Thermochromic microcapsules with highly transparent shells obtained through in-situ polymerization of urea formaldehyde around thermochromic cores for smart wood coatings

Encapsulation of thermochromic tetradecyl myristate/methyl red composite via full poplar-based cellulose/lignin/SiO2 framework for preparation of thermochromic wood with thermal response and storage

Thermochromic wood (TW), a smart material that can respond to temperature changes and store thermal energy, holds broad potential for application in the construction industry. This study fabricated thermochromic poplar (TP) by encapsulating a thermochromic phase change material (TPCM), consisting of tetradecyl myristate and methyl red, within a full poplar-based cellulose/lignin/SiO2 framework. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicate that the poplar matrix and the incorporated SiO2 formed an integrated cellulose/lignin/SiO2 framework, which encapsulated the TPCM within the poplar ducts. The TP exhibits a color change from light purple to dark purple within the temperature range of 30-48 °C, with a pronounced shift at approximately 42 °C, correlating with the sensation of scalding. Thus, TP-based products can alert users to the risk of scalding through a noticeable color change. The full poplar-based framework mitigates the impact of ultraviolet (UV) radiation on the TP and prevents the loss of TPCM during thermal processing. The mechanical properties of TP are enhanced to a strength grade comparable to that of Manchurian ash wood, making it suitable for load-bearing components in wooden structures. Additionally, the average temperature of TP is around 10 °C higher than that of untreated poplar within 25 min after the same thermal treatment. Consequently, TP can serve as a building material with capabilities for temperature response, thermal energy storage, and structural load-bearing.

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.

A Color-Changing Biomimetic Material Closely Resembling the Spectral Characteristics of Vegetation Foliage

Multispectral/hyperspectral technologies can easily detect man-made objects in vegetation by subtle spectral differences between the object and vegetation, and powerful reconnaissance increases the demand for camouflage materials closely resembling vegetation spectra. However, previous biomimetic materials have only presented static colors that cannot change color, and camouflage in multiple bands is difficult to achieve. To address this challenge, inspiration is drawn from the color change of foliage, and a color-change model is proposed with active and static pigments embedded in a matrix medium. The color of a composite material is dominated by the colored active pigment, which conceals the color of the static pigments and the color is revealed when the active pigment fades. A color-changing biomimetic material (CCBM) is developed with a solution casting method by adopting microcapsuled thermochromic pigments and chrome titanate yellow pigments as fillers in a base film with polyvinyl alcohol and lithium chloride. A Kubelka-Munk four-flux model is constructed to optimize the component proportions of the CCBM. The material has a reversible color change, closely resembles the foliage spectrum in UV-vis-NIR ranges, and imitates the thermal behavior of natural foliage in the mid-infrared regime. These results provide a novel approach to multispectral and hyperspectral camouflage.

Metal-polyphenol networks-modified tantalum plate for craniomaxillofacial reconstruction

Using three-dimensional (3D) printing technology to make the porous tantalum plate and modify its surface. The physicochemical properties, cytocompatibility, antioxidant capacity, and histocompatibility of the modified materials were evaluated to prepare for the repair of craniomaxillofacial bone defects. The porous tantalum plates were 3D printed by selective laser melting technology. Tantalum plates were surface modified with a metal polyphenol network. The surface-modified plates were analyzed for cytocompatibility using thiazolyl blue tetrazolium bromide and live/dead cell staining. The antioxidant capacity of the surface-modified plates was assessed by measuring the levels of intracellular reactive oxygen species, reduced glutathione, superoxide dismutase, and malondialdehyde. The histocompatibility of the plates was evaluated by animal experiments. The results obtained that the tantalum plates with uniform small pores exhibited a high mechanical strength. The surface-modified plates had much better hydrophilicity. In vitro cell experiments showed that the surface-modified plates had higher cytocompatibility and antioxidant capacity than blank tantalum plates. Through subcutaneous implantation in rabbits, the surface-modified plates demonstrated good histocompatibility. Hence, surface-modified tantalum plates had the potential to be used as an implant material for the treatment of craniomaxillofacial bone defects.

