Displaying publications 61 - 80 of 142 in total

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  1. Fulltext Detrimental Effects of UVB on Retinal Pigment Epithelial Cells and Its Role in Age-Related Macular Degeneration
    Mahendra CK, Tan LTH, Pusparajah P, Htar TT, Chuah LH, Lee VS, et al.
    Oxid Med Cell Longev, 2020;2020:1904178.
    PMID: 32855763 DOI: 10.1155/2020/1904178
    Retinal pigment epithelial (RPE) cells are an essential part of the human eye because they not only mediate and control the transfer of fluids and solutes but also protect the retina against photooxidative damage and renew photoreceptor cells through phagocytosis. However, their function necessitates cumulative exposure to the sun resulting in UV damage, which may lead to the development of age-related macular degeneration (AMD). Several studies have shown that UVB induces direct DNA damage and oxidative stress in RPE cells by increasing ROS and dysregulating endogenous antioxidants. Activation of different signaling pathways connected to inflammation, cell cycle arrest, and intrinsic apoptosis was reported as well. Besides that, essential functions like phagocytosis, osmoregulation, and water permeability of RPE cells were also affected. Although the melanin within RPE cells can act as a photoprotectant, this photoprotection decreases with age. Nevertheless, the changes in lens epithelium-derived growth factor (LEDGF) and autophagic activity or application of bioactive compounds from natural products can reverse the detrimental effect of UVB. Additionally, in vivo studies on the whole retina demonstrated that UVB irradiation induces gene and protein level dysregulation, indicating cellular stress and aberrations in the chromosome level. Morphological changes like retinal depigmentation and drusen formation were noted as well which is similar to the etiology of AMD, suggesting the connection of UVB damage with AMD. Therefore, future studies, which include mechanism studies via in vitro or in vivo and other potential bioactive compounds, should be pursued for a better understanding of the involvement of UVB in AMD.
    Matched MeSH terms: Ultraviolet Rays*
  2. Fulltext Viability and Antioxidant Effects of Traditional Cooling Rice Powder (bedak sejuk) Made from Oryza sativa ssp. Indica and Oryza sativa ssp. japonica on UVB-Induced B164A5 Melanoma Cells
    Ghazali AR, Muralitharan RV, Soon CK, Salyam T, Ahmad Maulana NN, Mohamed Thaha UAB, et al.
    Asian Pac J Cancer Prev, 2020 Nov 01;21(11):3381-3386.
    PMID: 33247699 DOI: 10.31557/APJCP.2020.21.11.3381
    BACKGROUND: Traditional cooling rice powder (bedak sejuk) is a fermented rice-based cosmetic that is applied topically on one's skin, as an overnight facial mask. According to user testimonies, bedak sejuk beautifies and whitens skin, whereby these benefits could be utilised as a potential melanoma chemopreventive agent.

    OBJECTIVE: Hence, this study aimed to determine the effects of bedak sejuk made from Oryza sativa ssp. indica (Indica) and Oryza sativa ssp. japonica (Japonica) on UVB-induced B164A5 melanoma cells, and also identify the antioxidant capacities of both types of bedak sejuk.

    METHODS: The optimum dose of Indica and Japonica bedak sejuk to treat the cells was determined via the MTT assay. Then, the antioxidant capacities of both types of bedak sejuk were determined using the FRAP assay.

    RESULTS: From the MTT assay, it was found that Indica and Japonica bedak sejuk showed no cytotoxic effects towards the cells. Hence, no IC50 can be obtained and two of the higher doses, 50 and 100 g/L were chosen for treatment. In the FRAP assay, Indica bedak sejuk at 50 and 100 g/L showed FRAP values of 0.003 ± 0.001 μg AA (ascorbic acid)/g of bedak sejuk and 0.004 ± 0.0003 μg AA/g of bedak sejuk. Whereas Japonica bedak sejuk at 50 g/L had the same FRAP value as Indica bedak sejuk at 100 g/L. As for Japonica bedak sejuk at 100 g/L, it showed the highest antioxidant capacity with the FRAP value of 0.01 ± 0.0007 μg AA/g of bedak sejuk which was statistically significant (p < 0.05) when compared to other tested concentrations.

