorbothane can withstand limited exposure to water—whether in the form of humidity, condensation, or brief immersion—without immediate structural failure. However, it does absorb moisture over time when exposed to continuous or submerged wet conditions.

Laboratory analyses show:
– Sorbothane’s moisture absorption rate is approximately 0.5% to 1.2% by weight when exposed to 95% relative humidity over 24 hours.
– Prolonged immersion in water leads to gradual softening, swelling, and reduced mechanical integrity.
– Absorbed moisture can compromise damping efficiency and reduce the material’s service life.

This behavior disqualifies Sorbothane from being classified as waterproof in engineering or material science contexts.

Testing Sorbothane in Real-World Wet Environments

Laboratory and Industrial Testing Results

Several independent studies and internal Sorbothane Corporation tests have evaluated the material’s performance under wet conditions using standardized methods like ASTM D570 (water absorption of plastics). The results consistently show that Sorbothane:

• Begins absorbing moisture within minutes of exposure to liquid water.
• Shows dimensional changes (usually slight swelling) after 24 to 48 hours of constant moisture exposure.
• Retains 70–80% of its original damping capabilities after moderate moisture exposure, but performance declines with prolonged exposure.

Case Study: Sorbothane in Marine Equipment

In a real-world application involving marine vibration isolators, Sorbothane mounts were placed in environments with constant high humidity and salt spray. After six months, inspectors noted:
– Surface tackiness increase due to moisture absorption.
– 10% reduction in shock absorption performance.
– No outright failure, but reduced lifespan compared to similar units in dry environments.

Engineers eventually replaced Sorbothane with closed-cell silicone foam or EPDM rubber in areas directly exposed to seawater, while still using Sorbothane in protected zones where water exposure was incidental.

Footwear and Outdoor Gear Experiences

In athletic shoes and hiking boots, Sorbothane is often employed as insoles or heel inserts for impact absorption. While these products may experience occasional water exposure (rain, puddles), they are typically designed with protective layers (e.g., moisture-wicking fabric, rubber outsoles) that limit direct contact with water.

Users report:
– Sorbothane inserts perform well in damp conditions when allowed to dry.
– Prolonged dampness leads to odors or breakdown of adhesives used in assembly.
– Full submersion during washing or deep cleaning is not recommended.

Factors Affecting Sorbothane’s Water Resistance

Several variables influence how Sorbothane behaves when near water. Understanding these helps optimize performance in moist environments.

Thickness and Density of the Material

Thicker, higher-density Sorbothane grades absorb water at a slower rate than thin, low-density foams. A 1-inch-thick Sorbothane pad will resist moisture penetration better than a 1/4-inch sheet of the same composition.

Use of denser grades is recommended in applications where incidental moisture exposure is expected.

Durability of Protective Coatings

Many Sorbothane components are sealed or coated with protective membranes such as polyurethane films, silicone coatings, or moisture barriers. These coatings can significantly extend performance in wet environments by reducing the rate of water absorption.

However:
– Coatings may wear over time.
– Scratches or cracks expose bare Sorbothane to water.
– Temperature fluctuations may cause delamination.

Exposure Duration and Water Type

Not all water is equal. The degree of Sorbothane degradation depends on:
– Duration: Brief splashes are acceptable; immersion for >24 hours risks performance loss.
– Water type: Freshwater causes slower degradation than saltwater or chemically treated water.
– Temperature: Warm or hot humid environments accelerate moisture absorption.

Effective Applications of Sorbothane in Damp Conditions

While not waterproof, Sorbothane remains an excellent choice for many damp or humid environments—provided it’s used wisely.

Industrial Machinery and Equipment

Sorbothane is widely used to isolate vibrations in motors, pumps, and compressors. In factories or data centers, where condensation may form, Sorbothane still performs well if:
– Mounts are enclosed in housings.
– Regular maintenance checks include drying or inspection for swelling.
– Redundant supports are used in high-risk areas.

For example, HVAC systems often use Sorbothane isolators under compressors. While coolant leaks or condensation occur, the rubber housing around the isolator typically prevents direct, prolonged wetting of Sorbothane.

Athletic Shoes and Insoles

Sorbothane is especially popular in premium running and walking shoes due to its cushioning ability. However, the shoe’s design plays a crucial role in protecting the material.

Design strategies include:
– Laminating Sorbothane between moisture-resistant foam layers.
– Using breathable but water-repellent upper fabrics.
– Adding midsole drainage or ventilation channels.

These features allow Sorbothane to perform optimally, even if internal dampness occurs from perspiration.

Medical Devices and Orthotics

In prosthetics, orthopedic inserts, or wheelchair padding, Sorbothane offers comfort and reduces the risk of pressure sores. Since these products may be exposed to sweat or cleaning fluids, manufacturers often encase the dampening cores in waterproof barriers like thermoplastic polyurethane (TPU) films.

This hybrid approach leverages Sorbothane’s performance while protecting it from moisture.

