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What is the difference between expanded polystyrene foam and extruded polystyrene foam

asked 2016-05-30 03:37:08 -0500

These foams are commonly used to make surfboards- how do they differ?

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answered 2016-05-30 03:53:24 -0500

updated 2016-05-30 10:36:59 -0500

EXPANDED (beaded foam) commonly known as Styrofoam:Expanded Polystyrene (EPS) open cell foam - used in molded boards

Used for molded surfboards and hand shaped surfboards. Expanded polysterene is inexpensive and light weight (1 to 2 lb.per cubic foot).

It is made mainly for insulation applications in the construction industry, because the cost is low compared to other foams.

The characteristics of this foam are like the ones you see in beer coolers and Christmas tree ornaments. It has many small spheres of foam bonded together (the reason it is also called beaded foam). The structure is based on an open cell that allows water to penetrate and travel inside the foam.

This foam comes in different cell sizes with different water absorption properties.

The disadvantages are the water aspiration, poor flex patterns, and low resistance to compression. Because it breaks easily, it requires excessive fiberglass reinforcement. The appearance of spheres in some (beaded) foam is noticeable. The small visible spheres also make the board difficult to fine shape and airbrush.

Extruded Polystyrene Foam (XTR)

XTR Closed cell extruded Polystyrene foam

XTR foam is a closed cell foam extruded at high speeds using expensive machinery.

The main advantages are strength and imperviousness to water absorbtion. It is very resistant to impact and compression.

One of the most significant and most misunderstood qualities of the close cell construction is that almost no water absorption occurs in open dings (less than 1%). This means that a surfboard with a ding will not gain weight or change color resulting in longer memory (resilience) of the materials.

Also, the flex patterns of extruded foam when glassed properly can result in enormous advantage for a positive responsive surfboard. It generates more speed that any other construction.

The reason closed cell foam has not been popular with surfboard builders is the delaminations or bubbles that occurred mainly right under the front foot before ThermoVent was introduced by Epoxy Pro in 2001..

Epoxy Pro has a patent pending system called THERMOVENTING that solves the delamination problem 100%.

XTR foam can be hand shaped or CNC machine shaped for production.

XTR extruded foam has a nice presentation. The foam has high whiteness and can be airbrushed for a custom surfboard.

Note: Epoxy Pro only uses only EXTRUDED closed cell foam. XTR is a trademark of Epoxy Pro.

Source: http://www.epoxysurfboards....

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Asked: 2016-05-30 03:37:08 -0500

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Last updated: May 30 '16