Special Issue "Laser Processing of Polymer Materials"

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Processing and Engineering".

Deadline for manuscript submissions: closed (15 November 2019).

Special Issue Editor

Dr. Esther Rebollar
E-Mail Website
Guest Editor
CSIC - Instituto de Química Física Rocasolano (IQFR), Madrid, Spain
Interests: laser micro- and nanoprocessing of polymers; mechanisms of laser ablation of polymers; laser-induced period surface structures in polymers; polymer thin films; applications of modified polymers; functional polymers
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Special Issue Information

Dear Colleagues,

Since the first laser was developed in 1960, laser technology has been growing, and the processing of polymers has now become an important field of applied and fundamental research. Laser techniques constitute attractive alternatives for processing of soft materials affording the sought versatility and reliability. Indeed, laser techniques can be used to fabricate substrates with a variety of high-precision patterns at different length scales and can be applied in noncontact and flexible set-ups under a great variety of environments. Moreover, laser processing can be adapted both to the materials’ properties and to the desired surface pattern by controlling the laser characteristics.

This Special issue “Laser Processing of Polymer Materials” aims to gather contributions on recent advances about the use of laser techniques for the processing of polymers, both concerning surface and bulk modification, micro- and nanostructuring, and considering both the fundamentals of laser processing and the applications of the modified polymer materials.

Dr. Esther Rebollar
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Laser microstructuring of polymers
  • Laser nanostructuring of polymers
  • Laser foaming
  • Laser ablation of polymers
  • Laser texturing of polymers
  • Laser polymerization
  • Laser deposition of polymers
  • Laser transfer and printing of polymers
  • Applications of polymers processed by laser
  • Modeling of laser processing of polymers

Published Papers (12 papers)

