Search Results (155)

Polychrome paintings on wooden artifacts are vital elements of cultural heritage, where plant-derived binders play a crucial role in color formation and durability. This study aims to systematically compare the chemical, optical, and surface characteristics of two traditional natural adhesives—acacia gum (AG) and tragacanth gum (TG)—to better understand their influence on the preservation and reproduction of wood-supported polychrome coatings. Fourier-transform infrared spectroscopy (FTIR) confirmed their polysaccharide-rich structures, with distinct ester and glycosidic linkages, while rheological tests demonstrated that TG exhibited higher viscosity at 1–3% concentrations, whereas AG showed a sharper increase at 5%, reflecting different molecular architectures. Colorimetric analysis combined with two-way ANOVA revealed that gum type significantly influenced color development in blue and red coatings (p < 0.001), while yellow and green coatings remained largely unaffected. Gum concentration (1–5%) generally showed no significant effect on color. All coatings exhibited a matte appearance (<3 GU), with statistical analysis indicating that gloss was mainly determined by pigment particle distribution rather than adhesive type. Surface roughness increased notably with gum concentration (p < 0.001), demonstrating that binder content strongly affects coating microtexture. Overall, pigment type was the dominant factor for color, whereas gum concentration critically influenced surface morphology. These findings provide practical guidance for optimizing natural adhesives in the conservation of traditional polychrome artifacts. Full article

Chinese lacquer (urushi), a traditional East Asian coating material, has been used for more than 7000 years due to its durability, gloss, and cultural significance. However, its long-term stability under natural light remains insufficiently studied, especially regarding the role of mineral pigments in modulating photoaging behavior. In this study, three traditional lacquer coatings pigmented with cinnabar (HgS), orpiment (As₂S₃), and lapis lazuli were subjected to natural light aging for nine weeks. Colorimetric analysis revealed rapid chromatic changes during the initial stage of exposure, followed by slower transformations, with cinnabar-based red lacquer showing superior stability compared to orpiment- and lapis-based coatings. Gloss measurements and surface roughness analyses demonstrated a strong negative correlation, with yellow lacquer exhibiting the most severe gloss loss (≈30%) and roughness increase (≈89%), consistent with scanning electron microscopy observations of microcracking and surface deterioration. Fourier-transform infrared spectroscopy (FTIR) indicated pigment-dependent oxidative degradation, characterized by intensified carbonyl and aromatic C=C bands. Collectively, the results confirm that mineral pigments strongly influence the optical, chemical, and structural stability of lacquer coatings. From a conservation perspective, cinnabar-based lacquers exhibit higher resilience, whereas orpiment- and lapis-colored coatings are highly vulnerable, underscoring the need for pigment-specific preservation strategies for lacquerware cultural heritage. Full article

Palm-leaf manuscripts (PLMs) represent a significant component of cultural heritage as a medium for information recording. However, the inherent fragility of these organic materials presents a major challenge for their long-term preservation. Therefore, enhancing the durability of PLMs to ensure longevity has become a critical issue in conservation research. This study includes an examination of the potential of two polymers, cationic polyacrylamide (CPAM) and chitosan quaternary ammonium salt (CQAS), for PLM encapsulation. The encapsulation effects of these materials were assessed through artificial moist heat-accelerated aging tests, enabling a comprehensive evaluation of structural and mechanical properties at both the macroscopic and microscopic levels. The results indicated that CPAM provided superior performance in terms of gloss, color stability, hydrophobicity, pH value, and tensile properties, whereas CQAS demonstrated notable antifungal efficacy. Both CPAM and CQAS possess distinct advantages and can significantly contribute to the preservation of PLMs. This work offers valuable insights for developing effective conservation strategies, emphasizing the potential of CPAM and CQAS as viable encapsulation materials in the face of conservation requirements. Full article

In this work, low-zinc epoxy powder coating primers with anticorrosive properties were developed. For this purpose, single-walled carbon nanotubes (SWCNTs) were introduced into powder coatings. The obtained coatings were evaluated by performing the following tests: adhesion to steel, roughness, gloss, color, water contact angle, salt spray, electrochemical impendance spectroscopy (EIS), and transmission scanning microscopy (TEM). The anticorrosion resistance of the powder coating primers obtained depends on the zinc and SWCNT content, as well as the degree of dispersion in the paint. The mechanism of anticorrosion activity was proposed. Full article

