Meaning
Stretched exponential functions used to describe non-Debye relaxation processes in disordered systems provide a mathematical framework for analyzing polymer aging. In cell design, the kohlrausch williams watts formulation characterizes the slow, non-linear stress relaxation of protective potting compounds and adhesives. This mathematical tool accounts for the complex molecular interactions within highly filled polymers.
The model stops being useful at temperatures far above the glass transition point where relaxation becomes simple and linear.
Physical Mechanism
Molecular movement in complex polymers does not follow a single, simple relaxation time due to the dense network of chains and fillers. The kohlrausch williams watts function captures this behavior by introducing a stretching parameter that represents the breadth of the relaxation time distribution. This parameter reveals how the material transitions from a rigid state to a relaxed state over weeks of constant compression.
Relaxation Rate
Predicting this slow decay is essential to ensure the battery pack does not lose its structural integrity over a decade of operation.
Assembly Benefit
Procurement teams reference these relaxation profiles to select sealants that resist cracking under dynamic service loads. Selecting a compound with a known relaxation behavior prevents premature joint failures in the field. This engineering check reduces warranty exposure for the vehicle manufacturer.
