Displaying publications 161 - 180 of 577 in total

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  1. Zawani M, Fauzi MB
    Polymers (Basel), 2021 Oct 23;13(21).
    PMID: 34771213 DOI: 10.3390/polym13213656
    Immediate treatment for cutaneous injuries is a realistic approach to improve the healing rate and minimise the risk of complications. Multifunctional biomaterials have been proven to be a potential strategy for chronic skin wound management, especially for future advancements in precision medicine. Hence, antioxidant incorporated biomaterials play a vital role in the new era of tissue engineering. A bibliographic investigation was conducted on articles focusing on in vitro, in vivo, and clinical studies that evaluate the effect and the antioxidants mechanism exerted by epigallocatechin gallate (EGCG) in wound healing and its ability to act as reactive oxygen species (ROS) scavengers. Over the years, EGCG has been proven to be a potent antioxidant efficient for wound healing purposes. Therefore, several novel studies were included in this article to shed light on EGCG incorporated biomaterials over five years of research. However, the related papers under this review's scope are limited in number. All the studies showed that biomaterials with scavenging ability have a great potential to combat chronic wounds and assist the wound healing process against oxidative damage. However, the promising concept has faced challenges extending beyond the trial phase, whereby the implementation of these biomaterials, when exposed to an oxidative stress environment, may disrupt cell proliferation and tissue regeneration after transplantation. Therefore, thorough research should be executed to ensure a successful therapy.
  2. Tezara C, Hadi AE, Siregar JP, Muhamad Z, Hamdan MHM, Oumer AN, et al.
    Polymers (Basel), 2021 Aug 31;13(17).
    PMID: 34503004 DOI: 10.3390/polym13172964
    Recently, the most critical issue related to the use of natural fibre-reinforced polymer composites (NFRPC) is the degradation properties of composites exposed to the environment. NFRPC's moisture absorption behaviour has adverse effects on the composite's mechanical properties and dimensional stability. The purpose of this study is to analyse the mechanical properties of epoxy composites reinforced by jute-ramie hybridisation. This study also analysed the effect of stacking sequence hybridisation of the jute-ramie composite on water absorption behaviour. A five-layer different type of stacking sequence of single and hybrid jute-ramie is produced with the hand lay-up method. The results obtained from this study found that the mechanical properties and water absorption behaviour of a single jute fibre are lower compared to a single ramie fibre. The hybrid of jute-ramie has been able to increase the performance of composite compared to pure jute composites. The mechanical properties of the hybrid jute-ramie composite show a reduction effect after exposure to an aqueous environment due to the breakdown of fibre matrix interfacial bonding. However, after 28 days of immersion, all types of the stacking sequence's mechanical properties are still higher than that of pure epoxy resin. In conclusion, the appropriate sequence of stacking and selecting the material used are two factors that predominantly affect the mechanical properties and water absorption behaviour. The hybrid composites with the desired and preferable properties can be manufactured using a hand-lay-up technique and used in the various industrial applications.
  3. Rihayat T, Hadi AE, Aidy N, Safitri A, Siregar JP, Cionita T, et al.
    Polymers (Basel), 2021 Nov 20;13(22).
    PMID: 34833315 DOI: 10.3390/polym13224019
    This study aims to produce and investigate the potential of biodegradable Polylactic Acid (PLA)-based composites mixed with chitosan and Turmeric Essential Oil (TEO) as an anti-microbial biomaterial. PLA has good barrier properties for moisture, so it is suitable for use as a raw material for making packaging and is included in the GRAS (Generally Recognized As Safe). Chitosan is a non-toxic and antibacterial cationic polysaccharide that needs to be improved in its ability to fight microbes. TEO must be added to increase antibacterial properties due to a large number of hydroxyl (-OH) and carbonyl functional groups. The samples were prepared in three different variations: 2 g of chitosan, 0 mL TEO and 0 mL glycerol (Biofilm 1), 3 g of chitosan, 0.3 mL TEO and 0.5 mL of glycerol (Biofilm 2), and 4 g of chitosan, 0.3 of TEO and 0.5 mL of glycerol (Biofilm 3). The final product was characterized by its functional group through Fourier transform infrared (FTIR); the functional groups contained by the addition of TEO are C-H, C=O, O-H, and N-H with the extraction method, and as indicated by the emergence of a wide band at 3503 cm-1, turmeric essential oil interacts with the polymer matrix by creating intermolecular hydrogen bonds between their terminal hydroxyl group and the carbonyl groups of the ester moieties of both PLA and Chitosan. Thermogravimetric analysis (TGA) of PLA as biofilms, the maximum temperature of a biofilm was observed at 315.74 °C in the variation of 4 g chitosan, 0.3 mL TEO, and 0.5 mL glycerol (Biofilm 3). Morphological conditions analyzed under scanning electron microscopy (SEM) showed that the addition of TEO inside the chitosan interlayer bound chitosan molecules to produce solid particles. Chitosan and TEO showed increased anti-bacterial activity in the anti-microbial test. Furthermore, after 12 days of exposure to open areas, the biofilms generated were able to resist S. aureus and E. coli bacteria.
