Nano coloração: revestimento de substratos têxteis com cristais fotónicos

Dissertação de mestrado integrado em Química TêxtilA indústria têxtil é considerada uma das indústrias mais poluentes a nível mundial. A procura de novos métodos mais ecológicos de processamento de substratos têxteis é de interesse contínuo e de permanente investigação. Uma das principais preocupações ecológicas é o elevado consumo de água utilizada em processamento têxtil e seus efluentes, que contêm uma alta carga de produtos químicos tóxicos para o ambiente. Sendo o tingimento um dos processos com maior consumo de água, devido às quantidades necessárias para a preparação do banho de corante e respetivas lavagens para remoção do corante em excesso que não tenha reagido/penetrado na fibra, é necessário arranjar uma alternativa ecológica. A coloração de substratos têxteis através da cor estrutural (interação física de luz com materiais que possuem variação nanoestrutural no índice de refração) pode ser a solução para este problema, pois o consumo de água é drasticamente reduzido, sendo apenas necessário água para a síntese dos cristais fotónicos, a partir dos quais a cor é conseguida. Através desta técnica é possível obter uma ampla gama de cores (consoante o tamanho dos cristais) com um brilho que não é possível obter com corantes tradicionais. Esta técnica também permite obter substratos têxteis com iridescência, uma propriedade caraterística dos cristais fotónicos, onde a cor do substrato muda consoante o ângulo de observação e o ângulo de incidência da luz. Assim sendo, este trabalho teve como objetivos principais (i) sintetizar cristais fotónicos com diferentes tamanhos, (ii) testar diferentes técnicas de deposição dos cristais, (iii) utilizar biopolímeros para melhorar a adesão e uniformidade dos cristais aos substratos e (iv) melhorar a solidez à lavagem e à fricção dos substratos revestidos. Em relação ao primeiro objetivo, foram sintetizados cristais fotónicos de poli(estireno-metilmetacrilatoácido acrilíco), com tamanhos entre os 170 e os 250 nm, através de uma reação de polimerização, alterando as condições reacionais. Em relação ao segundo objetivo, foram testados dois métodos de deposição diferentes, por deposição gravitacional e por dip-drawing. O método por dip-drawing foi o método onde se obtiveram melhores resultados de uniformidade, obtendo-se uma variada gama de cores (violeta, azul, verde, amarelo e vermelho), aquando da deposição dos cristais em tecidos de poliamida 6,6. Quanto ao terceiro objetivo, foi utilizada uma solução 15.00 g/L de quitosano como biopolímero. Este biopolímero também foi utilizado no quarto objetivo, onde infelizmente não foi possível obter melhorias de solidez significativas.The textile industry is considered one of the most polluting industries in the world. The search for new, greener methods of processing textile substrates is of continuous interest and ongoing research. One of the main ecological concerns is the high consumption of water used in textile processing and its effluents, which contain a high load of environmentally toxic chemicals. As dyeing is one of the most water consuming processes, due to the quantities required for the preparation of the dyebath and its washings to remove excess of not reacted/penetrated dye, an ecological alternative need to be found. Coloring of textile substrates by structural coloration (physical interaction of light with materials having nanostructural refractive index variation) may be the solution to this problem, as water consumption is drastically reduced, where water is only needed for the synthesis of photonic crystals from which color is achieved. Through this technique it is possible to obtain a wide range of colors (depending on the size of the crystals) with a brightness that is not possible to achieve with traditional dyes. This technique also provides iridescence to textile substrates, a characteristic property of photonic crystals, where the color of the substrate changes depending on the viewing angle and the angle of incidence of light. Therefore, the main objectives of this work were (i) to synthesize photonic crystals with different sizes, (ii) to test different crystal deposition techniques, (iii) to use biopolymers to improve crystal adhesion and uniformity to substrates and (iv) to improve the washing and rubbing fastness of the coated substrates. Regarding the first objective, poly (styrene-methylmethacrylate-acrylic acid) photonic crystals were synthesized, with sizes between 170 and 250 nm, through a polymerization reaction, by changing the reaction conditions. Regarding the second objective, two different deposition methods were tested, by gravitational deposition and by dip-drawing. The dip-drawing method was the method with the best uniformity results, obtaining a wide range of colors (violet, blue, green, yellow and red) when depositing crystals in polyamide 6,6 fabrics. As for the third objective, a 15.00 g/L solution of chitosan was used as biopolymer. This biopolymer was also used in the fourth objective, where, unfortunately, no significant fastness improvements where obtained

