ASTM-D8016 Standard Test Method for Silica, Precipitated, Hydrated—Sears Number

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Standard Test Method for Silica, Precipitated, Hydrated—Sears Number



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1.1 This test method is used to determine the number of silanol groups on the surface of silica by titration according to a method as developed by Sears. This test method is suitable for characterizing rubber-grade silicas.

1.2 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

Significance and Use

4.1 The rubber-filler interaction needed in silica technology for the rubber industry is based on the use of silane-coupling agents that react with the silanol groups on the surface of the silica during the processing step called silanization. Silane-coupling agents are multifunctional molecules able to create molecular bridges between the elastomer or rubber matrix and the silica surface.


Sears Number; silane; silanol groups; silica;; ICS Number Code 83.040.20 (Rubber compounding ingredients)

To find similar documents by ASTM Volume:

09.01 (Rubber, Natural and Synthetic -- General Test Methods; Carbon Black)

To find similar documents by classification:

83.040.20 (Rubber compounding ingredients Including carbon black, kaolin clay, etc.)

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Document Number


Revision Level

2018(E1) EDITION



Modification Type

Editorially changed

Publication Date

March 11, 2019

Document Type

Test Method

Page Count

4 pages

Committee Number