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Research

Open AccessArticle
Investigation on the Continuous Wave Mode and the ms Pulse Mode Fiber Laser Drilling Mechanisms of the Carbon Fiber Reinforced Composite
Polymers 2020, 12(3), 706; https://doi.org/10.3390/polym12030706 - 23 Mar 2020
Cited by 1 | Viewed by 775
Abstract
The near infrared (NIR) laser drilling of a carbon fiber reinforced polymer (CFRP) composite in the continuous wave (CW) mode and the ms pulse mode was investigated by an experiment and a numerical simulation. The relationships between the laser penetrating time, entrance hole [...] Read more.
The near infrared (NIR) laser drilling of a carbon fiber reinforced polymer (CFRP) composite in the continuous wave (CW) mode and the ms pulse mode was investigated by an experiment and a numerical simulation. The relationships between the laser penetrating time, entrance hole diameter, surface heat affected zone (HAZ) width, and material ablation rate and the laser irradiation time and laser peak power densities were obtained from the experiment. For the same average power density of the laser output, 3.5 kW/cm2, it was found that the ms pulse laser mode, which had a higher peak power density, had a higher drilling efficiency. When drilling the same holes, the pulse laser mode, which had the highest peak power density of 49.8 kW/cm2, had the lowest drilling time of 0.23 s and had the smallest surface HAZ width of 0.54 mm. In addition, it was found that the laser penetrating time decreased sharply when the peak power density was higher than 23.4 kW/cm2. After analyzing the internal gas pressure by the numerical simulation, it was considered that a large internal gas pressure appeared, which resulted from polymer pyrolysis, causing a large amount of the mechanical erosion of the composite material to improve the drilling efficiency. Therefore, the ms pulse laser showed its potential and advantage in laser drilling the CFRP composite. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Laser Welding of Transmitting High-Performance Engineering Thermoplastics
Polymers 2020, 12(2), 402; https://doi.org/10.3390/polym12020402 - 10 Feb 2020
Viewed by 931
Abstract
Laser processing is a rapidly growing key technology driven by several advantages such as cost and performance. Laser welding presents numerous advantages in comparison with other welding technologies, providing high reliability and cost-effective solutions. Significant interest in this technology, combined with the increasing [...] Read more.
Laser processing is a rapidly growing key technology driven by several advantages such as cost and performance. Laser welding presents numerous advantages in comparison with other welding technologies, providing high reliability and cost-effective solutions. Significant interest in this technology, combined with the increasing demand for high-strength lightweight structures has led to an increasing interest in joining high-performance engineering thermoplastics by employing laser technologies. Laser transmission welding is the base method usually employed to successfully join two polymers, a transmitting one through which the laser penetrates, and another one responsible for absorbing the laser radiation, resulting in heat and melting of the two components. In this work, the weldability of solely transmitting high-performance engineering thermoplastic is analyzed. ERTALON® 6 SA, in its white version, is welded by a pulsed Nd:YAG laser. Tensile tests were performed in order to evaluate the quality of each joint by assessing its strength. A numerical model of the joint is also developed to support the theoretical approaches employed to justify the experimental observations. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
High-Repetition-Rate Femtosecond Laser Processing of Acrylic Intra-Ocular Lenses
Polymers 2020, 12(1), 242; https://doi.org/10.3390/polym12010242 - 20 Jan 2020
Cited by 4 | Viewed by 943
Abstract
The study of laser processing of acrylic intra-ocular lenses (IOL) by using femtosecond laser pulses delivered at high-repetition rate is presented in this work. An ultra-compact air-cooled femtosecond diode laser (HighQ2-SHG, Spectra-Physics) delivering 250 fs laser pulses at the fixed wavelength of 520 [...] Read more.
The study of laser processing of acrylic intra-ocular lenses (IOL) by using femtosecond laser pulses delivered at high-repetition rate is presented in this work. An ultra-compact air-cooled femtosecond diode laser (HighQ2-SHG, Spectra-Physics) delivering 250 fs laser pulses at the fixed wavelength of 520 nm with a repetition rate of 63 MHz was used to process the samples. Laser inscription of linear periodic patterns on the surface and inside the acrylic substrates was studied as a function of the processing parameters as well as the optical absorption characteristics of the sample. Scanning Electron Microscopy (SEM) Energy Dispersive X-ray Spectroscopy (EDX), and micro-Raman Spectroscopy were used to evaluate the compositional and microstructural changes induced by the laser radiation in the processed areas. Diffractive characterization was used to assess 1st-order efficiency and the refractive index change. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Picosecond Laser Ablation of Polyhydroxyalkanoates (PHAs): Comparative Study of Neat and Blended Material Response
Polymers 2020, 12(1), 127; https://doi.org/10.3390/polym12010127 - 05 Jan 2020
Cited by 2 | Viewed by 1408
Abstract
Polyhydroxyalkanoates (PHAs) have emerged as a promising biodegradable and biocompatible material for scaffold manufacturing in the tissue engineering field and food packaging. Surface modification is usually required to improve cell biocompatibility and/or reduce bacteria proliferation. Picosecond laser ablation was applied for surface micro [...] Read more.
Polyhydroxyalkanoates (PHAs) have emerged as a promising biodegradable and biocompatible material for scaffold manufacturing in the tissue engineering field and food packaging. Surface modification is usually required to improve cell biocompatibility and/or reduce bacteria proliferation. Picosecond laser ablation was applied for surface micro structuring of short- and medium-chain length-PHAs and its blend. The response of each material as a function of laser energy and wavelength was analyzed. Picosecond pulsed laser modified the surface topography without affecting the material properties. UV wavelength irradiation showed halved ablation thresholds compared to visible (VIS) wavelength, revealing a greater photochemical nature of the ablation process at ultraviolet (UV) wavelength. Nevertheless, the ablation rate and, therefore, ablation efficiency did not show a clear dependence on beam wavelength. The different mechanical behavior of the considered PHAs did not lead to different ablation thresholds on each polymer at a constant wavelength, suggesting the interplay of the material mechanical parameters to equalize ablation thresholds. Blended-PHA showed a significant reduction in the ablation threshold under VIS irradiation respect to the neat PHAs. Picosecond ablation was proved to be a convenient technique for micro structuring of PHAs to generate surface microfeatures appropriate to influence cell behavior and improve the biocompatibility of scaffolds in tissue engineering. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Poly(ethylene terephthalate) Powder—A Versatile Material for Additive Manufacturing