Multiscale photoacoustic tomography using reversibly switchable thermochromics

SIGNIFICANCE

Based on acoustic detection of optical absorption, photoacoustic tomography (PAT) allows functional and molecular imaging beyond the optical diffusion limit with high spatial resolution. However, multispectral functional and molecular PAT is often limited by decreased spectroscopic accuracy and reduced detection sensitivity in deep tissues, mainly due to wavelength-dependent optical attenuation and inaccurate acoustic inversion.

AIM

Previous work has demonstrated that reversible color-shifting can drastically improve the detection sensitivity of PAT by suppressing nonswitching background signals. We aim to develop a new color switching-based PAT method using reversibly switchable thermochromics (ReST).

APPROACH

We developed a family of ReST with excellent water dispersion, biostability, and temperature-controlled color changes by surface modification of commercial thermochromic microcapsules with the hydrophilic polysaccharide alginate.

RESULTS

The optical absorbance of the ReST was switched on and off repeatedly by modulating the surrounding temperature, allowing differential photoacoustic detection that effectively suppressed the nonswitching background signal and substantially improved image contrast and detection sensitivity. We demonstrate reversible thermal-switching imaging of ReST in vitro and in vivo using three PAT modes at different length scales.

CONCLUSIONS

ReST-enabled PAT is a promising technology for high-sensitivity deep tissue imaging of molecular activity in temperature-related biomedical applications, such as cancer thermotherapy.

Reversible Thermochromic Microcapsules and Their Applications in Anticounterfeiting

The common, commercial reversible thermochromic (RT) melamine-formaldehyde resin microcapsules containing formaldehyde are very harmful to human health. To address this issue, we successfully prepared a novel formaldehyde-free microcapsule via interfacial polymerization using RT compositions as the core and poly(urethane-urea) (PUU) as the shell. The core material consisted of a color former (crystal violet lactone), a developer (bisphenol AF), and a solvent (methyl stearate). To optimize the synthesis of the microcapsules, an L₉ (3⁴) orthogonal design and single-factor experiments were employed to analyze the effects of four factors (N3300-to-L75 shell material mass ratio, core-to-shell material mass ratio, emulsifier concentration, and shear rate during emulsification) on the encapsulation efficiency. The results showed that the optimal parameter values were as follows: a shear rate of 2500 rpm, N3300-to-L75 shell material mass ratio of 1:4, core-to-shell material mass ratio of 11:5, and emulsifier concentration of 3.5%. The influence of the shear rate on the particle size and distribution, surface morphology, dispersibility, and reversible thermochromic properties of the microcapsules was investigated. Furthermore, analyses on the phase-change characteristics, thermal stability, ultraviolet aging, and solvent and acid-base resistances of the microcapsules were conducted systematically. Finally, a reversible thermochromic mark containing the RTPUU microcapsules was designed and fabricated, which could be used against falsification. Moreover, these RTPUU microcapsules can be potentially used for anticounterfeiting applications.

Preparation of Healable Shellac Microcapsules and Color-Changing Microcapsules and Their Effect on Properties of Surface Coatings on Hard Broad-Leaved Wood Substrates

In order to protect the wood surface and improve the properties of coatings, microcapsules with healable and discoloration functions are produced, and their healable function is obtained using shellac, which can be cured at room temperature, as the repairing agent. In this paper, self-made shellac microcapsules and color-changing microcapsules were added to varnish in different proportions to form the composite coating on a wood board, and the color difference of the coating was measured at different temperatures to study the influence of microcapsules on the degree of surface color on the substrate. The effect of microcapsules on the healable performance of coatings on a wood board was studied by scratching the surface of the coating with a utility knife and observing the process of repair. The optimal sample was selected from the orthogonal experiment for the independent experiment. The surface roughness, hardness, infrared spectrum, and scanning electron microscopy of the optimal sample were tested, and the content in the optimal sample was further investigated. The results show that color-changing microcapsules have a color-changing effect on surface coatings based on wood boards, and shellac microcapsules inhibit the color-changing effect of color-changing microcapsules. Composite microcapsules can repair the cracks on the surface coatings of wood boards. In cases where shellac microcapsules can self-repair the coating, the color-changing effect is best when the content of color-changing powder is 15.0%.

