How Crosslinked Are Your Polymers?
Crosslinking plays a crucial role in determining the properties and performance of many polymer materials.
Using several techniques, our scientists can tell you the degree of crosslinking in your:
- Epoxy resins
- Elastomers
- Hydrogels
- Plastics
Crosslinking influences mechanical strength, swelling behavior, chemical resistance and wear properties. Measurement of crosslinking is essential for quality control and optimizing material performance.
Key Testing Methods
Swell ratio testing is usually conducted on crosslinked materials. In this test, a sample is placed in a good solvent at a particular temperature, and the change in height of the sample is monitored as a function of time. The crosslink density and molecular weight between crosslinks can be calculated from the final swell ratio using details of thermodynamic interaction between the sample and the solvent.
What test methods are appropriate for crosslinking determination?
The following tests will report swell ratio, crosslink density, and other parameters associated with crosslinking.
- ASTM F2214 Standard Test Method for In Situ Determination of Network Parameters of Crosslinked Ultra High Molecular Weight Polyethylene
- ASTM D2765 Standard Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics
Dynamic mechanical analysis (DMA)
DMA provides valuable insights into crosslinking by measuring viscoelastic properties:
- Storage modulus (E’) and loss modulus (E”) across a temperature range
- Glass transition temperature (Tg)
- Crosslink density estimation from rubbery plateau modulus
We can perform DMA in shear, tension, or compression modes to suit different sample geometries.
Rheology can also be used to differentiate the degree of crosslinking in materials.
Microscopy Techniques
We utilize advanced microscopy for visual assessment of network structure:
- Optical microscopy for swelling behavior of bulk samples
- Scanning electron microscopy (SEM) for detailed network morphology
Density Measurements
Density often correlates with crosslink density. Density is commonly performed by two techniques at Cambridge Polymer Group:
- ASTM D1505 Standard Test Method for Density of Plastics by the Density-Gradient Technique
- ASTM D792 Standard Test Method for Density and Specific Gravity (Relative Density) of Plastics By Displacement
Customized Testing Solutions
Our polymer scientists can design tailored testing protocols for your specific materials and applications. We can combine multiple techniques to provide comprehensive crosslinking characterization. Contact us to discuss your project requirements with one of our scientists about your project.