  4. Chee SS, Jawaid M, Alothman OY, Fouad H
    Polymers (Basel), 2021 Jan 27;13(3).
    PMID: 33513718 DOI: 10.3390/polym13030395
    Current work aims to study the mechanical and dynamical mechanical properties of non-woven bamboo (B)/woven kenaf (K)/epoxy (E) hybrid composites filled with nanoclay. The nanoclay-filled BK/E hybrid composites were prepared by dispersing 1 wt.% nanoclay (organically-modified montmorillonite (MMT; OMMT), montmorillonite (MMT), and halloysite nanotube (HNT)) with high shear speed homogenizer followed by hand lay-up fabrication technique. The effect of adding nanoclay on the tensile, flexural, and impact properties of the hybrid nanocomposites were studied. Fractography of tensile-fractured sample of hybrid composites was studied by field emission scanning electron microscope. The dynamic mechanical analyzer was used to study the viscoelastic properties of the hybrid nanocomposites. BK/E-OMMT exhibit enhanced mechanical properties compared to the other hybrid nanocomposites, with tensile, flexural, and impact strength values of 55.82 MPa, 105 MPa, and 65.68 J/m, respectively. Statistical analysis and grouping information were performed by one-way ANOVA (analysis of variance) and Tukey method, and it corroborates that the mechanical properties of the nanoclay-filled hybrid nanocomposites are statistically significant. The storage modulus of the hybrid nanocomposites was improved by 98.4%, 41.5%, and 21.7% with the addition of OMMT, MMT, and HNT, respectively. Morphology of the tensile fracture BK/E-OMMT composites shows that lesser voids, microcracks and fibers pull out due to strong fiber-matrix adhesion compared to other hybrid composites. Hence, the OMMT-filled BK/E hybrid nanocomposites can be utilized for load-bearing structure applications, such as floor panels and seatbacks, whereby lightweight and high strength are the main requirements.
  5. Kong N, Khalil NZ, Fricke H
    Polymers (Basel), 2021 Jun 02;13(11).
    PMID: 34199568 DOI: 10.3390/polym13111850
    In the current work, an attempt has been made to investigate the effect of Graphene Nanoplatelets (GNP) reinforcement to water absorption behavior and mechanical properties of adhesive bonding with epoxy. Epoxy adhesive with various GNP content (i.e., 0.0~2.0 wt%) was utilized to joint aluminum adherend subjected to various immersion periods (i.e., 0~60 days). Subsequently, the effect of GNP reinforcement on water uptake, water absorption rate and tensile shear strength was investigated. Depending on GNP content, two distinct behaviors in water uptake and moisture absorption rate have been observed; specimens with lower GNP content (0.5~1.0 wt%) have demonstrated increased/retention of water uptake and water absorption rate regardless of immersion period. Meanwhile, at higher GNP content (1.5~2.0 wt%), decreased water uptake and water absorption rate are generally observed. At similar GNP content, regardless of immersion periods, water immersed specimens generally demonstrate higher or retention of shear strength when compared to specimens at 0-day immersion period. These observations suggest that the relation between moisture absorption behavior and mechanical properties of GNP-reinforced adhesive with GNP content are rather complex which might be attributed to the interplay of several possible mechanisms.
  6. Malviya R, Tyagi A, Fuloria S, Subramaniyan V, Sathasivam K, Sundram S, et al.
    Polymers (Basel), 2021 May 10;13(9).
