A Study into the Influence of Paper Coatings on Paper Properties and Print Quality of Dye Sublimation Thermal Prints

The need for good quality paper for dye sublimation transfer printing has been reported previously as a principal requirement for the process. Pigmented coated papers have gained acceptance in the traditional paper printing industry, but, despite their importance, have inspired very few reports in literature about their application in heat transfer printing.

In the current work, we studied the influence of both clay and ground calcium carbonate (GCC) pigments and the incorporation of plastic pigment on the surface structure and mechanical properties of the coated paper used for transfer printing. The results showed that paper coating significantly reduced the surface roughness of the paper. The mechanical properties of the prepared coated paper, including tensile strength, stretch, tensile energy absorption (TEA), and burst index, were improved when coated compared to those of uncoated paper. The addition of plastic pigment to the coating mixture helped improve the paper's properties.

The optical density of the transfer-printed polyester fabric using the prepared coated paper was also compared with that of uncoated paper. It was shown that a slight increase in optical density was evident in the coated paper.

The possibility of producing a second polyester print from the exhaust paper was also investigated. Coated paper incorporating plastic pigment, in particular, showed higher optical density than did uncoated paper.

We found that coated paper based on clay, GCC, clay/plastic pigment, or GCC/plastic pigment consumed less dye paste than uncoated paper though producing printed fabric with higher optical density—especially in the second print.     

甘油中水合TiO2及不同晶型纳米TiO2光致变色现象

系统地研究了甘油中水合TiO₂及不同晶型纳米TiO₂的光致变色现象。实验结果显示无定型水合TiO₂具有最明显的变色行为,锐钛型纳米TiO₂变色程度次之,金红石型纳米TiO2没有明显变色现象发生,混晶型(金红石和锐钛)纳米TiO₂的变色程度介于金红石型和锐钛型之间。XPS结果表明TiO₂的光致变色是由Ti³⁺引起的。从电子-空穴对复合率影响Ti ³⁺形成的角度对实验现象作出了详细解释,电子-空穴对复合率越高,Ti³⁺形成率越低,从而变色程度越浅;并运用双注入机制和小极子模型阐述了不同晶型TiO₂的光致变色机理。分析了甘油环境对TiO₂光致变色现象的影响,得出甘油对TiO₂的光致变色行为有促进作用。     

Effect of Sn4+ doping on the photoactivity inhibition and near infrared reflectance property of mica-titania pigments for a solar reflective coating

The influence of Sn⁴⁺ doping on the photoactivity inhibition and near infrared reflectance property of mica-titania pigments was investigated. X-ray diffraction analysis confirmed that Sn⁴⁺doping promoted phase transformation from anatase to rutile. The rutile promoting effect of Sn⁴⁺ can be ascribed to the distortion of the crystal structure of anatase after the replacement of Ti⁴⁺ by Sn⁴⁺. Sn⁴⁺ doping had a great influence on the photoactivity of mica-titania pigments. The photoactivity of mica-titania pigments was enhanced at low dopant levels, whereas its photoactivity was inhibited at high dopant levels. Remarkably, the degradation rate constant of mica-titania pigments doped with 1.0 wt% of SnCl₄ was approximately 12.9% of that of the undoped sample. A possible mechanism for this effect was proposed. Moreover, the near-infrared solar reflectance of mica-titania pigments reached 0.97. An approximately 8.3 °C decrease in temperature was obtained for the inner surface of a calcium silicate board coated with mica-titania pigments. Furthermore, a solar reflective coating coloured with low photocatalytic mica-titania pigments exhibited high photostability against weathering conditions. Therefore, mica-titania pigments with high levels of the Sn⁴⁺dopant are excellent candidates for use in solar reflective coatings.     

