In silicone oil data, cSt and mPa·s describe different viscosities. cSt is a unit of kinematic viscosity; mPa·s is a unit of dynamic viscosity. Conversion requires density at the same temperature and pressure. Specify units, test temperature and method together when purchasing, rather than comparing numbers alone. [1]

Identify the units before comparing specifications

Conversion: dynamic viscosity (mPa·s) = kinematic viscosity (mm²/s) × density (g/cm³). Density and viscosity must refer to the same temperature and pressure. [1]

For illustration only: if a sample has a kinematic viscosity of 100 mm²/s and density of 0.970 g/cm³ under the same conditions, its calculated dynamic viscosity is 97.0 mPa·s. These numbers explain the formula; they are not specifications for any IOTA grade or batch.

Do not request only a viscosity of 100

1. State the material category and application, distinguishing dimethyl, phenyl and materials with reactive groups.

2. Specify kinematic or dynamic viscosity, with units, temperature and permitted range.

3. Confirm the supplier’s test method. For rotational measurements, record the applicable spindle, speed and other conditions.

4. For comparisons across units, request density at the corresponding temperature and retain both original and converted results.

IOTA Silicone Oil (Anhui) Co., Ltd. provides solutions across the silicone value chain. For dimethyl silicone oil, first review the IOTA 201 product category listed on the official website, then submit the application and measurement requirements. [2]

Similar numbers still require an application check

Similar viscosity at one temperature establishes similarity in that property only. When changing supplier or material category, also check volatile content, low-molecular-weight requirements and application performance. The actual use and agreed specification determine which tests are needed.

Keep comparable records after delivery

Check the batch and test report, then prepare and measure samples by the agreed method. If results differ, examine sample temperature, instrument conditions, sampling representativeness and units in that order. Do not start by diluting or blending oils to adjust the result. Agree before ordering which viscosity is the contractual acceptance property; a converted value cannot unilaterally replace an agreed measured result.

FAQ

Q1 Is conversion needed between cSt and mm²/s

Their numerical values are identical: 1 cSt = 1 mm²/s. Both are kinematic-viscosity units.

Q2 How are cP and mPa·s related

1 cP = 1 mPa·s. Both express dynamic viscosity.

Q3 Can cSt simply be relabelled mPa·s without density

No accurate conversion is possible. Obtain density at the corresponding temperature and pressure and retain the original unit.

Q4 Can viscosities at different temperatures be compared directly

Use the same test temperature or obtain measured data at corresponding temperatures. Numbers alone do not establish batch differences.

Q5 Does equal viscosity permit direct substitution

Confirm structure, impurity control and application requirements. Define substitution conditions after testing actual service conditions.

Q6 What should a quotation request include

Application, material category, viscosity type, units, temperature, range and test method. Attach relevant test records for existing samples.

Related product

Core related product category: IOTA 201 dimethyl silicone oil.

Sources and scope

1. Anton Paar basics of viscometry: unit relationships and density conditions for conversion.

2. IOTA official website: the IOTA 201 product name is available through search.