If you have ever wondered what actually goes into a polyurethane foam, the answer starts with two ingredients: an isocyanate and a polyol. The isocyanate gets a lot of attention, but the polyol is just as important — it is the backbone that decides whether your foam is a soft pillow or a rigid insulation board.
What is a polyol?
A polyol is simply an alcohol with multiple reactive hydroxyl (–OH) groups. Those –OH groups react with the isocyanate to form the urethane linkages that give polyurethane its name. The structure of the polyol — how big it is and how many reactive groups it has — sets the character of the finished material.
The two main types of polyol
Polyether polyols
The most common type, prized for flexible foam. They offer excellent hydrolytic stability, low viscosity and easy processing, which is why they dominate furniture foam, mattresses, automotive seating and packaging. Explore our polyether polyols.
Polyester polyols
These bring higher rigidity, abrasion resistance and chemical resistance. They suit rigid foam, shoe soles, coatings and adhesives — anywhere strength and durability matter more than softness.
The numbers that matter
- Hydroxyl (OH) value: a measure of how many reactive –OH groups are present. It drives reactivity and crosslink density.
- Functionality: the average number of reactive groups per molecule. Higher functionality pushes toward rigid, highly crosslinked networks.
- Molecular weight: higher molecular weight generally means a softer, more flexible product.
Together these three numbers let a formulator dial in firmness, density and resilience.
Specialty polyols
Graft or polymer polyols boost load-bearing capacity for high-resilience foam, while bio-based polyols — such as those derived from castor oil — offer a more sustainable route without sacrificing performance.
Choosing the right polyol
Start from the product you want: soft and flexible points to a polyether polyol; hard and durable points to a polyester. Then refine by OH value and functionality, and pair with the correct isocyanate — TDI for flexible foam, MDI for rigid. Our team can recommend a grade against your target specification.
Creston Chem supplies polyols, TDI, MDI and polyurethane additives to manufacturers across India. For grade-specific guidance, talk to our desk.