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Effects of graphene nanoplatelets on crystallization, mechanical performance and molecular dynamics of the renewable poly(propylene furanoate)
Polymer ( IF 4.6 ) Pub Date : 2020-01-14 , DOI: 10.1016/j.polymer.2020.122172
Lazaros Papadopoulos , Panagiotis A. Klonos , Dimitrios Tzetzis , George Z. Papageorgiou , Apostolos Kyritsis , Dimitrios N. Bikiaris

Poly(propylene furanoate), PPF, is a new bio-based polyester produced from renewable resources and belongs in a class of materials expected to replace their fossil-based homologues. Envisaging its future applications, critical is the optimization of the material properties such as the mechanical performance. The latter is strongly connected with the degree of polymer crystallinity, CF, which in the case of PPF is rather slow. As in previous work in semicrystalline polymers, in order to facilitate crystallization we introduce here graphene nanoplatelets at the amounts of 0.5, 1.0 and 2.5 wt% as fillers into the PPF matrix. The study involves measurements by calorimetry (DSC), X-ray diffraction (XRD), nanoindentation testing and dielectric spectroscopy (BDS) on samples in the amorphous (melt quenched) and semicrystalline (annealed) states. DSC confirmed the aimed facilitation of crystallinity, as the crystallization time of PPF at the relatively mild temperature of 100 °C is significantly reduced in the nanocomposites. In next, we were able to estimate the rigid amorphous fraction, RAF, in the two polymer states, i.e. the interfacial polymer due to the fillers and around the formed crystals. The filler addition results in direct improvement of the mechanical performance of the amorphous samples (increase in the elastic modulus and hardness); whereas, upon the additional involvement of crystallization the mechanical properties are improved further. Interestingly, these improvements were found to correlate quite well with the amounts of formed RAF and CF. In addition, we proceed with the exploration of molecular dynamics (local β and segmental α relaxations) of PPF in the bulk and in the presence of the nanofillers, of polymer crystals as well as of introduced water traces. The severe effects on molecular dynamics were found, as expected, to arise from crystallization rather than by the fillers themselves. Results on segmental mobility (calorimetric and dielectric glass transition) were connected to the expected alternations in the semicrystalline morphology, the latter being partially supported by XRD. Finally, in the nanocomposites, an additional filler-induced relaxation was recorded (αf) which demonstrates independency from crystallization, however being influenced by the aforementioned water traces. Most possibly, αf arises from the polymer located at the fillers’ surface.



中文翻译:

石墨烯纳米片对可再生聚呋喃丙酸酯的结晶,力学性能和分子动力学的影响

聚呋喃丙酸酯(PPF)是一种由可再生资源生产的新型生物基聚酯,属于有望替代其化石基同系物的一类材料。考虑到其未来的应用,至关重要的是优化材料性能,例如机械性能。后者与聚合物结晶度CF紧密相关,在PPF的情况下,CF相当慢。如先前在半结晶聚合物中的工作一样,为了促进结晶,我们在这里将含量为0.5、1.0和2.5 wt%的石墨烯纳米片作为填充剂引入PPF基质中。该研究涉及通过量热法(DSC),X射线衍射(XRD),纳米压痕测试和介电谱(BDS)对处于非晶态(熔融淬火)和半结晶态(退火)的样品进行测量。DSC确认了促进结晶的目的,因为在纳米复合材料中,PPF在相对温和的100°C温度下的结晶时间显着减少。接下来,我们能够估计两种聚合物状态下的刚性无定形部分RAF,即由于填料和形成的晶体周围的界面聚合物。填料的添加直接改善了非晶态样品的机械性能(增加了弹性模量和硬度)。然而,在另外参与结晶的情况下,机械性能得到进一步改善。有趣的是,发现这些改进与形成的RAF和CF的量非常相关。此外,我们继续探索分子动力学(局部 因为在纳米复合材料中,PPF在相对温和的100°C温度下的结晶时间显着减少。接下来,我们能够估计两种聚合物状态下的刚性无定形部分RAF,即由于填料和形成的晶体周围的界面聚合物。填料的添加直接改善了非晶态样品的机械性能(增加了弹性模量和硬度)。然而,在另外参与结晶的情况下,机械性能得到进一步改善。有趣的是,发现这些改进与形成的RAF和CF的量非常相关。此外,我们继续探索分子动力学(局部 因为在纳米复合材料中,PPF在相对温和的100°C温度下的结晶时间显着减少。接下来,我们能够估计两种聚合物状态下的刚性无定形部分RAF,即由于填料和形成的晶体周围的界面聚合物。填料的添加直接改善了非晶态样品的机械性能(增加了弹性模量和硬度)。然而,在另外参与结晶的情况下,机械性能得到进一步改善。有趣的是,发现这些改进与形成的RAF和CF的量非常相关。此外,我们继续探索分子动力学(局部 我们能够估算两种聚合物状态下的刚性无定形部分RAF,即由于填料和形成的晶体周围的界面聚合物。填料的添加直接改善了非晶态样品的机械性能(增加了弹性模量和硬度)。然而,在另外参与结晶的情况下,机械性能得到进一步改善。有趣的是,发现这些改进与形成的RAF和CF的量非常相关。此外,我们继续探索分子动力学(局部 我们能够估算两种聚合物状态下的刚性无定形部分RAF,即由于填料和形成的晶体周围的界面聚合物。填料的添加直接改善了非晶态样品的机械性能(增加了弹性模量和硬度)。然而,在另外参与结晶的情况下,机械性能得到进一步改善。有趣的是,发现这些改进与形成的RAF和CF的量非常相关。此外,我们继续探索分子动力学(局部 填料的添加直接改善了非晶态样品的机械性能(增加了弹性模量和硬度)。然而,在另外参与结晶的情况下,机械性能得到进一步改善。有趣的是,发现这些改进与形成的RAF和CF的量非常相关。此外,我们继续探索分子动力学(局部 填料的添加直接改善了非晶态样品的机械性能(增加了弹性模量和硬度)。然而,在另外参与结晶的情况下,机械性能得到进一步改善。有趣的是,发现这些改进与形成的RAF和CF的量非常相关。此外,我们继续探索分子动力学(局部大量和存在纳米填料,聚合物晶体以及引入的水痕迹的情况下,PPF的β和分段α弛豫)。如所预期的,发现对分子动力学的严重影响是结晶而不是填料本身引起的。分段迁移率(量热和介电玻璃化转变)的结果与半结晶形态的预期变化有关,后者由XRD部分支持。最后,在纳米复合材料,附加的填料引起的舒张记录(α ˚F),其从结晶演示独立性,但是由上述的痕量水的影响。最有可能,α ˚F 由位于填料表面的聚合物产生。

更新日期:2020-01-14
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