Centa Urška Gradišar, Oseli Alen, Mihelčič Mohor, Kralj Aleš, Žnidaršič Matjaž, Halilovič Miroslav, Perše Lidija Slemenik
Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva 6, 1000 Ljubljana, Slovenia.
Reflex Gornja Radgona d.o.o., Podgrad 4, 9250 Gornja Radgona, Slovenia.
Polymers (Basel). 2023 Dec 20;16(1):22. doi: 10.3390/polym16010022.
Polyisobutylene (PIB) is commonly used as a primary sealant in multi-layer insulating glazing elements, where temperatures often exceed 100 °C. At such conditions, PIB undergoes structural changes, causing different relaxation dynamics and leading to decreased lifetime of the material. Understanding thermal behavior is therefore imperative for achieving effective insulation of these materials for long-term use in insulating application. The present study was focused on the temperature dependence of viscoelastic behavior of two commercially available polyisobutylene (PIB) materials, which are commonly used as primary sealants for energy-efficient multi-layer glazing units. The long-term viscoelastic behavior of the materials before and after thermal treatment at high temperatures was studied by using time-temperature superposition (tTS). Van-Gurp-Palmen plots were obtained directly from experimental data and enabled the study of thermally induced changes, while the relaxation time spectra were calculated from master curves and enabled the calculation of molecular weight distribution. The results showed that, after thermal treatment, the structure of PIB materials changes from linear to branched, while the molecular weight distributions transition from monomodal to bimodal. The untreated samples exhibited viscous-like behavior, while the thermally stabilized samples exhibited solid-like behavior, extending the material response for ~6 decades towards a longer timescale. Moreover, the presented results can be directly used to simulate the mechanical responses of the sealants using currently available FEM software packages to predict their functional and structural lifetime.
聚异丁烯（PIB）通常用作多层隔热玻璃元件中的主要密封剂，在这种元件中温度常常超过100°C。在这样的条件下，PIB会发生结构变化，导致不同的松弛动力学，并致使材料的使用寿命缩短。因此，了解热行为对于实现这些材料的有效隔热以在隔热应用中长期使用至关重要。本研究聚焦于两种市售聚异丁烯（PIB）材料的粘弹性行为的温度依赖性，这两种材料常用作节能多层玻璃单元的主要密封剂。通过使用时间 - 温度叠加（tTS）研究了高温热处理前后材料的长期粘弹性行为。直接从实验数据获得范 - 古尔普 - 帕尔门图，从而能够研究热诱导变化，而从主曲线计算出松弛时间谱，并能够计算分子量分布。结果表明，热处理后，PIB材料的结构从线性变为支化，而分子量分布从单峰转变为双峰。未处理的样品表现出类似粘性的行为，而热稳定的样品表现出类似固体的行为，将材料响应在长达约6个数量级的时间尺度上进行了扩展。此外，所呈现的结果可直接用于使用当前可用的有限元软件包模拟密封剂的机械响应，以预测其功能和结构寿命。
