Endo- and exothermal mechanocaloric response in rubbers

• Published in: Journal of thermal analysis and calorimetry 2024-07
• Main Authors: Matsuo, Takasuke, Takajo, Daisuke
• Format: Article
• Language: English
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-024-13361-8

We investigated mechanocaloric properties of two silicone rubbers using an in-house made apparatus. Tension $$f$$ f and temperature change $$\Delta T$$ Δ T of the rubber samples in the form of tapes were measured as they were extended up to a normalized length $$\lambda \approx 2$$ λ ≈ 2 at a constant rate. Endothermal and exothermal components of the thermal response were observed and separated. The engineering stress and (decrease of) the entropy density derived from the data were analyzed. The number densities of the partial chains and the coefficients of the positive (endothermal) entropy contribution were determined as material constants of the rubbers. Non-idealities were revealed by the large difference between the work done on the rubber for the extension and the heat that evolved in the process. It decreased to a considerable extent when the heat was corrected for the endothermal effect arising from the above-mentioned endothermal entropy contribution. This may be understood as an indication of hidden near-ideality of silicone rubbers. Dissipation of the work into heat is quantified using the difference between the temperature changes on extension and contraction.