Visual presentation for monitoring layer-wise curing quality in DLP 3D printing

Purpose This paper aims to address the problem of uncertain product quality in digital light processing (DLP) three-dimensional (3D) printing, a scheme is proposed to qualitatively estimate whether a layer is printed with the qualified quality or not cured . Design/methodology/approach A thermochromic pigment whose color fades at 45°C is prepared as the indicator and it is mixed with the resin. A visual surveillance framework is proposed to monitor the visual variation in a period of the entire curing process. The exposure region is divided into 30 × 30 sub-regions; gray-level variation curves (curing curves) in all sub-regions are classified as normal or abnormal and a corresponding printing control strategy is designed to improve the percentage of qualified printed objects. Findings The temperature variation caused by the releasing reaction heat on the exposure surface is consistent in different regions under the homogenized light intensity. The temperature in depth begins to rise at different times. The temperature in the regions near the light source rises earlier, and that far from the light source rises later. Thus, the color of resin mixed with the thermochromic pigment fades gradually over a period of the entire solidification process. The color variation in the regions with defects of bubbles, insufficient material filling, etc., is much different from that in the normal curing regions. Originality/value A temperature-sensitive organic chromatic chemical pigment is prepared to present the visual variation over a period of the entire curing process. A novel 3D printing scheme with visual surveillance is proposed to monitor the layer-wise curing quality and to timely stop the possible unqualified printing resulted from bubbles, insufficient material filling, etc.

Fabrication of Thermochromic Membrane and Its Characteristics for Fever Detection

Body temperature is an important indicator of the health status of the human body. Thus, numerous studies have been conducted in various fields to measure body temperature. In this study, a biocompatible thermochromic membrane that changes its color when the temperature becomes higher than the transition temperature for thermochromism was fabricated using an extrusion-based three-dimensional printing process. The printing material was prepared by mixing a thermochromic pigment and a thermoplastic polymer in various ratios. The effects of mixing ratio on the various properties of the fabricated membranes were experimentally investigated. It is presented that the fabricated lattice membrane had excellent thermochromic reaction, which was experimentally evaluated using a measurement of color brightness. The pigment content affected the diameter and surface morphology of the printed filament. The elastic modulus decreased, and thermochromic response became faster as the pigment concentration increased. Subsequently, a patch for fever detection was developed and then attached to the skin to demonstrate its color change according to body temperature. Results show that the fabricated thermochromic patch could be successfully applied to fever detection.

Influence of Thermochromic Pigment Powder on Properties of Waterborne Primer Film for Chinese Fir

This study chose organic thermochromic pigment powder and waterborne wood primer as the paint base, and Chinese fir board as the substrate to prepare thermochromic waterborne coatings with different concentrations of thermochromic pigment powder. The best concentration of thermochromic pigment powder for waterborne primer film on Chinese fir surface was explored. The experimental results showed that the color-changing property of the primer film was the best when the concentration of pigment powder in primer film was 5.0%–10%. There was a negative correlation between the gloss of the primer and the concentration of pigment powder. The gloss of the primer film was the highest when the concentration of pigment powder was 5%. When the concentration of pigment powder is 0%–20% and 25.0%–30%, the adhesion of the coating is grade 0 and grade 1, respectively. The resistance to the impact of primer film increased with the increase of concentration of pigment powder, but the resistance to the impact of primer film with 0%–30% of thermochromic pigment powder concentration was similar. Scanning electron microscopy showed that the higher the concentration of thermochromic pigment powder, the more particles and agglomeration. When the concentration of pigment powder was 5%, the distribution of particles was uniform and no agglomeration, and the microstructure of primer film was the best. Infrared spectroscopy showed that there was no difference in the composition of the paint film from 0% to 30%. The results showed that the comprehensive property of waterborne primer film on Chinese fir was better when the pigment concentration was 5%. Waterborne thermochromic primer film provides a potential application for the development of intelligent furniture in different temperature ranges.

RESEARCH ON PRODUCING TEMPERATURE INDUCED COLOR CHANGE IN FUCTIONAL RUBBER COMPOUNDS

Today, the rubber is used not only in technology products but also in household products. In this study, thermolchromic rubber exhibiting the available color changing property with the ambient temperature alteration is fabricated. The effects of thermochromic pigment content and silica filler on the mechanical properties and color-changing durability of the rubber compound are investigated. The results show that the introduction of thermolchromic pigment of 1 wt.% into the rubber phase does not adversely affect the mechanical property, while creating the novel color-changing property of the rubber compond. Furthermore, the color-changing durability of the rubber compound maintains after more than 100 cycles, while the original color does not change compared to before the durable test.

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.

Colorimetric properties and application of temperature indicator thermochromic pigment for thermal woven textile

Currently, the thermometer, infrared thermal imaging camera and temperature sensor are the main instruments for the temperature measurement of thermal products. However, these instruments are either inconvenient or too expensive to afford. For researchers, these are common to approach, whereas for designers or salespeople who work in the thermal textile field, new tools that are more convenient to access, easily affordable and have design possibilities need to be invented. This study aims to select a temperature indicator thermochromic pigment amount of four pigments (red, yellow, green and blue) for thermal woven textiles by analyzing the colorimetric properties and making a fast indicator demonstration prototype to achieve the concept. The pigment samples are heated respectively and the decolorization color at 40℃, 50℃, 60℃ and 70℃ under illuminant D65 are real-time measured by a spectroradiometer. The L*, a*, b*, ΔL*, Δa*, Δb*, K/ S and color difference CMC 2:1 values are calculated and analyzed. In this experiment, blue pigment has the best performance and thus results in the top selection of the indicator pigment, which is used in production for a fast, convenient and visualized temperature indicator for thermal woven textiles.