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Thermochromic and retro-reflective materials
Published in Vincenzo Costanzo, Gianpiero Evola, Luigi Marletta, Urban Heat Stress and Mitigation Solutions, 2021
Federico Rossi, Mattheos Santamouris, Samira Garshasbi, Marta Cardinali, Alessia Di Giuseppe
The three-component thermochromic materials based on leuco dye-colour developer-solvent have been extensively used as a commercially available organic thermochromic material for buildings application. Thermochromic leuco dyes are known to go from coloured phase to colourless phase by temperature. More precisely, the leuco-dye system is coloured due to the interactions between dye and colour developer at temperatures lower than the solvent’s melting temperature. The prevailing colour developer and solvent interactions result in the colourless phase at temperatures above the solvent’s melting temperature [32]. Microencapsulation is also necessary to protect the thermochromic leuco dyes against environmental condition and oxidation [52]. The microcapsule size can range between 1 to 50 µm. Melamine resin is a common microencapsulation method due to the great possibility for changing its porosity and elasticity and absence of side reactions with thermochromic components. Other types of organic thermochromic materials include Schiff bases and conjugated polymers with a thermochromic mechanism based on temperature-sensitive molecular rearrangements. Polydiacetylenes (PDAs) is a conjugated polymer with a thermochromic response from red to blue in the temperature range between 25°C and 70°C [53]. Poor mechanical properties and low reversibility seem to be the main obstacles for the application of polydiacetylenes. Salicyl Schiff bases are also known to change their colour from yellow to red with temperature [54]. Further research should be conducted to evaluate suitability of conjugated polymers and Schiff bases for the building application.
Smart and Intelligent Packaging Based on Biodegradable Composites
Published in Arbind Prasad, Ashwani Kumar, Kishor Kumar, Biodegradable Composites for Packaging Applications, 2023
Theivasanthi Thirugnanasambandan
CMC films are prepared by attaching with silver nanoparticles/polydiacetylene and glycerol. These films are tested as TTI. The color changes observed on the films are due to the changes in time and temperature of the packaging environment. Silver nanoparticles have a high thermal conductivity. Hence, a small temperature variation on the film can be clearly observed. Polydiacetylene possesses a high surface area that can support the effective sensing ability of the films. Glycerol can offer a symmetrical chemical structure to the films. The films are suitable for packaging fruits and vegetables (Saenjaiban et al., 2020).
Screen printing of cellulose electrospun nanofibres with PDA polymer
Published in The Journal of The Textile Institute, 2022
Alishba Javeed, Shamshad Ali, Awais Khatri, Raza Ali
Polydiacetylene (PDA) is a conjugated polymer that exhibit colour variations as a reaction to an external stimulus. PDAs are eye-catching as they reveal a blue-to-red colour shift which is observable to the naked eye once they exposed to external stimuli such as pH, temperature and the existence of bacterial cells and aromatic compounds (Yapor et al., 2017).