This work demonstrates the synergy between the thermo-mechanical and humidity induced degradation as well as the oxidation reactions in the kink-banded areas of ultra-high molar mass polyethylene (UHMMPE) fiber-based laminates used in body armor. For aged materials, the energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) results reveal high concentrations of oxygen containing products, and the EPR results demonstrate the presence of the peroxyl radicals (RO₂^•) in the kink-banded areas. After one year of dark ambient storage, very long-lived RO₂^• radicals were observed primarily in the samples exposed to ageing conditions of elevated temperatures, humidity, and mechanical stress. The total percentage of crystallinity, as measured by differential scanning calorimetry, of the kink-banded fibers was unchanged, indicating that the degradation occurs primarily in the amorphous region, and may also involve recrystallization processes of the degraded chains. However, the most abundant orthorhombic crystalline phase decreases from 77% to 70%. This decrease in the orthorhombic structure leads to more diffusion of oxygen into the kink-banded region, enhancing the oxidation processes. No changes are observed in the monoclinic phase of the kinked fibers, which remained constant and constituted ∼2% of the total crystallinity.

这项工作证明了用于防弹衣的超高摩尔质量聚乙烯（UHMMPE）纤维基层压板在扭结带区域中的热机械降解和湿度引起的降解以及氧化反应之间的协同作用。对于老化的材料，能量色散X射线光谱（EDS）和傅立叶变换红外光谱（FTIR）结果显示出高浓度的含氧产物，而EPR结果表明在材料中存在过氧自由基（RO ₂ ^•）。扭结带区域。黑暗环境保存一年后，很长的寿命RO ₂ ^•自由基主要在暴露于高温，高湿和机械应力的老化条件下的样品中观察到。通过差示扫描量热法测量的扭结带纤维的总结晶度百分比未改变，表明降解主要发生在非晶区，并且还可能涉及降解链的重结晶过程。但是，最丰富的正交晶相从77％降低到70％。正交晶结构的这种减少导致氧更多地扩散到扭结带区域中，从而增强了氧化过程。在扭结纤维的单斜晶相中未观察到变化，其保持恒定并构成总结晶度的〜2％。