POLYURETHANE FOAM

 

There are many types of Foam: Polystyrene, Neoprene, Polyethylene, Polyester-based Polyurethane, Polyether-based Polyurethane, and others.  Each is a synthetic plastic with two very desirable properties: easily malleable or shapeable , and capable of  “giving” and returning to its original shape.

HISTORY:  The First plastic was developed shortly after the American Civil War by John Hyatt and was named celluloid.  As an all-purpose plastic, celluloid found use in applications as far ranging as buttons, combs, and billiard balls.  It’s claimed that Hyatt played a large part in preserving the African elephant , since one of the major materials celluloid replaced was ivory.

More than fifty years passed before plastics grew to assume commercial importance.  In 1909, L.H. Backelund developed  Bakelite , which soon became widely used in insulation, phonograph records , and decorative applications.  Bakelite’s success turned plastics research from a laboratory curiosity into a major growth industry.  There were, it seems, big dollars to be made.

The birth of ester foam:  The plastics research, along with parallel breakthroughs in the development of a synthetic rubber, led almost by accident to the creation of commercially usable foams. The first was polyester-based polyurethane foam (now known as ester foam), developed in Germany during the late 40’s and early 50’s and still marketed today.

The birth of Polyurethane foam:  In the late 50’s, Polyether-based polyurethane foam (now know as polyurethane foam) cleared its last hurdle toward commercial production.  There had been problems with stabilizing the foam during the curing process ,   where the foam fixes.  But the refinement of a new silicon brought polyurethane foam into full-scale production.

Polyurethane vs. Ester:  Polyurethane (Ether) foam shows several advantages over the older, Ester foam:

1.      Greater stability in humid environments.  Dampness promotes ester foam disintegration.

2.      Because of the different raw materials used, Polyurethane foam usually cost less than Ester foam.

3.      When comfort is a prime consideration, Ester  foam’s rough, scratchy surface. Is less desirable than the smoother, softly polyurethane surface.

4.      Although both materials are Open Cell, Ester foam cells are generally smaller in structure; therefore they have a tighter airflow.  In effect, polyurethane is spongier and more yielding than ester foam.

Polyurethane foam is available in scores of formulations for a wide variety of uses.

WHAT IS POLYURETHANE FOAM

Component chemicals.  Polyurethane form is a mixture of several chemicals:

POLYOL is an organic compound with a high molecular weight.  Polyol makes up the largest percentage of the foam formulation.

TDI, (toluene disocyanate) is an organic compound of lower molecular weight than polyol. TDI forms an exceptionally strong cross-link structure with the polyol, almost a super molecule.

Water reacts with the TDI to release carbon dioxide gas, which helps the mixture rise.

Freon II and Methylene Chloride these compounds boil to add additional gas to the mix.  Without the gas from these compounds, the foam would be very hard.

Amine-Type Catalyst helps to energize the water/TDI reaction.

Organo-Tin Catalyst helps to energize the polyol/TDI reaction.

These seven main ingredients make up the basic foam formulation.  The extra proportions depend upon just what type of foam is being produced.  Other chemicals can be added for special purposes: color, combustion modification, high resiliency, ect.

As you might expect, turning out a finished product with the correct specifications demands a comprehensive knowledge of the details of the chemical interactions.  And a reliable, top-quality product comes only with experience.