This temperature-resistant, two-component, synthetic rubber compound is used for sealing and repairing fuel tanks and fuel cell cavities. This compound is designed for an operating environment that may vary between -65F and +250F. It is produced in the following classifications:

Class A Sealing material suitable for brush application

Class BSealing material suitable for application by extrusion gun and spatula

Class C Sealing material suitable for faying surface sealing

Dash numbers after the classification code indicate the allowed application time in hours before the curing cycle will have progressed to the point where it is no longer feasible to apply that particular batch of sealant. Class A dash numbers are 1/2 and 2. Class B dash numbers are 1/2, 2, and 4. Class C dash numbers are 20 and 80 (8 hours of application time with the remaining time allowed for working the material).

Example: Class A-2 designates a brushable material having an application time of 2 hours. Class B-1/2 designates an extrusion gun material having an application time of 1/2 hour. Class C-20 designates a faying surface sealant with an application time of 8 hours and a working life of 20 hours.

This accelerated, room temperature, curing synthetic rubber compound is used in sealing metal components on weapons and aircraft systems for protection against corrosion. This sealant contains magnesium chromate as a corrosion inhibitor. The classification of this sealant compound is of the following types:

Type II For extrusion application, gun or spatula

Dash numbers after the type code are used to designate the maximum application time in hours.

Type I dash numbers are 1/2 and 2. Type II dash numbers are 1/2, 2, and 4. The Type III dash number is 1.

Many of the sealants previously discussed maybe flammable or may produce toxic vapors. When you are using any material designated as flammable, all sources of ignition must be at least 50 feet away from the location of the work. Toxic vapors are produced by the evaporation of solvents or the chemical reaction taking place in the curing sealants. When you are using sealants in confined spaces, such as fuel cells, fuselage, or wing sections, adequate local exhaust ventilation must be used to reduce the vapors below the maximum allowable concentration. The vapors must be kept at that level until repairs have been completed. Do not eat or smoke when you are working with sealants.

RECOMMENDED READING LIST 

NOTE: you need to be sure that you are studying the latest revision.

General Advanced Composite Repair Manual, Tech Order 1-1-690, Secretary of the Air Force, Washington, D.C., 1 August 1990, Sections 1 through 6.

Structural Sandwich Composites, MIL-HDBK-23A, Department of Defense, Washington D. C., June 1974, Chapters 15 and 16.