Surface pretreatment significantly influences the hygroscopic behavior of wood, which in turn affects surface stability when exposed to variable climatic conditions. This study focuses on how different surface pretreatment methods impact the performance of protective coating applied on spruce wood (Picea abies (L.) Karst.) during one year of natural weathering. Samples were prepared using various surface treatments: milling and sanding with grit sizes P40, P80, and P120, respectively. Two types of coatings were applied: a solventborne coating (ADLER Pullex Plus-Lasur) and a waterborne coating (DColor FK 47 UV Protect). The samples were exposed for 12 months at an outdoor testing site in Suchdol, Czech. Surface properties were assessed through color changes in the CIE Lab* space, gloss measurements (ISO 2813), contact angle analysis, and visual inspection. The results showed that exposure to UV radiation and microbial activities led to the gradual degradation of the optical properties and aesthetic appearance of the wood. Surfaces with greater roughness preserved their aesthetic properties more effectively, indicating a higher absorption of the coating. Untreated wood exhibited low water repellency, while the coated surface demonstrated enhanced hydrophobicity. Notably, the waterborne coating showed a temporary increase in contact angle around the sixth month, indicating surface clogging by dust particles. In contrast, the solventborne coating had a rapid decrease in wettability during the first nine months. These findings suggested the importance of surface pretreatment and coating type in maintaining the long-term performance and aesthetic appearance for wood used in exterior conditions. Full article

Polyurethane-coated fabrics are widely employed as tarpaulin materials. However, due to the long duration and large space requirements of natural exposure tests, studies on fabric degradation remain scarce. To systematically investigate the natural aging patterns and mechanisms of polyurethane-coated fabrics, this study conducted 24-month natural aging tests in three representative regions: Xishuangbanna (tropical monsoon climate), Xiamen (subtropical maritime monsoon climate), and Jinan (temperate monsoon climate). Changes in appearance, mechanical properties, surface morphology, elemental composition, and microstructure were thoroughly analyzed. The results indicated that gloss decreased by over 60%, the color difference exceeded 5.8, and tear strength was reduced by more than 50%. SEM, ATR-FTIR, and XPS analyses revealed that hydrolysis and oxidation occurred in the coating, leading to coating thinning, fiber exposure, and even damage. In Xishuangbanna, high temperature, high humidity, and strong solar radiation are responsible for the most severe degradation of fabrics. High temperature, humidity, and salt fog synergistically accelerated the aging process. In Jinan, significant thermal strain contributed to deterioration, and fabrics exhibited the mildest degradation. This multi-region natural exposure study realistically simulates in-service aging behavior, providing important validation for accelerated laboratory aging methods, product reliability improvement, and service-life modeling. Full article

Hybrid computer-aided design and computer-aided manufacturing (CAD/CAM) materials have gained prominence in restorative dentistry due to their advantageous mechanical and esthetic properties; however, their long-term performance may be adversely affected by acidic oral environments, such as those associated with gastroesophageal reflux disease (GERD). This in vitro study aimed to investigate the effects of simulated gastric acid exposure on the surface roughness, gloss, color stability, and microhardness of two hybrid CAD/CAM materials: Vita Enamic and Cerasmart. Standardized rectangular specimens (2 mm thickness) were prepared and polished using a clinically relevant intraoral protocol. Baseline measurements were obtained for surface roughness, gloss, color change (ΔE), and Vickers microhardness. All specimens were then immersed in hydrochloric acid (pH 1.2) for 24 h to simulate prolonged gastric acid exposure, after which the same properties were re-evaluated. Post-immersion analysis revealed significant increases in surface roughness and reductions in gloss and microhardness for both materials (p < 0.05), with Vita Enamic demonstrating greater susceptibility to degradation. Color changes remained below the clinically perceptible threshold, with no significant differences between materials. These findings highlight the potential vulnerability of hybrid CAD/CAM materials to acidic environments and underscore the importance of careful material selection in patients predisposed to acid-related challenges. Full article