    PMID: 34068768 DOI: 10.3390/polym13091531
    Transdermal drug delivery is used to deliver a drug by eliminating the first-pass metabolism, which increases the bioavailability of the drug. The present study aims to formulate the chitosan-tamarind seed polysaccharide composite films and evaluate for the delivery of protein/peptide molecules. Nine formulations were prepared and evaluated by using different parameters, such as physical appearance, folding endurance, thickness of film, surface pH, weight variation, drug content, surface morphology, percentage moisture intake and uptake, drug release kinetics, and drug permeability. The film weight variance was observed between 0.34 ± 0.002 to 0.47 ± 0.003 g. The drug level of the prepared films was found to be between 96 ± 1.21 and 98 ± 1.33μg. Their intake of moisture ranged between 2.83 ± 0.002 and 3.76 ± 0.001 (%). The moisture absorption of the films ranged from 5.33 ± 0.22 to 10.02 ± 0.61 (%). SEM images revealed a smooth film surface, while minor cracks were found in the film after permeation tests. During the first 4 days, drug release was between 13.75 ± 1.64% and 22.54 ± 1.34% and from day 5 to day 6, it was between 72.67 ± 2.13% and 78.33 ± 3.13%. Drug permeation during the first 4 days was 15.78 ± 1.23 %. Drug permeation (%) during the first 4 days was between 15.78 ± 1.23 and 22.49 ± 1.29 and from day 5 to day 6, it was between 71.49 ± 3.21 and 77.93 ± 3.20.
  7. Malviya R, Sundram S, Fuloria S, Subramaniyan V, Sathasivam KV, Azad AK, et al.
    Polymers (Basel), 2021 Sep 07;13(18).
    PMID: 34577925 DOI: 10.3390/polym13183023
    Polymers from natural sources are widely used as excipients in the formulation of pharmaceutical dosage forms. The objective of this study was to extract and further characterize the tamarind gum polysaccharide (TGP) obtained from Tamarindus indica as an excipient for biomedical applications. Double distilled water was used as a solvent for the extraction of gum while Ethyl alcohol was used as an antisolvent for the precipitation. The results of the Hausner ratio, Carr's index and angle of repose were found to be 0.94, 6.25, and 0.14, respectively, which revealed that the powder is free-flowing with good flowability. The gum was investigated for purity by carrying out chemical tests for different phytochemical constituents and only carbohydrates were found to be present. The swelling index was found to be 87 ± 1%, which shows that TGP has good water intake capacity. The pH of the 1% gum solution was found to be neutral, approximately 6.70 ± 0.01. The ash values such as total ash, sulphated ash, acid insoluble ash, and water-soluble ash were found to be 14.00 ± 1.00%, 13.00 ± 0.05%, 14.04 ± 0.57% and 7.29 ± 0.06%, respectively. The IR spectra confirmed the presence of alcohol, amines, ketones, anhydrides groups. The contact angle was <90°, indicating favorable wetting and good spreading of liquid over the surface The scanning electron micrograph (SEM) revealed that the particle is spherical in shape and irregular. DSC analysis shows a sharp exothermic peak at 350 °C that shows its crystalline nature. The results of the evaluated properties showed that TGP has acceptable properties and can be used as a excipient to formulate dosage forms for biomedical applications.
  8. Khan TA, Azad AK, Fuloria S, Nawaz A, Subramaniyan V, Akhlaq M, et al.
    Polymers (Basel), 2021 Sep 29;13(19).
    PMID: 34641162 DOI: 10.3390/polym13193345
    The purpose of the present study was to develop emulsions encapsulated by chitosan on the outer surface of a nano droplet containing 5-fluorouracil (5-FU) as a model drug. The emulsions were characterized in terms of size, pH and viscosity and were evaluated for their physicochemical properties such as drug release and skin permeation in vitro. The emulsions containing tween 80 (T80), sodium lauryl sulfate, span 20, and a combination of polyethylene glycol (PEG) and T20 exhibited a release of 88%, 86%, 90% and 92%, respectively. Chitosan-modified emulsions considerably controlled the release of 5-FU compared to a 5-FU solution (p < 0.05). All the formulations enabled transportation of 5-FU through a rat's skin. The combination (T80, PEG) formulation showed a good penetration profile. Different surfactants showed variable degrees of skin drug retention. The ATR-FTIR spectrograms revealed that the emulsions mainly affected the fluidization of lipids and proteins of the stratum corneum (SC) that lead to enhanced drug permeation and retention across the skin. The present study concludes that the emulsions containing a combination of surfactants (Tween) and a co-surfactant (PEG) exhibited the best penetration profile, prevented the premature release of drugs from the nano droplet, enhanced the permeation and the retention of the drug across the skin and had great potential for transdermal drug delivery. Therefore, chitosan-coated 5-FU emulsions represent an excellent possibility to deliver a model drug as a transdermal delivery system.