Comparison with Alternative Dampening Materials

Let’s compare Sorbothane’s water resistance with other commonly used damping and cushioning materials.

As seen above, while Sorbothane outperforms many alternatives in damping efficiency, it does not surpass silicone or EPDM in water resistance. For applications where moisture is inevitable, combining Sorbothane with encapsulating materials may offer the best of both worlds.

Best Practices for Using Sorbothane in Moist Environments

To maximize Sorbothane’s performance and longevity when water is a concern, consider the following engineering and usage strategies.

Use Protective Enclosures or Barriers

Encapsulating Sorbothane components in waterproof housings made of plastic, rubber, or metal can prevent moisture ingress. This is common in:
– Marine mount systems
– Industrial control panels
– Sealed electronic devices

The enclosure protects the Sorbothane core while allowing it to function mechanically.

Leverage Hybrid Material Designs

Rather than relying solely on Sorbothane, many manufacturers use composite layers. For instance:
– A Sorbothane core sandwiched between silicone sheets
– Insoles combining Sorbothane, foam, and moisture-wicking fabric
– Industrial pads with Sorbothane bonded to EPDM base layers

These hybrids maintain Sorbothane’s superior shock absorption while shielding it from direct water contact.

Implement Dry Storage and Maintenance Protocols

If Sorbothane components must be used in periodically wet environments:
– Allow them to dry fully between uses.
– Store in low-humidity conditions.
– Clean with dry or slightly damp cloths—never soak.
– Inspect regularly for swelling, softening, or delamination.

For example, orthotic inserts with Sorbothane should not be machine-washed. Instead, wipe clean and air dry in a well-ventilated area.

Select the Right Grade for Your Application

Sorbothane comes in various grades and hardness levels (measured in Shore 00 scale):
– 30–40 Shore 00: Soft, highly absorptive, more prone to moisture retention
– 50–70 Shore 00: Firmer, better structural integrity, slower water absorption

Choosing a harder grade often improves resistance to both mechanical wear and water-related degradation.

Long-Term Effects of Water Exposure on Sorbothane

When used in persistent wet conditions, Sorbothane may experience irreversible changes:

Structural Breakdown

Over time, constant exposure to water weakens the polymer matrix. This can cause:
– Softening and loss of shape retention
– Reduced rebound resilience
– Increased creep under load

Microbial Growth and Odor

Like many organic polymers, damp Sorbothane can become a breeding ground for mold and mildew—especially in warm, dark environments. This not only causes unpleasant odors but can also accelerate material deterioration.

Impact on Adhesion and Bonding

In multi-component designs, Sorbothane is often bonded to other materials using urethane or epoxy adhesives. Moisture exposure can break these bonds through hydrolysis, leading to layer separation or failure.

Industries Where Sorbothane Excels Despite Wet Conditions

Despite its limitations in water exposure, Sorbothane remains indispensable in several fields where moisture is a secondary factor.

Footwear Industry

Running shoes, hiking boots, and work footwear frequently include Sorbothane heel inserts. While these products encounter rain or sweat, they are engineered to limit water contact and allow ventilation. Brands like Saucony and Brooks combine Sorbothane with technologies like moisture-wicking mesh and hydrophobic midsoles to maintain comfort and performance.

Audio and Recording Equipment

In high-end audio studios, Sorbothane is used under speakers, turntables, and sensitive microphones to isolate vibrations. These setups rarely encounter direct water, but air conditioning systems may introduce humidity. Still, due to the dry indoor conditions and protective casings, Sorbothane maintains peak performance for years.

Medical and Rehabilitation Devices

Sorbothane dampeners in prosthetic limbs or patient support systems often face sweat or cleaning fluids. But when encased in durable, washable TPU covers, the Sorbothane core remains protected and effective, contributing to long product life and improved patient comfort.

Conclusion: Is Sorbothane Waterproof?

To conclude: Sorbothane is not waterproof, but it is water-resistant under limited conditions. The material can tolerate brief exposure to moisture, high humidity, and incidental splashes. However, prolonged immersion, constant wetness, or exposure to wet-heat environments will degrade its mechanical properties and reduce its effectiveness.

For applications where water resistance is critical, the best approach is not to avoid Sorbothane altogether—but rather to engineer around it. By combining Sorbothane with protective coatings, sealed housings, or complementary materials like silicone or EPDM, designers can harness its unmatched shock absorption while minimizing moisture damage.

Ultimately, understanding Sorbothane’s limitations is just as important as celebrating its strengths. With smart design practices, Sorbothane remains one of the most versatile and high-performing damping materials available—whether in dry labs or occasionally damp factories.

For engineers, product designers, athletes, and medical professionals, the message is clear: respect water’s impact on Sorbothane, design with moisture in mind, and enjoy its exceptional performance where it belongs—protected, effective, and reliable.

Is Sorbothane completely waterproof?

