“…Loading more quantity of CNQDs into the chemical structure of the nanocomposites makes filling of empty spaces and creating of strong chemical interactions among CNQDs and polymer matrix, as a result, this leads looseness and motion of polymer chains to happen at higher temperatures. 21 Figure 10.E′ curves of UP and UP/CNQDs nanocomposites.…”
Section: Resultsmentioning
confidence: 99%
“…Loading more quantity of CNQDs into the chemical structure of the nanocomposites makes filling of empty spaces and creating of strong chemical interactions among CNQDs and polymer matrix, as a result, this leads looseness and motion of polymer chains to happen at higher temperatures. 21 Changes of the E 00 curves are shown in Figure 11. At a temperature of lower degrees, E 00 curves height is low, however, as temperature rises, these curves height soars, in such a manner that climaxes at 20-70°C.…”
Section: Viscoelastic Propertiesmentioning
confidence: 99%
“…19,20 Exposure to UV radiation could destroy many substances like polyester fibers, polyamide fibers, polyurethanes, epoxies, polymer coatings, plastics, building construction stones, wood constructions, colors and suchlike. 21,22 Polymer structures of lignin and cellulose existent in wood constructions undergo photochemical degradation in front of the UV from sunlight. 23,24 Amongst the wall cells of wood, lignin exhibits the highest reactivity exposed to 250-400 nm UV radiation, for, phenolic hydroxyl groups convert into phenoxy free radicals following the reaction with UV and consequently turn into quinoid structures because of reaction with oxygen.…”
Section: Introductionmentioning
confidence: 99%
“…19,20 Exposure to UV radiation could destroy many substances like polyester fibers, polyamide fibers, polyurethanes, epoxies, polymer coatings, plastics, building construction stones, wood constructions, colors and suchlike. 21,22…”
The present study has been conducted to investigate the protective effect of graphitic carbon nitride quantum dots (CNQDs) against high energetic and harmful ultraviolet (UV) rays in addition to strengthening impact of CNQDs over mechanical and viscoelastic properties of unsaturated polyester (UP). To achieve this purpose, CNQDs were synthesized using citric acid and extra urea via microwave-assisted method. Afterwards, several percentages of CNQDs (0.25, 0.5 and 0.75 wt%) were added to UP and after curing process, UP/CNQDs nanocomposites were obtained with different percentages. By certain microscopic and spectroscopic tests, correctness of CNQDs formation and various features of UP/CNQDs nanocomposites were examined. Adding CNQDs to the matrix of polyester resin allowed creation of nanocomposites with fluorescence emission ability, also blockage of UV rays by the strengthened samples. Strengthening UP by CNQDs resulted in growth of thermal stability, improvement of tensile strength, 10%–15% increase in flexibility, and progress in viscoelastic characteristics including storage modulus, Tg and cross-linking density.
“…Loading more quantity of CNQDs into the chemical structure of the nanocomposites makes filling of empty spaces and creating of strong chemical interactions among CNQDs and polymer matrix, as a result, this leads looseness and motion of polymer chains to happen at higher temperatures. 21 Figure 10.E′ curves of UP and UP/CNQDs nanocomposites.…”
Section: Resultsmentioning
confidence: 99%
“…Loading more quantity of CNQDs into the chemical structure of the nanocomposites makes filling of empty spaces and creating of strong chemical interactions among CNQDs and polymer matrix, as a result, this leads looseness and motion of polymer chains to happen at higher temperatures. 21 Changes of the E 00 curves are shown in Figure 11. At a temperature of lower degrees, E 00 curves height is low, however, as temperature rises, these curves height soars, in such a manner that climaxes at 20-70°C.…”
Section: Viscoelastic Propertiesmentioning
confidence: 99%
“…19,20 Exposure to UV radiation could destroy many substances like polyester fibers, polyamide fibers, polyurethanes, epoxies, polymer coatings, plastics, building construction stones, wood constructions, colors and suchlike. 21,22 Polymer structures of lignin and cellulose existent in wood constructions undergo photochemical degradation in front of the UV from sunlight. 23,24 Amongst the wall cells of wood, lignin exhibits the highest reactivity exposed to 250-400 nm UV radiation, for, phenolic hydroxyl groups convert into phenoxy free radicals following the reaction with UV and consequently turn into quinoid structures because of reaction with oxygen.…”