Effects of Thermochromic Fluorane Microcapsules and Self-Repairing Waterborne Acrylic Microcapsules on the Properties of Water-Based Coatings on Basswood Surface

The effect of the addition of fluorane microcapsules and urea formaldehyde resin (UF) waterborne acrylic resin microcapsules on the comprehensive properties of the water film on the surface of basswood was studied. Three-factor and two-level orthogonal experiments were carried out with "fluorane microcapsule content", "aqueous acrylic resin microcapsule content" and the "fluorane microcapsule addition method" to prepare a self-repairing thermochromic coating. The optical, mechanical, microstructure and self-repairing properties of the film were optimized by independent experiments on the maximum influence factors of the fluorane microcapsule content. It was concluded that the topcoat with 15% fluorane microcapsules and primer added with 15% water acrylic resin microcapsules had better comprehensive properties. The temperature range was 30-32 °C, the color difference at 32 °C was 72.6 ± 2.0, the 60° gloss was 3.3%, the adhesion was 0 grade, the hardness was 4 H, the impact resistance was 15.0 ± 0.8 kg∙cm, the elongation at break was 17.2% and the gap width was reduced by 3.5 ± 0.1 μm after the film was repaired. The repair rate reached 62.5%. By using microcapsule embedding technology, the repair agent and discoloration agent are embedded in the matrix. The waterborne acrylic resin microcapsules can effectively inhibit crack formation in the coating, and the fluorane microcapsules can achieve the thermochromic property of the coating. This study provides a new research idea for the self-repairing thermochromic dual function of a water-based coating.

The Microencapsulation of Tung Oil with a Natural Hydrocolloid Emulsifier for Extrinsic Self-Healing Applications

In this work, tung oil was utilised as a catalyst-free self-healing agent, and an in-situ polymerization process was applied to encapsulate the tung oil core with a poly(urea-formaldehyde) (PUF) shell. The conventional poly(ethylene-alt-maleic-anhydride) (PEMA) polymer was compared to a more naturally abundant gelatin (GEL) emulsifier to compare the microcapsules’ barrier, morphological, thermal, and chemical properties, and the crystalline nature of the shell material. GEL emulsifiers produced microcapsules with a higher payload (96.5%), yield (28.9%), and encapsulation efficiency (61.7%) compared to PEMA (90.8%, 28.6% and 52.6%, respectively). Optical and electron microscopy imaging indicated a more uniform morphology for the GEL samples. The thermal decomposition measurements indicated that GEL decomposed to a value 7% lower than that of PEMA, which was suggested to be attributed to the much thinner shell materials that the GEL samples produced. An innovative and novel focused ion beam (FIB) milling method was exerted on the GEL sample, confirming the storage and release of the active tung oil material upon rupturing. The samples with GEL conveyed a higher healing efficiency of 91%, compared to PEMA’s 63%, and the GEL samples also conveyed higher levels of corrosion resistance.

Preparation of Thermochromic Microcapsules of Bisphenol A and Crystal Violet Lactone and Their Effect on Coating Properties

Thermochromic microcapsules were prepared with a thermochromic compound as core material and urea formaldehyde as wall material. The molar ratio of urea and formaldehyde, the mass ratio of core material to wall material, the concentration of emulsifier, and rotating speed were selected to make a four-level and three-factor L9(34) orthogonal test. It was found that the molar ratio of urea and formaldehyde had the greatest influence on the coating rate of microcapsules. The effects of molar ratio of urea and formaldehyde on the discoloration temperature and coating rate of microcapsules were studied. When the molar ratio of urea to formaldehyde was 1:1.6, the core material: wall material ratio was 4:7, the concentration of emulsifier was 5.0%, and the rotating speed was 1600 rpm, the performance of the microcapsules was the best. When the microcapsule content was 20.0%, the color difference of the paint film was the largest, the gloss and hardness of the paint film decreased with increasing microcapsule content, and the impact resistance of the paint film first increased and then decreased with increasing microcapsule content. The adhesion of the paint film remained unchanged, and was grade 1. When the microcapsule content was 20.0%, the performance of the paint film was at its best. This provides a basis for the application of thermochromic coatings.