  9. Malviya R, Jha S, Fuloria NK, Subramaniyan V, Chakravarthi S, Sathasivam K, et al.
    Polymers (Basel), 2021 Feb 18;13(4).
    PMID: 33670569 DOI: 10.3390/polym13040610
    The rheological properties of tamarind seed polymer are characterized for its possible commercialization in the food and pharmaceutical industry. Seed polymer was extracted using water as a solvent and ethyl alcohol as a precipitating agent. The temperature's effect on the rheological behavior of the polymeric solution was studied. In addition to this, the temperature coefficient, viscosity, surface tension, activation energy, Gibbs free energy, Reynolds number, and entropy of fusion were calculated by using the Arrhenius, Gibbs-Helmholtz, Frenkel-Eyring, and Eotvos equations, respectively. The activation energy of the gum was found to be 20.46 ± 1.06 kJ/mol. Changes in entropy and enthalpy were found to be 23.66 ± 0.97 and -0.10 ± 0.01 kJ/mol, respectively. The calculated amount of entropy of fusion was found to be 0.88 kJ/mol. A considerable decrease in apparent viscosity and surface tension was produced when the temperature was raised. The present study concludes that the tamarind seed polymer solution is less sensitive to temperature change in comparison to Albzia lebbac gum, Ficus glumosa gum and A. marcocarpa gum. This study also concludes that the attainment of the transition state of viscous flow for tamarind seed gum is accompanied by bond breaking. The excellent physicochemical properties of tamarind seed polymers make them promising excipients for future drug formulation and make their application in the food and cosmetics industry possible.
    Matched MeSH terms: Polymers
  10. Teo KT, Hassan A, Gan SN
    Polymers (Basel), 2018 Dec 11;10(12).
    PMID: 30961299 DOI: 10.3390/polym10121374
    Palm fatty acid distillate (PFAD), is a by-product of the crude palm oil refining process. It comprises mainly of free fatty acids-around 45% palmitic and 33% oleic acids-as the major components. Ultra-violet (UV) curable urethane acrylate (UA) oligomers could be synthesized from PFAD, by the following procedure. A hydroxyl terminated macromer was first prepared by reacting PFAD with a mixture of isophthalic acid, phthalic anhydride, neopentagylcol (NPG), and pentaerythritol. The macromer was then reacted with 2-hydroxylethylacrylate (2HEA) and toluene diisocynate (TDI) to generate a resin, containing acrylate side chains for UV curable application. A series of UA resins were prepared by using 15, 25, 45, 55, and 70% of PFAD, respectively. The UA resin has Mw in the range of 3,200 to 27,000. They could be cured by UV irradiation at an intensity of 225 mW/cm². Glass transition temperature (Tg) of the cured film was measured by differential scanning calorimeter (DSC), and hardness of the film was determined by a pendulum hardness tester, according to American Society for Testing and Materials (ASTM)4366. The resins were used in a wood-coating application. All of the cured films showed good adhesion, hardness, and chemical resistance except for the one using the 70% PFAD, which did not cure properly.
  11. Shahabudin N, Yahya R, Gan SN
    Polymers (Basel), 2016 Apr 06;8(4).
    PMID: 30979216 DOI: 10.3390/polym8040125
    One of the approaches to prolong the service lifespan of polymeric material is the development of self-healing ability by means of embedded microcapsules containing a healing agent. In this work, poly(melamine-urea-formaldehyde) (PMUF) microcapsules containing a palm oil-based alkyd were produced by polymerization of melamine resin, urea and formaldehyde that encapsulated droplets of the suspended alkyd particles. A series of spherical and free-flowing microcapsules were obtained. The chemical properties of core and shell materials were characterized by Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance spectroscopy (¹H-NMR). Differential scanning calorimetry (DSC) analysis showed a glass transition around -15 °C due to the alkyd, and a melting temperature at around 200 °C due to the shell. Thermogravimetric analysis (TGA) results showed that the core and shell thermally degraded within the temperature range of 200⁻600 °C. Field emission scanning electron microscope (FESEM) examination of the ruptured microcapsule showed smooth inner and rough outer surfaces of the shell. Flexural strength and microhardness (Vickers) of the cured epoxy compound were not affected with the incorporation of 1%⁻3% of the microcapsules. The viability of the healing reactions was demonstrated by blending small amounts of alkyd with epoxy and hardener at different ratios. The blends could readily cure to non-sticky hard solids at room temperature and the reactions could be verified by ATR-FTIR.
