Displaying publications 61 - 80 of 115 in total

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  1. Investigation of the possibility of using waste cooking oil as a rejuvenating agent for aged bitumen
    Zargar M, Ahmadinia E, Asli H, Karim MR
    J Hazard Mater, 2012 Sep 30;233-234:254-8.
    PMID: 22818590 DOI: 10.1016/j.jhazmat.2012.06.021
    The ageing of the bitumen during storage, mixing, transport and laying on the road, as well as in service life, are the most important problems presented by the use of bitumen in pavements. This paper investigates the possibility of using waste cooking oil (WCO), which is a waste material that pollutes landfills and rivers, as an alternative natural rejuvenating agent for aged bitumen to a condition that resembles the original bitumen. With this target, the physical and chemical properties of the original bitumen, aged bitumen and rejuvenated bitumen were measured and compared by the bitumen binder tests - softening point, penetration, Brookfield viscosity, dynamic shear rheometer and Fourier transform infrared spectroscopy. In addition, the behaviour of the WCO rejuvenated bitumen is investigated and compared with virgin bitumen after using the rolling thin film oven ageing process. In general, the results showed that using 3-4% of WCO the aged bitumen group 40/50 was rejuvenated to a condition that closely resembled the physical, rheological properties of the original bitumen (80/100), however, there was a difference in the tendency to ageing between the WCO rejuvenated bitumen and the virgin bitumen during mixing, transport and laying on the road.
    Matched MeSH terms: Rheology
  2. Effect of temperature and salt concentration on rheological behavior of whey protein isolate-starch mixed dispersions
    Ravindra P, Chan ES, Reddy KU
    Int J Food Sci Nutr, 2007 Nov;58(7):542-7.
    PMID: 17852467
    Extensive studies have been carried out on the effect of temperature and salt concentration on the theological behavior of whey proteins and different starches individually, but not on mixed dispersions of whey protein isolates and starches. In the present studies, the rheological behavior of cross-linked waxy maize starch and whey protein isolate mixed dispersions during heating at 60-85 degrees C was investigated. Further, the effect of CaCl2 (25-100 mM ionic strengths) on the gelatinization of these dispersions was determined. It was found that at a 2:3 ratio and a 3:2 ratio of cross-linked waxy maize starch to whey protein isolate mixed gels form a compatible networkmM concentration the solution viscosity was higher.
    Matched MeSH terms: Rheology
  3. Effect of cream fermentation on microbiological, physicochemical and rheological properties of L. helveticus-butter
    Ewe JA, Loo SY
    Food Chem, 2016 Jun 15;201:29-36.
    PMID: 26868544 DOI: 10.1016/j.foodchem.2016.01.049
    The primary objective of this study was to evaluate the physicochemical and rheological properties of butter produced by Lactobacillus helveticus fermented cream. The incorporation of putative probiotic - the L. helveticus, to ferment cream prior to butter production was anticipated to alter the nutritional composition of butter. Changes in crude macronutrients and the resultant modification relating to textural properties of butter induced upon metabolic activities of L. helveticus in cream were focused in this research. Fermented butter (LH-butter) was produced by churning the cream that was fermented by lactobacilli at 37 °C for 24 h. Physicochemical analysis, proximate analysis and rheology properties of LH-butter were compared with butter produced using unfermented cream (control). LH-butter showed a significantly (P<0.05) higher fat content and acid value; lower moisture and ash; and was softer than the control. Cream fermentation modified nutritional and textural properties of butter in which LH-butter contained higher health beneficial unsaturated fatty acids than the control and thus rendered the product softer. Its enrichment with probiotics could thus further enhance its functional property.
    Matched MeSH terms: Rheology
  4. Fulltext Effect of Extra-Framework Cations of LTL Nanozeolites to Inhibit Oil Oxidation
    Tan KH, Cham HY, Awala H, Ling TC, Mukti RR, Wong KL, et al.
    Nanoscale Res Lett, 2015 Dec;10(1):956.
    PMID: 26058517 DOI: 10.1186/s11671-015-0956-6
    Lubricant oils take significant part in current health and environmental considerations since they are an integral and indispensable component of modern technology. Antioxidants are probably the most important additives used in oils because oxidative deterioration plays a major role in oil degradation. Zeolite nanoparticles (NPs) have been proven as another option as green antioxidants in oil formulation. The anti-oxidative behavior of zeolite NPs is obvious; however, the phenomenon is still under investigation. Herein, a study of the effect of extra-framework cations stabilized on Linde Type L (LTL) zeolite NPs (ca. 20 nm) on inhibition of oxidation in palm oil-based lubricant oil is reported. Hydrophilic LTL zeolites with a Si/Al ratio of 3.2 containing four different inorganic cations (Li(+), Na(+), K(+), Ca(2+)) were applied. The oxidation of the lubricant oil was followed by visual observation, colorimetry, fourier transform infrared (FTIR) spectroscopy, (1)H NMR spectroscopy, total acid number (TAN), and rheology analyses. The effect of extra-framework cations to slow down the rate of oil oxidation and to control the viscosity of oil is demonstrated. The degradation rate of the lubricant oil samples is decreased considerably as the polarizability of cation is increased with the presence of zeolite NPs. More importantly, the microporous zeolite NPs have a great influence in halting the steps that lead to the polymerization of the oils and thus increasing the lifetime of oils.
    Matched MeSH terms: Rheology
  5. Observations of acoustic streaming fields around an oscillating ultrasonic file
    Ahmad M, Roy RA, Kamarudin AG
    Endod Dent Traumatol, 1992 Oct;8(5):189-94.
