In a silanization reaction, silanes chemically bond with silica during mixing, and then attach to rubber at vulcanization, which as a positive effect on the resulting compound properties in terms of improving filler-to-rubber reaction. The degree of silanization achieved during mixing is one of the key factors to control the quality of processing, rubber reinforcement and other compound properties.

Authors of the paper “Silanization characterization and compound properties of silica-filled rubber containing a blocked mercapto silane” Chenchy J. Lin, W. Michael York, Russell J. Cody; developed a feasible and reliable method to quantify silanization using a Premier RPA (Rubber process analyzer) from Alpha Technologies. The method was based on the fact that the degree of filler network developed is inversely proportional to the exposed silica surface coverage by a silane, therefore the amount of silane reacted with the exposed silica surface can be calculated. in their paper, an indirect method was demonstrated using rheology, which may be more convenient and practical for typical tire plants. Specifically, the authors propose to measure a silane’s capability to suppress silica filler network formation (flocculation) and to correlate those measurements to the resultant compound properties. 

The authors evaluated three types of silane coupling agents and adapted the test methods to shop floor Quality Control environments, making some modifications to make it user friendly and to create a test that can be conducted after each stage of mixing. The test sequence involves conditioning of the sample and determination of storage modulus before and after sample conditioning step. Delta of storage modulus after different mixing stage is being used to calculate the silanization.