Prediction of Cross-Link Density of Prevulcanized Latex Using InGaAs NIR Spectroscopy

Area of Science:

• Polymer Science
• Spectroscopy
• Materials Science

Background:

• Cross-link density is crucial for prevulcanized (PV) latex properties.
• Accurate prediction of cross-link density is vital for PV latex manufacturing quality control.

Purpose of the Study:

• To assess near-infrared (NIR) spectroscopy's feasibility for predicting PV latex cross-link density.
• To evaluate InGaAs-based NIR instruments for this application.
• To integrate process variables for enhanced predictive models.

Main Methods:

• Utilized two InGaAs NIR spectrometers (MicroNIR and AvaSpec) in the 960-1700 nm range.
• Developed partial least-squares regression (PLSR) models using spectral data and industrial process variables.
• Validated cross-link density using Toluene Swelling Index (TSI) and Prevulcanizate Relaxed Modulus (PRM) methods.

Main Results:

• Models using only NIR spectra showed limited predictive power.
• Integrating process variables (holding time, latex grade) significantly improved model accuracy.
• TSI-based models outperformed PRM models, with TSI-3 h being the most reliable.
• Noncontact MicroNIR achieved high accuracy (R²=0.96 for TSI-3 h).

Conclusions:

• Combining InGaAs NIR spectroscopy with process variables enables accurate, rapid, and non-destructive prediction of TSI-based cross-link density.
• Noncontact NIR measurement is practical for PV latex manufacturing.
• This approach offers a significant advancement in real-time quality control for PV latex.