Extruded vs Expanded foam What's the difference

There are many iterations of foam: rigid, plain styrofoam sheets, extruded, and expanded. The afterwards two, extruded and expanded, will be the most popular with regards to home building projects in all probability, but what’s the difference?

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Expanded called Beadboard Often, sheets are created from stable beads of polystyrene. These beads will be expanded by injecting and dissolving handful of pentane gas in to the base materials during production. Under temperature, the gas expands the beads to form closed cells. These cells are approx. 4o times the quantity of the initial bead, and can become molded to form insulation boards, blocks, or shapes. While a closed cell structure and resistant to water even now, it isn't as resistant to moisture as XPS is going to be, but that could be splitting hairs. It really is generally cheaper than it ‘extruded’ cousin and scientific tests have shown EPS to have a lower impact on the surroundings and can be recycled easier than XPS.

Extruded, this foam begins with stable polystyrene crystals. The crystals, and also other additives will be fed into an extruder. Within the extruder itself, ruthless and heat form the mixture right into a plastic fluid. This thick liquid plastic is then forced right into a die where it emerges and expands to a foam. This foam is shaped, cooled, and cut. Due to extrusion process, XPS can maintain its thermal and/or physical properties more uniformly than EPS and makes an excellent substitute for corrugated cardboard, it gained in status amongst architectural modelers thus. Another benefit of XPS is usually it’s strength: because it put through higher compression through the manufacturing process, it really is slightly more rigid than EPS. Also, because the closed cell structure is definitely finer than that of EPS, XPS resists wetness better. I suppose once this became the defacto amongst these modelers, it migrated over to railway modelers. Manufacturers add dye often, which has no influence on the XPS other than identification of the manufacturer.

So which is better? Well, after reading numerous content it does certainly seem that Extruded foam includes a few slight positive aspects after all. But let me note the focus on slight. For some railway modelers with simple layouts, there probably is not any difference since the foam will be covered anyhow by other materials such as for example plaster. In the end, it seems the three main variances are: Expense, where EPS gets the advantage; Durability, where XPS stacks up a little better and retains its rigidity, and finally, Moisture resistance, where once again, XPS has a minor advantage.

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