Dynamic Mechanical Shift Factor Extraction for Thermosetting Polymer Physical Aging Analysis
Extracting physical aging shift factors in thermosets requires momentary loading below Tg, sub-tenth Kelvin stability, and frame compliance corrections.
Time Aging Time Superposition
Analytical Concept
Predictive modeling of the long-term viscoelastic relaxation of polymers employs scaling factors to relate the effects of time and chemical aging. Applying time aging time superposition enables researchers to construct a single master curve representing material behavior over extended periods by combining shorter-duration tests conducted at different stages of aging. This method is used for estimating the lifespan of sensor housings and polymer potting compounds.
Master Curve
Horizontal and vertical shifting of experimental relaxation curves along the log-time axis creates a continuous projection of material decay. Through time aging time superposition, the accelerated effects of chemical or physical aging are quantified, allowing long-term stiffness changes to be simulated in a fraction of the actual time. This projection is evaluated at a specified reference state.
Material Parameter
Extraction of aging shift factors reveals how the relaxation times scale as the polymer structure densifies or degrades over time. When utilizing time aging time superposition, the relationship between the shift factors and the aging time is typically modeled to confirm that the underlying relaxation mechanisms remain constant. This analysis ensures the validity of the accelerated aging models.
Accuracy Limitation
Non-linear mechanical behavior and unforeseen degradation pathways can disrupt the scaling relationship at extreme temperatures. High-temperature testing using time aging time superposition must be verified against real-time baseline data to ensure that new chemical reactions have not been activated. This precaution prevents overestimating or underestimating component lifespan.