    CONCLUSION: In conclusion, Japonica bedak sejuk has a higher antioxidant capacity compared to Indica bedak sejuk despite both being not cytotoxic towards the cells. Regardless, further investigations need to be done before bedak sejuk could be developed as potential melanoma chemoprevention agents.

    Matched MeSH terms: Ultraviolet Rays/adverse effects*
  3. Variations of metabolites and proteome in Lonicera japonica Thunb. buds and flowers under UV radiation
    Zhu W, Zheng W, Hu X, Xu X, Zhang L, Tian J
    Biochim Biophys Acta Proteins Proteom, 2017 Apr;1865(4):404-413.
    PMID: 28087425 DOI: 10.1016/j.bbapap.2017.01.004
    Lonicera japonica Thunb., also known as Jin Yin Hua and Japanese honeysuckle, is used as a herbal medicine in Asian countries. Its flowers have been used in folk medicine in the clinic and in making food or healthy beverages for over 1500years in China. To investigate the molecular processes involved in L. japonica development from buds to flowers exposed to UV radiation, a comparative proteomics analysis was performed. Fifty-four proteins were identified as differentially expressed, including 42 that had increased expression and 12 that had decreased expression. The levels of the proteins related to glycolysis, TCA/organic acid transformation, major carbohydrate metabolism, oxidative pentose phosphate, stress, secondary metabolism, hormone, and mitochondrial electron transport were increased during flower opening process after exposure to UV radiation. Six metabolites in L. japonica buds and flowers were identified and relatively quantified using LC-MS/MS. The antioxidant activity was performed using a 1,1-diphenyl-2-picrylhydrazyl assay, which revealed that L. japonica buds had more activity than the UV irradiated flowers. This suggests that UV-B radiation induces production of endogenous ethylene in L. japonica buds, thus facilitating blossoming of the buds and activating the antioxidant system. Additionally, the higher metabolite contents and antioxidant properties of L. japonica buds indicate that the L. japonica bud stage may be a more optimal time to harvest than the flower stage when using for medicinal properties.
    Matched MeSH terms: Ultraviolet Rays*
  4. Optimization of photocatalytic degradation of palm oil mill effluent in UV/ZnO system based on response surface methodology
    Ng KH, Cheng YW, Khan MR, Cheng CK
    J Environ Manage, 2016 Dec 15;184(Pt 3):487-493.
    PMID: 27784576 DOI: 10.1016/j.jenvman.2016.10.034
    This paper reports on the optimization of palm oil mill effluent (POME) degradation in a UV-activated-ZnO system based on central composite design (CCD) in response surface methodology (RSM). Three potential factors, viz. O2 flowrate (A), ZnO loading (B) and initial concentration of POME (C) were evaluated for the significance analysis using a 2(3) full factorial design before the optimization process. It is found that all the three main factors were significant, with contributions of 58.27% (A), 15.96% (B) and 13.85% (C), respectively, to the POME degradation. In addition, the interactions between the factors AB, AC and BC also have contributed 4.02%, 3.12% and 1.01% to the POME degradation. Subsequently, all the three factors were subjected to statistical central composite design (CCD) analysis. Quadratic models were developed and rigorously checked. A 3D-response surface was subsequently generated. Two successive validation experiments were carried out and the degradation achieved were 55.25 and 55.33%, contrasted with 52.45% for predicted degradation value.
    Matched MeSH terms: Ultraviolet Rays*
  5. Fulltext UV/O3 treatment as a surface modification of rice husk towards preparation of novel biocomposites
    Rajendran Royan NR, Sulong AB, Yuhana NY, Chen RS, Ab Ghani MH, Ahmad S
    PLoS One, 2018;13(5):e0197345.