Structural color for enhanced camouflage textiles

Apresentação efetuada na 3rd World Conference on Advanced Materials for Defense - AuxDefense 2022, em Guimarães, Portugal, 2022Fundação para a Ciência e a tecnologia (FCT

Effect of color substrate in structurally colored PES fabrics

Textile Industry is one of the most pollutant industries in world, thus serious efforts are required to decrease its chemical and water demand, especially during dyeing processes. [1] One strategy to achieve this is the use of photonic crystals (PCs), where color is produced by interactions between light and highly organized nanostructures, called structural coloration. [2] Structural coloration is a more ecological method to add color to fabrics due to its low water consumption, as water is only needed in the synthesis of the photonic crystals. Also, PCs produce brilliant and iridescent colors that are not possible to obtain with conventional dyeing processes. [3] Therefore, in this work an alternative to conventional dyeing is presented, where PCs are applied onto dyed polyester fabrics through a dip-drawing method, and color properties are analyzed

The influence of chemical reaction conditions upon poly(styrene‐methyl methacrylate‐acrylic acid) synthesis: Variations in nanoparticle size, colour and deposition methods

Monodisperse latex nanospheres of poly(styrene‐methyl methacrylate‐acrylic acid) with different sizes were synthetised by soap‐free emulsion copolymerisation and applied onto polyamide 6,6 fabrics by two methods, ie, gravitational sedimentation and dip‐drawing. Different‐sized nanospheres were synthetised by varying temperature and stirring velocity as reaction parameters. Scanning electron microscopy and scanning transmission electron microscopy were used to evaluate nanosphere sizes and deposition structures. The results showed two different nanosphere structural arrangements on the fabric surface, a hexagonal packed centre structure in the even surfaces and a square arrangement in the out‐of‐plane surfaces. Different colours were observed according to particle size, namely, violet (ca. 170 nm), blue (ca. 190 nm), green (ca. 210 nm), yellow (ca. 230 nm) and red (ca. 250 nm). An iridescence effect was also observed, displaying different colours at different observation angles. By controlling the size of the nanospheres it was possible to obtain different, brilliant and iridescent colours. Using different nanosphere sizes it was possible to obtain different interplanar distances and to control the light scattering in the crystalline lattice planes, obtaining Bragg diffraction patterns.Fundação para a Ciência e a Tecnologia, Grant/Award Number: IF/00071/2015, PTDC/CTM-TEX/28295/2017 , SFRH/BD/145269/2019 and UID/CTM/00264/2019; European Regional Development funds (FEDER); Competitiveness and Internationalization Operational Program (POCI)—COMPETE, Grant/Award Number: POCI-01-0145-FEDER-0071

Combining photonic crystals of different sizes and tuning structural colors by color addition

[Excerpt] Photonic crystals (PCs) are dielectric materials, capable of controlling the propagation of light due to the photonic bandgap (PBG) and self-assemble in highly organized nano and microstructures. PCs are found in nature and can be used for signaling, communication or camouflage purposes. PCs structural coloration of textiles is ecological relevant due to the inherent considerable reduction of water and chemical requirements. Furthermore, PCs can be used to develop smart textiles able to change color through external stimuli such as: humidity, light, pH, electrical and magnetic fields. This textiles can be applied in anti-counterfeiting materials, wearable functional textiles, sensors, among others

