The material. Polymer foams are made by the controlled expansion and solidification of a liquid or melted through a blowing agent; physical, chemical, or mechanical blowing agents are possible. The resulting cellular material has a lower density, stiffness, and strength than the parent material, by an amount that depends on its relative density—the volume fraction of solid in the foam. Rigid foams are made from polystyrene, phenolic, polyethylene, polypropylene, or derivatives of polymethylmethacrylate. They are light and stiff and have mechanical properties that make them attractive for energy management and packaging and for lightweight structural use. Open-cell foams can be used as filters, closed-cell foams as flotation. Self-skinning foams, called structural or syntactic, have a dense surface skin made by foaming in a cold mold. Rigid polymer foams are widely used as cores of sandwich panels.
Composition
Hydrocarbon.
|
General properties
|
|
Mechanical properties Young’s modulus |
0.08 |
– 0.2 |
GPa |
|
Yield strength (elastic limit) |
0.4 |
– 3.5 |
MPa |
|
Tensile strength |
0.65 |
– 5.1 |
MPa |
|
Compressive strength |
0.95 |
– 3.5 |
MPa |
|
Elongation |
2 |
– 5 |
% |
|
Hardness—Vickers |
0.095 |
– 0.35 |
HV |
|
Fatigue strength at 107 cycles |
*0.455 |
– 2.8 |
MPa |
|
Fracture toughness |
*0.0066 |
– 0.048 |
MPa. m1/2 |
|
Thermal properties Glass temperature |
67 |
– 157 |
°C |
|
Maximum service temperature |
67 |
– 157 |
°C |
|
Thermal conductor or insulator? |
Good insulator |
||
|
Thermal conductivity |
0.027 |
– 0.038 |
W/m. K |
|
Specific heat capacity |
1120 |
– 1910 |
J/kg. K |
|
Thermal expansion coefficient |
20 |
– 70 |
p, strain/°C |
Rigid polymer foam is used as the core of the GFRP sandwich shell for ultra-lightweight designs such as this glider.
Typical uses. Thermal insulation, cores for sandwich structures, panels, partitions, refrigeration, energy absorption, packaging, buoyancy, floatation.
