Chaoxia Wang

Synthesis of polymeric dyes based on waterborne polyurethane for improved color stability

A waterborne polyurethane covalently bonded anthraquinone dye chromophore was successfully synthesized via incorporating micromolecule Disperse Red 91 into the polyurethane skeleton. The number- and weight-average molecular weights of the waterborne polyurethane based polymeric dye were about 6.57k and 10.3k, respectively. The maximum absorption wavelengths are 260 nm, 520 nm and 555 nm, which show a hypsochromic effect compared with the corresponding micromolecule dye. Thermal stability and centrifugal stability can be distinctly enhanced after the micromolecule dyes are covalently bonded to the polyurethane skeleton. The solubility of waterborne polyurethane based polymeric dye also offers reversibility and good color stability at different pH values. Thermal migration properties of this polymeric dye are improved by 82.4%, compared to that of a simple mixture of dye and polyurethane. The polymeric dye with enhanced color stability under centrifugation, acid, alkaline and thermal conditions can upgrade the product quality as it is employed in dyeing, coating or printing ink.

Facile synthesis of a nanocomposite based on graphene and ZnAl layered double hydroxides as a portable shelf of a luminescent sensor for DNA detection

Recently, nanocomposites based on graphene and layered double hydroxides (LDH) have been developed and used in many fields. However, to the best of our knowledge, there is no report on the luminescence sensor applications of graphene/LDH composites. Herein, a hybrid graphene–ZnAl-LDH nanocomposite has been developed using a facile one-step process and the presence of LDH in the composite can effectively prevent the restacking of graphene and improve both its luminescence properties and thermal stability. Furthermore, the composite can be used as a portable shelf of the Ru(phen)3Cl2 (tris(1,10-phenanthroline)ruthenium(II) dichloride) sensor to selectively discriminate DNA. It was found that the graphene–ZnAl-LDH composite can effectively quench the emission of the Ru(phen)3Cl2 sensor. After the addition of a certain amount of DNA into the system, Ru(phen)3Cl2 was released from the graphene–ZnAl-LDH composite and it interacted with DNA immediately, leading to the luminescence recovery of the sensor. The results indicate that the RGO–ZnAl-LDH composite displayed an excellent luminescence response and good linear correlation to DNA. Therefore, the composite can be employed as a portable shelf of Ru(phen)3Cl2 to discriminate DNA. Moreover, both the shelf and the sensor can be easily collected and made ready for the next sample if there is no DNA in the solution. The proposed method was further applied to detect the immunodeficiency virus gene (HIV), thus providing a new field of application for hybrid graphene/LDH composites.

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.

Synthesis of polymeric dyes based on UV curable multifunctional waterborne polyurethane for textile coating

Three novel UV curable polymeric dyes (UVPDs) based on multifunctional waterborne polyurethanes have been successfully developed to overcome the drawbacks of thermo-curing. The functionality of the UVPDs is tailored by end-capping with 2-hydroxyethyl acrylate (HEA), pentaerythritol triacrylate (PETA) and dipentaerythritol pentaacrylate (DPEPA). The chemical structure, molecular weight and carbon–carbon double bond (CC) content of the UVPDs were investigated. The thermal properties, curing behavior and color properties of the UVPDs are also discussed. It is found that the thermal stability of the UVPDs is improved upon increasing the functionality. The incorporation of chromophores into the polyurethane chain reduces the curing efficiency. The curing behavior observations demonstrate that the UVPDs can cure rapidly upon UV irradiation, especially the ones with higher functionality. A higher degree of cross-linking and better water resistance are obtained when UVPD films are cured with 5% photoinitiator. Furthermore, the UVPDs show outstanding UV light stability. The maximum absorption wavelength and curve trend of the cotton fabrics coated with the UVPDs remain unchanged while the color of the coated cotton fabrics slightly lightens when prolonging the UV curing time. The color fastness to rubbing and washing of the coated cotton fabrics with UVPD10 can be enhanced up to 4–5 grade after curing for 60 s.

Facile preparation of self-healing waterborne superhydrophobic coatings based on fluoroalkyl silane-loaded microcapsules

Superhydrophobic surfaces have attracted tremendous attraction because of their novel aspects of surface physics and important applications ranging from self-cleaning materials to microfluidic devices. However, most artificial superhydrophobic surfaces easily lose their superhydrophobicity under natural sunlight irradiation, physical rubbing or organic contamination. Here, fluoroalkyl silane (FAS)-loaded microcapsules, photocatalytic TiO2 nanoparticles and FAS modified SiO2 nanoparticles were mixed with waterborne polysiloxane resins to obtain waterborne self-healing superhydrophobic coatings. Superhydrophobic surfaces were formed by casting the coatings on the substrates after UV-irradiation and could sustain their superhydrophobicity even after 360 h accelerated weathering test. Meanwhile, the coating was durable enough to withstand water blasting and the attacks of strong acid or basic solutions without apparently changing its superhydrophobicity. More importantly, after being mechanically damaged or contaminated with organics, these coatings could restore their superhydrophobicity under UV light. All these characteristics ensure that the coatings have excellent long-term superhydrophobicity for outdoor service.

