Molecular weight oligo-polyols

Equation 3.3 is a fundamental equation in oligo-polyol chemistry, having very important practical applications. The number average molecular weight, of an oligo-polyol is easily calculated with this formula, if the functionality and the OH are known ... 

OH = hydroxyl number of oligo-polyol in mg KOH/g, Mn = number average molecular weight (g/mol), f = functionality, the number of OH groups/mol, and 56,100 = equivalent weight of KOH, in milligrams. 

A broad MWD represents a large number of macromolecules which have a wide distribution of molecular weights. The MWD of oligo-polyols is currently determined by GPC using tetrahydrofuran as solvent [21]. 

To conclude, the common physico-chemical characteristics of oligo-polyols for polyurethanes determined by standard analytical methods are hydroxyl number, hydroxyl percentage, primary hydroxyl content, molecular weight, equivalent weight, molecular weight distribution, viscosity, specific gravity, acidity and colour (See Chapters 3.1-3.11). 

For crosslinked polymers (in this category they are the majority of polyurethanes, for example flexible, semiflexible and rigid PU foams, etc.), which have a MW that is practically infinite [12], the molecular weight between the branching points (Mc) is considered. The value of Mc depends strongly on the oligo-polyol structure. 

This behaviour concerning the cumulative effect of functionality and molecular weight of oligo-polyols is observed in the case of PU foams (flexible, semiflexible and rigid) based on stress-strain relationship [2, 12]. 

All oligo-polyols are low molecular weight polymers, in the range of oligomer s molecular weight of 400-12000 daltons ... 

The transformation of oligo-polyols in polyurethanes is based on a reactive process (the formation of high molecular weight polyurethane is a consequence of a chemical process) ... 

The majority of oligo-polyols are liquid or very low melting point solids and due to the low viscosities (much lower than those of melted polymers) are very easy and economical to process to form high molecular weight polyurethanes. 

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