Glossary and Basic Review of Polyurethanes



Glossary and Basic Review of Polyurethanes

Polyols:

Hydroxyl Number (OH Number) : expressed in mg KOH/g, represents the relative content of hydroxyl groups in one gram of polyol as determined by titrating the polyol against KOH.  Lower hydroxyl numbers indicate longer polyol chain lengths and higher molecular weight. 

Functionality is based on the initiator used in the polyol manufacture

Equivalent Weight: the mass of a compound per reactive site.  In polyols, this number is Pan average since polyols are polymers with a range of molecular weights, functionalities, and hydroxyl values.

| Equivalent Weight =   |    56,100†_   |

| | OH Number |

  †56,100 represents the molecular weight of KOH in mg/mole

Equivalents (of a polyol): represents the reactive sites available to react with an equal number of isocyanate Equivalents

|Equivalents of Polyol =   |    Mass of Polyol_   |

| | Equivalent Weight |

Molecular Weight (MW): (average) of a polyol is determined by multiplying the equivalent weight by the functionality.

MW = Equivalent Weight x Functionality

Polyol Types offered by Tri-iso:

Polyether Polyols

 Polytetramethylene glycol Polyols (PTMEG)

 

 High Performance Polyester Polyols (Polycaprolactones)

 High Performance Polyester Polyols (Castor)

Super Hydrophobic Polyols

Polycarbonate Diols

Isocyanates:

   

Isocyanate Equivalent Weight= number of grams of an isocyanate or prepolymer in order to have one equivalent of isocyanate groups (NCO).  One equivalent of NCO groups = 42.02 grams

 

%NCO:  represents the weight percent of an isocyanate or prepolymer comprised of NCO. 

| %NCO =   |    4202†_   |

| | NCO Equivalent Weight |

  †4202 represents the molecular weight of NCO in mg/mole

 Functionality : represents the number of NCO groups per isocyanate or prepolymer.  Typically, lower functionality yields less crosslinking, which results in more flexible, softer products, and higher functionality yields higher crosslinking and resulting stiffer, harder products.

 

Types of Isocyanates offered by Tri-iso:

Methylene diphenyl diisocyanate (MDI) and Toluene diisocyanate (TDI)

 

Hexamethylene diisocyanate Trimer (HDI Trimer)

Please contact your Tri-iso Technical Sales Representative if you would like additional information or samples of any of the polyols or isocyanates offered by Tri-iso. Alternatively, please send an email to jscott@tri-

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