Effect of titania particles preparation on the properties of Ni–TiO2 electrodeposited composite coatings

In this paper, the effect of titania particles preparation on the properties of Ni–TiO₂ electrocomposite coatings has been addressed. Titania particles were prepared by precipitation method using titanium tetrachloride as the precursor. The titanyl hydroxide precipitate was subjected to two different calcinations temperatures (400 and 900 °C) to obtain anatase and rutile titania particles. These particles along with commercial anatase titania particles were separately dispersed in nickel sulfamate bath and electrodeposited under identical electroplating conditions to obtain composite coatings. The electrodeposited coatings were evaluated for their microhardness, wettability, corrosion resistance, and tribological behavior. The variation of microhardness with current density exhibited a similar trend for all the three composite coatings. The composite coating containing anatase titania particles exhibited higher microhardness and improved wear resistance. However, the corrosion resistance of the composite coating containing commercial titania powder was superior to that of plain nickel, Ni–TiO₂ composite coatings containing anatase and rutile titania particles. The poor corrosion resistance of these composite coatings was attributed to the higher surface roughness of the coatings. This problem was alleviated by incorporating ball-milled titania powders. The composite coatings with higher surface roughness were modified with a low surface energy material like fluoroalkyl silane to impart hydrophobic and superhydrophobic properties to the coatings. Among these coatings, Ni–TiO₂–9C coating exhibited the highest water contact angle of 157°.     

Influence of the seed layer on photoactivity inhibition of mica–titania pigments

The influence of the seed layer on the phase composition and photoactivity inhibition of mica–titania pigments was investigated. The prior deposition of MnO₂ or SnO₂ as a seed layer resulted in a complete rutile TiO₂ coating without calcinations, while the prior deposition of ZnO led to a mixture of anatase and rutile. The rutile promoting effect of MnO₂ and SnO₂ could be ascribed to the small lattice mismatch (＜5%) between the seed layer and the rutile TiO₂. Moreover, the seed layer had a great influence on the photoactivity inhibition of mica–titania pigments. A seed layer of MnO₂ inhibited the photoactivity of the pigments, whereas a seed layer of SnO₂ or ZnO enhanced the photoactivity of the pigments. The degradation rate constant of mica–MnO₂–TiO₂ was approximately 72.7% that of mica–TiO₂, while the degradation rate constant of mica–SnO₂–TiO₂ was approximately 4.5 times as high as that of mica–TiO₂. The influence of the seed layer on the photoactivity of mica–titania pigments depended on the transfer process of electron–hole pairs between the seed layer and TiO₂.     

Photocatalytic partial oxidation of methylpyridine isomers on TiO2 particles under an anaerobic condition

Photocatalytic oxidation of methylpyridine isomers (2-methylpyridine, 3-methylpyridine, and 4-methylpyridine) was investigated in a mixed solution of acetonitrile and water or acetonitrile using various kinds of TiO₂ powders as photocatalysts. The main products from methylpyridine isomers were pyridinecarboxaldehyde isomers (2-pyridinecarboxaldehyde, 3-pyridinecarboxaldehyde, and 4-pyridinecarboxaldehyde). Rutile large TiO₂ particles showed the highest level of activity for oxidation of 2-methylpyridine probably because band bending was necessary for the oxidation of 2-methylpyridine. On the other hand, a fine particle having an anatase or rutile phase showed a higher level of activity than large TiO₂ particles for oxidation of 3-methylpyridine. A rutile fine particle showed the highest level of activity for the reaction. It was found that pure rutile or pure anatase particles were inactive for oxidation of 4-mathylpyridine. If the particles are not extremely small, pure rutile and pure anatase powders show fairly high levels of activity, and those containing both anatase and rutile phases show the highest level of activity. The activity of pure rutile particles was also enhanced by physically mixing them with a small amount of small anatase particles, which were inactive for this reaction. These results can be explained by the synergism between rutile and anatase particles. All of these reactions effectively proceeded even under anaerobic conditions. Photocatalytic reduction of methylpyridine isomers concomitantly proceeded on TiO₂ particles under the conditions used. These results suggest that the activities of TiO₂ photocatalysts for oxidation of methylpyridine isomers are dominated by the oxidation potential of alkylpiridine and band bending of TiO₂ particles.     

Formation of the Ti4O7 phase through interaction between coated carbon and TiO2

Fine particles ofphotocatalytic anatase TiO₂ prepared through hydrolysis of titanium tetraisopropoxide were coated by carbon. A reduced phase, Ti₄O₇, was formed through interaction between TiO₂ and the coating carbon. EXAFS analysis on this Ti₄O₇ phase showed an intermediate Ti-Ti distance between those in anatase and rutile, which agreed with the structure composed of two-dimensional slabs of Ti-O octahedra separated by a shear plane. This carbon-coated Ti₄O₇ was confirmed to have photocatalytic activity, even though a little lower than anatase, examining the decomposition of methylene blue in water under LTV irradiation.     

