Polyurethane Foam 101

Polyurethane foams are made from a reaction of isocyanates (derived from petroleum sources - primarily benzene) with polyols (long-chain alcohols derived from vegetable sources) along with catalysts and other process additives.

Another key ingredient of polyurethane foam is the "Blowing Agent." The blowing agent could be a very-low boiling-point solvent such as HFC-245fa, pentane, methylene chloride, or Carbon Dioxide (created as a by-product of the chemical reaction between isocyanate and polyol making foam).

The final, cured properties of polyurethane foam are directly related to:

• The isocyanate and polyol used in making foam
• The foam-making process itself
• The blowing agent used
• The resulting final density of the finished product

A wide variation is possible within all of these constraints.

Each of these attributes will influence the performance of particular polyurethane foam in a specific application, but the most significant attribute influencing the performance of rigid polyurethane foam in almost any application is density (however you measure it, in terms of mass per unit volume of material).

Polyurethane foam can be divided into two categories, closed cell and open cell foam. The closed cell foams are plastics where each bubble that creates the foam is continuous and completely spherical or oblong. Open cell foams are plastics where the cell walls are incomplete and contain holes through which liquid and air can easily travel.

Foam Production

• Polyurethane foams are always made by combining polyols and isocyanates. However, the ways these chemicals are combined may vary.
• Most producers of foams use foam-mixing guns to dispense reacting chemicals. These guns use either mechanical mixing, or high-pressure impingement-mix heads to combine fast-reacting foams for spray use or for molding parts.

The GP Difference

• Foam chemicals are fully-mixed in large batches before insertion into molds
• Buns are put through an extensive stress-relieving process to eliminate warp and/or bow
• Buns can be up to 30" x 48" x 120" in size, depending on foam density. Please feel free to inquire about custom block size availability and cost.
• Density-gradient throughout sheets and buns is less than +/- 10% of nominal density (often closer to +/- 5%)
• Buns are saw-cut on horizontal bandsaws to create sheets
• No mold release is used in making buns, hence no contaminants for other bonding and laminating processes
• Surface finish is smooth, consistent
• We can provide machine tolerance from .005" to 0.060"
• Sheets are cut to be square and true (starts with bun-trims process)