    PMID: 29847568 DOI: 10.1371/journal.pone.0197345
    The use of rice husks (RH) to reinforce polymers in biocomposites are increasing tremendously. However, the incompatibility between the hydrophilic RH fibers and the hydrophobic thermoplastic matrices leads to unsatisfactory biocomposites. Surface modification of the fiber surface was carried out to improve the adhesion between fiber and matrix. In this study, the effect of surface modification of RH via alkali, acid and ultraviolet-ozonolysis (UV/O3) treatments on the properties of composites recycled high density polyethylene (rHDPE) composites was investigated. The untreated and treated RH were characterized by Fourier Transform Infrared (FTIR) and Scanning Electron Microscope (SEM). The composites containing 30 wt% of RH (treated and untreated) were then prepared via extrusion and followed by compression molding. As compared to untreated RH, all surface treated RH exhibited rougher surface and showed improved adhesion with rHDPE matrix. Tensile strength of UV/O3-treated RH composites showed an optimum result at 18.37 MPa which improved about 5% in comparison to the composites filled with untreated RH. UV/O3 treatment promotes shorter processing time and lesser raw material waste during treatment process where this is beneficial for commercialization in the future developments of wood plastic composites (WPCs). Therefore, UV/O3 treatment can be served as an alternative new method to modify RH surface in order to improve the adhesion between hydrophilic RH fibre and hydrophobic rHDPE polymer matrix.
    Matched MeSH terms: Ultraviolet Rays*
  6. Fulltext UV induced surface modification on improving the cytocompatibility of metallocene polyethylene
    Jaganathan SK, Prasath MM
    An Acad Bras Cienc, 2018 4 12;90(1):195-204.
    PMID: 29641759 DOI: 10.1590/0001-3765201820170736
    Demand for medical implants is rising day by day as the world becomes the place for more diseased and older people. Accordingly, in this research, metallocene polyethylene (mPE), a commonly used polymer was treated with UV rays for improving its biocompatibility. Scanning electron microscopy (SEM) images confirmed the formation of crests and troughs, which depicts the improvement of surface roughness of mPE substrates caused by UV etching. Accordingly, the contact angle measurements revealed that the wettability of mPE-2.5 J/cm2 (68.09º) and mPE-5 J/cm2 (57.93º) samples were found to be increased compared to untreated mPE (86.84º) indicating better hydrophilicity. Further, the UV treated surface exhibited enhanced blood compatibility as determined in APTT (untreated mPE- 55.3 ± 2.5 s, mPE-2.5 J/cm2 - 76.7 ± 4.1 s and mPE-5 J/cm2 - 112.3 ± 2 s) and PT (untreated mPE - 24.7 ± 1.5 s, mPE- 2.5 J/cm2 - 34.3 ± 1.1 s and mPE-5 J/cm2 - 43 ± 2 s) assay. Moreover, the treated mPE-2.5 J/cm2 (4.88%) and mPE-5 J/cm2 (1.79%) showed decreased hemolytic percentage compared to untreated mPE (15.40%) indicating better safety to red blood cells. Interestingly, the changes in physicochemical properties of mPE are directly proportional to the dosage of the UV rays. UV modified mPE surfaces were found to be more compatible as identified through MTT assay, photomicrograph and SEM images of the seeded 3T3 cell population. Hence UV-modified surface of mPE may be successfully exploited for medical implants.
    Matched MeSH terms: Ultraviolet Rays*
  7. Fulltext Towards producing novel fish gelatin films by combination treatments of ultraviolet radiation and sugars (ribose and lactose) as cross-linking agents
    Bhat R, Karim AA
    J Food Sci Technol, 2014 Jul;51(7):1326-33.
    PMID: 24966426 DOI: 10.1007/s13197-012-0652-9
    Developing novel fish gelatin films with better mechanical properties than mammalian gelatin is a challenging but promising endeavor. Studies were undertaken to produce fish gelatin films by combining treatments with different sugars (ribose and lactose) followed 'by' 'and' ultraviolet (UV) radiation, as possible cross-linking agents. Increase in tensile strength and percent elongation at break was recorded, which was more significant in films without sugars that were exposed to UV radiation. Films with added ribose showed decreased solubility after UV treatment and exhibited higher swelling percentage than films with added lactose, which readily dissolved in water. FTIR spectra of all the films showed identical patterns, which indicated no major changes to have occurred in the functional groups as a result of interaction between gelatin, sugars and UV irradiation. The results of this study could be explored for commercial use, depending on industrial needs for either production of edible films or for food packaging purposes.
    Matched MeSH terms: Ultraviolet Rays
  8. New para-substituted non-symmetric isoflavones for their fast photo-switching ability: synthesis and their liquid crystal characterization
    Yuvaraj AR, Yam WS, Chan TN, Goh YP, Hegde G
    Spectrochim Acta A Mol Biomol Spectrosc, 2015 Jan 25;135:1115-22.
