Yunjie Yin

Anthraquinone chromophore covalently bonded blocked waterborne polyurethanes: synthesis and application

Dye-bonded blocked waterborne polyurethanes were developed to synchronously realize coloring and finishing of textiles and improve colorfastness using an anthraquinone chromophore and a methyl ethyl ketoxime blocking agent. The number-average molecular weight of the dye-bonded blocked polyurethane is 2303 g mol−1 and the polydispersity is 1.06, indicating a narrow molecular weight distribution. The maximum absorption wavelengths do not shift after the monomolecular chromophores are bonded to the polyurethane. The self-colored polyurethanes provide better centrifugal stability and water solubility than the dye-mixed blocked polyurethanes. The dye-bonded blocked polyurethane offers good thermal stability below 100 °C and undertakes de-blocking at about 150 °C. The covalent bonding of the anthraquinone moiety with the polyurethane chain and temporary blocking of the terminal isocyanate groups are conducive to enhancing the tinting strength and colorfastness of the treated cotton fabrics. The self-colored blocked polyurethanes with good elasticity and toughness can improve the recovery angle of the treated cotton up to 120°, which can also endow the fabric with wrinkle resistance.

A new approach for the preparation of durable and reversible color changing polyester fabrics using thermochromic leuco dye-loaded silica nanocapsules

Durable, reversible color changing polyester fabrics were successfully fabricated via a new approach of dyeing with thermochromic leuco dye-loaded silica nanocapsules (TLD@SiO2). TLD@SiO2 was prepared via tetraethyl orthosilicate hydrolyzation and condensation on the surfaces of emulsified thermochromic leuco dye (TLD) nano-droplets by a sol–gel method. The TLD@SiO2 was about 20 nm in size, and its shell could provide protection for TLD. The color of TLD@SiO2 changed from dark blue (25 °C) to light blue (45 °C) and white (80 °C), reversibly. The thermochromic mechanism originated from the conjugation structure conversion of the crystal violet lactone which was confirmed by density functional theory calculations. The shell materials (Si–O–Si) of TLD@SiO2 could be hydrated in water with temperature increase and produced hydrophilic hydroxyl groups for further treating polyester fabrics. These resulting polyester fabrics exhibited excellent thermochromic performance with a color transition temperature of 45 °C. Their color reversibly changed from dark blue (K/S = 12) to light blue (K/S = 2) at 610 nm for more than 50 times. Meanwhile, thermochromic polyester fabrics dyed at 130 °C displayed good color fastness. The washing, dry rubbing and wet rubbing fastness of the thermochromic polyester fabrics all reached above 4 grades, and the thermochromic polyester fabrics showed good solvent resistance.

Improvement of ink-jet printing performances using β-cyclodextrin forming inclusion complex on cotton fabric

Cotton fabric was modified with β-cyclodextrin (β-CD) forming inclusion complex to yield color strength, pattern sharpness, and color fastness for ink-jet printing. The modified cotton fabric was confirmed with the presence of new strong absorption peaks around 1713 cm-1 and 1243 cm-1 in FT-IR. β-CD had been covalently grafted on cotton fabric via the esterification reaction of citric acid (CTR) with cellulose and β-CD. The results indicated that printing performances of the ink-jet printed fabric were enhanced through β-CD modification. The K/S value was enhanced from 4.21 to 6.72, the width of printed line was decreased from 1.48 mm to 1.25 mm, and the color fastness was improved to 3-4 level. These improvements were due to the truncated cone structure of β-CD, which can form inclusions with water-based pigment. Meanwhile, the crease recovery performance was also improved with the aid of CTR. A comparison between the unmodified and modified cotton fabric suggested that the crease recovery angle of β-CD modified cotton fabric was increased by 25.0 % in the warp direction. Therefore, printing performance and crease recovery performance of β-CD modified and water-based pigment printed cotton fabric were enhanced remarkably.

