Rahman Saadman Sakib, Mahmud Mayesha Binte, Omranpour Hosseinali, Salehi Amirmehdi, Monfared Ali Reza, Park Chul B
Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G8.
ACS Appl Mater Interfaces. 2024 Aug 14;16(32):42687-42703. doi: 10.1021/acsami.4c08654. Epub 2024 Jul 31.
In this paper, we develop high aspect ratio nanofibrils from a polycaprolactone-based thermoplastic polyurethane (TPU) and evaluate their performance as a toughening agent. Poly(methyl methacrylate) (PMMA) was chosen as the matrix material because of its inherent brittleness and low resistance to sudden shocks and impact. We show that the addition of as little as 3 wt % of TPU nanofibrils with an average diameter of ∼98 nm and very high aspect ratio can significantly improve both the tensile toughness (∼212%) and impact strength (∼40%) of the chosen matrix (i.e., PMMA) without compromising its original strength, stiffness, and transparency. We compare the performance of TPU nanofibrils with TPU spherical particles─the form TPU typically manifests into when melt-mixed with an immiscible polymer. Our findings highlight that the structure of TPU plays a crucial role in determining the critical concentration of TPU needed for the brittle-ductile transition of the matrix. We also provide new and valuable insights into the unique interfacial interaction (i.e., formation of fibrillar bridges) observed between the PMMA matrix and TPU. We also show that the inclusion of 3 wt % of TPU nanofibrils can notably enhance resistance to creep deformation, even at temperatures close to the glass transition temperature of the matrix. Finally, we evaluate recyclability and demonstrate that the composite containing 3 wt % of TPU nanofibrils can be mechanically recycled without losing any properties. The proposed TPU nanofibrils can withstand repeated reprocessing at temperatures up to 190 °C due to their very high melting point and thermal stability. This presents the opportunity for them to be utilized not just with amorphous PMMA, but also with a range of other materials that can be processed at or below this temperature to remarkably improve their toughness without sacrificing strength and stiffness.
在本文中，我们从基于聚己内酯的热塑性聚氨酯（TPU）制备了高长径比纳米纤维，并评估了它们作为增韧剂的性能。聚甲基丙烯酸甲酯（PMMA）因其固有的脆性以及对突然冲击和撞击的低抗性而被选为基体材料。我们表明，添加低至3 wt%的平均直径约为98 nm且长径比非常高的TPU纳米纤维，可显著提高所选基体（即PMMA）的拉伸韧性（约212%）和冲击强度（约40%），同时不损害其原始强度、刚度和透明度。我们将TPU纳米纤维的性能与TPU球形颗粒的性能进行了比较——TPU与不相容聚合物熔融混合时通常呈现的形态。我们的研究结果突出表明，TPU的结构在决定基体脆韧转变所需的TPU临界浓度方面起着关键作用。我们还对在PMMA基体和TPU之间观察到的独特界面相互作用（即形成纤维桥）提供了新的有价值的见解。我们还表明，即使在接近基体玻璃化转变温度的温度下，加入3 wt%的TPU纳米纤维也能显著提高抗蠕变变形能力。最后，我们评估了可回收性，并证明含有3 wt%TPU纳米纤维的复合材料可以进行机械回收而不损失任何性能。由于其非常高的熔点和热稳定性，所提出的TPU纳米纤维能够在高达190°C的温度下经受反复再加工。这为它们不仅与无定形PMMA一起使用，而且与一系列可在该温度或低于该温度下加工的其他材料一起使用提供了机会，从而在不牺牲强度和刚度的情况下显著提高它们的韧性。
