El Choufi Nadim, Mustapha Samir, Tehrani-Bagha Ali R, Grady Brian P
Chemical Engineering Department, American University of Beirut, Beirut 1107 2020, Lebanon.
Laboratory of Smart Structures and Structural Integrity (SSSI), Department of Mechanical Engineering, American University of Beirut, Beirut 1107 2020, Lebanon.
Polymers (Basel). 2022 Aug 30;14(17):3575. doi: 10.3390/polym14173575.
Self-healing polymers such as poly(ethylene-co-methacrylic acid) ionomers (PEMAA) can heal themselves immediately after a projectile puncture which in turn lowers environmental pollution from replacement. In this study, the thermal-mechanical properties and self-healing response of a library of 15 PEMAA copolymers were studied to understand the effects of the ionic content (Li, Na, Zn, Mg) and neutralization percentage (13 to 78%) on the results. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile testing were used to study the thermo-mechanical properties of PEMAA copolymers while the self-healing response was studied using the projectile test. Puncture sites were observed using scanning electron microscopy (SEM) and the healing efficiency was quantitatively measured using the water leakage test. Five different self-healing responses were observed and correlated to ionic content and neutralization. At high neutralization, divalent neutralizing ions (Zn and Mg) that have stronger ionic interactions exhibited brittle responses during projectile testing. PEMAA samples neutralized with Mg and Li at low concentrations had a higher healing efficiency than PEMAA samples neutralized with Zn and Na at low neutralization. The PEMAA copolymers with higher tensile stress and two distinct peaks in the graph of loss factor versus temperature that indicate the presence of sufficient ionic aggregate clusters had improved healing efficiency. By increasing the neutralization percentage from 20% to 70%, the tensile strength and modulus of the samples increased and their self-healability generally increased. Among the investigated samples, the copolymer with ~50% neutralization by Li salt showed the highest healing efficiency (100%). Overall, the strength and elastic response required for successful self-healing responses in PEMAA copolymers are shown to be governed by the choice of ion and the amount of neutralization.
诸如聚（乙烯 - 共 - 甲基丙烯酸）离聚物（PEMAA）之类的自修复聚合物在被射弹刺穿后能够立即自我修复，这反过来降低了因更换而产生的环境污染。在本研究中，对15种PEMAA共聚物的库进行了热机械性能和自修复响应研究，以了解离子含量（锂、钠、锌、镁）和中和百分比（13%至78%）对结果的影响。采用差示扫描量热法（DSC）、动态力学分析（DMA）和拉伸试验来研究PEMAA共聚物的热机械性能，同时使用射弹试验研究自修复响应。使用扫描电子显微镜（SEM）观察穿刺部位，并通过漏水试验定量测量愈合效率。观察到五种不同的自修复响应，并将其与离子含量和中和相关联。在高中和度下，具有较强离子相互作用的二价中和离子（锌和镁）在射弹测试期间表现出脆性响应。在低浓度下用镁和锂中和的PEMAA样品比在低中和度下用锌和钠中和的PEMAA样品具有更高的愈合效率。具有较高拉伸应力且在损耗因子与温度的曲线图中有两个明显峰值（表明存在足够的离子聚集体簇）的PEMAA共聚物具有更高的愈合效率。通过将中和百分比从20%提高到70%，样品的拉伸强度和模量增加，并且它们的自修复能力总体上增加。在所研究的样品中，用锂盐中和约50%的共聚物显示出最高的愈合效率（100%）。总体而言，PEMAA共聚物成功实现自修复响应所需的强度和弹性响应表明受离子选择和中和量的控制。