  12. Kunnan Singh JS, Ching YC, Abdullah LC, Ching KY, Razali S, Gan SN
    Polymers (Basel), 2018 Mar 20;10(3).
    PMID: 30966373 DOI: 10.3390/polym10030338
    This paper investigated the effects of polytetrafluoroethylene (PTFE) micro-particles on mechanical properties of polyoxymethylene (POM) composites. Since PTFE is immiscible with most polymers, the surface was etched using sodium naphthalene salt in tetrahydrofuran to increase its surface energy. The effects of two variables, namely PTFE content and PTFE etch time, on the mechanical properties of the composite were studied. Experiments were designed in accordance to response surface methodology (RSM) using central composite design (CCD). Samples were prepared with different compositions of PTFE (1.7, 4.0, 9.5, 15.0, or 17.3 wt %) at different PTFE etch times (2.9, 5.0, 10.0, 15.0, or 17.1 min). Four mechanical properties of the POM/GF/PTFE composites, that is, strength, stiffness, toughness, and hardness, were characterized as a function of two studied variables. The dependency of these mechanical properties on the PTFE etch conditions was analyzed using analysis of variance (ANOVA). Overall desirability, D global index, was computed based on the combination of these mechanical properties for POM/GF/PTFE composites. The D global index was found to be 87.5%, when PTFE content and PTFE etch time were 6.5% and 10 min, respectively. Good correlation between experimental and RSM models was obtained using normal probability plots.
  13. Alakbari FS, Mohyaldinn ME, Muhsan AS, Hasan N, Ganat T
    Polymers (Basel), 2020 May 07;12(5).
    PMID: 32392770 DOI: 10.3390/polym12051069
    The chemical sand consolidation methods involve pumping of chemical materials, like furan resin and silicate non-polymer materials into unconsolidated sandstone formations, in order to minimize sand production with the fluids produced from the hydrocarbon reservoirs. The injected chemical material, predominantly polymer, bonds sand grains together, lead to higher compressive strength of the rock. Hence, less amounts of sand particles are entrained in the produced fluids. However, the effect of this bonding may impose a negative impact on the formation productivity due to the reduction in rock permeability. Therefore, it is always essential to select a chemical material that can provide the highest possible compressive strength with minimum permeability reduction. This review article discusses the chemical materials used for sand consolidation and presents an in-depth evaluation between these materials to serve as a screening tool that can assist in the selection of chemical sand consolidation material, which in turn, helps optimize the sand control performance. The review paper also highlights the progressive improvement in chemical sand consolidation methods, from using different types of polymers to nanoparticles utilization, as well as track the impact of the improvement in sand consolidation efficiency and production performance. Based on this review, the nanoparticle-related martials are highly recommended to be applied as sand consolidation agents, due to their ability to generate acceptable rock strength with insignificant reduction in rock permeability.
    Matched MeSH terms: Polymers
  14. Ali I, Ahmad M, Ganat T
    Polymers (Basel), 2021 Sep 28;13(19).
    PMID: 34641136 DOI: 10.3390/polym13193320
    Drilling mud's rheological characteristics, such as plastic viscosity and yield point, are adversely affected with an inappropriate mud formulation. Native starch is one of the most important components in water-based mud because it improves the rheological and filtration characteristics of the mud. The native starch stability under various temperature and exposure time regimes is an important concern for utilizing starch in oil and gas drilling operations. In this work, tapioca starch was modified using carboxymethylation for the first time in order to improve its performance in non-damaging water-based muds. The modified starch was characterized by Fourier-transform infrared spectroscopy and X-ray diffraction. The thermal stability was tested using thermal gravimetric analysis. Various mud blends were formulated based on the experimental design using response surface methodology (RSM) to investigate their performance at various temperature conditions. Thirty experimental runs were carried out based on the selected factors and responses considering the optimal (custom) design, and the results were analyzed through ANOVA. The Fourier-transform infrared spectroscopy and X-ray diffraction results confirmed the carboxymethylation of starch. The TGA analysis revealed strong thermal stability after modification. Additionally, the Power law model (PLM) described the obtained rheological data for the selected formulations, resulting in determination coefficients of more than 0.95. Furthermore, the examined samples showed a reduction in the flow behavior index from 0.30 to 0.21 and an increase in the consistency index from 5.6 to 15.1. Optimization and confirmation results revealed the adequacy of the generated empirical models for both plastic viscosity and yield point. The obtained consistency index values provided a direct relationship with the modified starch concentration, indicating an improvement in the cutting carrying capacity of mud. Based on the current literature survey, the studied formulation has not been reported in the literature.
