Real-Time Monitoring of Component Conversion during the Foaming and Curing Process of Self-expanding Polyurethane Grouts

Xiao-Long Li; Xuan-Xuan Zi; Xiao-Feng Liu; Ming Guo; Yan-Hui Zhong; Bei Zhang

doi:10.1007/s10118-026-3604-y

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Real-Time Monitoring of Component Conversion during the Foaming and Curing Process of Self-expanding Polyurethane Grouts

RESEARCH ARTICLE | Updated：2026-05-30

- Real-Time Monitoring of Component Conversion during the Foaming and Curing Process of Self-expanding Polyurethane Grouts
- Chinese Journal of Polymer Science Vol. 44, Issue 6, Pages: 1843-1854(2026)
- Affiliations：
  
  School of Water Conservancy and Transportation, Zhengzhou University, Zhengzhou 450001, China
- Author bio：
  
  lxf1997@zzu.edu.cn
- Funds：
- DOI：10.1007/s10118-026-3604-y
  CLC：
- Received：16 December 2025，
  
  Accepted：29 January 2026，
  
  Online First：20 May 2026，
  
  Published：05 June 2026
- Accepted：
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Li, X. L.; Zi, X. X.; Liu, X. F.; Guo, M.; Zhong, Y. H.; Zhang, B. Real-time monitoring of component conversion during the foaming and curing process of self-expanding polyurethane grouts. Chinese J. Polym. Sci. 2026, 44, 1843–1854

Xiao-Long Li, Xuan-Xuan Zi, Xiao-Feng Liu, et al. Real-Time Monitoring of Component Conversion during the Foaming and Curing Process of Self-expanding Polyurethane Grouts[J]. Chinese Journal of Polymer Science, 2026, 44(6): 1843-1854.
Li, X. L.; Zi, X. X.; Liu, X. F.; Guo, M.; Zhong, Y. H.; Zhang, B. Real-time monitoring of component conversion during the foaming and curing process of self-expanding polyurethane grouts. Chinese J. Polym. Sci. 2026, 44, 1843–1854 DOI： 10.1007/s10118-026-3604-y.

Xiao-Long Li, Xuan-Xuan Zi, Xiao-Feng Liu, et al. Real-Time Monitoring of Component Conversion during the Foaming and Curing Process of Self-expanding Polyurethane Grouts[J]. Chinese Journal of Polymer Science, 2026, 44(6): 1843-1854. DOI： 10.1007/s10118-026-3604-y.

摘要

A real-time approach quantifies polyol

water

and apparent isocyanate conversions in high ―NCO polyurethane grouts by ATR-FTIR (carbamate C―O) and LiDAR volume tracking

revealing three-stage kinetics with faster foaming than gelation.

Abstract

Polyurethane polymer grouting materials with rapid expansion and solidification characteristics have been widely applied for infrastructure repair and reinforcement. An accurate characterization of the chemical reaction process of the slurry is essential for investigating its grouting mechanism. However

the high concentration of isocyanate groups in such polymer systems causes a “flat-top phenomenon” in Fourier transform infrared (FTIR) spectroscopy

rendering it difficult to accurately determine the conversion rate. To address this issue

a real-time method for measuring the reaction conversion rates of slurry components was proposed. The polyol conversion rate was obtained by tracking the integral area changes of the C―O bond peak in the carbamate product relative to the internal standard. The total slurry volume was determined at different time intervals using light detection and ranging (LiDAR)-based point cloud scanning

from which the gas volume was estimated. Combined with the solubility curve of the physical blowing agent and ideal gas law

the conversion rate of the chemical blowing agent was calculated. The isocyanate conversion rate was indirectly inferred based on the measured polyol and chemical blowing agent conversions. This method was applied to a polyurethane grouting material used in an engineering project

and the time-resolved conversion curves of all components throughout the reaction were obtained. The results revealed a three-stage evolution: a slow initial increase

a rapid rise in the middle stage

and a gradual deceleration in the later stage. The foaming reaction proceeded consistently faster than the gelation reaction did. These findings provide a foundation for further research on the diffusion mechanisms of polyurethane polymer slurries.

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