Effect of pigment particle character on dyeing performance of cotton fabrics

The cotton fabrics were dyed by exhaust method using the pigment dispersions as colorant, and meanwhile the effects of particle character on dyeing performance were further investigated. The results showed that the larger zeta potentials, the higher K/S value, pigment uptakes, rubbing and washing fastness of the dyed cotton fabrics were. Adsorption isotherms were belonging to Langmuir type when zeta potentials were about 0.46 mV and 31.39 mV respectively. The cotton fabrics that dyed by the pigment dispersions with small particles had high K/S value, rubbing and washing fastness. The chemical structure of pigment had little influence on pigment uptakes, and all kind of pigment dispersions reach to 98 % uptakes after 30 min but exhibit various uptake rates at initial stage.

A recycled foam coloring approach based on the reversible photo-isomerization of an azobenzene cationic surfactant

Development of a non-polluting process for cotton coloring is essential for the textile industry in view of ecological and economical reasons. In order to recycle the residual foam in the foam technique, a photo-responsive azobenzene cationic surfactant (4-butoxy-4′-(trimethylaminoethoxy)azobenzene, BTAEAzo) was synthesized for obtaining switchable foam based on its sensitive and reversible photo-isomerization capability. Trans → cis isomerization of BTAEAzo occurred only within 1 s UV light irradiation and cis → trans conversion could be achieved after 8 min visible light irradiation. Besides, BTAEAzo showed good thermal stability which was stable up to 225 °C. BTAEAzo was able to reversibly switch foam between the stable (t1/2 of 19.09 min) and unstable (t1/2 of 2.93 min) states by light stimulation. Furthermore, dye-bonded blocked waterborne polyurethane, a polymeric dye, was applied in the switchable system and showed no influence on the foam switching capability of BTAEAzo. The coated cotton presented superior color properties including the K/S value, color evenness and fastness with the switchable foam. Most importantly, the residual color foam can be re-used during the coating process with excellent color repeatability. These results demonstrated that the recycled foam coloring process containing only two types of chemicals is a rapid and nearly zero-pollution process, fostering a clean and green textile industry.

Synthesis of blocked waterborne polyurethane polymeric dyes with tailored molecular weight: thermal, rheological and printing properties

A series of polymeric dyes based on blocked waterborne polyurethanes (BWPUs) with varied molecular weights have been synthesized successfully. The influence of molecular weight on the thermal, rheological, and printing properties of the BWPUs are mainly investigated. The molecular weight of the BWPUs are tailored in the range of 2860–24 600 by selecting different chain lengths of polyethylene glycol (PEG0/400/600/1000/2000) as soft segments. The glass transition temperature (Tg) of the BWPUs decreased from 5.1 °C to −52.6 °C with increasing molecular weight of the soft segment, which implied a better film-forming property. Additionally, BWPUs with higher molecular weight offered better thermal stability. It is also found that BWPUs with a higher molecular weight show a more distinct shear thinning behavior and viscous behavior. The synthesized BWPUs were further applied in textile printing as both a colorant and adhesive to investigate their application performances. The printing viscosity index (PVI) values of all BWPUs pastes are below 0.3, suggesting that they are preferred for printing fine patterns on hydrophilic fibers. The color fastness of the printed cotton fabrics was found to be improved to 4–5 grade as the molecular weight of the BWPUs and baking temperature were increased. Consequently, the polymeric dyes could provide a novel route for obtaining high-quality printing products and shortening the textile coloring process.

Isolation and recovery of cellulose from waste nylon/cotton blended fabrics by 1-allyl-3-methylimidazolium chloride

Development of a simple process for separating cellulose and nylon 6 from their blended fabrics is indispensable for recycling of waste mixed fabrics. An efficient procedure of dissolution of the fabrics in an ionic liquid 1-allyl-3-methylimidazolium chloride ([AMIM]Cl) and subsequent filtration separation has been demonstrated. Effects of treatment temperature, time and waste fabrics ratio on the recovery rates were investigated. SEM images showed that the cotton cellulose dissolved in [AMIM]Cl while the nylon 6 fibers remained. The FTIR spectrum of regenerated cellulose (RC) was similar with that of virgin cotton fibers, which verified that no other chemical reaction occurred besides breakage of hydrogen bonds during the processes of dissolution and separation. TGA curves indicated that the regenerated cellulose possessed a reduced thermal stability and was effectively removed from waste nylon/cotton blended fabrics (WNCFs). WNCFs were sufficiently reclaimed with high recovery rate of both regenerated cellulose films and nylon 6 fibers.

Removal of spandex from nylon/spandex blended fabrics by selective polymer degradation:

As the use of fabrics containing spandex for apparel applications is expanding, developing eco-friendly technologies to recycle the industrial as well as post-consumer waste for spandex blended fabrics becomes increasingly important. As is known in the industry and demonstrated in this study, spandex may be removed from blended fabrics by dissolving it in solvents such as N,N-dimethylformamide, but the use of such solvents is undesirable for economical and environmental reasons. The main focus of this study was to develop an alternative process for removing the spandex component in a nylon/spandex blended fabric (NSBF) by selective degradation so that the nylon component can be recovered for recycling. In this process, the fabric first underwent a heat treatment step, followed by a washing process. For the heat treatment, the effect of temperature, water-to-fabric ratio, and pressure were studied. Treatment at 220℃ for 2 hours under atmospheric pressure was found to be very effective, allowing the degraded spandex residues to be readily washed off in ethanol, while the nylon component retained its original morphology. With the removal of spandex in NSBF, a decrease in -CON- absorption peaks in the Fourier transform infrared–attenuated total reflectance spectra of the fabrics was observed.