Polymers

Research

17 pages, 2946 KiB

Open AccessArticle

The Impact of Selected Laser-Marking Parameters and Surface Conditions on White Polypropylene Moldings

by Piotr Czyżewski, Dariusz Sykutera and Mateusz Rojewski

Polymers 2022, 14(9), 1879; https://doi.org/10.3390/polym14091879 - 4 May 2022

Cited by 5 | Viewed by 3507

Laser marking of polymer materials is a technology that is increasingly used in industry. Polypropylene (PP) shows a low ability to absorb electromagnetic radiation in the near-infrared range (λ = 1064 nm). The paper presents the influence of the surface condition of white-colored [...] Read more.

Laser marking of polymer materials is a technology that is increasingly used in industry. Polypropylene (PP) shows a low ability to absorb electromagnetic radiation in the near-infrared range (λ = 1064 nm). The paper presents the influence of the surface condition of white-colored polypropylene moldings on the efficiency of their marking with a laser beam. In addition, the operation of the commercial laser marking additive (LMA) Lifolas M 117009 UN, intended to support the process of laser marking of polyolefin surfaces, was verified. The study is an attempt to combine laser operating parameters, material, and geometric properties of PP moldings to obtain the expected quality of graphic symbols. The test samples were made by injection molding method with the use of a specially designed modular injection mold. The molding cavities were prepared with various methods of metal processing, thanks to which obtained moldings differed in surface condition. The marking effects were assessed based on colorimetric tests and digital image analysis. The 0.5 wt% LMA content resulted in obtaining a graphic sign with high contrast in comparison to the background. The gradual increase in the modifier content resulted in a further increase in contrast. These values depended on the degree of surface finish of the samples, and therefore on the roughness parameters. Samples with a rough surface finish showed higher contrast compared to surfaces with a high surface finish. It was also found that for the analyzed moldings, the laser-marking process should be performed with the use of a low head velocity (450–750 mm/s) and a high concentration of the laser beam (0.03–0.05 mm). Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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22 pages, 7681 KiB

Open AccessArticle

Investigating the Recyclability of Laser PP CP 75 Polypropylene Powder in Laser Powder Bed Fusion (L-PBF)

by Fredrick M. Mwania, Maina Maringa and Jacobus G. van der Walt

Polymers 2022, 14(5), 1011; https://doi.org/10.3390/polym14051011 - 3 Mar 2022

Cited by 5 | Viewed by 2450

Abstract

In the present study, recyclability of Laser PP CP 75 polypropylene powder from Diamond Plastics GmbH was determined by characterizing and comparing the used powder after each cycle with material from previous cycles and with fresh powder. The melt flow index of Laser [...] Read more.

In the present study, recyclability of Laser PP CP 75 polypropylene powder from Diamond Plastics GmbH was determined by characterizing and comparing the used powder after each cycle with material from previous cycles and with fresh powder. The melt flow index of Laser PP CP 75 was affected by recycling since it was observed to change by 30.62% after the 8th 100% re-use cycle, a lower value than PA 12 of 66.04%, for the 6th re-use cycle. Parts printed with virgin Laser PP CP 75 had an average dimensional error of 3.02% (virgin material) and 4.06% after the 4th 100% re-use cycle, which raises concerns about the commercial viability of the material. After the 4th re-use cycle, the printed parts had distorted edges and failed to print after the 9th print cycle. Lastly, tensile testing revealed a skewed bell-shaped curve of strength versus the number of recycles with the highest ultimate tensile strength occurring for the second 100% re-use cycle (7.4 MPa). The curves for elastic modulus and percentage elongation were inverted with minimum points for the 2nd 100% re-use cycle. Overall, the experimental work confirmed that the properties of polypropylene powder were affected by recycling in polymer laser sintering, but the powder exhibited superior characteristics upon recycling to those of the predominantly used PA 12 powder. Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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9 pages, 2594 KiB

Open AccessArticle

Tunable WGM Laser Based on the Polymer Thermo-Optic Effect

by Shuai Zhang, Tianrui Zhai, Libin Cui, Xiaoyu Shi, Kun Ge, Ningning Liang and Anwer Hayat

Polymers 2021, 13(2), 205; https://doi.org/10.3390/polym13020205 - 8 Jan 2021

Cited by 13 | Viewed by 2933

Abstract

In this work, the thermo-optic effect in polymers was used to realize a temperature-tunable whispering-gallery-mode laser. The laser was fabricated using a capillary tube filled with a light-emitting conjugated polymer solution via the capillary effect. In the whispering-gallery-mode laser emission wavelength can be [...] Read more.

