Polycarbonate

Résumé

vignette|110px|Code d'identification de la résine PC. Le « O » signifie « Others » (autres) qui peut aussi être indiqué en toutes lettres. Ce code peut également identifier d'autres résines. Le polycarbonate est une matière plastique disposant d'excellentes propriétés mécaniques et d'une résistance thermique permettant une utilisation entre et . Ce polymère est issu de la polycondensation du bisphénol A (BPA) et d'un carbonate ou du phosgène, ou par transestérification. Le matériau a été découvert en 1953 par trois chercheurs travaillant pour Bayer AG, Schnell, Bottenbruch et Krimm. Sa première mise sur le marché date de 1958. Il est commercialisé sous plusieurs noms : Makrolon de Covestro, Lexan de Sabic, Hammerglass, Xantar de Mitsubishi engineering plastics ou Durolon d'Unigel plasticos. Propriétés physiques et applications La très grande transparence de cette matière est exploitée pour la fabrication de verres optiques, des CD et DVD, des lentilles de caméras thermiq

Source officielle

https://fr.wikipedia.org/wiki/Polycarbonate

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Dopant-free hole-transporting materials (HTMs) and interface modification are two effective approaches for developing sustainable perovskite solar cells (PSCs). In this work, dopant-free HTM (GW-4) containing an N- ethyl-carbazole with two rotatable vinyl linkages is first synthesized by a green chemical method without any metal catalysts. The GW-4 cost is only 22.43% of the price of commercial 2,2'7,7'-tetrakis[N,N-di(4-methox-yphenyl)amino]-9,9 & PRIME;-spirobifluorene (spiro-OMeTAD). In the device fabrication, the concentrations of doped GW-4 (20 mg mL(-1)) and pristine GW-4 solutions (10 mg mL(-1)) are much lower than that of spiro-OMeTAD solution (doped, 72.3 mg mL-1). The power conversion efficiency (PCE) of doped GW-4-based cell is 20.45%, superior to that of spiro-OMeTAD-based cell (19.59%). As the optimal concentration of dopant-free GW-4 is insufficient to completely cover the perovskite layer, a polycarbonate (PC) polymer with carbonyl groups is first introduced to modulate perovskite grain boundaries and improve film-forming property of pristine GW-4. The cell with PC/pristine GW-4 has a slightly higher PCE (17.92%) than the cell with pristine GW-4 (17.66%). Regarding humid stability, after 455 h, the doped GW-4 and spiro-OMeTAD based PSCs retain only 11.71% and 2.27% of the initial efficiency, respectively. In striking contrast, after 850 h, the pristine GW-4 and PC/pristine GW-4 based devices retain 69.74% and 97.53% of the initial efficiency, respectively. This study provides both a new molecular design strategy to develop highly efficient dopant-free HTMs and an ingenious interfacial contrivance to overcome the defects of incomplete coverage of HTM film on perovskite layer and understand the charge dynamics at interfacial layers.

ELSEVIER SCIENCE SA2022

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Microfabrication of curved sidewall grooves using scanning nanosecond excimer laser ablation

Jing Gong, Patrik Hoffmann, André Gabriel Kostro, Josef Andreas Schuler, Georgios Violakis

Novel glazing with embedded micro-mirrors can significantly reduce the energy consumption due to cooling and lighting in buildings. Especially promising are large arrays of periodic micro compound-parabolic-concentrators (CPCs) with angular-selected transmittance. For the production of micro CPCs, curved sidewall grooves with a controlled optical surface and an aspect ratio of about 2.3 are fabricated on polycarbonate substrates by scanning nanosecond 248-nm excimer laser ablation. The likewise obtained microstructures can be used as master mold for replication. The cross-sections of the micro grooves are characterized by confocal microscopy, and the extracted morphologies are used for the ray-tracing simulation of the optical devices. Prior to the scanning ablation using a suitable mask in the optical path, the depth profiles under static ablation are investigated to identify ablation rate, imaging resolution and produced surface. Interestingly for the width of the mask opening being less than 6 μm, the ablation rate is increased due to optical interference and /or less shielding by debris. Concerning the scanning ablation, the depth of the curved sidewall grooves ranges from 48 μm to 114 μm, corresponding to the width of the groove opening being in the range from 20 μm to 50 μm. The observed final shapes in cross-sections are in good agreement with the design of the mask. For both theoretical and fabricated groove shapes, the angular-selected transmittance profiles predicted from ray-tracing simulations are highly similar. Scanning nanosecond excimer laser ablation is therefore a promising approach for the realization of high-quality micro CPCs.

SPIE2018

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En route to CO2-containing renewable materials: catalytic synthesis of polycarbonates and non-isocyanate polyhydroxyurethanes derived from cyclic carbonates

Felix Daniel Bobbink, Paul Joseph Dyson, Antoine Philippe Van Muyden

Combining CO2-chemistry with biomass conversion allows renewable polymeric materials including polycarbonates and polyhydroxyurethanes (PHUs) to be generated. The demand for robust materials with modular properties that can be prepared on an industrial scale is important and, to date, the most important polymeric materials are derived from petrochemicals. These materials inevitably result in CO2 emissions, and therefore making robust materials from renewable sources will contribute to a more sustainable society. An attractive way to address this challenge is to combine biomass transformations with CO2-fixation and material science. An identified target that combines all three aspects involves the preparation of PHUs (or non-isocyanate polyurethanes, NIPUs) via the polymerization of fully renewable cyclic carbonates derived from biomass and CO2 with a diamine compound that can also been derived from biomass sources. In this review, we critically analyze the progress in catalyst development for the efficient transformation of epoxides and CO2 to cyclic carbonates and polycarbonates. We also discuss the synthesis of PHUs from cyclic carbonates and diamines (not restricted to fully renewable compounds), including challenges in regiocontrol and biodegradability, as well as the role catalysts play in the synthesis of these polymers.

2019

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