Section: Introductionmentioning
confidence: 99%
“…19,20 Exposure to UV radiation could destroy many substances like polyester fibers, polyamide fibers, polyurethanes, epoxies, polymer coatings, plastics, building construction stones, wood constructions, colors and suchlike. 21,22…”
The present study has been conducted to investigate the protective effect of graphitic carbon nitride quantum dots (CNQDs) against high energetic and harmful ultraviolet (UV) rays in addition to strengthening impact of CNQDs over mechanical and viscoelastic properties of unsaturated polyester (UP). To achieve this purpose, CNQDs were synthesized using citric acid and extra urea via microwave-assisted method. Afterwards, several percentages of CNQDs (0.25, 0.5 and 0.75 wt%) were added to UP and after curing process, UP/CNQDs nanocomposites were obtained with different percentages. By certain microscopic and spectroscopic tests, correctness of CNQDs formation and various features of UP/CNQDs nanocomposites were examined. Adding CNQDs to the matrix of polyester resin allowed creation of nanocomposites with fluorescence emission ability, also blockage of UV rays by the strengthened samples. Strengthening UP by CNQDs resulted in growth of thermal stability, improvement of tensile strength, 10%–15% increase in flexibility, and progress in viscoelastic characteristics including storage modulus, Tg and cross-linking density.
“…Although we used a very small amount of K-GO in this research work, we found the same correlation, that is, absorbance is increasing while increasing the amount of K-GO in the epoxy composites. 30 As shown in Figure 6, the UV absorbance is directly proportional to the concentration of K-GO in the epoxy composites (Figure 6, up). Also, an epoxy composite with a K-GO concentration of 0.05 wt% shows noticeably higher fluorescence intensity than a sample with a low K-GO concentration (0.025 wt%) (Figure 6, down).…”
Section: Optimization Of Fluorescence Propertymentioning
Fluorescent polymers have exciting applications in sensing, imaging, and probes. Agricultural waste is increasingly being used to develop fluorescent nanomaterials due to technology, cost, and waste management advantages. This study developed fluorescent carbon‐based nanomaterials, that is, potassium doped graphene oxide (K‐GO) from Quercus ilex waste and used them to optimize fluorescent epoxy nanocomposites. The resulting nanocomposites showed significant enhancement in tensile strength with only 0.05 wt% of the renewable nanomaterial. The developed fluorescent epoxy nanocomposites have enhanced thermal and mechanical properties and can be used in sensing, imaging, and other applications.Highlights
A greener and easier approach to synthesizing K‐GO from Quercus ilex seeds.
Development of fluorescent epoxy composites with K‐GO.
Tensile strength is enhanced by adding only 0.05 wt% K‐GO.
Thermal stability was improved by adding K‐GO.
Developed composites can be applied to sensing and UV‐shielding in the future.
Carbon dots (CDs) have wide applications due to their unique physicochemical properties. Converting coal pitch into CDs is a valuable avenue toward new applications of traditional fossil fuels. The obtained CDs derived from coal pitch usually exhibit blue emission. Herein, a simple approach to tailor the optical properties of the coal pitch-derived blueemissive CDs (b-CDs) is developed by post-hydrothermal treatment of b-CDs in sodium hydroxide solution. The obtained warm yellow-emissive CDs (y-CDs) show a broad emission from 400 to 800 nm range, with the maximum emission peak centered at ∼600 nm. The redshifted emission of y-CDs can be ascribed to the surface states with the improved extent of the π-electron system caused by the post-hydrothermal treatment, which effectively increases the graphitization degree. The potential application of the obtained y-CDs as phosphors for a lightemitting diode (LED) is demonstrated. This study offers a feasible way to tailor the optical properties of CDs derived from coal pitch for wider applications.
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