In this work, the thermo-optic effect in polymers was used to realize a temperature-tunable whispering-gallery-mode laser. The laser was fabricated using a capillary tube filled with a light-emitting conjugated polymer solution via the capillary effect. In the whispering-gallery-mode laser emission wavelength can be continuously tuned to about 19.5 nm using thermo-optic effect of polymer. The influence of different organic solvents on the tuning rate was studied. For a typical lasing mode with a bandwidth of 0.08 nm, a temperature-resolved tuning rate of ~1.55 nm/°C was obtained. The two-ring coupling effect is responsible for the suppression of the WGM in the micro-cavity laser. The proposed laser exhibited good reversibility and repeatability as well as a sensitive response to temperature, which could be applied to the design of photothermic and sensing devices. Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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11 pages, 5008 KiB

Open AccessArticle

Evaluation of the Joining Response of Biodegradable Polylactic Acid (PLA) from Fused Deposition Modeling by Infrared Laser Irradiation

by J. M. Vazquez-Martinez, D. Piñero, J. Salguero and M. Batista

Polymers 2020, 12(11), 2479; https://doi.org/10.3390/polym12112479 - 26 Oct 2020

Cited by 7 | Viewed by 2166

Abstract

The development of high-complexity geometry parts is one of the main goals of additive manufacturing technology. However, the failure of printed structures and the joining of different parts to create complex assemblies represents a real challenge in the research of efficient and sustainability [...] Read more.

The development of high-complexity geometry parts is one of the main goals of additive manufacturing technology. However, the failure of printed structures and the joining of different parts to create complex assemblies represents a real challenge in the research of efficient and sustainability techniques for the permanent assembly of polymers. Laser welding processes have been used as a single-step method to join metals for years. Nowadays, the growing trend in the use of thermoplastics for additive manufacturing has led to the need to adapt this technique to materials with a very specific nature and which are more sensitive to thermal effects. In addition, the possibility of transmitting the laser beam through transparent polymer layers allows to us focus the energy supply on internal sections of the assembled components. In this research, an infrared laser marking system was used to join two different samples of polylactic acid manufactured by fused deposited modeling technology. In order to increase the effectiveness of the bonding process, a transparent and a dark sample have been used as assembly material, focusing the laser beam on the interface area of the two parts. By means of tensile tests, dimensional measurement and the use of optical microscopy techniques, a basis was established that links the supplied energy by laser to the joining performance. Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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13 pages, 4177 KiB

Open AccessArticle

The Efficiency of UV Picosecond Laser Processing in the Shaping of Surface Structures on Elastomers

by Bogdan Antoszewski, Szymon Tofil and Krystian Mulczyk

Polymers 2020, 12(9), 2041; https://doi.org/10.3390/polym12092041 - 8 Sep 2020

Cited by 7 | Viewed by 2168

Abstract

Elastomers are used as construction materials in numerous industries, and in particular the biomedical industry, mechatronics, electronics, the automotive industry, and chemical devices. The paper presents the results of tests involving the effects of microprocessing of elastomeric materials using a UV laser emitting [...] Read more.

Elastomers are used as construction materials in numerous industries, and in particular the biomedical industry, mechatronics, electronics, the automotive industry, and chemical devices. The paper presents the results of tests involving the effects of microprocessing of elastomeric materials using a UV laser emitting picosecond pulses. In particular, it presents an analysis of the influence of the parameters of processing on its efficiency. The paper provides a recommendation of the most advantageous processing parameters for materials such as polyurethane and silicone (MVQ). The authors see prospects for the use of the developed technology in the techniques of sealing and microfluidisation. The final part of the paper presents examples of surface structures generated on elements made of artificial materials and the results of tests involving reduction of friction resistance of sealing rings in a pneumatic actuator. Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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23 pages, 4958 KiB

Open AccessArticle

Surface Characteristics of Polymers with Different Absorbance after UV Picosecond Pulsed Laser Processing Using Various Repetition Rates

by Seung Sik Ham and Ho Lee

Polymers 2020, 12(9), 2018; https://doi.org/10.3390/polym12092018 - 4 Sep 2020

Cited by 6 | Viewed by 3134

Abstract

We experimented with two polymer materials with different ultraviolet (UV) wavelength absorption characteristics, which are commonly used in flexible devices, by applying an ultrashort-pulsed laser of a 355-nm UV wavelength for 10 ps. The laser parameters studied were pulse repetition rate, laser irradiation [...] Read more.

We experimented with two polymer materials with different ultraviolet (UV) wavelength absorption characteristics, which are commonly used in flexible devices, by applying an ultrashort-pulsed laser of a 355-nm UV wavelength for 10 ps. The laser parameters studied were pulse repetition rate, laser irradiation method, and laser power condition. Previous studies using polyethylene terephthalate (PET), which does not exhibit linear absorption at a UV wavelength, have focused on processing trends resulting in minimal collateral damage around the laser-induced ablation. However, our results showed a trend of accumulating such damage irrespective of the laser parameters. Meanwhile, polyimide (PI) exhibited a completely different behavior depending on the laser parameters. At low pulse repetition rates, minimal collateral damage was observed, whereas at high repetition rates, the morphology varied considerably. The electrical characteristics of the laser-processed materials were found to be correlated with the variations in morphology. In the case of PI, such variations in electrical resistance and morphology indicated that the material was carbonized. The findings of this study are expected to provide a useful reference when selecting parameters for the laser processing of similar polymer materials. Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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15 pages, 2541 KiB

