KB value, short for Kauri‑Butanol value, is a standard measure used to evaluate the solvency strength of hydrocarbon solvents, especially for resins, oils, greases, and similar organic materials.
It is determined by titrating a standard kauri gum‑butanol solution with the solvent sample until a defined turbidity endpoint is reached. The higher the KB value, the stronger the solvent’s ability to dissolve resins and hydrocarbon‑based substances.
This index is widely used in coatings, cleaning agents, thinners, and industrial solvent characterization, following test standards such as ASTM D1133 and GB/T 11134.
Test Standards and Methods
Applicable standards: GB/T 11134-1989/2025 or ASTM D1133.
Core Reagents
Kauri-butanol solution (20 g of kauri gum dissolved in 2 kg of n-butanol, allowed to stand for 48 hours and then filtered).
Calibration
At 25 °C, titrate 20 g of the above solution with toluene to the specified turbidity; consumption volume = 105 mL (KB = 105).Titrate with a mixture of 75% n-heptane + 25% toluene; consumption volume = 40 mL (KB = 40).Calibrate the solution based on these values.
Titration
At 25 °C, titrate 20 g of the calibrated kauri-butanol solution with the sample until turbidity appears. Record the consumption volume V (mL).
Calculation
KB = (105 − 40) × (20 − V) / V + 40 (general formula)
Key Notes
Scope: Hydrocarbon solvents with initial boiling point > 40 °C and dry point < 300 °C.
Interferences: Water or impurities in the sample will lead to low results; dehydration is required prior to testing.
Endpoint determination: Take the first stable turbidity as the endpoint. Conduct 2–3 parallel tests and use the average value.