In the construction and machinery industry, heat is a major factor causing damage and destruction. The safety and efficiency of most machines and structures are greatly affected by temperature, and temperature management and control are essential. In this study, a carbon nanotube (CNT) based temperature sensing coating that can be applied to machines and structures having various structural types was fabricated, and characteristics analysis and temperature sensing performance were evaluated. The surface coating, which detects temperature through resistance change is made of a nanocomposite composed of carbon nanotubes (CNT) and epoxy (EP). We investigated the electrical properties by CNT concentration and temperature sensing performance of CNT/EP coating against static and cyclic temperatures. In addition, the applicability of the CNT/EP coating was investigated through a partially heating and cooling experiment. As a result of the experiment, the CNT/EP coating showed higher electrical conductivity as the CNT concentration increased. In addition, the CNT/EP coating exhibits high sensing performance in the high and sub−zero temperature ranges with a negative temperature coefficient of resistance. Therefore, the proposed CNT/EP coatings are promising for use as multi-functional coating materials for the detection of high and freezing temperatures.

The availability of carbon nanotube (CNT)-based polymer composites allows the development of surface-attached self-sensing crack sensors for the structural health monitoring of reinforced concrete (RC) structures. These sensors are fabricated by integrating CNTs as conductive fillers into polymer matrices such as polyurethane (PU) and can be applied by coating on RC structures before the composite hardens. The principle of crack detection is based on the electrical change characteristics of the CNT-based polymer composites when subjected to a tensile load. In this study, the electrical conductivity and electro-mechanical/environmental characterization of smart skin fabricated with various CNT concentrations were investigated. This was performed to derive the tensile strain sensitivity of the smart skin according to different CNT contents and to verify their environmental impact. The optimal CNT concentration for the crack detection sensor was determined to be 5 wt% CNT. The smart skin was applied to an RC structure to validate its effectiveness as a crack detection sensor. It successfully detected and monitored crack formation and growth in the structure. During repeated cycles of crack width variations, the smart skin also demonstrated excellent reproducibility and electrical stability in response to the progressive occurrence of cracks, thereby reinforcing the reliability of the crack detection sensor. Overall, the presented results describe the crack detection characteristics of smart skin and demonstrate its potential as a structural health monitoring (SHM) sensor.

Traffic accidents caused by road icing are a serious global problem, and conventional de-icing methods like spraying chemicals have several limitations, including excessive manpower management, road damage, and environmental pollution. In this study, the carbon nanotubes reinforced de-icing coating for the road system with a self-heating function was developed as part of the development of a new system to prevent accidents caused by road icing. The electrical characteristics of the fabricated coating were analyzed, and the carbon nanotube coating heating performance experiment was conducted to measure the temperature increments by applying a voltage to the coating at a sub-zero temperature using an environmental chamber. In addition, the coating was installed on the road pavement and the applicability was investigated through a heating test in winter. As a result of the experiment, the coating made with the higher carbon nanotube concentration presented higher heating owing to its higher electrical conductivity. In addition, the coating showed sufficient heating performance, although the maximum temperature by Joule heating decreased for the entire coating at sub-zero temperatures. Finally, field tests demonstrated the potential of electrically conductive coatings for de-icing applications.

Polyethylene terephthalate (PET) is a common plastic widely used in food packaging, especially plastic bottles, and in fibers and textiles. The widespread use of PET and its intentional and unintentional release and disposal over the past few decades have placed significant pressure on the environment, necessitating the development of green, low-cost, and efficient recycling technologies to mitigate this impact. This article reviews recent advances in microwave-assisted catalytic depolymerization of PET. It begins by outlining the fundamental principles of PET materials science and depolymerization mechanisms. The article then reviews the historical evolution of this research and presents a benchmark comparison of different depolymerization methodologies. Finally, through a critical analysis and comparison of state-of-the-art approaches, the article identifies emerging trends and highlights promising directions for future research in the field. A comprehensive comparison of conventional and microwave heating methods is presented, indicating that catalyst-assisted microwave systems can shorten reaction times and achieve high product yields under optimized conditions. Key advantages and limitations are highlighted, and persistent challenges are discussed. Overall, this article surveys the latest progress in the chemical recycling of PET and provides critical insights for future research and further development of microwave-assisted catalytic PET depolymerization technology.

Conventional construction safety helmets provide passive protection but do not record impact occurrence or location. Recording this information could support post-impact inspection, motivating the integration of distributed sensing onto the curved helmet shell. This study develops a screen-printed carbon nanotube (CNT)/epoxy sensor array for multichannel impact monitoring. Rheological and electrical characterization guided sensor fabrication, while impact tests examined how CNT loading and sensing-disc geometry affected response magnitude and variability. A 5.0 wt.% CNT formulation with a 10 mm sensing disc was selected and integrated onto the inner shell as a 19-channel array. Channel-specific resistor-substitution calibration enabled resistance-based response analysis. Three independently fabricated arrays detected all 240 crown impacts at nominal energies of 0.2–4.0 J. Across 90 impacts at three off-crown positions, the median angular deviation was 6.2°. These findings demonstrate an approach to extending helmet functionality through low-energy impact detection and regional localization using printed CNT/epoxy sensors.