Thermochromic microcapsules were synthesized and optimized using crystal violet lactone, bisphenol A, and decanol as the core materials, a dispersible cationic red dye as the color-modifying additive, and urea-formaldehyde resin as the wall material, based on orthogonal and single-factor experiments. The effects of the proportion of cationic red dye in the core material, the mass ratio of formaldehyde to urea, the emulsifier HLB value, and the core–wall mass ratio on yield, encapsulation rate, thermochromic ΔE, and formaldehyde release of microcapsules were systematically investigated. The results showed that the core–wall ratio was the key factor affecting the comprehensive performance of the microcapsules. Through the comparison of orthogonal and single-factor tests, 11# microcapsule was identified as having the best overall performance in terms of ΔE, and encapsulation rate. The ΔE value was increased by about 165% compared with the lowest-performing sample, significantly enhancing the thermochromic response. The encapsulation rate was improved by nearly 40%, effectively enhancing the encapsulation quality and core stability, with overall performance standing out. The best preparation process was to add 0.5% of the core material mass of dispersible cationic red dye, the mass ratio of formaldehyde and urea was 1.2:1, the HLB value of emulsifier was 10, and the core–wall ratio was 1:1.1. The yield of 11# microcapsules prepared under this condition was 31.95%, the encapsulation rate was 68%, the thermochromic ΔE was 9.292, and the formaldehyde release concentration was 1.381 mg/m³. Furthermore, 11# microcapsules with different addition levels were introduced into the UV primer to evaluate their effects on the mechanical and optical properties of the coating. The results showed that the addition of microcapsules weakened the gloss and light transmittance of the coating, increased the surface roughness, and decreased the elongation at break. When the addition amount was 5%, the coating exhibited the best overall performance: UV-visible light transmittance reached 91.92%, 60° gloss was 42.2 GU, elongation at break was 9.3%, and surface roughness was 0.308 μm. This study developed a purple thermochromic microcapsule system by regulating the dispersible dye content and interfacial conditions. In coating applications, the system exhibited a strong ΔE response and excellent overall performance, offering great advantages over existing similar systems in terms of color-change efficiency, ΔE enhancement, and coating adaptability. Full article

Despite extensive research on the effect of nitrogen flow rate on titanium nitride (TiN) coating properties, its influence on esthetic and engineering performance through microstructure control remains insufficiently explored. To simultaneously meet the requirements for surface strengthening and decorative esthetics in high-end stainless-steel crafts, TiN coatings were deposited on 304L stainless-steel substrates using multi-arc ion plating. The regulatory mechanisms and synergistic evolution laws of nitrogen flow rates (100, 200, and 300 sccm) on the microstructure, decorative properties (color and gloss), and engineering performance (adhesion strength, hardness, wear resistance, and corrosion resistance) of the coatings were investigated. At a nitrogen flow rate of 200 sccm, the coating exhibited a uniform and dense columnar crystal structure, as well as a saturated golden hue with high surface gloss. Additionally, the film–substrate adhesion, microhardness, tribological properties, and corrosion resistance reached optimal levels. In contrast, excessively low (100 sccm) or high (300 sccm) nitrogen flow rates resulted in coarse particles and blurred grain boundaries owing to uncontrolled droplet ejection or target poisoning, respectively, thereby deteriorating both appearance and engineering performance. These findings can inform the optimization of TiN coatings, enabling the design of surfaces that simultaneously meet esthetic and high-performance engineering requirements. Full article