Trends in Chemical Wood Surface Improvements and Modifications: A Review of the Last Five Years

Increasing the use of wood in buildings is regarded by many as a key solution to tackle climate change. For this reason, a lot of research is carried out to develop new and innovative wood surface improvements and make wood more appealing through features such as increased durability, fire-retardancy, superhydrophobicity, and self-healing. However, in order to have a positive impact on the society, these surface improvements must be applied in real buildings. In this review, the last five years of research in the domain of wood surface improvements and modifications is first presented by sorting the latest innovations into different trends. Afterward, these trends are correlated to specifications representing different normative, ecologic and economic factors which must be considered when expecting to introduce a wood treatment to the market. With this review, the authors hope to help researchers to take into consideration the different factors influencing whether new innovations can leave the research laboratory or not, and thereby facilitate the introduction of new wood surface treatments in the society.

Effect of Microcapsules with Waterborne Coating as Core Material on Properties of Coating for Tilia Europaea and Comparison with Other Microcapsules

Urea formaldehyde was used as wall material and waterborne coatings as a core material to prepare microcapsules. So as to explore the influence of mass ratio of core to shell, reaction temperature and standing time on the performance of microcapsules, the orthogonal test of three factors and two levels was put into effect. The orthogonal experimental results showed the mass ratio of core to shell was the most important factor. With the increase of the mass ratio of core to shell, the output and clad ratio of microcapsules increased first and then decreased. The microcapsule with the mass ratio of core to shell of 0.67:1 had better appearance, output, and encapsulation performance. The optical properties of waterborne wood coating with the microcapsules of waterborne coating as core materials did not decrease significantly, while the hardness, impact resistance, and toughness were improved. At the same time, the microcapsules have a certain self-repairing effect on coating micro-cracks. Compared with the properties of waterborne coatings with other microcapsules, the coating with waterborne coating as core material has better comprehensive performance. The results provide a new research idea for the performance enhancement and self-healing of wood waterborne coating.

Preparation and Performance of Thermochromic and Self-Repairing Dual Function Paint Film with Lac Resin Microcapsules and Fluorane Microcapsules

Microcapsules with lac resin as the core material and urea-formaldehyde resin as the wall material were prepared by in situ polymerization, and then the lac resin microcapsules and fluorane microcapsules were added into a water-based primer or topcoat, respectively, to prepare water-based coatings with dual functions of thermochromic and self-repair. The effects of different methods of adding microcapsules on the optical properties, mechanical properties, self-repairing properties, and the aging resistance of water-based paint film were investigated, so as to prepare water-based paint film with the best discoloration and self-repairing functions. The results showed that the paint film with 10.0% fluorane microcapsules in the topcoat and 5.0% lac resin microcapsules in the primer had better comprehensive properties, and the paint film changed from yellow to colorless at 32 °C, with a color difference of 68.9, hardness of 3H, adhesion grade of 0, impact resistance of 13.0 kg∙cm, and elongation at break of 20.0%. The resistance of the paint film to NaCl, ethanol, and detergent was grade 2, with slight discontinuous marks, and the resistance to red ink was grade 3, with slight marks. The lac resin microcapsules have good aging resistance, which can enhance the aging resistance of the paint film with fluorane microcapsules. The gap width of the paint film was repaired by 2.1 µm, the self-repairing rate was 12.3%, and the paint film with lac resin microcapsules had a better crack inhibition effect. The results have provided a reference for multifunctional wood coatings.

