Hydroxyl number polymer polyols

Spectroscopic techniques have been employed extensively for monitoring and control of processes in different fields. Since a detailed review of the applications of spectroscopic techniques in distinct areas is certainly beyond the objectives of the chapter, the interested reader should refer to textbooks and surveys for additional details [ 10,27,30,33,43,44]. It is also important to emphasize that most publications available in the field of polymer and polymerization reactions make use of spectrometers for off-line characterization of polymer properties. Typical applications include identification of polymer materials [82], evaluation of copolymer and polymer blend compositions [83, 84], evaluation of monomer and polymer compositions during polymerizations [85], determination of additive content in polymer samples [86, 87], and estimation of end-use properties of polymer materials. End-use properties analyzed include the degree of crystallinity of polymer samples [88], the degree of orientation of polymer films [85], the hydroxyl number of polyols [89], the melt flow index of polymer pellets [90], and the intrinsic viscosity of polymer powders [91], the morphology of... 

Fig. 22 Respirometry of vegetable oil-based polyurethanes made from the following polyols triolein-met arrowhead), soy-HF (filled square), soy-met 180 (open diamond), soy-met 206 (open circle), and linseed met (open square). Also shown is ESO/BF3 polymer (open triangle) and soybean oil control (filled circle). Temperature was increased from 30°C to 55°C on day 71. Note that hydroxyl number of 180 has the functionality of 3.3 and that of hydroxyl 206 is 4.0. Met refers to polyol made from ESO and methanol HF refers to polyol from hydroformylation and reduced ESO. Reproduced from [152] by permission of Journal of Polymers and the Environment...

Polymer Polyol, 20% Solids, with a Hydroxyl Number of 28. 

The hydroxyl number of a polymer polyol is lower than the hydroxyl number of the initial polyether polyol used for grafting. The hydroxyl number decrease is a function of the polymer polyol solid content (generally the solid part has no hydroxyl groups). For the estimated hydroxyl number calculation at a known solid content, equation 6.17 is used ... 

Therefore, by grafting a polyether polyol with an OH of 36 mg KOH/g with 20% vinylic monomers, the theoretical hydroxyl number of the resulting polymer polyol is 28.8 mg KOH/g. 

The solid fraction of PIPA polymer polyols has an appreciable concentration of hydroxyl groups (see formula 6.24). As an immediate consequence, the PIPA polyol frequently has a higher hydroxyl number than the initial polyol used as liquid medium for reaction 6.24. As a general rule, for better accuracy of hydroxyl number determination, for all polymer polyols, it is preferable to use the method of the reaction with para toluene sulfonyl isocyanate mentioned before (see Chapter 3). 

Polyols are identified by their hydroxyl numbers. If the polyol is initiated using ethylene glycol, and the polyol can be identified as a diol, with a functionality of 2, the average molecular weight can be determined. Hydroxyl number is defined as the number of milliweights (or milligrams) of potassium hydroxide equivalent to the active functions (hydroxyl content) of 1 g of the compound or polymer. 

To determine the average hydroxyl functionality of a sample of polyester polyol of M = 3,000 about 1 g of the dry sample was treated with bromoacetyl bromide (BrCH2COBr) to convert hydroxyl to bromoacetyl end groups. The treated polymer was found to contain 4.88% Br by elemental analysis. Estimate the average number of hydroxyl groups on each molecule of the polyol. 

They are linear block copolymers of the (AB) type in which A is the "soft" segment derived from the polyol and B is the "hard" segment derived from the diisocyanate and chain extender. Theoretically, infinite molecular weight would be achieved at an isocyanate to total hydroxyl ratio of 1.0. Thus the number of moles of diisocyanate is equal to the sum of the number of moles of polyol and chain extender as shown. Hardness of the materials can be varied by altering the molar ratio of chain extender to polyol which in turn affects the weight ratio of hard segment to soft segment in the polymer. 

It can be seen that the polymer chains contain multiple alkali-resistant ether linkages and end in hydroxyl groups. Thus the number of hydroxyl groups in the polymer is the number of hydroxyl groups in the polyol starting ingredient. Molecular weights vary from 400 to 4000. 

Polyurethanes are a broad class of polymers produced by the polyaddition reaction of a diisocyanate or a polymeric isocyanate with a polyol, in the presence of suitable catalysts and additives. Under the name of polyurethanes, a practically unlimited number of structures can be involved. The only necessary condition is in general reduced to the presence of the urethane group, (-NHC0-0-) on the macromolec-ular chain with a more or less frequency. The urethane group is usually formed by reaction between isocyanate and hydroxyl groups, although alternative routes such as from bischloroformates and amines are used in special cases. 

---