Rodríguez-Beltrán René I, Prada-Rodrigo Javier, Crespo Ana, Ezquerra Tiberio A, Moreno Pablo, Rebollar Esther
Grupo de Aplicaciones del Láser y Fotónica (ALF-USAL), Universidad de Salamanca, Pl. de la Merced s/n, 37008 Salamanca, Spain.
CONACYT-Centro de Investigación Científica y de Educación Superior de Ensenada, Unidad Foránea Monterrey, Alianza Centro 504, PIIT, Apodaca 66629, Mexico.
Polymers (Basel). 2022 Dec 1;14(23):5243. doi: 10.3390/polym14235243.
In this work, the formation of laser-induced periodic surface structures (LIPSS) on the surfaces of thin films of poly(ethylene terephthalate) (PET) and PET reinforced with expanded graphite (EG) was studied. Laser irradiation was carried out by ultraviolet (265 nm) and near-infrared (795 nm) femtosecond laser pulses, and LIPSS were formed in both materials. In all cases, LIPSS had a period close to the irradiation wavelength and were formed parallel to the polarization of the laser beam, although, in the case of UV irradiation, differences in the formation range were observed due to the different thermal properties of the neat polymer in comparison to the composite. To monitor the modification of the physicochemical properties of the surfaces after irradiation as a function of the laser wavelength and of the presence of the filler, different techniques were used. Contact angle measurements were carried out using different reference liquids to measure the wettability and the solid surface free energies. The initially hydrophilic surfaces became more hydrophilic after ultraviolet irradiation, while they evolved to become hydrophobic under near-infrared laser irradiation. The values of the surface free energy components showed changes after nanostructuring, mainly in the polar component. Additionally, for UV-irradiated surfaces, adhesion, determined by the colloidal probe technique, increased, while, for NIR irradiation, adhesion decreased. Finally, nanomechanical properties were measured by the PeakForce Quantitative Nanomechanical Mapping method, obtaining maps of elastic modulus, adhesion, and deformation. The results showed an increase in the elastic modulus in the PET/EG, confirming the reinforcing action of the EG in the polymer matrix. Additionally, an increase in the elastic modulus was observed after LIPSS formation.
在这项工作中，研究了聚对苯二甲酸乙二酯（PET）薄膜以及用膨胀石墨（EG）增强的PET薄膜表面上激光诱导周期性表面结构（LIPSS）的形成。通过紫外（265 nm）和近红外（795 nm）飞秒激光脉冲进行激光辐照，两种材料中均形成了LIPSS。在所有情况下，LIPSS的周期都接近辐照波长，并且与激光束的偏振方向平行，不过，在紫外辐照的情况下，由于纯聚合物与复合材料的热性能不同，观察到了形成范围的差异。为了监测辐照后表面物理化学性质随激光波长和填料存在情况的变化，使用了不同的技术。使用不同的参考液体进行接触角测量，以测量润湿性和固体表面自由能。最初亲水的表面在紫外辐照后变得更加亲水，而在近红外激光辐照下则演变为疏水表面。表面自由能分量的值在纳米结构化后发生了变化，主要是在极性分量方面。此外，对于紫外辐照的表面，通过胶体探针技术测定的粘附力增加，而对于近红外辐照，粘附力降低。最后，通过峰值力定量纳米力学映射方法测量纳米力学性能，获得弹性模量、粘附力和变形的图谱。结果表明PET/EG中的弹性模量增加，证实了EG在聚合物基体中的增强作用。此外，在LIPSS形成后观察到弹性模量增加。