Poplar-based thermochromic composites that change colour at 38 °C to 46 °C

The red thermochromic dye (R-TD) is the tetradecanoic acid tetradecyl ester (C28H56O2) and methyl red (C15H15N3O2) mixture that has better permeability enabling its infiltration into wood and better thermochromic properties changing its colour at above 30 °C after about 0.5 min. Thicker poplar-based thermochromic composite specimens (R-PTC, thickness: 5.0 mm) were prepared by filling the R-TD into pre-treated poplar veneer (thickness: 5.0 mm) thus allowing better penetration after pre-treatment. After R-TD infiltration, the R-PTC samples were covered by polypropylene wax for preventing R-TD from overflowing from R-PTC under the action of phase-change temperature. This R-PTC, whose colour can change from light-red to dark-red at 38 °C to 46 °C, can recover to light-red at below 38 °C after about 14 h, and the peak of colour change is at about 42 °C. R-PTC will be suitable for materials used in thermochromic furniture that can indicate the surface temperature to potential users, thus allowing assessment of likely scalded pain when used the furniture.

Unraveling driving regimes for destabilizing concentrated emulsions within microchannels

Coalescence is the most widely demonstrated mechanism for destabilizing emulsion droplets in microfluidic chambers. However, we find that depending on the channel wall surface functionalization, surface zeta potential, type of surfactant, characteristics of the oil as a dispersed phase, or even the presence of externally-induced stress, other different destabilization mechanisms can occur in subtle ways. In general, we observe four regimes leading to destabilization of concentrated emulsions: (i) coalescence, (ii) emulsion bursts, (iii) a combination of the two first mechanisms, attributed to the simultaneous occurrence of coalescence and emulsion bursts; and (iv) compaction of the droplet network that eventually destabilizes to fracture-like behavior. We correlate various physico-chemical properties (zeta potential, contact angle, interfacial tension) to understand their respective influence on the destabilization mechanisms. This work provides insights into possible ways to control or inflict emulsion droplet destabilization for different applications.

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.

Advances and Opportunities of Oil-in-Oil Emulsions

Emulsions are mixtures of two immiscible liquids in which droplets of one are dispersed in a continuous phase of the other. The most common emulsions are oil-water systems, which have found widespread use across a number of industries, for example, in the cosmetic and food industries, and are also of advanced scientific interest. In addition, the past decade has seen a significant increase in both the design and application of nonaqueous emulsions. This has been primarily driven by developments in understanding the mechanism of effective stabilization of oil-in-oil (o/o) systems, either using block copolymers (BCPs) or solid (Pickering) particles with appropriate surface functionality. These systems, as highlighted in this review, have enabled emergent applications in areas such as pharmaceutical delivery, energy storage, and materials design (e.g., polymerization, monolith, and porous polymer synthesis). These o/o emulsions complement traditional emulsions that utilize an aqueous phase and allow the use of materials incompatible with water. We assess recent advances in the preparation and stabilization of o/o emulsions, focusing on the identity of the stabilizer (BCP or particle), the interplay between stabilizer and oils, and highlighting applications and opportunities associated with o/o emulsions.

Influence of the PVC of Glass Fiber Powder on the Properties of a Thermochromic Waterborne Coating for Chinese Fir Boards

A thermochromic waterborne coating with thermal insulation efficacy was prepared by adding thermochromic microcapsules and glass fiber powder. The influence of the pigment volume concentration (PVC) of a glass fiber powder on the performance of the thermochromic coating for Chinese fir boards was investigated. It was found that a coating with a PVC of glass fiber powder of 0–22.0% had better discoloration properties. When the PVC of the glass fiber powder was more than 4.0%, with the increase of the PVC, the gloss of the coating decreased gradually, while, the adhesion, impact resistance, and liquid resistance were not affected. When the PVC of the glass fiber powder was 10.0%–30.0%, it showed thermal insulation efficacy and high hardness. The coating with a PVC of 16.0% glass fiber powder had better wear resistance. The discoloration property of the coating with thermal insulation efficacy was not affected by time. These results exhibit great potential for the application of a wood surface thermochromic and thermal insulation coating.