    PMID: 25173529 DOI: 10.1016/j.saa.2014.08.009
    The first example of non-symmetric isoflavone-based fast photo-switchable liquid crystals with different functional groups at the terminal position were synthesized and characterized. Polarizing optical microscopy study revealed that the compounds showed least ordered nematic phase. Optical photo switching study exhibited very fast photoisomerization effect in solution. The E-Z and Z-E conversion occurred around 3-5s and 40-700 s respectively. This is also the first example of para-substituted non-symmetric isoflavone liquid crystals exhibiting very fast photo switching property in solution. Argument based on non-symmetrical behaviour might be the reason for the observed behaviour.
    Matched MeSH terms: Ultraviolet Rays
  9. Ag-ZnO nanoreactor grown on FTO substrate exhibiting high heterogeneous photocatalytic efficiency
    Tan ST, Ali Umar A, Balouch A, Nafisah S, Yahaya M, Yap CC, et al.
    ACS Comb Sci, 2014 Jul 14;16(7):314-20.
    PMID: 24919039 DOI: 10.1021/co400157m
    This Research Article reports an unusually high efficiency heterogeneous photodegradation of methyl orange (MO) in the presence of Ag nanoparticle-loaded ZnO quasi-nanotube or nanoreactor (A-ZNRs) nanocatalyst grown on FTO substrate. In typical process, photodegradation efficiency of as high as 21.6% per μg per Watts of used catalyst and UV power can be normally obtained within only a 60-min reaction time from this system, which is 10(3) order higher than the reported results. This is equivalent to the turnover frequency of 360 mol mol(-1) h(-1). High-density hexagonal A-ZNRs catalysts were grown directly on FTO substrate via a seed-mediated microwave-assisted hydrolysis growth process utilizing Ag nanoparticle of approximately 3 nm in size as nanoseed and mixture aqueous solution of Zn(NO3)·6H2O, hexamethylenetetramine (HMT), and AgNO3 as the growth solution. A-ZNRs adopts hexagonal cross-section morphology with the inner surface of the reactor characterized by a rough and rugged structure. Transmission electron microscopy imaging shows the Ag nanoparticle grows interstitially in the ZnO nanoreactor structure. The high photocatalytic property of the A-ZNRs is associated with the highly active of inner side's surface of A-ZNRs and the oxidizing effect of Ag nanoparticle. The growth mechanism as well as the mechanism of the enhanced-photocatalytic performance of the A-ZNRs will be discussed.
    Matched MeSH terms: Ultraviolet Rays
  10. Fulltext Modified microwave method for the synthesis of visible light-responsive TiO2/MWCNTs nanocatalysts
    Alosfur FK, Jumali MH, Radiman S, Ridha NJ, Yarmo MA, Umar AA
    Nanoscale Res Lett, 2013;8(1):346.
    PMID: 23919496 DOI: 10.1186/1556-276X-8-346
    Recently, TiO2/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO2/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO2/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light.
    Matched MeSH terms: Ultraviolet Rays
  11. Fulltext Effect of ZnO on the physical properties and optical band gap of soda lime silicate glass
    Zaid MH, Matori KA, Aziz SH, Zakaria A, Ghazali MS
    Int J Mol Sci, 2012;13(6):7550-8.
    PMID: 22837711 DOI: 10.3390/ijms13067550
    This manuscript reports on the physical properties and optical band gap of five samples of soda lime silicate (SLS) glass combined with zinc oxide (ZnO) that were prepared by a melting and quenching process. To understand the role of ZnO in this glass structure, the density, molar volume and optical band gaps were investigated. The density and absorption spectra in the Ultra-Violet-Visible (UV-Visible) region were recorded at room temperature. The results show that the densities of the glass samples increased as the ZnO weight percentage increased. The molar volume of the glasses shows the same trend as the density: the molar volume increased as the ZnO content increased. The optical band gaps were calculated from the absorption edge, and it was found that the optical band gap decreased from 3.20 to 2.32 eV as the ZnO concentration increased.
    Matched MeSH terms: Ultraviolet Rays
  12. Fulltext Hydrothermal preparation of silver telluride nanostructures and photo-catalytic investigation in degradation of toxic dyes
    Gholamrezaei S, Salavati-Niasari M, Ghanbari D, Bagheri S
    Sci Rep, 2016;6:20060.
