PPG PR1422 vs. PR1440: What's the Difference Between AMS-S-8802 Type I and Type II Aircraft Fuel Tank Sealants?

Aircraft fuel tank sealants are often identified by specifications such as AMS-S-8802 Type I or AMS-S-8802 Type II, but many aircraft maintenance technicians are unsure what these designations actually mean. Since both types are qualified under the same aerospace specification and offer similar sealing performance, it's easy to assume they're interchangeable. In reality, the "Type" designation refers primarily to the sealant's curing chemistry and qualification.

The History of AMS-S-8802

Before 1999, aircraft fuel tank sealants were qualified under the military specification MIL-S-8802. As part of the military's transition to industry-managed standards, responsibility for the specification was transferred to SAE International, where it became AMS-S-8802. Although the governing organization changed, the performance requirements for qualified sealants remained substantially the same.

Why Was Type II Introduced?

Type II was not introduced because Type I sealants were failing or considered inferior. Instead, SAE expanded the specification to recognize an alternative curing chemistry while maintaining essentially the same performance requirements.

The primary distinction is the curing system:

Both types are designed to provide long-term resistance to aviation fuels, hydraulic fluids, water, and environmental exposure while remaining flexible after curing.

Why Didn't PPG Simply Reformulate PR1422?

Aircraft sealants are qualified products. If PPG had changed the chemistry of PR1422 from a Type I formulation to a Type II formulation, it would no longer have been the same qualified material.

Thousands of aircraft drawings, maintenance manuals, and OEM engineering specifications specifically reference PR1422 or AMS-S-8802 Type I. Changing the chemistry under the same product name could have affected those approvals.

Instead, PPG introduced PR1440 as a separately qualified Type II sealant while continuing to manufacture PR1422 for applications that require a Type I product.

Why Is PR1422 Still Available?

One of the biggest misconceptions is that Type I sealants have been discontinued worldwide.

In reality, PPG announced the withdrawal of PR1422 only in Europe due to the impact of REACH regulations on certain raw materials used in the Type I formulation. Customers in the United States and many other regions continued to have access to PR1422, while PR1440 became the recommended replacement in Europe.

As a result, PR1422 remains widely available throughout North America and continues to be specified for many maintenance applications.

Is PR1440 Better Than PR1422?

Not necessarily.

PPG markets both products as high-performance aircraft fuel tank sealants that provide:

• Excellent adhesion

• Outstanding fuel resistance

• Resistance to aviation hydraulic fluids

• Flexible cured properties

• Service temperatures from approximately −65°F to +250°F (-54°C to +121°C)

The primary distinction is the curing chemistry and the specification type—not a dramatic improvement in sealing performance.

Which One Should You Use?

The correct sealant is determined by the aircraft manufacturer's approved maintenance data.

• If the Aircraft Maintenance Manual (AMM) specifies AMS-S-8802 Type I, a qualified Type I sealant such as PPG PR1422 should be used.

• If the manual specifies AMS-S-8802 Type II, a qualified Type II sealant such as PPG PR1440 should be used.

• If the documentation simply specifies AMS-S-8802, consult the OEM maintenance data or the applicable Qualified Products List before substituting one type for another.

Aircraft maintenance technicians should never assume that Type I and Type II are interchangeable unless the approved maintenance documentation specifically permits substitution.

Conclusion

AMS-S-8802 Type I and Type II sealants are both proven aircraft fuel tank sealing systems with similar performance characteristics. Their primary difference lies in the curing chemistry and the qualification requirements established by the aerospace specification.

Understanding the distinction between Type I and Type II helps maintenance professionals select the correct sealant for the application while remaining compliant with OEM maintenance instructions and applicable aerospace standards.