Effect of Concentration of Thermochromic Ink on Performance of Waterborne Finish Films for the Surface of Cunninghamia Lanceolata

Thermochromic Polymer Nanocomposites for the Heat Detection System: Recent Progress on Properties, Applications, and Challenges

Reversible thermochromic polymers have emerged as compelling candidates in recent years, captivating attention for their application in heat detection systems. This comprehensive review navigates through the multifaceted landscape, intricately exploring both the virtues and hurdles inherent in their integration within these systems. Their innate capacity to change colour in response to temperature fluctuations renders reversible thermochromic nanocomposites promising assets for heat detection technologies. However, despite their inherent potential, certain barriers hinder their widespread adoption. Factors such as a restricted colour spectrum, reliance on external triggers, and cost considerations have restrained their pervasive use. For instance, these polymer-based materials exhibit utility in the domain of building insulation, where their colour-changing ability serves as a beacon, flagging areas of heat loss or inadequate insulation, thus alerting building managers and homeowners to potential energy inefficiencies. Nevertheless, the limited range of discernible colours may impede precise temperature differentiation. Additionally, dependency on external stimuli, such as electricity or UV light, can complicate implementation and inflate costs. Realising the full potential of these polymer-based materials in heat detection systems necessitates addressing these challenges head-on. Continuous research endeavours aimed at augmenting colour diversity and diminishing reliance on external stimuli offer promising avenues to enhance their efficacy. Hence, this review aims to delve into the intricate nuances surrounding reversible thermochromic nanocomposites, highlighting their transformative potential in heat detection and sensing. By exploring their mechanisms, properties, and current applications, this manuscript endeavours to shed light on their significance, providing insights crucial for further research and potential applications.

Reversible thermochromic fibers with excellent elasticity and hydrophobicity for wearable temperature sensors

Color-changing fibers, which can intuitively convey information to the human eye, can be used to facilely add functionality to various types of clothing. However, they are often expensive and complex, and can suffer from low durability. Therefore, in this study, we developed highly elastic and hydrophobic thermochromic fibers as wearable temperature sensors using a simple method that does not require an electric current. A thermochromic pigment was embedded inside and outside hydrophobic silica aerogel particles, following which the thermochromic aerogel was fixed to highly elastic spandex fibers using polydimethylsiloxane as a flexible binder. In particular, multi-strand spandex fibers were used instead of single strands, resulting in the thermochromic aerogels penetrating the inside of the strands upon their expansion by solvent swelling. During drying, the thermochromic aerogel adhered more tightly to the fibers by compressing the strands. The thermochromic fiber was purple at room temperature (25 °C), but exhibited a two-stage color change to blue and then white as the temperature increased to 37 °C. In addition, even after 100 cycles of tension-contraction at 200%, the thermochromic aerogel did not detach and was strongly attached to the fiber. Additionally, it was confirmed that color change due to temperature was stable even after exposure to 1 wt% NaCl (artificial sweat) and 0.1 wt% detergent solutions. The developed thermochromic fiber therefore exhibited excellent elasticity and hydrophobicity, and is expected to be widely utilized as an economical wearable temperature sensor as it does not require electrical devices.

Influence of the Bottom Color Modification and Material Color Modification Process on the Performance of Modified Poplar

According to the old surface coating process of European and American furniture, the surface of modified poplar is first differentiated pre-treatment, and then the bottom color modification and material color modification are respectively applied to the modified poplar after the surface differentiation treatment. The visual physical quantity and physical and chemical properties were measured and compared with mahogany, which is commonly used in old furniture in Europe and America to explore the effect of colorants and coloring steps, as well as different surface pretreatments on the coloring effect. Finally, it is concluded that continuous coloring operations can narrow the difference in brightness and red color value in the coloring layer of modified poplar and mahogany. Continuous coloring operations increase the difference between the yellow-green color values of modified poplar and mahogany. Therefore, the coloring difference between modified poplar and mahogany was affected by the colorant and coloring steps. Through color accumulation, the gap between the two in the target color coloring effect can be reduced, thereby reducing the difference between the coloring effect of modified poplar and mahogany.