    PMID: 26805744 DOI: 10.1038/srep20060
    Different morphologies of Ag2Te nanostructures were synthesized using TeCl4 as a new precursor and hydrazine hydrate as reducing agent by a hydrothermal method. Various parameters that affect on morphology and purity of nanostructures were optimized. According to our experiments the best time and temperature for preparation of this nanostructure are 12 h and 120 °C. The photo-catalytic behaviour of nanostructures in presence of UV-visible light for degradation of methyl orange was investigated. Results show that the presence of UV light is necessary for an efficient degradation of dye in aqueous solution. On the other hand, as observations propose the Ag2Te reveal a strong photoluminescence peak at room temperature that could be attributed to high level transition in the semiconductor. Nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) techniques and UV-visible scanning spectrometer (UV-Vis).
    Matched MeSH terms: Ultraviolet Rays
  13. The study of dipole moment of some substituted acetic acids in an electronically excited state
    Murthy MB, Daya Sagar BS, Patil RL
    Spectrochim Acta A Mol Biomol Spectrosc, 2003 Apr;59(6):1277-80.
    PMID: 12659896
    The electronic absorption spectra of eight substituted acetic acids have been measured at room temperature in several solvents. The ground state dipole moments are evaluated experimentally for these molecules. These ground state values are used in conjunction with the spectral results to evaluate their first electronically excited state dipole moments. For all the molecules investigated here the dipole moments in the excited state are higher than their ground state values.
    Matched MeSH terms: Ultraviolet Rays
  14. Fulltext Photocatalytic Properties of Graphene/Gold and Graphene Oxide/Gold Nanocomposites Synthesized by Pulsed Laser Induced Photolysis
    Chen LH, Shen HT, Chang WH, Khalil I, Liao SY, A Yehye W, et al.
    Nanomaterials (Basel), 2020 Oct 07;10(10).
    PMID: 33036455 DOI: 10.3390/nano10101985
    Graphene (Gr)/gold (Au) and graphene-oxide (GO)/Au nanocomposites (NCPs) were synthesized by performing pulsed-laser-induced photolysis (PLIP) on hydrogen peroxide and chloroauric acid (HAuCl4) that coexisted with Gr or GO in an aqueous solution. A 3-month-long aqueous solution stability was observed in the NCPs synthesized without using surfactants and additional processing. The synthesized NCPs were characterized using absorption spectroscopy, transmission electron microscopy, Raman spectroscopy, energy dispersive spectroscopy, and X-ray diffraction to prove the existence of hybrid Gr/Au or GO/Au NCPs. The synthesized NCPs were further evaluated using the photocatalytic reaction of methylene blue (MB), a synthetic dye, under UV radiation, visible light (central wavelength of 470 nm), and full spectrum of solar light. Both Gr/Au and GO/Au NCPs exhibited photocatalytic degradation of MB under solar light illumination with removal efficiencies of 92.1% and 94.5%, respectively.
    Matched MeSH terms: Ultraviolet Rays
  15. Control of microbiologically influenced corrosion using ultraviolet radiation
    Akrima Abu Bakar, Muhammad Khairool Fahmy Mohd Ali, Norhazilan Md. Noor, Nordin Yahaya, Mardhiah Ismail, Ahmad Safuan A. Rashid
    Sains Malaysiana, 2017;46:1323-1331.
    Baram Delta Operation had been producing oil and gas since 1960's and serious pipelines failure was reported in the year of 2005. The final investigation has concluded that one of the species of bacteria that has been identified to cause microbiologically influenced corrosion, specifically known as sulfate reducing bacteria (SRB) was found to be one of the potential contributing factors to the incidents. This work investigates the potential use of ultraviolet (UV) radiation to inhibit the SRB consortium that was cultivated from the crude oil in one of the main trunk lines at Baram Delta Operation, Sarawak, Malaysia. The impact of UV exposure to bio-corrosion conditions on carbon steel coupon in certain samples for 28 days was discussed in this study. The samples were exposed to UV radiation based on variations of parameters, namely: time of UV exposure; and power of UV lamp. The significant changes on the amount of turbidity reading and metal loss of the steel coupon were recorded before and after experiment. The results showed that SRB growth has reduced rapidly for almost 90% after the UV exposure for both parameters as compared to the abiotic samples. Metal loss values were also decreased in certain exposure condition. Additionally, field emission scanning electron microscopy (FESEM) coupled with energy dispersive spectroscopy (EDS) was performed to observe the biofilm layer formed on the metal surface after its exposure to SRB. The evidence suggested that the efficiency of UV treatment against SRB growth could be influenced by the particular factors studied
    Matched MeSH terms: Ultraviolet Rays
  16. Fulltext Green Synthesis and Characterization of Pullulan Mediated Silver Nanoparticles through Ultraviolet Irradiation
    Khan MJ, Kumari S, Shameli K, Selamat J, Sazili AQ
    Materials (Basel), 2019 Jul 26;12(15).