Synthesis of photo-responsive azobenzene molecules with different hydrophobic chain length for controlling foam stability

To obtain an aqueous foam photo-switch, azobenzene molecules [4-hydroxy-4′-oxoalkyl azobenzene (HCnAzo) n = 4, 8, and 12] were synthesized. The hydrophobic chain length affected both photo-responsive properties and foam stability controllability. trans → cis isomerization of HCnAzo occurred by exposing to UV light for 1 s and the cis → trans process for HC4Azo, HC8Azo and HC12Azo was carried out by visible light irradiation for 12 min, 13 min and 14 min, respectively. The reversible isomerization was repeatable, maintaining high sensitivity. Due to the small steric effect and isomerization barrier, photo-isomerization of HC4Azo was more rapid than HC8Azo and HC12Azo. With the increase of the hydrophobic chain length, the decrease of thermal isomerization barrier resulted in less cis isomer and more trans isomer in photo-stationary state via UV and visible light irradiation, respectively. The combination of visible light and heat can accelerate the cis → trans isomerization speed. trans HC4Azo, HC8Azo and HC12Azo increased foam life from 6.67 min to 10.38, 9.91 and 7.74 min, respectively, resulting from the absorption on the air–water interface and a high affinity. cis HC4Azo, HC8Azo and HC12Azo decreased foam life from 6.67 min to 5.12, 5.49 and 6.02 min, respectively, attributed to the interfacial desorption and increase of surface tension. HC4Azo with sensitive photo-isomerization and effective foam stability controllability was the best choice for an aqueous foam photo-switch.

Preparation and characterization of highly dispersed silica nanoparticles via nonsurfactant template for fabric coating

Abstract Highly dispersed silica nanoparticles used for fabric coating were synthesized via nonsurfactant template sol–gel reaction with tetraethoxysilane (TEOS) and γ-glycidyloxypropyltrimethoxysilane (GPTMS) in the presence of dodecanol, alkaline catalyzer, and ethanol. With the optimum conditions of 4 g of dodecanol, 3 mL of alkaline catalyzer, and 30 wt% GPTMS, the silica particle size was 305 nm and the polydispersity index was 0.022. FT-IR spectra confirmed that the alkyl chain and epoxy group of GPTMS had been bonded onto the surface of silica nanoparticles due to the characteristic peaks at 2980 and 910 cm−1. The GPTMS-modified silica nanoparticles presented higher dispersion compared with the unmodified particles from SEM micrographs. The anti-ultraviolet property and rubbing fastness of the coated fabrics were enhanced as the doped amount of modified silica nanoparticles were increased to 5 wt%. The nonsurfactant template sol–gel method presents simple, facile, and cost-effective potential on the promising application of preparing highly dispersed silica nanoparticles.

One-bath one-step low-temperature dyeing of polyester/cotton blended fabric with cationic dyes via β-cyclodextrin modification

With the aim of polyester/cotton fabric one-bath one-step dyeing, polyester fabric low-temperature dyeing with cationic dyes was investigated based on β-cyclodextrin (β-CD) modification. After β-CD/citric acid (CA) modification, the hydrophilicity of the modified polyester fabric was improved obviously, which was demonstrated via moisture regain and contact angle, as well as wicking property. The optimal dyeing temperature and crosslinking agent were selected through comparing the color strength of the dyed polyester fibers. Modified polyester fabric obtained significantly enhanced color strength from 0.12 to 4 with a good leveling property when dyeing at 70℃ using CA as the crosslinking agent. β-CD modified polyester/cotton fabric displayed a K/S value of 8.61, much higher than the value of 0.71 of the unmodified fabric with cationic dyes, showing a highly improved dyeing ability. The color fastness of β-CD modified polyester/cotton fabrics, including washing fastness, rubbing fastness, perspiration fastness and light fastness, are all over grade 3–4 when the curing temperature of 180℃ is adopted for β-CD modification, demonstrating that polyester/cotton fabric one-bath one-step dyeing can be realized based on β-CD modification.

Investigation of disperse fluorescent ink formulation via thermal transfer printing for polyester substrate

Disperse fluorescent ink was controllably prepared via the cyclic sander grinding process and used for thermal transfer printing on a polyester substrate. Via process optimization, 0.1% pH regulator triethanolamine and 0.15% surfactant NP-12 were added in the disperse fluorescent ink. The lightness L* of the polyester substrate was 101.84 and the saturation C* was 84.21 within thermal transfer printing on the polyester substrate. Compared with flat screen printing, the bending rigidity and bending hysteresis moment of the ink-jet printed polyester substrate presented a slight change. The fluorescent effect of the printed polyester substrate was increased to 165.65, and the fluorescence reflectivity increased 4.1% at the maximum emission wavelength λmax = 510 nm. The color fastness of the printed polyester substrate was improved. In particular, the wet rubbing fastness was enhanced by one grade after the ink-jet thermal transfer printing.