异晶型TiO2／云母珠光颜料的制备及性能研究

本文着重研究了涂层为锐钛和金红石两种晶型的云母钛珠光颜料的制备方法，晶型转化的影响因素及各自的性能特征：工艺参数，涂层结构与光学性能之间的关系。     

Photocatalytic activity of oxide coatings on fired clay substrates

The coating of fired clay substrates with various metal oxides, such as anatase, rutile, zinc oxide and tin oxide was achieved using a simple spraying technique followed by a thermal treatment. The photocatalytic activity of the layer was characterized through measurement of the absorption spectrum, in the range 400–800 nm, of methylene blue deposited on top of the coating. Results show that the presence of anatase enhances the degradation of methylene blue when it is exposed to ultraviolet light. Thermal treatment at 1050 °C transforms anatase crystals into thermodynamically stable rutile. This results in a decrease of the photocatalytic activity, which can be explained by increase of the grain size and by a difference in the crystal structure. Measurements of the photocatalytic activity of ZnO and SnO₂ show that these two oxides also exhibit photocatalytic properties. In particular, ZnO is a promising alternative material to anatase.     

Low temperature synthesis and characterization of rutile TiO2-coated mica–titania pigments

Rutile TiO₂-coated mica–titania pigments were prepared by hydrolysis of TiCl₄ ethanolic solution in water at 70 °C. MnO₂ as a rutile promoting additive was deposited onto mica prior to TiO₂. X-ray diffraction and Raman spectra analysis verified that use of only 2.07 wt% MnO₂ with respect to mica weight began to provide a complete rutile TiO₂ coating without calcination. The rutile promoting effects of MnO₂ could be ascribed to the structural similarity of rutile and pyrolusite. Scanning electron microscopy analysis showed that MnO₂ also had a pronounced effect on the morphology of TiO₂ coatings. The prior deposition of MnO₂ onto mica lead to the formation of rutile TiO₂ films composed of highly oriented fine needles on the mica surface and nanoflower structures on the needle structures. The as-obtained rutile-TiO₂ coated mica–titanium pigments are shown to exhibit a high photostability under UV illumination.     

Immobilization of hydrothermally produced TiO2 with different phase composition for photocatalytic degradation of phenol

Hydrothermally produced TiO₂ powders with different phase composition (anatase, rutile and mixed phase) were immobilized on glass fibers and tested in the phenol mineralization process. Both H₂O₂ and O₂ were used as oxygen donors, and their performances were compared with those of the same TiO₂ samples as slurries.The catalytic properties of the immobilized different crystalline phases, rutile and anatase, show the same trend as the slurry samples: pure rutile displays the highest catalytic efficiency in the presence of H₂O₂, while samples containing anatase improve the photodegradation efficacy with O₂. It was suggested that the stability of the photogenerated electron–hole couple allows high activity of rutile in the presence of H₂O₂, while the relevant oxygen chemisorption on anatase causes high catalytic activity in the presence of O₂. A four parameters kinetics model shows that both reaction steps, the phenol degradation and the mineralization of the intermediates, are photoactivated by TiO₂.Photoactivity of the coated glass fibers is generally lower than that of slurries, even if their efficiencies are almost comparable when the oxidation is performed by H₂O₂, while much lower when the oxygen donor is O₂. As a matter of fact, the morphology of immobilized catalysts shows the presence of chestnut burr aggregates of large rutile crystalline rods on the glass fiber, which are much less compact than the aggregates of small anatase particles. This preserves rutile surface area from the coarsening effects; thus, when rutile is the more active species, as in the presence of H₂O₂, the photocatalytic activity is less affected by immobilization.     