Sorbothane is not completely waterproof, but it exhibits a high degree of water resistance. While it can withstand exposure to moisture and brief contact with water without significant degradation, prolonged submersion or constant exposure to high humidity can affect its physical properties over time. This is because Sorbothane is a viscoelastic polyurethane material that can absorb small amounts of water through diffusion, potentially leading to swelling or reduced performance in damp environments.

For applications where continuous water exposure is expected—such as in marine or outdoor settings—additional protective measures are recommended. Encasing Sorbothane components in sealed housings or using coatings that repel water can help maintain their integrity. It’s important to note that short-term exposure, like splashing or damp conditions, generally does not compromise Sorbothane’s functionality, making it suitable for many indoor environments with occasional moisture.

How does water affect Sorbothane’s shock absorption properties?

Water exposure can temporarily alter Sorbothane’s viscoelastic behavior, which directly impacts its shock absorption capabilities. When Sorbothane absorbs moisture, its molecular structure may soften slightly, reducing its ability to dissipate energy as effectively as when dry. This diminished performance is more pronounced after extended exposure or when the material is saturated, leading to a loss of damping efficiency and resilience.

However, Sorbothane typically regains its original properties once it has dried completely. The material’s self-recovery ability allows it to return to its standard performance level after moisture evaporates. To prevent performance degradation, it is advisable to minimize prolonged exposure to water and ensure proper ventilation in wet environments. Regular inspection and maintenance can help confirm that the Sorbothane continues to function within its intended parameters.

Can Sorbothane be used in outdoor applications where it may get wet?

Sorbothane can be used in certain outdoor applications, provided it is shielded from direct and sustained water exposure. For example, when used in vibration isolation mounts or protective padding on outdoor machinery, Sorbothane can perform well if installed under covers or within enclosures that limit rain or condensation contact. Its resistance to UV light and moderate temperature fluctuations enhances its suitability for outdoor use under controlled conditions.

Nevertheless, users should avoid placing Sorbothane in environments where pooling water, heavy rainfall, or high humidity is common without protective housing. Supplemental sealing with gaskets or waterproof membranes can significantly enhance its durability in these settings. Testing the specific application under realistic conditions is recommended to ensure long-term effectiveness and material integrity.

Does Sorbothane degrade when exposed to saltwater?

Prolonged exposure to saltwater can accelerate the degradation of Sorbothane compared to freshwater environments. The dissolved salts in seawater may contribute to chemical interactions that alter the polymer matrix and increase the rate of water absorption. This leads to faster swelling, softening, and potential reduction in mechanical performance such as damping and load-bearing capacity.

Despite this, Sorbothane can still be employed in marine contexts if properly protected. For instance, when used in shock mounts on boats or marine equipment, encapsulating the material in a corrosion-resistant, waterproof casing prevents direct contact with saltwater. Regular cleaning and maintenance to remove salt residue from surrounding areas can also extend the useful life of Sorbothane components in such environments.

How should Sorbothane be maintained after water exposure?

After Sorbothane has been exposed to water, it should be wiped dry with a clean cloth to remove surface moisture. The material should then be allowed to air dry in a well-ventilated, low-humidity environment to facilitate the evaporation of any absorbed water. Avoid using heat sources like hair dryers or ovens, as excessive heat may deform or damage the Sorbothane.

Once fully dried, inspect the material for any signs of deformation, softening, or surface deterioration before returning it to service. If the Sorbothane has been exposed to contaminants like salt, oil, or chemicals, a mild soap and water rinse followed by thorough drying is recommended. Regular maintenance helps preserve its functional properties and ensures long-term reliability in damp or humid conditions.

Are there waterproof alternatives or coatings for Sorbothane?

While Sorbothane itself is not entirely waterproof, various protective coatings can enhance its resistance to moisture. Silicone-based sealants, polyurethane coatings, or rubberized encapsulation materials can be applied to create a barrier against water penetration. These coatings help preserve the material’s damping characteristics by reducing moisture absorption, especially in challenging environments.

Additionally, manufacturers sometimes offer Sorbothane components pre-encased in waterproof housings designed for specific industrial or consumer applications. These integrated solutions provide long-term protection while maintaining the core benefits of Sorbothane. Selecting the appropriate coating or enclosure depends on the application’s environmental demands, including humidity levels, temperature range, and exposure frequency.

What practical applications benefit from Sorbothane’s water resistance?

Sorbothane’s water resistance makes it valuable in applications where moderate moisture exposure is expected but full waterproofing isn’t required. It is commonly used in industrial machinery mounts, where occasional spills or washdowns occur, as it maintains structural integrity and vibration damping during short-term wet conditions. Medical devices and laboratory equipment also benefit from its ability to withstand cleaning agents and damp sterilization environments.

Consumer products such as footwear insoles, sports equipment padding, and protective cases for electronics often utilize Sorbothane due to its durability in humid or sweat-exposed conditions. While not ideal for submersion, its ability to handle ambient moisture and occasional splashes enables reliable performance across a broad range of indoor and semi-outdoor uses where shock absorption and comfort are prioritized.