Hydroxyl equivalent

Chaiges Wt,g Moles of hydroxyl Hydroxyl equivalents Hydroxyl number contribution... 

The hydroxyl equivalent is the weight of resin containing one equivalent weight of hydroxyl groups. It may be determined by many techniques but normally by reacting the resin with acetyl chloride. 

Hydroperoxylation of silyl dienol ethers was effected by the in t7/ -generated reagent triphenyl phosphite ozonide (Equation 26). The yields are moderate and the products are always accompanied by the hydroxylated equivalents. The mechanism was studied and it was found that the oxygen attached to the carbon came from the central O of the ozonide <2001JOC3548>. 

Hydroxyl equivalent = [(titer of blank - titer of sample) X normalityj/sample wt,... 

Similarly, the hydroxyl equivalent weight is the weight of the resin containing one equivalent of hydroxyl group, and it may also be expressed as equivalents per 100 g. Several studies have demonstrated that the hydroxyl content greatly influences the adhesion of the epoxy resin.3,4 These results are best explained by the polar character of the... 

The hydroxyl equivalent weight of epoxy resins can be determined by several methods. The most common is esterification with acids, reaction with acetyl chloride, and reaction with lithium aluminum hydride. Infrared spectroscopy may also be used. 

Hydroxyl equivalent. The hydroxyl equivalent is the weight of epoxy resin containing one equivalent of hydroxyl group. It is important in calculating average molecular weights. It is determined by various methods (Lee and Nivelle, 1967), such as esterification with acids, reaction with lithium aluminium hydride, reaction with acetyl chloride and near-infra-red spectroscopy. 

Initiator 9 reacts with methyl methacrylate at -78 C in THF to produce a quantitative yield of acetal-ended polymer with n from 1 to 500 and Mw/Mn <1.2. DP s determined by NMR agree well with GPC molecular weights and hydroxyl equivalents. The presence of the blocked hydroxyl group in the polymer was verified by the presence of the phenyl protons in the correct proportion, and by the weak signals from the methine proton of the acetal group. This methine signal is too weak, however, to... 

This simple and rapid HPLC analysis provides direct proof of the structure of the polymers. The classical approach which compares measured Mn to measured hydroxyl equivalent shows only that on average there is one hydroxyl group per molecule. Chromatography has been used to do similar analyses of hydrocarbon polymers such as polystyrene and polybutadiene. Our work shows that this technique is general and can be applied to more polar polymers. 

When f = 1, p = 100%, and the equation predicts that no gelation occurs when bifunctional compounds are used. Therefore, alkyd chemists tend to use formulations in which / = approximately 2.0 in order to get alkyd resins which will not gel during manufacture. In other words, the molar equivalents of hydroxyl should equal the molar equivalents of carboxyl groups. In actual practice an excess of hydroxyl equivalents is used to give specific properties, especially in baking coatings. For example, a typical alkyd with 20% excess of hydroxyl and a functionality of 2 is prepared from phthalic anhydride, 1.0 mole (2 equivalents) glycerol, 1.0 mole (3 equivalents) and soya fatty acids (soyal oil), 0.5 mole (1.5 equivalents). 

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