The FR-3700 Flame-Retardant Core for Aerospace and Nuclear Industries

The FR-3700 is a CFC-free, rigid, closed-cell, flame-retardant polyurethane foam with densities ranging from 3 to 40 pounds per cubic foot. Its cellular structure and cross-linked resin allows it to have a high strength-to-weight ratio. The closed-cell structure of the LAST-A-FOAM® FR-3700 has great resistance to water absorption, and it does not split, crack, or swell on exposure to water. This non-abrasive series can be machined with standard high-speed steel (HSS) cutting tools. It can also be cut cleanly with traditional wood-carving tools and water jets. This flame-retardant polyurethane (PU) foam extends its support particularly to the following industries.


The requirements of aircraft BMS 8-133 is met by the FR-3700 meets. This rigid, polyurethane foam is comparable to the FR-6700 in flammability performance, temperature resistance and strength. However, the FR-3700 is considered to be tougher (less friable) for cutting crisper edges.


The high-density rigid polyurethane FR-3700 foam is used to simulate human bone as a test medium within the medical device industry.


The FR-3700 foams are ideal for transportation of extremely hazardous waste and nuclear material applications. It is possible to engineer the FR-3700 when it is used as an impact- and fire-insulation liner in transport containers in order to provide the ultimate in fire and collision protection for outperforming wood, hazardous cargo and other polymeric materials. The customized design of the FR-3700 allows predictable impact-absorption performance under dynamic loading. It also provides an intumescent char layer that is capable of insulating and protecting hazardous materials, even when exposed to pool-fire conditions.

To be more specific, the FR-3700 foam has a solid history of being successfully used in radioactive materials (RAM) transportation packages. The regulations governing RAM packages often need energy absorption of 30-foot free drops and exposure to a 1,475 °F, 30-minute fire under accident conditions. The FR-3700 series foam is considered to be one of very few materials capable of supporting the RAM package design in mitigating both thermal and mechanical energy.


The LAST-A-FOAM® 3700 Performance Core Series can be used for constructing weatherproof, durable radomes. Transparent to radio signals and impervious to moisture, they protect aerospace, marine and recreational microwave antennas. Their high Tg suits prepregs that cure at higher temperatures. General Plastics’ Production Services team use fiberglass prepregs from specs to fabricate completed radomes.


The key advantages of the FR-3700 area are as follows:

  • Flame retardant
  • Inert and stable
  • High strength-to-weight ratio from cross-linked resin
  • Easily shaped with common woodworking tools
  • Performs well as wood replacement
  • Will not support fungal growth
  • Resistant to most solvents and chemicals


The main applications of the FR-3700 include:

  • Load bearing
  • Models and design prototypes
  • Composite core, especially where flame retardation is important
  • Impact- and fire-insulation liner for hazardous waste containers
  • Vacuum form dies and mold patterns
  • Radioactive materials (RAM) transportation packages
  • Core material for composite prostheses
  • Artificial human bone test media
  • Honeycomb edge closeout for aircraft interior sandwich panels used in lavatories, galleys, passenger cabin class dividers and overhead storage bins

Sizing Chart


FR-3703 3 24 48 96
FR-3704 4 24 48 96
FR-3705 5 24 48 96
FR-3706 6 24 48 96
FR-3707 7 24 48 96
FR-3708 8 24 48 96
FR-3710 10 24 48 96
FR-3712 12 18 18 100
FR-3718 18 18 18 100
FR-3730 30 12 24 96
FR-3740 40 10 18 100
FR-3740 40 10 24 100



FR-3703 48 60 120 240
FR-3704 64 60 120 240
FR-3705 80 60 120 240
FR-3706 96 60 120 240
FR-3707 112 60 120 240
FR-3708 128 60 120 240
FR-3710 160 60 120 240
FR-3712 192 45 45 250
FR-3718 288 45 45 250
FR-3730 481 30 60 240
FR-3730 481 45 45 250
FR-3740 641 25 45 250
FR-3740 641 25 60 250

Shown are maximum standard stock sizes based on density. Custom sizes are available. Cut sizes are available from 0.125 inches (3.175 mm) up to standard stock heights as listed above.

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