Views: 1 Author: Site Editor Publish Time: 2025-04-09 Origin: Site
Monitoring the curing process of adhesives and sealants is a critical step to ensure that their performance (such as bond strength, durability, etc.) meets expectations. The following are some commonly used monitoring methods, their principles and applications:
Hardness test (such as Shore hardness meter, Bakol hardness meter):
Principle: Indirectly judge the degree of curing by measuring the change of the surface hardness of the material over time.
Application: Suitable for elastic or semi-solid materials (such as silicone, polyurethane).
Advantages: Simple operation and low cost.
Disadvantages: Contact measurement is required, which may damage the surface.
Tensile/Shear Strength Test:
Principle: Mechanical tests are performed on the sample at different stages of curing, and the curing progress is evaluated through strength changes.
Application: Laboratory or quality control link.
Disadvantages: Destructive testing, unable to monitor in real time.
Fourier transform infrared spectroscopy (FTIR):
Principle: Detect the absorption peak changes of specific chemical bonds (such as epoxy groups, isocyanate groups) during the curing process.
Application: Laboratory research, suitable for thermosetting resins (such as epoxy resins, polyurethanes).
Advantages: High precision, quantitative analysis.
Disadvantages: Professional equipment is required and the cost is high.
Differential scanning calorimetry (DSC):
Principle: measure the heat change of the curing reaction (such as exothermic peak) and calculate the curing degree by the reaction enthalpy.
Application: Study on curing kinetics of thermosetting materials.
Advantages: Quantitative analysis, suitable for formula development.
Disadvantages: Sampling is required, and real-time monitoring cannot be carried out.
Thermogravimetric analysis (TGA):
Principle: Monitor the volatilization rate of volatiles or solvents during curing and judge the curing stage.
Application: Solvent-containing adhesives (such as acrylates).
Disadvantages: Only applicable to systems with quality changes.
Principle: By measuring the change of energy storage modulus (E') and loss modulus (E'') of the material with temperature or time, the transition from liquid to solid during curing is analyzed.
Application: Studying curing kinetics and glass transition temperature (Tg).
Advantages: High sensitivity, microstructure changes can be studied.
Disadvantages: The equipment is expensive and requires a laboratory environment.
Principle: The propagation speed or attenuation change of ultrasonic waves in the material reflects the change in elastic modulus during curing.
Application: Real-time online monitoring (such as composite bonding).
Advantages: Non-destructive, automated integration.
Disadvantages: Calibration is required, affected by material thickness.
Principle: Measuring the changes in the dielectric constant and conductivity of a material, reflecting the polarity and crosslinking degree of molecules.
Application: Real-time monitoring of the curing process of thermosetting resin.
Advantages: Suitable for complex shapes and online monitoring.
Disadvantages: Electrode contact is required, which may be disturbed by ambient humidity.
Fiber Optical Sensor:
Principle: Use changes in the refractive index or light intensity of optical fiber to monitor volume shrinkage or refractive index changes caused by curing.
Application: Structural adhesive monitoring in the aerospace field.
Advantages: High precision, anti-electromagnetic interference.
Raman spectrum:
Principle: Analyze chemical bond changes through molecular vibration spectroscopy and monitor the reaction process in real time.
Application: Laboratory or high-precision industrial scenarios.
Temperature-time integral:
Principle: By monitoring the curing temperature and time (such as calculating the 'T-Tol' value), predict the curing degree.
Application: Process control of thermally cured adhesives (such as the automotive industry).
Advantages: Low cost, easy to integrate into production lines.
Material type: Thermoset, UV curing or moisture curing requires different methods.
Monitoring scenarios: laboratory research vs. real-time monitoring of production lines.
Cost and Accuracy: High-precision equipment (such as DSC) is suitable for research and development, while low-cost methods (such as hardness meter) are suitable for field.
Destructive: Non-destructive methods (such as ultrasound) are more suitable for finished product inspection.
By combining multiple methods, the curing process can be more comprehensively evaluated to ensure that the performance of the adhesive and sealant meets standards.
