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Investigation of the track width-dependent melt pool characteristics during laser-sintering of polyamide 12 in correlation to various focus diameters
摘要： Factors such as not only costs, production time, reproducibility, but also the quality of the components are decisive factors in assessing the economic efficiency of a manufacturing process. With additive manufacturing processes, component production is made possible directly from a 3D CAD model. This means that small series and prototypes can already be produced economically today. In this area, the laser-sintering process, in particular, offers great potential for series production due to its high strength values and ductility. With laser-sintering systems that allow an optical widening of the laser focus, a faster exposure of the component and thus a shortening of the building time is possible. We developed a laser-sintering system whose laser focus diameter is adjustable in its cross-sectional area from 0.47 to 2 mm. The goal for the future is to produce large-area components significantly faster by widening the focus diameter, thus making laser-sintering more productive. In this paper, the focus-dependent melt pool formation is examined in correlation to different hatch distances during the laser-sintering of polyamide 12. For this purpose, a test specimen was developed which can display single tracks as well as a multitude of different track widths for all feasible focus level variations. This knowledge is required to determine and investigate the track width-dependent melt pool formation as a function of the focal diameter of the component cross sections.
关键词： Laser-sintering,Focus diameter,Single track,Polyamide 12
更新于2025-09-23 15:21:01
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Impact of environmental variables on the degradation of photovoltaic components and perspectives for the reliability assessment methodology
摘要： Backsheet cracking has been a major issue observed in the field; however, standardized qualification tests, such as IEC61215, are inadequate to reliably identify such failures of PV modules due to the lack of the critical weathering factors applied sequentially or in combination, such as those found in the service environments. To address this problem, we investigated the effects of various environmental variables on the degradation and failure behaviors of the polyamide-based backsheet in PV modules retrieved from five different locations, encompassing a variety of climates, including humid subtropical, hot-summer Mediterranean, tropical savanna climate and hot arid. The correlations between the degradation indicators and the weathering variables were further demonstrated by principle components analysis (PCA). We found strong relationships between: carbonyl formation and reflected solar radiation; hydroxyl formation and module temperature; yellowness and NO2 concentration, while no simple correlation could be found between a specific weathering factor and cracking. By introducing additional stress factors to the aged polyamide-based backsheet films with the novel “fragmentation test”, we successfully reproduced the field cracking behaviour. This study has demonstrated that different degradation modes of PV components respond differently to the environmental stresses encountered in service. Thereby, any accelerated laboratory test based on a single set condition or lacking key environmental variables would be inadequate to assess the long-term performance of PV modules and components. A new reliability-based methodology is proposed to quantitatively link laboratory testing with field results for the service life prediction of PV materials.
关键词： Reliability,Backsheet,Photovoltaic modules,Principle components analysis,Polyamide,Weathering
更新于2025-09-23 15:19:57
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Surface modification of polyamide 12 angioplasty balloons by photochemical reaction with an aromatic azide
摘要： Polyamide 12 (PA12) is used in a variety of applications when low moisture absorption, good dimensional stability, and toughness are required. Polyamide 12 is one of the polymers most frequently employed to fabricate angioplasty balloon catheters; however, its high hydrophobicity and chemical inertness require the application of coatings to make its surface more hydrophilic and biocompatible. In this work, an alternative method, based on the photochemical reaction of PA12 with a hydrophilic aromatic azide, was developed. Static and dynamic contact angle measurements evidenced that the surface modification process was able to improve PA12 wettability and that the effects were retained even after 12 months from surface treatment. Polyamide 12 modification resulted in an increase of its surface free energy, as evaluated by the van Oss, Good, and Chaudhury method. X‐ray photoelectron spectroscopy confirmed the presence of the aromatic azide on PA12 surface. Finally, compliance tests showed that the modification process did not reduce the mechanical performance of balloons.
关键词： contact angle,polyamide 12,angioplasty balloon catheter,surface free energy,surface modification
更新于2025-09-23 15:19:57
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Morphology of CdSe-Based Coatings Formed on Polyamide Substrate
摘要： Cadmium selenide (CdSe)-based layers were formed on the surface of polyamide 6 (PA) substrate film by treating PA film samples with potassium selenotrithionate (K2SeS2O6) solution (seleniumization) and then with cadmium(II) acetate, Cd(CH3COO)2, solution (cadmiumization). The morphology of CdSe-based layers was investigated by atomic force and scanning electron microscopies. It was determined that the formation of CdSe-based layers proceeds unevenly in the form of islands, which later tends to agglomerate. Therefore the surface of the layers formed is relatively uneven and rather rough. After seleniumization and cadmiumization procedures the average height of this layer have tendency to decrease from 337 after 1 h of seleniumization to 153 nm at 2.5 and 3.5 h of seleniumization. It was also determined that the RMS of formed layers slightly increases (from 32 to 42 nm) with the prolongation of PA seleniumization (from 1 to 2.5 hours) and it decreases (from 43 to 22 nm) with the increase of the temperature (from 50 °C to 70 °C) of seleniumized PA treatment by the solution containing Cd(II) salt. XPS data show that in coatings, substantial amounts of both cadmium hydroxide (Cd(OH)2) and cadmium oxide (CdO) are formed on the surface and within deeper layers of formed coatings. It was also determined that only a small fraction (～0.1%–2%) of cadmium selenide is present on the surface of formed coating after seleniumization and cadmiumization, while within in the deeper layers the concentrations of both Cd and Se were much higher and the fractions of Cd(OH)2 and CdO decreased.
关键词： SEM,Polyamide,Potassium Selenotrithionate,AFM,Morphology,CdSe-Based Layers
更新于2025-09-19 17:15:36
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Laser Welding of Transmitting High-Performance Engineering Thermoplastics
摘要： 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.