Polymers 2019, 11(12), 2041; https://doi.org/10.3390/polym11122041 - 09 Dec 2019
Cited by 3 | Viewed by 950
Abstract
The 3D printing of articles by the effect of a directed laser beam on a plastic powder is a demanding process, and unlike injection molding, very few polymers work well enough with it. Recently, we reported that poly(ethylene terephthalate) (PET) powder has intrinsically [...] Read more.
The 3D printing of articles by the effect of a directed laser beam on a plastic powder is a demanding process, and unlike injection molding, very few polymers work well enough with it. Recently, we reported that poly(ethylene terephthalate) (PET) powder has intrinsically good properties for 3D printing. Basic mechanical properties were shown earlier and it was demonstrated that unfused but heat-exposed PET powder does not degrade quickly allowing good re-use potential. In this work, we conducted a detailed comparison of the mechanical properties of PET and polyamide 12 from different build orientations. PET powders with two different molecular weights were used. With the high molecular weight powder, the processing parameters were optimized, and the printed bars showed little difference between the different orientations, which means there is low anisotropy in mechanical properties of built parts. Based on processing experience of the first powder, the second powder with a lower molecular weight was also very printable and complex parts were made with ease from the initial printing trials; since the process parameters were not optimized then, lower mechanical properties were obtained. While the intrinsic material properties of PET (melting and re-crystallization kinetics) are not the best for injection molding, PET is eminently suitable for powder bed fusion. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Pump Polarization and Size Effects on the Performance of Polymer Lasers
Polymers 2019, 11(12), 2031; https://doi.org/10.3390/polym11122031 - 07 Dec 2019
Cited by 1 | Viewed by 776
Abstract
The parameters of a pump have a marked influence on the performance of distributed feedback polymer lasers. Our polymer laser consisted of a grating and a polymer film. We fabricated the grating using interference lithography. The polymer film was spin coated on the [...] Read more.
The parameters of a pump have a marked influence on the performance of distributed feedback polymer lasers. Our polymer laser consisted of a grating and a polymer film. We fabricated the grating using interference lithography. The polymer film was spin coated on the grating. A half-wave plate was used to change the pump polarization, and an x-y slit was used to change the pump size. The direction of grating lines were parallel to the x axis of the slit. The laser performance was modified by changing the polarizations and sizes of the pump beam. The lasing threshold increased more rapidly with decreasing pump size in the y direction than in the x direction. The influence of the pump polarization on the lasing threshold for decreasing pump size in the x direction was greater than that for decreasing pump size in the y direction. These results may be useful for the miniaturization of distributed feedback polymer lasers. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Influence of Bulk Temperature on Laser-Induced Periodic Surface Structures on Polycarbonate
Polymers 2019, 11(12), 1947; https://doi.org/10.3390/polym11121947 - 27 Nov 2019
Cited by 6 | Viewed by 1418
Abstract
In this paper, the influence of the bulk temperature (BT) of Polycarbonate (PC) on the occurrence and growth of Laser-induced Periodic Surface Structures (LIPSS) is studied. Ultrashort UV laser pulses with various laser peak fluence levels F 0 and various numbers of overscans ( N OS ) were applied on the surface of pre-heated Polycarbonate at different bulk temperatures. Increased BT leads to a stronger absorption of laser energy by the Polycarbonate. For N OS < 1000 High Spatial Frequency LIPSS (HSFL), Low Spatial Frequency LIPSS perpendicular (LSFL-I) and parallel (LSFL-II) to the laser polarization were only observed on the rim of the ablated tracks on the surface but not in the center of the tracks. For N OS 1000 , it was found that when pre-heating the polymer to a BT close its glass transition temperature ( T g ), the laser fluence to achieve similar LIPSS as when processed at room temperature decreases by a factor of two. LSFL types I and II were obtained on PC at a BT close to T g and their periods and amplitudes were similar to typical values found in the literature. To the best of the author’s knowledge, it is the first time both LSFL types developed simultaneously and consistently on the same sample under equal laser processing parameters. The evolution of LIPSS from HSFL, over LSFL-II to LSFL I, is described, depending on laser peak fluence levels, number of pulses processing the spot and bulk temperature. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Correlations between Process Parameters and Outcome Properties of Laser-Sintered Polyamide
Polymers 2019, 11(11), 1850; https://doi.org/10.3390/polym11111850 - 09 Nov 2019
Cited by 13 | Viewed by 842
Abstract
As additive manufacturing (AM) becomes more accessible, correlating process parameters with geometric and mechanical properties is an important topic. Because the number of process variables in AM is large, extensive studies must be conducted in order to underline every particular influence. The study [...] Read more.