Preparation of core‐shell latexes for paper coatings

Novel core‐shell latices with a partially crosslinked hydrophilic polymer core and a hard hydrophobic shell of polystyrene were prepared to improve optical properties of coated paper such as gloss and brightness. These core‐shell latices were prepared by sequential addition of a monomer mixture of styrene, n‐butylacrylate and methacrylic acid. Different crosslinkers were used to form the polymer core and in the second stage styrene to form the hard shell component. In addition, attempts were made to further improve optical properties by introducing a new polymerizable optical brightener, i.e., 1‐[(4‐vinylphenoxy)methyl]‐4‐(2‐phenylethylenyl)benzene during polymerization either into the core or into the shell. The prepared core‐shell latex particles were used as specialty plastic pigments for paper coating together with kaolin as the primary pigment. The runability of paper coating formulation by either using a laboratory scale Helicoater or pilot scale JET‐coating machine was very good. The produced coated papers were printed on both sides employing a heat set web offset (HSWO) printer to study the quality of image reproduction in terms of print gloss, print mottle, print through, etc. The core‐shell latices improved the overall print quality. Furthermore, the results demonstrated that by optimizing polymer composition one can significantly enhance the optical properties and surface smoothness of coated paper. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Treatment of malachite green dye using combined oxidation techniques based on different irradiation

We investigated the treatment of malachite green (MG) dye using sonocatalytic, photocatalytic and sonophotocatalytic techniques. The percentage of decolorization for sonophotolysis (65.5±3.3%) was much higher than the individual effects of sonolysis (55.2±2.4%) and photolysis (52.1±2.6%). The efficiency of the sonophotocatalytic process increased in the presence of photocatalysts such as anatase TiO₂ (82.2±4.1%) and ZnO (75.7±3.8%). The decolorization rate further enhanced in the presence of nano-TiO₂ (anatase, rutile ratio 75: 25 and particle size ≤100 nm). The enhancement in decolorization was marginal for sonophotocatalysis (95.9±4.8%) as compared to sonocatalysis (93.0±4.3%) and photocatalysis (93.2±4.6%). The intensification of decolorization in the presence of nano-TiO₂, due to lower recombination of hydroxyl ions on the photocatalytic surface and nano-particle size of a catalyst, increased cavitational activity. The total organic carbon was found to be maximum for sonophotocatalytic in the presence of nano-TiO₂ (67.1±3.3%).     

Carbon coating of anatase-type TiO2 through their precipitation in PVA aqueous solution

Fine particles of photocatalytic anatase-type TiO₂ prepared through hydrolysis of titanium-tetraisopropoxide were coated by carbon through their precipitation in poly(vinyl alcohol) (PVA) aqueous solution, followed by heat treatment at high temperatures of 400-1000 °C in a flow of high purity Ar. Without carbon coating, the phase transformation from anatase to rutile started above 600 °C, but it was suppressed up to 800 °C with carbon coating. Suppression of the phase transformation depended on the amount of carbon coated, apparent suppression being observed with carbon content above 5 mass%. The amount of carbon coated on anatase was controlled by changing the concentration of PVA in the solution. In order to have a carbon content of about 5 mass%, a PVA solution with more than 2 mass% had to be used.     

TiO2 based nanopowder coatings over stainless steel plates for UV-C photocatalytic degradation of methylene blue

Immobilizing the photocatalyst in a water treatment process design is essential; however, the immobilization method may affect the photoactivity of the photocatalyst. In this work, photocatalyst powders were successfully coated on 316 L stainless steel plates by a novel brush coating method. Three combinations of photocatalyst mixtures (pure TiO₂ anatase, anatase doped with WO₃, or TiO₂ rutile) were and annealed at different temperatures between 460-540°C. The ~ 10 μm thick coatings demonstrated full plate coverage and strong adhesion and adequate durability. Surface roughness increased with annealing temperature. The doping and annealing process enabled band gap reduction to the visible light spectrum for all coatings, with the smallest band gap being 2.48 eV (1 eV = 1.6 × 10⁻¹⁹ J). Subsequent methylene blue degradation tests under UV-C showed that the coatings annealed in 460°C exhibited the best performance and with the highest degradation rate constant of 5.59 hours⁻¹.     

Calcium sulphate as pigment for improved functional properties of coated paper

In the last few years, interest and demand of high bright paper have forced paper manufacturers to think new ways to improve brightness and whiteness of coated paper. Pigment coating is widely used to enhance the optical properties such as brightness, whiteness, and gloss of paper and paperboard. These optical properties are the most important for end user and also determine the final cost of coated paper. Calcium sulphate has inherent better optical properties compared to other conventional pigments for example ground calcium carbonate, precipitated calcium carbonate and kaolin clay. The present study was carried out with an aim to synthesize calcium sulphate using waste procured from phosphoric acid industry and to study its impact on the rheology of coating color as well as optical properties of coated paper. Addition of calcium sulphate improved the water retention property of coating color which can be helpful for improving the machine runnability. The results also revealed that calcium sulphate can be used as a pigment to produce coated paper of high brightness and whiteness. The brightness and whiteness of the coated paper were improved 4 and 15 points, respectively by using 50 parts of calcium sulphate as a pigment replacing clay from the coating formulation. The surface strength in terms of IGT pick value of coated sheets was found significantly comparable using calcium sulphate as pigment. The print gloss results were observed analogous with matt grade coated paper.     

