Chemical Resistance – Testing Durability Against Chemicals

Example: Polymer Functional Component for a Military Vehicle
Resistance to Contamination by Fluids

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Background

Military vehicles operate in environments where equipment is frequently exposed to operational fluids and chemical contamination. These fluids may originate from:

• hydraulic systems
• lubricants and gear oils
• fuel
• de-icing agents
• cleaning chemicals
• cooling liquids

Plastic functional components used in vehicles—such as control housings, connector modules, or mounting structures—must maintain mechanical integrity and functionality even after prolonged exposure to such fluids.
To ensure operational reliability, a polymer functional component used inside a military armored vehicle was tested according to:
DIN EN IEC 60068-2-74 – Environmental testing – Contamination by fluids.
This test verifies whether materials and assemblies remain mechanically and functionally stable after exposure to potentially aggressive fluids.

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Test Objective

The objective of the test program was to determine whether the polymer component is resistant to chemical degradation caused by fluids typically present in military vehicle environments.
Potential failure modes include:

• swelling of the polymer material
• stress cracking
• softening or embrittlement
• degradation of sealing interfaces
• loss of dimensional stability

The test simulates long-term exposure to operational fluids encountered during service life.

Device Under Test (DUT)

The DUT was tested both as a complete assembly and with representative material specimens taken from the housing.

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Test Fluids

According to IEC 60068-2-74, representative fluids were selected to simulate realistic exposure conditions in military vehicles.
These fluids represent typical chemical exposures inside military ground vehicles.

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Test Method

The DUT and material samples were exposed to the selected fluids under controlled laboratory conditions.
The procedure included both: complete immersion testing and localized contamination simulation (surface wetting).

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Evaluation Criteria

After exposure, the DUT was evaluated according to the following criteria:
Visual inspection

• discoloration
• surface degradation
• cracking or deformation

Mechanical inspection

• dimensional stability
• mounting interface integrity

Functional inspection

• connector interface function
• electronic operation

Material samples were additionally tested for:

• mass change
• swelling behavior
• hardness variation

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Test Results

Measured mass change of material specimens remained below 0.4 %, indicating excellent chemical resistance of the PA-GF material.

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Engineering Interpretation

The results demonstrate that the polymer component provides sufficient chemical resistance for military vehicle applications.
Key observations:

• The glass-fiber reinforcement significantly reduced swelling effects.
• No micro-cracks or stress cracking occurred.
• Mounting points maintained mechanical strength.

The tested material therefore shows high compatibility with typical vehicle operational fluids.

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Conclusion

The polymer functional component successfully passed the fluid contamination test according to DIN EN IEC 60068-2-74.
The component maintained:

• mechanical integrity
• dimensional stability
• full functional capability

This confirms the suitability of the material and design for use in harsh military vehicle environments where exposure to operational fluids is unavoidable.

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Relevance for Military Equipment Development

Testing according to IEC 60068-2-74 helps manufacturers:

• validate chemical compatibility of materials
• prevent premature component degradation
• ensure long-term operational reliability of military systems

For military vehicle manufacturers, such testing is essential to guarantee that polymer components maintain performance despite exposure to aggressive operational fluids.

Environmental Qualification according to MIL-STD-810H – Method 504.3 (Contamination by Fluids)

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Background

Armored combat vehicles operate in environments where mechanical and hydraulic systems are continuously exposed to fuels, lubricants, hydraulic fluids, cleaning agents, and decontamination chemicals. These fluids may come into contact with electronic components, housings, seals, and connectors during maintenance operations or combat use.
One typical accessory installed in a tank is a control module housing for auxiliary vehicle systems, such as:

• lighting control units
• sensor interface modules
• turret subsystem controllers
• auxiliary power distribution electronics

These devices are often mounted in compartments where accidental fluid exposure can occur due to:

• hydraulic line leaks
• fuel refilling operations
• lubricants used during maintenance
• battlefield contamination

Exposure to such fluids can degrade materials by causing:

• swelling of seals
• deterioration of polymer components
• loss of coating adhesion
• corrosion or electrical failure

To ensure operational reliability, these components must demonstrate resistance to fluid contamination according to MIL-STD-810H Method 504.3 (Contamination by Fluids).

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Test Objective

The objective of the test was to evaluate the resistance of an electronic control module housing and its sealing system when exposed to typical fluids encountered in armored vehicle operation.
The test focused on:

• compatibility of housing materials with operational fluids
• resistance of sealing materials to swelling or degradation
• coating stability when exposed to fuels and lubricants
• continued functionality of the module after exposure

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Device Under Test (DUT)

Equipment:
Auxiliary electronic control module housing for armored vehicles.
Application:
Integration in vehicle electronics bay of a main battle tank.
Construction:
The device was mounted in a representative installation fixture to replicate its position inside the vehicle compartment.

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Test Setup

Testing was conducted in a laboratory environment capable of controlled exposure of equipment to operational fluids.
Test methods included:

• direct fluid application
• partial immersion
• controlled surface exposure

The DUT was exposed to a series of representative fluids typically encountered in armored vehicle operation.

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Test Fluids

Typical fluids defined in MIL-STD-810H Method 504.3 include operational liquids used in military vehicles.
The following fluids were selected for the test:

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Test Conditions

Each fluid exposure was performed according to the guidelines of MIL-STD-810H Method 504.3.
After exposure, the specimen was allowed to dry before inspection and functional testing.

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Post-Test Inspection

Following the fluid exposure tests, the DUT was inspected to detect any material degradation.
Inspection procedures included:

• visual inspection for coating damage
• seal integrity verification
• connector sealing check
• operational functional test of electronics

Additionally, the housing was opened to inspect internal components for fluid ingress.