Preparation and Optimization of Waterborne Acrylic Core Microcapsules for Waterborne Wood Coatings and Comparison with Epoxy Resin Core

Microcapsules were prepared by in situ polymerization with urea formaldehyde resin as the wall material and Dulux waterborne acrylic acid as the core material. The effects of the core–wall ratio, water bath temperature and depositing time on the morphology, particle size, yield and encapsulation ratio of microcapsules were investigated by orthogonal experiment of three factors and two levels. The results showed that the core–wall ratio had the greatest influence on the performance of microcapsules. When the core–wall ratio was 0.58:1, the water bath temperature was 70 °C, and the depositing time was 5 d, the microcapsule performance was the best. With the increase in depositing time, the yield of microcapsule particles increased gradually, and the microcapsules appeared to show an adhesive phenomenon. However, the long-term depositing time did not lead to complete deposition and agglomeration of microcapsules. When 10.0% concentration of the waterborne acrylic microcapsules with 0.58:1 of core–wall ratio was added to the coatings, the mechanical and optical properties of the coatings did not decrease significantly, but the elongation at break increased significantly. Therefore, this study offers a new prospect for using waterborne acrylic microcapsules to improve the toughness of waterborne paint film which can be cured at room temperature on a wood surface.

Mechanical and Optical Properties of Thermochromic Reversible Waterborne Primer Film on Tilia europaea with 1,2-Benzo-6-diethylaminofluorane Based Microcapsules

A waterborne thermochromic primer film containing thermochromic reversible microcapsules on the surface of Tilia europaea was prepared. The influences of different microcapsule concentrations on the reversible thermochromic, optical, mechanical and liquid resistance properties of the primer films were investigated. Not only were the morphology and structure of microcapsules and films observed, but also the chemical compositions of the microcapsules and films were analyzed. The results showed that for the primer film with microcapsules, the microcapsule concentration had a more significant influence on color difference. The primer film with microcapsules can achieve thermochromic reversibility. The temperature of color change was 32 °C and it had a good color recovery. The film gloss was negatively correlated with the microcapsule concentration, and the film with 5.0%-15.0% concentration had the best gloss. Adding an appropriate concentration of microcapsules can effectively improve the mechanical properties of the film. The film with 0-15.0% microcapsules had better liquid resistance to detergent, i.e., grade 1. The bonding form between the primer film added with microcapsules and Tilia europaea was physical bonding. This study provides a technical reference for the development of modern intelligent discoloration wood products.

Effect of Sanding Processes on the Surface Properties of Modified Poplar Coated by Primer Compared with Mahogany

The surface roughness, static and dynamic liquid wettability of modified poplar wood were measured by different surface treatment of brushing primer and sanding. With the increase of the number of grinding paper, the depth parameters Ra, Ry, Rz and Rp of surface roughness of modified poplar decreased, and the density parameter Sm (the average spacing of micro unevenness of contour) decreased at first and then increased. With the increase of number of the grinding paper, the contact angle of water and glycerol for modified poplar wood decreased at first and then increased. After the modified poplar wood was brushed with the primer and sanded with 240# sandpaper, the density parameter Sm was 0.307, the equilibrium contact angle of distilled water was 34.88, and the equilibrium contact angle of glycerin was 36.46, all of which were the lowest number. At this time, the surface roughness was improved, and the modified poplar has the good wettability that is greater than the mahogany wood wettability. Compared with mahogany, the rough depth parameters of the modified poplar are smaller to those of mahogany, but the Sm of modified poplar wood is greater than that of the mahogany. After the same surface pretreatment, the wetting speed of glycerol on the surface of mahogany is higher than that of the modified poplar.

Investigation of the Properties of Color-Changing Powder Water-Based Coating

The suitable coating process and discoloration effect of the waterborne paint added with color-changing powder on the surface of Chinese fir were investigated using an orthogonal method from three factors of the number of primers, topcoats, and the way of adding color-changing powder. It was found that the number of primers showed the greatest significance on the color difference of paint film, and the method of adding the color-changing powder had the most influence on the gloss of the paint film. Meanwhile, the impact resistance, paint film adhesion, liquid film resistance level, the gloss of coatings, and the composition of waterborne coatings were not affected by the three factors. The results indicated that two primers, two topcoats with color-changing powder, were the most suitable coating technologies for the reversible color waterborne coating to obtain a stable and sustainable discoloration effect. These results will provide a reference for the construction and application of a color-changing coating.