TiO2对聚氯乙烯紫外光稳定与催化降解的影响

综述了普通和纳米TiO_2对聚氯乙烯(PVC)的紫外光稳定和催化降解的机理及研究进展,以及包覆和掺杂改性对TiO_2光稳定和光催化性能的作用。金红石型纳米TiO_2具有优异的紫外光稳定特性,锐钛型纳米TiO_2表现出极强的光催化活性。无机包覆过的金红石型TiO_2对PVC有明显的保护作用。有机改性则能提高锐钛型TiO_2的分散性,从而提高其对聚合物的光催化效率。过渡金属离子掺杂可在TiO_2晶格中引入缺陷位置或改变结晶度,从而改变PVC的光降解速率。     

Photocatalytic Nb2O5-doped TiO2 nanoparticles for glazed ceramic tiles

TiO₂ nanoparticles are currently used as coating for self-cleaning building products. In order to achieve high self-cleaning efficiency for outdoor applications, it is important that titania is present as anatase phase. Moreover, it is desirable that the particle sizes are in nano-range, so that a large enough surface area is available for enhanced catalytic performance. In this work, TiO₂ nanoparticles doped with 0–5 mol% Nb₂O₅ were synthesized by co-precipitation. Nb₂O₅ postponed the anatase to rutile transformation of TiO₂ by about 200 °C, such that after calcination at 700 °C, no rutile was detected for 5 mol% Nb₂O₅-doped TiO₂, while undoped TiO₂ presented 90 wt% of the rutile phase. A systematic decreasing on crystallite size and increasing on specific surface area of TiO₂ were observed with higher concentration of Nb₂O₅ dopant. Photocatalytic activity of anatase polymorph was measured by the decomposition rate of methylene blue under ultraviolet and daylight illumination and compared to commercial standard catalyst (P25). The results showed enhanced catalysis under UV and visible light for Nb₂O₅-doped TiO₂ as compared to pure TiO₂. In addition, 5 mol% Nb₂O₅-doped TiO₂ presented higher photocatalytic activity than P25 under visible light. The enhanced performance was attributed to surface chemistry change associated with a slight shift in the band gap.     

Effects on the size of nano-TiO2 powders prepared with sol-emulsion-gel method

Small and uniform nano-TiO₂ particles were obtained by sol-emulsion-gel method. Optimum preparation conditions include the surfactant concentration at the critical micelle concentration (CMC) and the pH value at 8-9. The calcinations could improve the crystallization of TiO₂ powders and accelerated the phase transformation from amorphous phase to anatase or rutile. Seen from the TEM, the spherical and uniform nano-TiO₂ particles were obtained as calcined at 500 °C, and the gradual shape change of the particles in the process of calcination was noticed: Formed sphere → Rod → Sphere → Distorted sphere.     

Color parameters of Y2Cu2O5 green-blue nanopigments fabricated by the sol-gel combustion method and their efficiency for coloring the glazed tiles

Non-toxic Y₂Cu₂O₅ nanopigments were synthesized by sol-gel combustion method and the effects of synthesis parameters on their chromatic properties have been studied. The chromatic properties of the samples were studied by UV-vis reflectance spectroscopy and the L^*a^*b^* coordinates were evaluated using the CIE Lab1976 color scales. The results showed that the chromatic properties of nanopigments were changed by altering the synthesis conditions such as pH and the molar ratio of the fuel to oxidizer. Also some Y₂Cu₂O₅ micro sized pigments were synthesized by solid state reaction and the measurements showed that the chromatic properties of the nanopigments were slightly bigger than those of the large particles indicating that the nanopigments were more stunning. Using DTA analysis it was found that the nanopigments were very stable in the temperature range of 50–950 °C. The measurements of a^* and b^* showed that the nanopigments are also very stable in glazes.