As additive manufacturing (AM) becomes more accessible, correlating process parameters with geometric and mechanical properties is an important topic. Because the number of process variables in AM is large, extensive studies must be conducted in order to underline every particular influence. The study focuses on two variables—part orientation in the orthogonal horizontal plane and energy density—and targets two outcomes—geometric and tensile properties of the parts. The AM process was conducted on selective laser sintering (SLS) machine EOS Formiga P100 using EOS white powder polyamide (PA2200). After finishing the sinterization process, the parts were postprocessed, measured, weighted, and mechanically tested. The geometric evaluation and mass measurements of every sample allowed us to compute the density of all parts according to the sinterization energy and orientation, and to determine the relative error of every dimension. By conducting the tensile testing, the elastic and strength properties were determined according to process variables. A linear trend regarding sample density and energy density was identified. Also, large relative dimensional errors were recorded for the lowest energy density. Mechanical properties encountered the highest value for the highest energy density at a 45° orientation angle. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Stripping of PFA Fluoropolymer Coatings Using a Nd:YAG Laser (Q-Switch) and an Yb Fiber Laser (CW)
Polymers 2019, 11(11), 1738; https://doi.org/10.3390/polym11111738 - 24 Oct 2019
Cited by 1 | Viewed by 671
Abstract
Fluoropolymers such as PFA are used as coatings for the protection of metal substrates due to their high chemical inertia and non-stick properties. These are “wear and tear” coatings and they degrade, at which point they should be removed for a new application. [...] Read more.
Fluoropolymers such as PFA are used as coatings for the protection of metal substrates due to their high chemical inertia and non-stick properties. These are “wear and tear” coatings and they degrade, at which point they should be removed for a new application. The removal of these types of coating by laser is of interest due to the process’s flexibility, precision, ease of automation, and environmental sustainability. The efficiency of the procedure was shown with the use of a source in a pulsed Nd:YAG and a source in continuous mode of fiber (Yb). The rates of stripping (cm2/min) and fluence (J/cm2) were analyzed and related to the power of the laser sources. Variations of the substrate after stripping were studied: roughness and hardness. The properties of the coating, thickness, roughness, water sliding angle, and microhardness were also evaluated. It was concluded that the laser in continuous mode was more efficient than the pulsed laser; laser removal of fluoropolymers has a strong relationship with reflectivity, and the mechanical and surface properties of the substrate after stripping remained virtually unchanged. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Controlling the Performance of Polymer Lasers via the Cavity Coupling
Polymers 2019, 11(5), 764; https://doi.org/10.3390/polym11050764 - 01 May 2019
Cited by 5 | Viewed by 849
Abstract
The polarization and threshold of distributed feedback (DFB) polymer lasers were controlled by adjusting the cavity coupling. The cavity of DFB polymer lasers consisted of two gratings, which was fabricated by a two-beam multi-exposure holographic technique. The coupling strength of the cavity modes [...] Read more.
The polarization and threshold of distributed feedback (DFB) polymer lasers were controlled by adjusting the cavity coupling. The cavity of DFB polymer lasers consisted of two gratings, which was fabricated by a two-beam multi-exposure holographic technique. The coupling strength of the cavity modes was tuned by changing the angle between the two gratings. The threshold of the polymer lasers decreased with reducing the coupling strength of the cavity modes. A minimum threshold was observed at the lowest coupling strength. Moreover, the azimuthally polarized output of the polymer lasers was modified by changing the cavity coupling. These results may provide additional perspectives to improve the performance of DFB polymer lasers. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Flexible Random Laser Using Silver Nanoflowers
Polymers 2019, 11(4), 619; https://doi.org/10.3390/polym11040619 - 03 Apr 2019
Cited by 8 | Viewed by 1289
Abstract
A random laser was achieved in a polymer membrane with silver nanoflowers on a flexible substrate. The strong confinement of the polymer waveguide and the localized field enhancement of silver nanoflowers were essential for the low-threshold random lasing action. The lasing wavelength can [...] Read more.
A random laser was achieved in a polymer membrane with silver nanoflowers on a flexible substrate. The strong confinement of the polymer waveguide and the localized field enhancement of silver nanoflowers were essential for the low-threshold random lasing action. The lasing wavelength can be tuned by bending the flexible substrate. The solution phase synthesis of the silver nanoflowers enables easy realization of this type of random lasers. The flexible and high-efficiency random lasers provide favorable factors for the development of imaging and sensing devices. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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Open AccessArticle
Study on the Main Influencing Factors in the Removal Process of Non-Stick Fluoropolymer Coatings Using Nd:YAG Laser
Polymers 2019, 11(1), 123; https://doi.org/10.3390/polym11010123 - 12 Jan 2019
Cited by 5 | Viewed by 1421
Abstract
The coatings with fluoropolymer resins rich in fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) are applied as anti-adherent coatings on aluminum–magnesium substrates for use in food containers. In many cases, due to wear, they must be stripped for the application of a new [...] Read more.
The coatings with fluoropolymer resins rich in fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) are applied as anti-adherent coatings on aluminum–magnesium substrates for use in food containers. In many cases, due to wear, they must be stripped for the application of a new coating on the same substrate. There are several processes for this: blasting, plasma, pyrolysis, chemical processes, laser, high pressure water, and combinations of these. This work focuses on the characterization of the main factors that condition the FEP coating removal process by a continuous wave (CW) Nd:YAG laser, and on the determination of the efficiency of this type of technology used for this purpose. Stripping surface per unit of time and energy consumption per unit area has been determined among other efficiency indicators. Regarding the characterization of the coating object of study, its thickness, surface roughness, contact angle, microhardness and absorbance-reflectance responses have been determined, and the results have been compared with those obtained in the case of PTFE. In addition, to evaluate the mechanical damage caused in the substrate after coating removal by (CW) Nd:YAG laser, the tensile strength, Vickers hardness, Ra and Rz roughness, and the substrate thickness have been measured and analyzed. Full article
(This article belongs to the Special Issue Laser Processing of Polymer Materials)
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