Objective: The aim of this study was to evaluate and compare the clinical behavior of indirect onlays/overlays made of lithium disilicate and composite resin and to investigate risk factors associated with restoration failures. Methods: 112 indirect partial coverage posterior restorations (onlays and overlays) placed in 51 adult patients between January 2014 and December 2020 were examined. The restorations were evaluated using selected FDI criteria (color match, surface gloss, anatomic form, fracture of restorative material, tooth cracks and fractures, marginal discoloration, marginal integrity and recurrence of initial pathology). The survival of the restorations was analyzed using Kaplan–Meier method. Risk factors (type of restoration, type of tooth, tooth vitality, smoking) were investigated using Cox regression analysis. Risk estimation was conducted for each evaluated criterion (p < 0.05). Results: For composite restorations, the estimated survival rate was 94.2% after 5 years, dropping to 74.3% in 7.9 years and continued falling to less than 60% after 8.2 years. On the contrary, for lithium disilicate restorations the estimated survival rate was 90.9% after 5 years, dropped to 85.2% after 5.5 years remaining stable thereafter. Lithium disilicate onlays demonstrated significantly better performance than lithium disilicate overlays. Cox regression analysis did not reveal any significant association between the survival of the indirect partial restorations and restoration material, tooth type, restoration type and history of endodontic treatment. However, smoking was found to be a statistically significant risk factor (p < 0.05). Conclusions: Lithium disilicate and composite indirect restorations exhibited comparable survival rates at the early observation period. However, lithium disilicate partial coverage restorations demonstrated more favorable clinical behavior compared to composite in the long term, with statistical significance observed in ceramic vs. composite onlays. Full article

Self-healing coatings can replace conventional coatings and are capable of self-healing and continuing to protect the substrate after coating damage. In this study, two types of self-healing resins were synthesized as coatings: Type-A via Diels–Alder crosslinking of furfuryl-modified diglycidyl ether bisphenol A with bismaleimide, and Type-B through epoxy blending/curing to form a semi-interpenetrating network. FTIR and Raman spectroscopy confirmed the formation of Diels–Alder (DA) bonds, while GPC tests indicated incomplete monomer conversion. Both resins were applied to glass and wood substrates, with performance evaluated through TGA, colorimetry (ΔE), gloss analysis, and scratch-healing tests (120 °C/30 min). The results showed that Type-A resins had a higher healing efficiency (about 80% on glass substrates and 60% on wood substrates), while Type-B resins had a lower healing rate (about 65% on glass substrates and 55% on wood substrates). However, Type-B is more heat-resistant, has a slower decomposition rate between 300 and 400 °C, higher gloss retention, and less color difference (ΔE) between wood and glass substrates. The visible light transmission of Type-B (74.14%) is also significantly higher. Full article

By incorporating microcapsules with self-healing properties into the coating, a self-healing coating can be obtained, which can repair cracks or damage. In this study, chitosan–sodium tripolyphosphate-coated tung oil microcapsules 1# and 2# with a high encapsulation efficiency were incorporated into a UV-cured topcoat on cherry wood surfaces at different ratios. The results showed that as the microcapsule content increased, the coating’s reflectivity and gloss loss increased, while its impact resistance improved. However, the coating’s adhesion and hardness decreased. The coating containing 6% microcapsule 1# exhibited optimal performance on cherry wood board. The reflectance of the ultraviolet–visible light of the coating was 41.14%, the lightness value was 58.35, the red-green value was 13.96, the yellow-blue value was 25.32, the color difference was 4.47, the gloss reduction rate was 66.84%, the roughness was 1.11 μm, the impact resistance grade was level 4, the adhesion was level 1, the hardness was 3H, and the recovery rate was 17.06%. Comparative analysis revealed that both the chitosan/arabic gum-encapsulated tung oil microcapsules and chitosan–sodium tripolyphosphate-coated tung oil microcapsules could impart self-healing functionality to UV-cured coatings when incorporated into the finish. Notably, the coating system containing 6% chitosan/arabic gum-encapsulated tung oil microcapsules demonstrated optimal performance characteristics when applied to cherry wood substrates. The research findings demonstrate the technical feasibility of achieving self-healing functionality in UV-cured coatings for cherry wood surfaces. Full article

This study enhanced the self-healing performance of cherry wood furniture coatings by incorporating chitosan gum arabic-coated tung oil (CGA-T) microcapsules (types 1 and 2) into UV topcoats at 3%–15% concentrations. Multi-layer coated samples were systematically evaluated for optical, mechanical, and self-healing properties. Results demonstrated that microcapsules conferred self-healing ability, but concentrations >9% reduced reflectance (min 39.20%), increased color difference (max ΔE = 8.35), decreased gloss (max 35.25% loss at 60°), and raised roughness (max 1.79 μm). Mechanically, impact resistance improved (to grade 3), while adhesion declined (to grade 3) and hardness decreased (4H→2H). Self-healing performance peaked at 9% microcapsule 2 content (31.32% healing rate), with optimal overall performance at 6%. The 6% microcapsule 2 formulation (Sample 7) achieved the best overall balance among optical, mechanical, and self-healing properties, demonstrating its suitability for practical applications. Full article