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Test Results

The module maintained full operational capability after exposure to all tested fluids.

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Engineering Assessment

The resistance to fluid contamination was attributed to the following design features:

• chemically resistant silicone sealing system
• robust epoxy protective coating on aluminum housing
• sealed military-grade connectors
• precision gasket compression preventing fluid ingress

These design elements prevented degradation and maintained the environmental protection of the module.

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Conclusion

The auxiliary electronic control module housing successfully passed environmental testing according to MIL-STD-810H Method 504.3 (Contamination by Fluids).
The equipment demonstrated full resistance to operational fluids typically encountered in armored vehicle environments.
This confirms the suitability of the component for deployment in military vehicle systems where exposure to fuels, lubricants, and maintenance fluids is expected.

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Marketing Summary

Reliable performance even when exposed to operational fluids.
Environmental testing according to MIL-STD-810H Contamination by Fluids verifies that military electronic systems maintain operational functionality even after exposure to fuels, lubricants, hydraulic fluids, and maintenance chemicals.
Through robust materials, advanced coatings, and sealed housing design, manufacturers can ensure long-term durability of mission-critical equipment in demanding military environments.

Fluid Susceptibility Testing according to RTCA/DO-160G Section 11

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The Challenge

Aircraft electronics are frequently exposed to operational fluids during aircraft operation, maintenance, or servicing procedures. These fluids can interact with external surfaces of avionics equipment and potentially degrade materials, seals, or protective coatings.
Typical aircraft fluids include:

• hydraulic fluids
• aviation fuels
• lubricating oils
• de-icing agents
• cleaning solvents

If materials used in electronic assemblies are not sufficiently resistant, fluid exposure may lead to:

• degradation of sealing materials
• swelling of polymer components
• corrosion of metal surfaces
• electrical malfunction or insulation failure

To ensure long-term reliability, avionics equipment must be evaluated for chemical resistance under controlled laboratory conditions. Environmental qualification testing according to RTCA/DO-160G includes a dedicated procedure to assess fluid susceptibility of airborne equipment.
This case study presents the fluid susceptibility testing of a sealed avionics control unit installed in a passenger aircraft system.

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Device Under Test (DUT)

The tested device was an aircraft control electronics module responsible for regulating auxiliary aircraft systems.
The electronics are housed in a sealed aluminum enclosure designed to protect sensitive internal components from environmental exposure.
Key characteristics of the DUT:
Although the device is normally protected inside the avionics bay, the manufacturer required chemical resistance verification to ensure the device remains unaffected when exposed to aircraft fluids.

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Test Objective

The purpose of the fluid susceptibility test is to determine whether exposure to common aviation fluids affects the performance or integrity of airborne equipment.
The test verifies that:

• housing materials resist chemical degradation
• seals and gaskets maintain their integrity
• connector materials are chemically stable
• electronic functionality remains unaffected

Functional verification of the DUT was performed before and after exposure to confirm reliable operation.

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Test Setup

Testing was conducted in a laboratory environment where representative aviation fluids were applied to the DUT under controlled conditions.
The device was positioned in a representative installation orientation, and selected surfaces of the housing and connectors were exposed to various aviation fluids.
The exposure method simulated realistic contamination scenarios that may occur during aircraft operation or maintenance.

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Test Conditions

Testing was performed according to RTCA/DO-160G Section 11 – Fluid Susceptibility.
Typical aviation fluids used in the test program include:
The fluids were applied to the external surfaces of the DUT and allowed to interact with the materials for defined exposure periods.

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Test Procedure

The test program followed the environmental qualification procedure defined in the standard.

1. Pre-Test Inspection
   Prior to exposure, the DUT underwent:
   • visual inspection
   • functional verification
   • doumentation of baseline condition
2. Fluid Exposure
   Representative aviation fluids were applied to:
   • housing surfaces
   • connectors
   • seals and gaskets
   Exposure durations were selected to simulate realistic operational contamination scenarios.
3. Exposure Period
   During the exposure period, the fluids were allowed to interact with the device surfaces.
4. Post-Test Inspection
   Following exposure, the DUT was inspected and tested to evaluate potential material degradation or functional impairment.

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Post-Test Inspection

After completion of the fluid exposure test, the DUT underwent detailed visual and functional evaluation.
Inspection activities included:

• assessment of surface coatings
• inspection of seals and gaskets
• connector condition evaluation
• verification of mechanical integrity
• electrical functional testing

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Results

The avionics control unit successfully completed the fluid susceptibility qualification test.
Key observations:
The anodized aluminum enclosure and selected materials demonstrated excellent resistance to chemical exposure.

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Conclusion

The tested avionics control module successfully passed the fluid susceptibility qualification according to RTCA/DO-160G Section 11.
The test confirmed that:

• materials used in the enclosure resist chemical degradation
• seals and connectors maintain their integrity
• electronic functionality remains unaffected after exposure

These results confirm the device’s suitability for long-term aircraft operation where exposure to aviation fluids may occur during maintenance or operation.

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Why Fluid Susceptibility Testing Matters

Fluid susceptibility testing is essential for ensuring that airborne equipment remains reliable when exposed to operational fluids.
Environmental qualification according to DO-160 helps manufacturers:

• validate material selection for aerospace applications
• detect chemical compatibility issues early in development
• ensure long-term durability of avionics equipment
• support certification of airborne systems

By verifying chemical resistance under controlled laboratory conditions, manufacturers can ensure that aircraft electronics maintain performance and safety throughout their operational lifetime.