what is foam
Foam is formed by trapping many gas bubbles in a liquid or solid. It is an extremely complex system consisting of polydisperse gas bubbles separated by draining films. These films solidify into the cellular structure, and the trapped gas maintains the volume that defines foam. While foams can be solid, liquid, or even semisolid, this paper investigates the potential of solid foams as a building material.
cell structure Solid Foams can be classified in two ways, either open cell or closed cell structures.
â€˘ Open cell structured foams contain pores that are connected to each other and form an interconnected network which is relatively soft. Open cell foam which will fill with whatever it is surrounded with. If filled with air this could be a relatively good insulator, but if the open cells fill with water, insulation properties would be reduced. Foam rubber is a type of open cell foam. â€˘ Closed cell foams do not have interconnected pores. Normally the closed cell foams have higher compressive strength due to their structures. However, closed cell foams are also generally denser, require more material, and consequentially are more expensive to produce. The closed cells can be filled with a specialized gas to provide improved insulation. The closed cell structure foams have higher dimensional stability, low moisture absorption coefficients and higher strength compared to open cell structured foams. All types of foam are widely used as core material in sandwich structured composite materials. 2
closed cell aluminum
gas injected aluminum
Foam is used across a spectrum of disciplines and industries. For example, foam has replaced wood in surfboards. It is regularly used in furniture. It is replacing previously considered industrial materials in large scale sculpture. It is also the civil engineers choice for earth fill in the form of geofoam. a product that is stable, 90% air, cheap, and non-toxic.
rigid board insulation
spray fill insulation
concrete insulation panel
expanding polyurethane insulation
decorative elements and formwork for complex geometries 6
Foam has been accepted by the building industry for its efficiency and sustainable aspects; however, The current industry application of foam is limited to insulation and decorative elements.
ABS ACRYLONITRILE BUTADIENE EPS EXPANDED POLYSTYRENE
• most InexpensiveMHighly Insulative • Able to cut with Hotwire • CFC - HCFC free • Manufactured all over the world • resistant to water • Commonly used as earth fill, wall insulation, and formwork for GFRG, Fiberglass, ect...
XPS EXTRUDED POLYSTYRENE
• Some trade names are “Styrofoam”, “INSUboard”, “Foamcore” • Because of the extrusion process, XPS is denser than EPS • Commonly known in the light blue and light pink color
• Open Cell Structure - meaning not water tight • Can either be a 2 part liquid that foams on site, or purchased as rigid board • Expanding PU sticks to anything it touches - commonly used as a filler and glue
PV POLYVINYLCHLORIDE EPP POLYPROPYLENE
Expanded Polystyrene is commonly used for packaging foam, earth fill, surf board blanks, insulation material, and molds. Its an obvious choice for its sustainable aspects, ease of cutting, high insulation value, and low cost.
EPS Foam Unit height: 8’-0” width: 4’-0” depth: 12” weight : 32 lbs
Standard CMU height: 8” width: 16” depth: 8” weight : 32 lbs
scale of unit diagram 12
EPS foam is 90% air. All of this air is trapped in the closed cells producing a zero thermal drift condition. This means the foam is highly insulative. Because of its light weight, transportation is a problem. Its large volume and light weight make it difficult to ship efficiently, and therefore eps foam manufacturers are scattered across the world.
Technological advances including CAD ensures that minimum waste occurs during the cutting phase so large amounts of expanded polystyrene are not discarded. Even the scrap which is discarded is recycled so it is a win win situation for the environment. Expanded polystyrene is completely free of CFCâ€™s and other harmful gases, and the environmentally friendly pentane is currently being used as its blowing agent.
expanded polystyrene beads
EPS is made of pre-expanded polystyrene beads. Sheets are commonly packaged as rigid panels (size 4 by 8 or 2 by 8 square feet in the United States), which are also known as “bead-board”. Thermal resistivity is usually about 28 m•K/W (or R-4 per inch in American customary units). Some EPS boards have a flame spread of less than 25 and a smoke-developed index of less than 450, which means they can be used without a fire barrier (but require a 15 minute thermal barrier) according to US building codes. A growing use of EPS in construction are Insulating concrete forms. The density range is about 16 - 35 kg/m3. 17
coatings the lack of tensile strenght in foam means it requires a coating. Most commonly OSB in the building industry, though EPS foam is not limited to this as its only coating.
• Some products (such as styrospray) do not eat away at the foam. • Potentially used as a spray pre coat for a stronger coat on top • medium value shore strength • no limitations on geometry
• Cheap and Easy • does not bond with the foam and could be removed easily for recycling purposes • no limitations on geometry
Epoxy EXTRUDED POLYSTYRENE
• Some trade names are “Styrofoam”, “INSUboard”, “Foamcore” • no limitations on geometry 18
• EPS foam requires a second coating to resist the head and chemicals of the epoxy eating away at the cell structure. • Commonly used with EPS as the formwork. Similar in comparison to GFRG • Potentially interior and exterior use • no limitations on geometry
Carbonfiber EPOXY RESIN
• EPS foam requires a second coating to resist the head and chemicals of the epoxy eating away at the cell structure. • Extremely strong tensile shore strength • Extremely light weight • Potentially interior and exterior use • no limitations on geometry
• Commonly used in conjunction with EPS foam, but in these cases the foam serves as a thermal break, not the construction unit.
EIFS Synthetic Stucco
• Extremely cheap and efficient exterior coating • no limitations on geometry
• Very labor intensive. • no limitations on geometry
GFRG GLASS FIBER REINFORCED GYPSUM
• Commonly used with foam as the mold to make the part. It is potential that the foam remains and serves as the compression wall member, as well as insulation • no limitations on geometry
GWB GYPSUM WALL BOARD • Great for Interior applications • limited to planar and ruled surfaces • must be glued on to foam
OSB ORIENTED STRAND BOARD • Most common use in SIPs panels. • Limited to planar surfaces