The color stability of dental ceramics in the oral cavity is influenced by multiple factors, including the patient’s dietary habits and oral hygiene practices, which can affect the optical and surface properties of resin-containing dental restorative materials. The purpose of this study was to evaluate the effects of surface finishing procedures and simulated tooth-brushing on the surface roughness, surface gloss, and color stability of resin matrix ceramics before and after coffee immersion. Forty specimens were prepared from a resin matrix ceramic and divided into four experimental groups according to surface finishing procedures, coffee immersion, and simulated tooth-brushing. The surface roughness, surface gloss, and color stability of the tested material were measured, and the data were statistically analyzed at a significance level of p < 0.05. The surface finishing procedures, measurement times, and application sequences affected surface roughness, surface gloss, and color stability. The most significant color differences occurred after coffee immersion; however, tooth-brushing had a more significant effect on the surface roughness and surface gloss. Coffee caused perceivable and clinically unacceptable color differences in the resin matrix ceramics. Tooth-brushing had a positive impact on the tested parameters. This study presents a novel approach by integrating both chemical (coffee immersion) and mechanical (tooth-brushing simulation) degradation processes to assess their combined and isolated effects on a resin matrix ceramic material. The findings provide clinically relevant insights into how finishing procedures and oral hygiene may influence the long-term esthetic performance of such restorative materials. Full article

Objectives: To examine the effects of surface treatments on the color stability, surface roughness, surface gloss, and wettability of monolithic polychromatic material jetting (MJT) 3D-printed denture material. Material and Methods: Twenty-one color variants of the same denture material (TrueDent; Stratasys, Eden, MN, USA) underwent two surface treatments (polishing only or polishing and glazing), creating 42 study groups with a total of 420 samples (n = 10 per group). The samples were manufactured using a PolyJet 3D printer (J5 DentaJet; Stratasys, Eden, MN, USA), a type of MJT 3D printer. Color measurements were taken with a digital spectrophotometer before and after the surface treatments, and quantitative color differences (ΔE₀₀ and ΔC*) were calculated using the CIE2000 system. Comparisons of ΔE₀₀ were made against the 50%:50% acceptability threshold (AT) of 1.8 and the 50%:50% perceptibility threshold (PT) of 0.8 for tooth shade, as well as the 50%:50% PT of 1.72 and the 50%:50% AT of 4.08 for gingival (pink) shade. After surface treatment, the gloss was measured using a glossmeter, surface roughness was measured with optical profilometry, and wettability was measured by contact angle measurements using an optical tensiometer. The significance of surface treatment on color changes for each color variant was evaluated using one-sided, one-sample t-tests against the AT and PT. The effects of surface treatment on surface gloss, surface roughness, contact angle, and ΔC* were analyzed using t-tests for each color variant. Pairwise comparisons between groups were made using Fisher’s Protected Least Significant Differences (α = 0.05). Results: In most cases, glazing caused the color change (ΔE₀₀) to exceed the AT and PT, with a few exceptions. Most materials exhibited a more vibrant (more saturated) appearance and statistically higher chroma, with glazed surface treatments compared to polished ones, though there were some exceptions. For all materials, the glazed samples had significantly higher gloss units than the polished ones (p < 0.0001). Additionally, all materials showed significantly higher surface roughness in glazed samples compared to polished ones (p < 0.0001 for most). The polished samples had significantly higher contact angles (p < 0.0001 for most). Conclusions: Surface treatments significantly influenced the color, surface gloss, surface roughness, and wettability of MJT 3D-printed denture materials. Glazing led to increased chroma and gloss and produced more hydrophilic surfaces, although it also increased surface roughness. These results highlight the importance of surface treatment selection in optimizing the clinical performance of MJT-fabricated dentures. Full article