Iridescence mimicking in fabrics: a ultraviolet/visible spectroscopy study

Poly(styrene-methyl methacrylate-acrylic acid) photonic crystals (PCs), with five different sizes (170, 190, 210, 230 and 250 nm), were applied onto three plain fabrics, namely polyamide, polyester and cotton. The PC-coated fabrics were analyzed using scanning electronic microscopy and two UV/Vis reflectance spectrophotometric techniques (integrating sphere and scatterometry) to evaluate the PCs’ self-assembly along with the obtained spectral and colors characteristics. Results showed that surface roughness of the fabrics had a major influence on the color produced by PCs. Polyamide-coated fabrics were the only samples having an iridescent effect, producing more vivid and brilliant colors than polyester and cotton samples. It was observed that as the angle of incident light increases, a hypsochromic shift in the reflection peak occurs along with the formation of new reflection peaks. Furthermore, color behavior simulations were performed with an illuminant A light source on polyamide samples. The illuminant A simulation showed greener and yellower structural colors than those illuminated with D50. The polyester and cotton samples were analyzed using scatterometry to check for iridescence, which was unseen upon ocular inspection and then proven to be present in these samples. This work allowed a better comprehension of how structural colors and their iridescence are affected by the textile substrate morphology and fiber type.This research was funded by Portuguese Foundation for Science and Technology (FCT), Portuguese Ministry of Science, Technology and Higher Education (MCTS), project UID/CTM/00264/2021 and PhD grant SFRH/BD/145269/2019

Modification of nanocellulose

Nanocellulose (NC) represents a pivotal material for the sustainable strategies of the future. NC comprises cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC), each exhibiting unique and exceptional physicochemical properties. These properties encompass high specific surface area, high tensile strength, lightweight, biodegradability, good barrier properties, and high processing versatility. However, the range of properties and applications can be significantly expanded through the modification of NC, involving both chemical and physical methodologies, which introduce a plethora of functional groups to the densely populated hydroxyl groups present in pristine NC. The modification processes discussed in this chapter encompass chemical and physical modifications that were reported mostly within the last 5 years. The described methodologies emphasize the potential of NC as a substrate for advanced functional and sustainable material

Chapter 34 - Biocompatibility of nanocellulose: Emerging biomedical applications

Nanocellulose already proved to be a highly relevant material for biomedical applications, ensued by its outstanding mechanical properties and, more importantly, its biocompatibility. Nevertheless, despite their previous intensive research, a notable number of emerging applications are still being developed. Interestingly, this drive is not solely based on the nanocellulose features, but also heavily dependent on sustainability. The three core nanocelluloses encompass cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and bacterial nanocellulose (BNC). All these different types of nanocellulose display highly interesting biomedical properties per se, after modification and when used in composite formulations. Novel applications that use nanocellulose includewell-known areas, namely, wound dressings, implants, indwelling medical devices, scaffolds, and novel printed scaffolds. Their cytotoxicity and biocompatibility using recent methodologies are thoroughly analyzed to reinforce their near future applicability. By analyzing the pristine core nanocellulose, none display cytotoxicity. However, CNF has the highest potential to fail long-term biocompatibility since it tends to trigger inflammation. On the other hand, neverdried BNC displays a remarkable biocompatibility. Despite this, all nanocelluloses clearly represent a flag bearer of future superior biomaterials, being elite materials in the urgent replacement of our petrochemical dependence

Antiviral properties of flame retardant bacterial nanocellulose modified with mordenite

[Excerpt] Bacterial nanocellulose (BNC) is a 100 % cellulose nano-nonwoven textile synthesized by bacteria, comprising impressive mechanical properties. Cellulosic materials require flame retardant finishing, thus to reduce flammability of BNC a zeolite mordenite (MOR) was incorporated in its nano structure, without any additives.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT), FEDER funds by means of Portugal 2020 Competitive Factors Operational Program (POCI) and the project UID/CTM/00264/2021 of Centre for Textile Science and Technology (2C2T). PTDC/CTM-TEX/28295/2017, PTDC/CTM-TEX/1213/2020, and ARCHKNIT POCI-01-0247- FEDER-039733, funded by FCT, FEDER, COMPETE, and MCTES. Liliana Melro and Rui D. V. Fernandes acknowledge their PhD grants 2020.04919.BD and SFRH/BD/145269/2019