Polyurethane is one of the most versatile materials in manufacturing. The same basic chemistry gives soft mattress foam, rigid insulation in refrigerators and panels, durable shoe soles and strong adhesives. If you make any of these, your raw materials fall into a few families.
The basic reaction
Polyurethane forms when a polyol, an alcohol with several reactive hydroxyl groups, reacts with an isocyanate. Catalysts control the speed, surfactants stabilise the foam cells, and a blowing agent, often water reacting to release carbon dioxide, creates the foam structure.
Polyols
- Polyether polyols are the most widely used. Flexible-foam grades, often around 3000 molecular weight, give soft and resilient foam. Rigid grades give stiff, closed-cell insulation.
- Polymer polyols (POP) contain fine styrene-acrylonitrile particles that raise the hardness and load-bearing of flexible foam without raising its density.
- Polyester polyols are used where better solvent and abrasion resistance are needed, such as in some coatings, adhesives and shoe soles.
Isocyanates
- TDI 80/20 (toluene diisocyanate) is the standard isocyanate for flexible slabstock foam in mattresses and furniture.
- Polymeric MDI is used for rigid foam insulation, panels, spray foam and wood binders. It is typically specified by NCO content, commonly around 31%.
Blended polyol systems
Many converters prefer a blended or formulated polyol: a ready-to-use mix of polyol, catalysts, surfactant and blowing agent that is designed to react with a matching isocyanate. It cuts mixing errors, shortens setup and gives a consistent foam. Systems are tailored by application, such as refrigerator insulation, sandwich panels, pipe sections, spray foam or shoe soles.
PU adhesives
One- and two-component polyurethane adhesives bond foam to foam, assemble footwear and laminate panels and flexible packaging films. Choose solvent-based, solvent-free or hot-melt types according to your process and local regulations.
Buying and handling tips
- Isocyanates react with moisture. Keep drums sealed, store them dry and within the recommended temperature range.
- TDI and MDI are hazardous and are shipped as regulated cargo. Confirm packing, labelling and shipping line acceptance.
- Check shelf life, especially for blended systems, and plan orders around it.
- Ask for the TDS, COA and SDS, and run a trial pour before a full production switch.
Rudra International supplies polyether and polymer polyols, blended polyol systems, polymeric MDI, TDI and PU adhesives. See the polyurethane solutions range.