What is the purpose of carbon dioxide in polyurethane foam?

The carbon dioxide is a gas, which is responsible for blowing the polymer into a foam. Several secondary reactions occur, when products of the primary reactions react with isocyanate to produce polyurea, biuret, and allophanate.

How do you increase the density of foam?

Higher amount of water leads to foams with larger cells. Moreover, water increases the temperature during the foaming due to the reaction heat of blowing reaction. This also promotes faster foaming, because the solubility of physical blowing agent is temperature dependent.

What is pouring foam?

A two-part liquid yielding a high strength, rigid, closed-cell foam for cavity filling and buoyancy applications. The foam may be used to fill cavities from 50mm to 300mm wide. The liquid is extremely simple to use.

How is polyurethane synthesized?

The synthesis of flexible PU foams often involves two major steps: blowing and gelling. From the blowing reaction, carbon dioxide and urea are produced, which expand and are entrapped by the reaction mixture, while the urethane linkages are formed by reactions of the isocyanate and hydroxyl group of the polyol.

What is polyol used for?

Polyols are reacted with diisocyanates to produce polyurethanes. Polyurethanes are used to make flexible foam for mattresses and seating, rigid foam insulation for refrigerators and freezers, elastomeric shoe soles, fibers (e.g. Spandex), coatings, sealants and adhesives.

How to increase the cure time of polyurethane?

It is well known that the addition of a small amount of benzoyl chloride to a polyol blend vastly increases the cure time of the polyurethane. This trick can be used when a batch has too much catalyst and reacts too quickly. It is also useful when the polyurethane is being applied in a climate with high ambient temperatures.

Can I add benzoyl chloride to polyurethane?

A note on retardation of the urethane reaction by benzoyl chloride. It is well known that the addition of a small amount of benzoyl chloride to a polyol blend vastly increases the cure time of the polyurethane. This trick can be used when a batch has too much catalyst and reacts too quickly.

How do you know when the foam is ready to use?

The foam then rises toward the top of the cup and outward (see image). The point when the foam stops rising is the ‘rise time’. The foam will still be viscoelastic at this point and it is touched repeatedly with the side of a spatula or the tip of a toothpick.

What are the extra ingredients in polyurethane?

Extra ingredients such as dyes/pigments, catalysts, blowing agents and flame retardants are added to the polyol blend. If the polyurethane is to be a foam, it will have some water in the polyol blend which reacts with the diisocyanate to form CO 2 as a blowing agent (bubbles).