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The “2000” in Polypropylene Glycol 2000 refers to its nominal molecular weight—not its purity or viscosity. For a buyer reviewing a specification sheet, that is only part of the picture. Another useful number is the hydroxyl value, particularly when the material will take part in a chemical reaction.
At Dotachem, we supply Polypropylene Glycol (PPG 2000) with a listed molecular weight range of 1,800–2,200 and a hydroxyl value of 51–62 mg KOH/g. These figures are related, but they describe different aspects of the material.
What Does Hydroxyl Value Measure?
Hydroxyl value indicates the concentration of hydroxyl groups in a material, expressed in mg KOH/g. It is not a measure of how much potassium hydroxide the product contains.
For PPG diols with the same nominal functionality, longer molecular chains generally mean fewer hydroxyl groups per gram and a lower hydroxyl value. A higher number is therefore not automatically better, nor does a lower number mean lower quality. The useful value is the one that fits the intended formulation.
Why It Matters in a Formulation
In polyurethane chemistry, hydroxyl groups react with isocyanate groups. The hydroxyl value helps formulators calculate the balance between these components; the grade name alone is not enough for that calculation.
For example, replacing a lower-molecular-weight PPG diol with PPG 2000 at the same weight generally reduces the amount of hydroxyl groups introduced. Keeping the rest of the recipe unchanged may alter the reaction balance and the finished material’s properties.
This does not mean every batch needs a new recipe. It means the formulation should have an acceptable specification range, with any proposed substitution checked against it.
What Else Should You Check?
Hydroxyl value cannot tell you everything about processing performance. Viscosity affects mixing and transfer, while moisture needs particular attention in moisture-sensitive reactions. Two products with similar hydroxyl values are not necessarily interchangeable.
Alongside PPG 2000, we supply PPG 400, PPG 1000 and PPG 4000. Each grade has a different molecular weight and hydroxyl value range, so the choice depends on the formulation and processing requirements.
As a Polypropylene Glycol supplier in China, we can discuss your required grade and specification limits before arranging supply. Contact Dotachem for PPG 2000 specifications, product documents and quotation details. Our team also provides order follow-up and after-sales support.
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