Long term natural aging changes the mechanical and thermal response of PDMS, and the stability of microfluidic devices is of concern

Research Background and Core Findings: A study published online in Polymer Testing (authored by Nicol á s Soto, Francisco Gonz á lez Varela, Alexander C ó rdoba, Constanza Maul é n, Enzo Brito, Esteban Zamora, Fabi á n Á lvarez Carrasco, Paula A. Zapata, Claudio Garc í a-Herrera, Diego A. Vasco, Mar í a Luisa Cordero, Aldo Abarca Ortega) examined the mechanical and thermal responses of polydimethylsiloxane (PDMS) after long-term natural aging in the context of microfluidic applications. Change. Research has shown that natural aging does not only bring about changes in surface appearance, but also simultaneously affects the mechanical behavior and thermal properties of materials. This means that the functional reliability of flexible polymers represented by PDMS needs to be re evaluated in long-term service. The value of this study lies in bringing “aging” back from laboratory accelerated conditions to real natural exposure scenarios. For the study of polymer aging, natural aging involves the synergistic effects of multiple factors such as ultraviolet irradiation, temperature cycling, humidity, and oxygen, and its action path is not completely consistent with a single accelerated test. Therefore, the mechanical and thermal response data obtained have reference significance for understanding actual failure modes.

Significance for the polymer additive industry

PDMS belongs to a special type of elastomer with a main chain of silicon oxygen bonds. Its degradation mechanism is different from that of carbon chain polymers, but the aging process also involves free radical oxidation, chain segment rearrangement, and changes in crosslinking density.

. The observed changes in mechanics and thermal response in the study suggest that in long-term use scenarios, the cross-linking network and molecular chain mobility of the material will change, which is directly related to the goal of the antioxidant system to inhibit oxidative degradation and maintain network structure stability. For microfluidic chips, flexible sensors, and biomedical devices that require outdoor or long-term continuous operation, weather resistance stability should be taken into consideration in formulation design, rather than just focusing on initial mechanical indicators. From the perspective of stabilization technology, the sensitivity of the silicon oxygen system to UV and oxidation differs from that of carbon chain polymers. The applicability of HALS (hindered amine light stabilizer) and UVA (UV absorber) needs to be judged based on the chemical structure of the substrate. The study did not provide a specific additive scheme, but its results indicate that relying solely on a single stabilizing method is difficult to cover the performance drift caused by the coupling of multiple factors in natural aging. The idea of a composite system, which is designed to synergistically address the two pathways of oxidation and photoaging, is more practical in ensuring long-term stability. For the development of formulations based on PDMS, the compatibility between the antioxidant system and photostable components can be the focus of validation, and the stability effect can be evaluated through mechanical and thermal characterization before and after aging.

Inspiration from Detection and Characterization

The study adopts mechanical and thermal response as aging evaluation indicators, which has reference value for polymer aging detection.

. Conventional aging evaluations often focus on appearance, color, or single mechanical strength, while changes in thermal response can reflect changes in segment motion and aggregated structure, and when combined with mechanical data, can more fully characterize the degree of aging. For additive suppliers and product companies, introducing multidimensional characterization during the screening stage of weather resistant stable formulas can help identify synergistic or antagonistic effects in the complex system, avoiding misjudgment based solely on a single indicator. It should be noted that this study focuses on the natural aging behavior of PDMS in microfluidic applications, and does not involve the specific effects of adding antioxidants, HALS, or UVA varieties, nor does it provide comparative data for stabilizing formulations. Therefore, its conclusion should be understood as a prompt for aging phenomena and evaluation methods, rather than a direct verification of a certain additive system. The polymer additive industry can focus on the long-term performance evolution of silicon-based elastomers under real exposure conditions, and carry out targeted aging verification based on its own formulation system.

Information source:Long-term natural aging alters the mechanical and thermal response of PDMS for microfluidic applications， Organized by Herun Chemical.