关键词： pulsed Nd:YAG laser welding,numerical model,polyamide 6,ERTALON 6 SA,high-performance engineering thermoplastic,mechanical testing
更新于2025-09-19 17:13:59
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Comparative study of selected indoor concentration from selective laser sintering process using virgin and recycled polyamide nylon (PA12)
摘要： Additive manufacturing (AM) stands out as one of the promising technologies that have huge potential towards manufacturing industry. The study on additive manufacturing impact on the environment and occupational exposure are attracting growing attention recently. However, most of the researcher focus on desktop and fused deposition modelling type and less attention given to the industrial type of AM. Usually, during the selective laser sintering process, recycle powder will be used again to reduce cost and waste. This article compares the PM 2.5, carbon dioxide (CO2) and total volatile organic compound (TVOC) concentration between virgin and recycles powder using polyamide-nylon (PA12) towards indoor concentration. Four phases of sampling involve during air sampling accordingly to the Industry Code of Practice on Indoor Air Quality 2010 by DOSH Malaysia. It was found that PM 2.5 and CO2 are mainly generated during the pre-printing process. The recycle powder tended to appear higher compared to virgin powder in terms of PM 2.5, and CO2. The peak value of PM 2.5 is 1452 μg/m3 and CO2 is 1218 ppm are obtained during the pre-printing process during 8 hours of sampling. TVOC concentration from recycling powder is slightly higher during the post- printing phase where confirm the influence of the powder cake and PA12 temperature from the printing process. In summary, this work proves that elective laser sintering (SLS) machine operators are exposed to a significant amount of exposure during the SLS printing process. Mitigation strategies and personal protective equipment are suggested to reduce occupational exposure.
关键词： selective laser sintering,occupational exposure,indoor air quality,polyamide-nylon,Additive manufacturing
更新于2025-09-16 10:30:52
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Preparation of ZnO nanoparticle-reinforced polyamide 6 composite by <i>in situ</i> -coproduced method and their properties
摘要： Polyamide 6/ZnO nanocomposites (noted as PA6/ZnO) were prepared by an in situ co-producing method, during which Zn2(OH)2CO3 decomposed into nano-ZnO in the process of the opening-ring polymerization of caprolactam at high temperature. Transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were used to analyze the size and dispersive properties of nano-ZnO, the crystallization and melting properties, the thermal properties, and crystal structure of PA6/ZnO composite, respectively. The results showed that the nano-ZnO derived from Zn2(OH)2CO3 via in situ polymerization of PA6-ZnO was uniformly dispersed in PA6 matrix. However, the overall nano-ZnO crystallization rate and crystal size in the PA6 matrix were hindered by the bulky PA6 molecular chains. The mechanical properties were evaluated using universal tensile and impact testing instruments. The results revealed that PA6/ZnO composite with 0.2% nano-ZnO content possessed excellent tensile strength, enhanced by 75% in comparison with the pure PA6. The nano-ZnO had little influence on the impact strength of PA6.
关键词： friction property,mechanical performance,nanocomposites,polyamide 6,nano-ZnO,polyamides,composite
更新于2025-09-09 09:28:46
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The structure of PA-Se-S-Cd composite materials probed with FTIR spectroscopy
摘要： Composite organic-inorganic functional materials are of significant importance in various applications of science and technology. In this work, PA-Se-S and PA-Se-S-Cd composite materials obtained by employing the sorption-diffusion method are discussed. A single precursor – K2SeS2O6 – was used as the source of both sulfur and selenium. In the aqueous solution, SeS2O6 2? and its decomposition products diffused into the polymer where they reacted with Cd2+ ions so that to form cadmium chalcogenide particles. Fourier-transform infrared (FTIR) spectroscopy was used to characterize the interactions between polyamide 6 and inorganic constituents, namely, K2SeS2O6, CdS and CdSe. The spectral behavior of amide I, II, A and B bands evidenced the competing formation of complex bonding structures based on the formation of covalent, electrostatic and hydrogen bonding between the PA 6 amide (NHCO) groups and the inorganic constituents. The number and the type of the formed bonds depend on the polyamide 6 exposure time in the K2SeS2O6 precursor solution. Such a complex interaction induces obvious conformational changes of the polyamide 6 chains. A possible bonding mechanism has been proposed to explain the observed spectral phenomena.
关键词： Inorganic-organic hybrid materials,Cadmium chalcogenides,Polyamide 6,Infrared spectra,Potassium selenotrithionate
更新于2025-09-04 15:30:14
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Evaluation of Exfoliated Graphite to Graphene in Polyamide 66 Using Novel High Shear Elongational Flow
摘要： Graphene has been publicized as the game changing material of this millennium. To this day, scalable production leading to exceptional material properties has been difficult to attain. Most methods require harsh chemicals, which result in destroying the graphene surface. A method was developed, exploiting high speed elongational flow in a novel designed batch mixer; creating a distribution of pristine few to many layer graphene flakes. The method focuses on exfoliating in a molten polyamide 66 (PA66) matrix, creating a graphene reinforced polymer matrix composite (G-PMC). The process revealed that high speed elongational flow was able to create few layer graphene. Graphite exfoliation was found driven in part by diffusion, leading to intercalation of PA66 in graphite. The intercalated structure lead to increases in the hydrogen bonding domain, creating anisotropic crystal domains. The thermal stability of the G-PMC was found to be dependent to the degree of exfoliation, PA66 crystal structure and composite morphology. The aim of this research is to characterize uniquely produced graphene containing polymer matrix composites using a newly created elongational flow field. Using elongational flow, graphite will be directly exfoliated into graphene within a molten polymer.
关键词： polyamide 66,elongational flow,graphene polymer matrix composite,hydrogen bond,graphene
更新于2025-09-04 15:30:14