Open AccessArticle

Laser-Induced Periodic Surface Structuring of Poly(trimethylene terephthalate) Films Containing Tungsten Disulfide Nanotubes

by Javier Prada-Rodrigo, René I. Rodríguez-Beltrán, Sandra Paszkiewicz, Anna Szymczyk, Tiberio A. Ezquerra, Pablo Moreno and Esther Rebollar

Polymers 2020, 12(5), 1090; https://doi.org/10.3390/polym12051090 - 10 May 2020

Cited by 5 | Viewed by 4022

Abstract

We report the study of the formation of Laser Induced Periodic Surface Structures (LIPSS), with UV femtosecond laser pulses (λ = 265 nm), in free-standing films of both Poly(trimethylene terephthalate) (PTT) and the composite PTT/tungsten disulfide inorganic nanotubes (PTT-WS₂). We characterized [...] Read more.

We report the study of the formation of Laser Induced Periodic Surface Structures (LIPSS), with UV femtosecond laser pulses (λ = 265 nm), in free-standing films of both Poly(trimethylene terephthalate) (PTT) and the composite PTT/tungsten disulfide inorganic nanotubes (PTT-WS₂). We characterized the range of fluences and number of pulses necessary to induce LIPSS formation and measured the topography of the samples by Atomic Force Microscopy, the change in surface energy and contact angle using the sessile drop technique, and the modification in both Young’s modulus and adhesion force values with Peak Force-Quantitative Nanomechanical Mapping. LIPSS appeared parallel to the laser polarization with a period close to its wavelength in a narrow fluence and number of pulses regime, with PTT-WS₂ needing slightly larger fluence than raw PTT due to its higher crystallinity and heat diffusion. Little change was found in the total surface energy of the samples, but there was a radical increase in the negative polar component (γ−). Besides, we measured small variations in the samples Young’s modulus after LIPSS formation whereas adhesion is reduced by a factor of four. This reduction, as well as the increase in γ−, is a result of the modification of the surface chemistry, in particular a slight oxidation, during irradiation. Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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16 pages, 6533 KiB

Open AccessArticle

Development of Method Enhanced Laser Ablation Efficiency According to Fine Curvature of the Polymer through the Preliminary Preparation Process Using UV Picosecond Laser

by Seung Sik Ham and Ho Lee

Polymers 2020, 12(4), 959; https://doi.org/10.3390/polym12040959 - 20 Apr 2020

Cited by 4 | Viewed by 3366

Abstract

In processes using the ultrashort pulsed laser, the phenomenon that the ablation efficiency is reduced due to the increase of the shielding effect of the generated plume is increasingly caused by the use of the high power and high repetition rate. A new [...] Read more.

In processes using the ultrashort pulsed laser, the phenomenon that the ablation efficiency is reduced due to the increase of the shielding effect of the generated plume is increasingly caused by the use of the high power and high repetition rate. A new method is needed to prevent a decrease in ablation efficiency in processing using an ultrashort pulsed laser. In this study, the proposed a processing method that can improve the ablation efficiency by providing an efficient escape path of plume, and examine the feasibility of a new processing method. The new method we proposed is a method of laser processing after generating a fine curvature in the polymer as a preliminary preparation. The fine curvature of the polymer produced by the preliminary preparation induces an artificial chimney-like opening along the path of the incident beam during laser processing, thereby enabling the plume to be effectively removed. The experiment for examine the feasibility through a new method was conducted using a 10-picosecond laser of UV wavelength with two optical systems. As a new processing method, when processing with ultrashort pulse laser, it was observed that the ablation efficiency improved. Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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8 pages, 2603 KiB

Open AccessArticle

Tailoring Whispering Gallery Lasing and Random Lasing in A Compound Cavity

by Zhiyang Xu, Junhua Tong, Xiaoyu Shi, Jinxiang Deng and Tianrui Zhai

Polymers 2020, 12(3), 656; https://doi.org/10.3390/polym12030656 - 13 Mar 2020

Cited by 24 | Viewed by 4174

Abstract

A compound cavity was proposed to achieve both whispering gallery mode (WGM) lasing and random lasing. The WGM-random compound cavity consisted of a random structure with an annular boundary, which was fabricated by a method combining both inkjet printing and metal-assisted chemical etching [...] Read more.

A compound cavity was proposed to achieve both whispering gallery mode (WGM) lasing and random lasing. The WGM-random compound cavity consisted of a random structure with an annular boundary, which was fabricated by a method combining both inkjet printing and metal-assisted chemical etching methods. An ultrathin polymer membrane was attached to the WGM-random compound cavity, forming a polymer laser device. A transformation from WGM lasing to random lasing was observed under optical pumping conditions. The laser performance could be easily tailored by changing the parameter of the WGM-random compound cavity. These results provide a new avenue for the design of integrated light sources for sensing applications. Full article

(This article belongs to the Special Issue Laser Processing of Polymer Materials II)

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