    PMID: 31357398 DOI: 10.3390/ma12152382
    Nanoparticles (NPs) are, frequently, being utilized in multi-dimensional enterprises. Silver nanoparticles (AgNPs) have attracted researchers in the last decade due to their exceptional efficacy at very low volume and stability at higher temperatures. Due to certain limitations of the chemical method of synthesis, AgNPs can be obtained by physical methods including sun rays, microwaves and ultraviolet (UV) radiation. In the current study, the synthesis of pullulan mediated silver nanoparticles (P-AgNPs) was achieved through ultraviolet (UV) irradiation, with a wavelength of 365 nm, for 96 h. P-AgNPs were formed after 24 h of UV-irradiation time and expressed spectra maxima as 415 nm, after 96 h, in UV-vis spectroscopy. The crystallographic structure was "face centered cubic (fcc)" as confirmed by powder X-ray diffraction (PXRD). Furthermore, high resolution transmission electron microscopy (HRTEM) proved that P-AgNPs were covered with a thin layer of pullulan, with a mean crystalline size of 6.02 ± 2.37. The average lattice fringe spacing of nanoparticles was confirmed as 0.235 nm with quasi-spherical characteristics, by selected area electron diffraction (SAED) analysis. These green synthesized P-AgNPs can be utilized efficiently, as an active food and meat preservative, when incorporated into the edible films.
    Matched MeSH terms: Ultraviolet Rays
  17. Performance of a novel casing made of chitosan under traditional sausage manufacturing conditions
    Adzaly NZ, Jackson A, Kang I, Almenar E
    Meat Sci, 2016 Mar;113:116-23.
    PMID: 26656870 DOI: 10.1016/j.meatsci.2015.11.023
    The goal of this study was to validate the commercial feasibility of a novel casing formed from chitosan containing cinnamaldehyde (2.2%, w/v), glycerol (50%, w/w) and Tween 80 (0.2% w/w) under traditional sausage manufacturing conditions. Meat batter was stuffed into both chitosan and collagen (control) casings and cooked in a water bath. Before and after cooking, both casings were compared for mechanical, barrier, and other properties. Compared to collagen, the chitosan casing was a better (P≤0.05) barrier to water, oxygen, liquid smoke, and UV light. In mechanical and other properties, the chitosan casing had higher (P≤0.05) tensile strength, lower (P≤0.05) elongation at break and tensile energy to break, and better (P≤0.05) transparency whereas a similar (P>0.05) water solubility to the collagen casing. Overall, the chitosan casing was less affected by sausage manufacturing conditions than the collagen casing, indicating that chitosan casing has potential as an alternative to the current collagen casing in the manufacture of sausages.
    Matched MeSH terms: Ultraviolet Rays
  18. Fulltext Transparent Blend of Poly(Methylmethacrylate)/Cellulose Acetate Butyrate for the Protection from Ultraviolet
    Mahmood Raouf R, Abdul Wahab Z, Azowa Ibrahim N, Abidin Talib Z, Chieng BW
    Polymers (Basel), 2016 Apr 14;8(4).
