Quality Control of Silicone rubber

Importance of the topic

The accurate determination of vinyl content in silicone rubber is essential for controlling material properties such as crosslinking behavior, mechanical strength, and chemical resistance. Conventional gas chromatography methods are time‐consuming and require chemical reagents and skilled operators, creating bottlenecks in quality control workflows.

Objectives and study overview

This study aimed to demonstrate a fast, reagent‐free alternative for quantifying vinyl content in silicone rubber using visible near‐infrared (Vis-NIR) spectroscopy. A calibration model was developed and compared against the standard GC method to assess accuracy, precision, and time efficiency.

Methodology

Silicone rubber samples were measured directly, without any chemical treatment or sample preparation, using a DS2500 Solid Analyzer in transflection mode across the full wavelength range of 400–2500 nm. Spectra were collected with a DS2500 Slurry Cup and a 1 mm gold diffuse reflector to ensure consistent path length. Data acquisition and model development were performed with Vision Air Complete software, applying multivariate calibration techniques to relate spectral features to reference GC measurements of vinyl content.

Instrumentation used

• DS2500 Solid Analyzer (transflection, 400–2500 nm)
• DS2500 Slurry Cup with 1 mm gold diffuse reflector
• Vision Air Complete spectroscopy software

Key results and discussion

• Calibration model displayed excellent correlation with GC references (R² = 0.989).
• Standard error of calibration was 0.0076 % vinyl; cross‐validation error was 0.0089 %.
• Vis-NIR predictions matched primary method values across the vinyl content range, confirming model robustness.

Benefits and practical applications

• Measurement time reduced to under one minute per sample, compared to over one hour for GC.
• Eliminates the need for chemical reagents and complex sample preparation.
• Suitable for routine quality control in both laboratory and production environments, enabling rapid decision making.

Future trends and opportunities

Advances in portable Vis-NIR analyzers and integration with process analytical technology (PAT) are likely to expand on‐line monitoring capabilities. Further application of advanced chemometric algorithms may improve detection limits and enable simultaneous analysis of multiple functional groups in polymer systems. The approach could also be extended to other polymeric materials, enhancing quality control across diverse industrial processes.

Conclusion

Vis-NIR spectroscopy using the DS2500 Solid Analyzer provides a rapid, accurate, and reagent‐free method for determining vinyl content in silicone rubber. The method offers significant time and cost savings compared to conventional GC, making it an attractive tool for routine quality control and process monitoring.