A Novel Approach to Non-Destructive Rubber Vulcanization Monitoring by the Transient Radar Method.

Area of Science:

• Materials Science
• Electrical Engineering
• Polymer Science

Background:

• Raw rubber requires curing to enhance mechanical strength, with process parameters like time and temperature critically affecting final properties.
• Traditional vulcanization monitoring methods can be intrusive or lack real-time feedback capabilities.
• The transient radar method (TRM) presents a novel, non-contact approach for monitoring the rubber curing process.

Purpose of the Study:

• To investigate the feasibility and robustness of the transient radar method (TRM) for monitoring rubber vulcanization.
• To explore the correlations between curing time, dielectric permittivity, and mechanical stiffness in polyurethane-rubber samples.
• To establish TRM as a potential tool for real-time, contact-free monitoring of rubber curing.

Main Methods:

• Three polyurethane-rubber samples were prepared with distinct curing times (2, 4, and 5.5 minutes).
• The transient radar method (TRM) was employed to measure the complex permittivity of the samples.
• Unidirectional tensile tests were conducted to determine the mechanical stiffness of the cured samples.

Main Results:

• TRM successfully differentiated samples based on curing times, with complex permittivity values of 17.33 - 2.41j, 17.09 - 4.90j, and 23.60 - 14.06j for 2, 4, and 5.5 min curing, respectively.
• Mechanical stiffness increased with curing time, measuring 0.29, 0.35, and 0.38 kPa.
• High correlation coefficients were observed between curing time and stiffness (0.99), and between curing time and the imaginary part of permittivity (0.92), indicating TRM's sensitivity to vulcanization progress.

Conclusions:

• The transient radar method (TRM) demonstrates significant potential for non-contact monitoring of rubber vulcanization.
• TRM can effectively track the impact of curing time on dielectric properties, which correlate with mechanical stiffness.
• This study validates TRM as a robust and feasible alternative for real-time quality control in rubber manufacturing processes.