    PMID: 30979233 DOI: 10.3390/polym8040128
    The use of transparent polymers as an alternative to glass has become widespread. However, the direct exposure of these materials to climatic conditions of sunlight and heat decrease the lifetime cost of these products. The aim of this study was to minimize the harm caused by ultraviolet (UV) radiation exposure to transparent poly(methylmethacrylate) (PMMA), which usually leads to changes in the physical and chemical properties of these materials and reduced performance. This was achieved using environmentally friendly cellulose acetate butyrate (CAB). The optical, morphological, and thermal properties of CAB blended with transparent PMMA was studied using UV-VIS spectrophotometry, scanning electron microscopy, X-ray diffraction, dynamic mechanical analysis, and thermal gravimetric analysis. The results show that CAB was able to reduce the effects of UV radiation by making PMMA more transparent to UV light, thereby preventing the negative effects of trapped radiation within the compositional structure, while maintaining the amorphous structure of the blend. The results also show that CAB blended with PMMA led to some properties commensurate with the requirements of research in terms of a slight increase in the value of the modulus and the glass transition temperature for the PMMA/CAB blend.
    Matched MeSH terms: Ultraviolet Rays
  19. Fulltext Carbon Nanotube Reinforced High Density Polyethylene Materials for Offshore Sheathing Applications
    Okolo C, Rafique R, Iqbal SS, Saharudin MS, Inam F
    Molecules, 2020 Jun 27;25(13).
    PMID: 32605124 DOI: 10.3390/molecules25132960
    Multiwall carbon nanotube (CNT)-filled high density polyethylene (HDPE) nanocomposites were prepared by extrusion and considered for their suitability in the offshore sheathing applications. Transmission electron microscopy was conducted to analyse dispersion after bulk extrusion. Monolithic and nanocomposite samples were subjected to accelerated weathering and photodegradation (carbonyl and vinyl indices) characterisations, which consisted of heat, moisture (seawater) and UV light, intended to imitate the offshore conditions. The effects of accelerated weathering on mechanical properties (tensile strength and elastic modulus) of the nanocomposites were analysed. CNT addition in HDPE produced environmentally resilient nanocomposites with improved mechanical properties. The energy utilised to extrude nanocomposites was also less than the energy used to extrude monolithic HDPE samples. The results support the mass substitution of CNT-filled HDPE nanocomposites in high-end offshore applications.
    Matched MeSH terms: Ultraviolet Rays
  20. Effect of tropical outdoor weathering on the surface roughness and mechanical properties of maxillofacial silicones
    Rahman AM, Jamayet NB, Nizami MMUI, Johari Y, Husein A, Alam MK
    J Prosthet Dent, 2021 Jan 17.
    PMID: 33472753 DOI: 10.1016/j.prosdent.2020.07.026
    STATEMENT OF PROBLEM: The climate of tropical Southeast Asia includes high humidity and ultraviolet radiation that reduce the lifespan of silicone prostheses by inducing changes in their mechanical properties and color stability. Studies on the surface roughness (SR) and mechanical properties of different silicone elastomers (SEs) subjected to the natural tropical weather of Southeast Asia are lacking.

    PURPOSE: The purpose of this in vitro study was to evaluate the SR, tensile strength (TS), and percentage elongation (% E) of different SEs subjected to outdoor weathering in the Malaysian climate.

    MATERIAL AND METHODS: Type-II dumbbell-shaped specimens (N-120) (nonweathered=15, weathered=15) were made from 3 room-temperature vulcanized (A-2000, A-2006, and A-103) and 1 heat-temperature vulcanized (M-511) silicone (Factor II). For 6 months, weathered specimens were subjected to outdoor weathering inside a custom exposure rack. Simultaneously, the nonweathered specimens were kept in a dehumidifier. Subsequently, the SR was measured with a profilometer; TS and % E were measured by using a universal testing machine. Two-way ANOVA was used to compare the means of the tested properties of the nonweathered and weathered specimens, and pairwise comparison was carried out between the silicones (α=.05).

    RESULTS: After outdoor weathering, the SR, TS, and % E were adversely affected by weathering in the Malaysian environment. Among the silicone materials, A-2000 showed the least TS changes (2.51 MPa), while A-2006 demonstrated significant changes in percentage elongation after outdoor weathering (266.5%). M-511 exhibited the highest mean value (2.50 μm) for SR changes. In addition, A-103 SE showed statistically significant differences in most pairwise comparisons for all 3 dependent variables.

    CONCLUSIONS: Based on the evaluation of mechanical properties, A-103 can be suggested as a suitable silicone for maxillofacial prostheses fabricated for tropical climates. However, A-2000 can be a suitable alternative, although significant changes to surface roughness were detected after outdoor weathering.

    Matched MeSH terms: Ultraviolet Rays
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