  15. Akbari S, Mahmood SM, Tan IM, Ling OL, Ghaedi H
    Polymers (Basel), 2017 Oct 04;9(10).
    PMID: 30965788 DOI: 10.3390/polym9100480
    The viscosity of four new polymers was investigated for the effect of aging at high temperature, with varying degrees of salinity and hardness. The four sulfonated based polyacrylamide co-polymers were FLOCOMB C7035; AN132 VHM; SUPERPUSHER SAV55; and THERMOASSOCIATIF copolymers. All polymer samples were aged at 80 °C for varying times (from zero to at least 90 days) with and without isobutyl alcohol (IBA) as an antioxidant. To see the effect of divalent ions on the polymer solution viscosity, parallel experiments were performed in a mixture of CaCl₂-NaCl of the same ionic strength as 5 wt % NaCl. The polymers without IBA showed severe viscosity reduction after aging for 90 days in both types of preparation (5 wt % NaCl or CaCl₂-NaCl). In the presence of IBA, viscosity was increased when aging time was increased for 5 wt % NaCl. In CaCl₂-NaCl, on the other hand, a viscosity reduction was observed as aging time was increased. This behavior was observed for all polymers except AN132 VHM.
    Matched MeSH terms: Polymers
  16. Al-Asbahi BA, Hj Jumali MH, AlSalhi MS, Qaid SMH, Fatehmulla A, Mujamammi WM, et al.
    Polymers (Basel), 2021 Feb 18;13(4).
    PMID: 33670613 DOI: 10.3390/polym13040611
    The influence of SiO2/TiO2 nanocomposites (STNCs) content on non-radiative energy transfer (Förster-type) from poly (9,9'-dioctylfluorene-2,7-diyl) (PFO) to poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) using steady-state and time-resolved photoluminescence spectroscopies was investigated at room temperature. The improved energy transfer from PFO to MEH-PPV upon an increment of the STNCs was achieved by examining absorbance, emission (PL) and photoluminescence excitation (PLE) spectra. The shorter values of the quantum yield (φDA) and lifetime (τDA) of the PFO in the hybrid thin films compared with the pure PFO, indicating efficient energy transfer from PFO to MEH-PPV with the increment of STNCs in the hybrid. The energy transfer parameters can be tuned by increment of the STNCs in the hybrid of PFO/MEH-PPV. The Stern-Volmer value (kSV), quenching rate value (kq), Förster radius (R0), distance between the molecules of PFO and MEH-PPV (RDA), energy transfer lifetime (τET), energy transfer rate (kET), total decay rate of the donor (TDR), critical concentration (Ao), and conjugation length (Aπ) were calculated. The gradually increasing donor lifetime and decreasing acceptor lifetime, upon increasing the STNCs content, prove the increase in conjugation length and meanwhile enhance in the energy transfer.
    Matched MeSH terms: Polymers
  17. Ahmed R, Abd Rahman R, Jamal A, Salem AA, Saman B, Lau KY, et al.
    Polymers (Basel), 2022 Jan 27;14(3).
    PMID: 35160504 DOI: 10.3390/polym14030516
    In-depth understanding of the pollution problems such as dry bands and the polymeric aging process requires better determination of electric field strength and its distribution over the polymeric surface. To determine the electric field distribution over the insulator surface, this research proposes utilizing a novel approach model based on nonlinear electrical characteristics derived from experimental results for polluted polymer insulators. A case study was carried out for a typical 11 kV polymeric insulator to underline the merits of this new modeling approach. The developments of the proposed pollution model and the subsequent computational works are described in detail. The study is divided into two main stages; laboratory measurements and computer simulations. In the first stage, layer conductance tests were carried out to develop nonlinear field-dependent conductivity for the pollution modeling. In the second part, equipotential and electric field distributions along the leakage were computed using the finite element method (FEM). Comparative field studies showed that the simulation using the proposed dynamic pollution model results in more detailed and realistic field profiles around insulators. This may be useful to predict the formation of dry bands and the initiation of electrical discharges on the polymeric surface.
