Model Effect of Temperature Cycling for R&D, Stability and Processing
Temperature sweep probes rheological changes across a temperature ramp or over one or more heat-cool cycles. Does your product reversibly or irreversibly change after storage in a hot or cold car? Is your product sensitive to temperature changes during manufacturing that impact product efficacy and quality? A temperature ramp or up/down cycle is well designed to efficiently probe this important property. This assay can be performed in the rotational mode under either a constant shear rate (1/sec) or shear stress (Pa) or in the oscillatory mode under a constant frequency and either strain or stress with the LVER.
Figure 1 demonstrates how temperature sweep quantifies the difference in spreadability of 2 butter products under constant frequency. The less stiff, more spreadable butter (red line) has a lower G' (elastic modulus = solid nature) between refrigerator and room temperatures.
Figure 2 shows the benefit of multiple heating and cooling cycles resulting in an irreversible rheological change. A more rheologically stable form of the material is identified and confirmed with subsequent heating and cooling cycles.
Figure 3 shows results comparing generic (blue curve) and RLD (red) creams with a multiple 5 to 50C temperature cycling assay performed with a single frequency (1Hz) under 1% strain (previously determined with an amplitude sweep). This assay modeled the potential impact of processing temperatures that may induce rheological changes. Duplicate assays show small, yet consistent differences between to 2 samples.