Reversible Thermochromic Nanoparticles Composed of a Eutectic Mixture for Temperature-Controlled Photothermal Therapy

Photothermal therapy (PTT) is an effective approach to cancer therapy. However, the high temperature during the therapy increases the damage to surrounding normal tissues. Thermochromic material, which exhibits temperature-activated color change and optical absorption, is a promising photothermal agent for precisely temperature-controlled PTT. Nevertheless, the construction of nanosized thermochromic particles with an appropriate transition temperature (44-47 °C) is still a great challenge. Here, thermochromic nanoparticles with the transition temperature at 45 °C based on a leuco dye-developer-solvent system are developed for thermostatic photothermal tumor therapy. Below the temperature, the nanoparticles take a dark green color to absorb light and convert it into heat efficiently. Once the temperature reaches the transition point, the colored nanoparticles switch to a colorless state, maintaining the temperature at the predefined level and allowing deeper light penetration. The autoregulated nanoparticles exhibit a prominent therapeutic effect for the tumor without destroying normal tissues.

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

Using Cunninghamia lanceolata as a substrate, the thermochromic ink was added to the waterborne finish to test the optical properties and mechanical properties of the finish film. The results showed that the discoloration performance of the finish film with 15.0% and 30.0% of the thermochromic ink was better. The gloss of the finish film changes irregularly when the concentration increases. The finish film with a thermochromic ink concentration of 10.0% has the highest gloss, and with a concentration of 30.0% has the lowest gloss. When the thermochromic ink concentration exceeds 15.0%, the impact resistance of the finish film is slightly enhanced. The concentration is not related to the liquid resistance of the finish film. When the thermochromic ink concentration was 0-15.0%, the particle distribution uniform reunion was not much. The discoloration mechanism of discolored finish film can be considered to be as follows. After adding thermochromic ink, when the finish film temperature rises, it fades from red to colorless. When the temperature is lowered, the thermochromic ink changes to its original colour again, and the thermochromic effect is stable and sustainable. On the basis of the above results, when the thermochromic ink concentration is 15.0%, the general performance of the waterborne finish film on the Cunninghamia lanceolata surface is the best. This study provides new prospects in using thermochromic ink for waterborne finish film.

Reversible Nontoxic Thermochromic Microcapsules

Thermochromic materials exhibit a color change in response to a change in temperature. Creating nontoxic microcapsules containing thermochromic materials for applications in ink and film materials is historically challenging. In this study, we develop a nontoxic chlorophenol red (CPR)-water thermochromic system and its microcapsules with silicone shells via a reaction between water and octadecyltrichlorosilane (OTS) at the interface of a w/o emulsion. The obtained microcapsules exhibit a clear color change with full reversibility and are successfully used as inks by screen printing and as additives in films. Nontoxicity of both microcapsules and films is demonstrated through cell cytotoxicity assays. These features make these novel materials applicable to the next generation of intelligent sensors, coating, and food packaging materials.

Effect of the Concentration of Pigment Slurry on the Film Performances of Waterborne Wood Coatings

Wood surface decoration and protection has become a topic of public concern. In this paper, a temperature-sensitive and reversible thermochromic waterborne wood coating was prepared by using Chinese fir board as the base material and a waterborne wood coating with the pigment slurry of thermochromic microcapsules as the paint base. The optical properties, mechanical properties and chemical resistance of the waterborne wood coating were tested, and its microstructure was analyzed. The results showed that when the concentration of thermochromic pigment slurry was 30.0%, the thermochromic property of the waterborne wood coating was best. The gloss of the waterborne wood coating with 15.0% pigment slurry of thermochromic microcapsules was high. The concentration of thermochromic pigment slurry had no effect on the adhesion, impact resistance, or chemical resistance of the waterborne wood coating. Based on the above results, the waterborne wood coating on Chinese fir had the best comprehensive performance when the concentration of thermochromic pigment slurry was 15.0%. This work will provide a technical reference for the industrialization of the thermochromic coating film on wood.