Nano to microscale deformation behavior of different carboxylated styrene-butadiene co-polymer Latexes were investigated using a commercial nanoindentation device. The latexes differed primarily in their glass transition temperature (T g). The bulk dynamic rheological properties, as determined from a rheometer, dictate the axismmetric deformation behavior of the latexes. Results from dynamic tests performed on latexes were analyzed using the theories in contact and fracture mechanics. Two theories of linear viscoelastic fracture mechanics (LVEFM) were employed to model the adhesion hysteresis (loading-unloading cycle) curves to obtain meaningful cohesive zone (fracture process zone) parameters and a stress intensity functional (K I(t)) for an entire cycle. The stress intensity functional, extracted from the deformation behavior, is independent of the loading history and was shown to depend only on the crack propagation velocity, (da/dt), for the entire cycle. The quantitative values of stress intensities were then discussed in the light of polymer molecular phenomenon's such as viscous chain desorption. Nanoindetation was developed as a tool for systematically investigating both the bulk as well as the cohesive zone properties of viscoelastic polymers.; Effect of plastic deformation on the deformation behavior of high pigment volume concentration (PVC) coatings was also analyzed. Polystyrene plastic pigment, CaCO3 and Clay pigments were used to form the coatings layers. High PVC coatings are viscoelastic due to the latex present but also contain air, the third phase, which could explain the plastic deformation if a certain critical yield stress is exceeded. At PVC's greater than 70%, the coatings showed significant plastic (permanent) deformation, which has to be accounted for in modeling the hysteresis curves. The residual plastic deformation was confirmed by imaging the indent over a period of time. Modeling the curves resulted in a compressive yield stress (σY) value, which is an important parameter in predicting the calendaring performance of these coatings.
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机译：使用商用纳米压痕装置研究了不同羧化苯乙烯-丁二烯共聚物胶乳的纳米级至微米级变形行为。胶乳的主要区别在于其玻璃化转变温度（T g ）。由流变仪确定的整体动态流变性质决定了胶乳的轴测变形行为。使用接触和断裂力学中的理论分析了对乳胶进行动态测试的结果。利用线性粘弹性断裂力学（LVEFM）的两种理论来模拟粘着滞后（装卸循环）曲线，以获得有意义的内聚区（断裂过程区）参数和整个周期的压力强度函数（ K I （ t ））。从变形行为中提取的应力强度函数与载荷历史无关，并且在整个循环过程中，应力强度函数仅取决于裂纹扩展速度（da / dt）。然后根据聚合物分子现象，例如粘性链解吸，讨论了应力强度的定量值。纳米指数是一种用于系统研究粘弹性聚合物的体积以及 cohesive 区域特性的工具。还分析了塑性变形对高颜料体积浓度（PVC）涂层变形行为的影响。聚苯乙烯塑料颜料，CaCO 3 和粘土颜料用于形成涂层。高PVC涂层由于存在胶乳而具有粘弹性，但其中还包含空气（第三相），如果超过一定的临界屈服应力，则可以解释塑性变形。当PVC大于70％时，涂层表现出明显的塑性（永久性）变形，这在建模滞后曲线时必须加以考虑。通过在一段时间内对压痕成像可以确认残余的塑性变形。对曲线进行建模会产生压缩屈服应力（σ Y ）值，这是预测这些涂层的压延性能的重要参数。
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