  18. Joohari IB, Giustozzi F
    Polymers (Basel), 2020 Apr 18;12(4).
    PMID: 32325743 DOI: 10.3390/polym12040945
    In this study, the mechanical and rheological properties of hybrid polymer-modified bitumen (PMB) have been investigated. For this purpose, nine different polymers-including crumb rubber, elastomers and plastomers at varying content-were studied to evaluate their mechanical performance as single polymers, first, and as a combination of two or more polymers as a hybrid polymer blend. Subsequently, the hybrid polymer blends were added in a relatively small percentage into the base bitumen to study its influence on the rheological performance of hybrid PMB. The mechanical properties identified from the analysis of the stress-strain curve of the single polymers were the Young's Modulus, tensile stress, and elongation at break. The chemical structure of the polymer hybrid blends was analysed using FTIR, followed by frequency sweep tests conducted using the dynamic shear rheometer (DSR) to determine the bitumen rheological properties. Results showed that hybrid PMB enhances the viscoelastic behaviour of bitumen at both low and high temperature compared to other PMBs only including single polymers.
    Matched MeSH terms: Polymers
  19. Alrimawi BH, Chan MY, Ooi XY, Chan SY, Goh CF
    Polymers (Basel), 2021 Feb 15;13(4).
    PMID: 33671895 DOI: 10.3390/polym13040578
    Rice starch is a promising biomaterial for thin film development in buccal drug delivery, but the plasticisation and antiplasticisation phenomena from both plasticisers and drugs on the performance of rice starch films are not well understood. This study aims to elucidate the competing effects of sorbitol (plasticiser) and drug (antiplasticiser) on the physicochemical characteristics of rice starch films containing low paracetamol content. Rice starch films were prepared with different sorbitol (10, 20 and 30% w/w) and paracetamol contents (0, 1 and 2% w/w) using the film casting method and were characterised especially for drug release, swelling and mechanical properties. Sorbitol showed a typical plasticising effect on the control rice starch films by increasing film flexibility and by reducing swelling behaviour. The presence of drugs, however, modified both the mechanical and swelling properties by exerting an antiplasticisation effect. This antiplasticisation action was found to be significant at a low sorbitol level or a high drug content. FTIR investigations supported the antiplasticisation action of paracetamol through the disturbance of sorbitol-starch interactions. Despite this difference, an immediate drug release was generally obtained. This study highlights the interplay between plasticiser and drug in influencing the mechanical and swelling characteristics of rice starch films at varying concentrations.
  20. Kondal R, Kalia A, Krejcar O, Kuca K, Sharma SP, Luthra K, et al.
    Polymers (Basel), 2021 Aug 27;13(17).
    PMID: 34502927 DOI: 10.3390/polym13172887
    The impact of polymer-based slow-release urea formulations on soil microbial N dynamics in potatoes has been sparingly deciphered. The present study investigated the effect of a biodegradable nano-polymer urea formulation on soil enzymatic activities and microflora involved in the N cycling of potato (Solanum tuberosum L.). The nano-chitosan-urea composite (NCUC) treatment significantly increased the soil dehydrogenase activity, organic carbon content and available potassium compared to the conventional urea (CU) treatment. The soil ammonical nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) contents and urease activity were significantly decreased in the NCUC-amended soil. The slow urea hydrolysis rate led to low concentrations of NH4+-N and NO3--N in the tested potato soil. Furthermore, these results corroborate the low count of ammonia oxidizer and nitrate reducer populations. Quantitative PCR (q-PCR) studies revealed that the relative abundance of eubacterial (AOB) and archaeal ammonia-oxidizing (AOA) populations was reduced in the NCUC-treated soil compared to CU. The abundance of AOA was particularly lower than AOB, probably due to the more neutral and alkaline conditions of the tested soil. Our results suggest that the biodegradable polymer urea composite had a significant effect on the microbiota associated with soil N dynamics. Therefore, the developed NCUC could be used as a slow N-release fertilizer for enhanced growth and crop yields of potato.
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