    PMID: 1302678
    The steady acoustic streaming generated around straight and precurved oscillating ultrasonic files driven by the Piezon-Master 400 unit was examined in the free field and in small channels using a stereomicroscope. In addition, the effect of file-wall contact on streaming production was also investigated. The results indicated that the ultrasonic files can generate acoustic streaming both in the free field and in the small channel. Higher velocity streaming was observed when smaller size files were employed and when the file was precurved. Light file-wall contact did not totally inhibit streaming while severe file-wall contact inhibited movement of the file and, as a result, no streaming was observed. The positions and length scales of the streaming vortices appeared to be influenced by the presence of boundaries. In the free field, two rows of vortices were situated along the sides of the file while in the small channel, the vortices were positioned above the surface of the file. These results indicated that it is possible for acoustic streaming to occur in a confined space as in a root canal provided that severe file-wall contact is avoided. It is therefore recommended that light filing or allowing the file to freely vibrate during some stage of treatment should be carried out in order to generate streaming in the root canal.
    Matched MeSH terms: Rheology
  6. Fulltext Influence of Multiwalled Carbon Nanotubes on the Rheological Behavior and Physical Properties of Kenaf Fiber-Reinforced Polypropylene Composites
    Abdul Azam F', Razak Z, Md Radzi MKF, Muhamad N, Che Haron CH, Sulong AB
    Polymers (Basel), 2020 Sep 13;12(9).
    PMID: 32933225 DOI: 10.3390/polym12092083
    The incorporation of kenaf fiber fillers into a polymer matrix has been pronounced in the past few decades. In this study, the effect of multiwalled carbon nanotubes (MWCNTs) with a short kenaf fiber (20 mesh) with polypropylene (PP) added was investigated. The melt blending process was performed using an internal mixer to produce polymer composites with different filler contents, while the suitability of this melt composite for the injection molding process was evaluated. Thermogravimetric analysis (TGA) was carried out to investigate the thermal stability of the raw materials. Rheological analyses were conducted by varying the temperature, load factor, and filler content. The results demonstrate a non-Newtonian pseudoplastic behavior in all samples with changed kenaf fillers (10 to 40 wt %) and MWCNT contents (1 to 4 wt %), which confirm the suitability of the feedstock for the injection molding process. The addition of MWCNTs had an immense effect on the viscosity and an enormous reduction in the feedstock flow behavior. The main contribution of this work is the comprehensive observation of the rheological characteristics of newly produced short PP/kenaf composites that were altered after MWCNT additions. This study also presented an adverse effect on the composites containing MWCNTs, indicating a hydrophilic property with improved water absorption stability and the low flammability effect of PP/kenaf/MWCNT composites. This PP/kenaf/MWCNT green composite produced through the injection molding technique has great potential to be used as car components in the automotive industry.
    Matched MeSH terms: Rheology
  7. Fulltext Determination of Temperature-Dependent Coefficients of Viscosity and Surface Tension of Tamarind Seeds (Tamarindus indica L.) Polymer
    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: Rheology
  8. Fulltext Assessment of Polyacrylamide Based Co-Polymers Enhanced by Functional Group Modifications with Regards to Salinity and Hardness
    Akbari S, Mahmood SM, Tan IM, Ghaedi H, Ling OL
    Polymers (Basel), 2017 Nov 27;9(12).
    PMID: 30965947 DOI: 10.3390/polym9120647
    This research aims to test four new polymers for their stability under high salinity/high hardness conditions for their possible use in polymer flooding to improve oil recovery from hydrocarbon reservoirs. The four sulfonated based polyacrylamide co-polymers were FLOCOMB C7035; SUPERPUSHER SAV55; THERMOASSOCIATIF; and AN132 VHM which are basically sulfonated polyacrylamide copolymers of AM (acrylamide) with AMPS (2-Acrylamido-2-Methylpropane Sulfonate). AN132 VHM has a molecular weight of 9⁻11 million Daltons with 32 mol % degree of sulfonation. SUPERPUSHER SAV55 mainly has about 35 mol % sulfonation degree and a molecular weight of 9⁻11 million Daltons. FLOCOMB C7035, in addition, has undergone post-hydrolysis step to increase polydispersity and molecular weight above 18 million Daltons but it has a sulfonation degree much lower than 32 mol %. THERMOASSOCIATIF has a molecular weight lower than 12 million Daltons and a medium sulfonation degree of around 32 mol %, and also contains LCST (lower critical solution temperature) type block, which is responsible for its thermoassociative characteristics. This paper discusses the rheological behavior of these polymers in aqueous solutions (100⁻4500 ppm) with NaCl (0.1⁻10 wt %) measured at 25 °C. The effect of hardness was investigated by preparing a CaCl₂-NaCl solution of same ionic strength as the 5 wt % of NaCl. In summary, it can be concluded that the rheological behavior of the newly modified co-polymers was in general agreement to the existing polymers, except that THERMOASSOCIATIF polymers showed unique behavior, which could possibly make them a better candidate for enhanced oil recovery (EOR) application in high salinity conditions. The other three polymers, on the other hand, are better candidates for EOR applications in reservoirs containing high divalent ions. These results are expected to be helpful in selecting and screening the polymers for an EOR application.
    Matched MeSH terms: Rheology
  9. Fulltext Characterization and stability of short-chain fatty acids modified starch Pickering emulsions
    Abdul Hadi N, Marefati A, Matos M, Wiege B, Rayner M
    Carbohydr Polym, 2020 Jul 15;240:116264.
    PMID: 32475554 DOI: 10.1016/j.carbpol.2020.116264
    Acetylated, propionylated and butyrylated rice and quinoa starches at different levels of modification and starch concentrations, were used to stabilize oil-in-water starch Pickering emulsions at 10% oil fraction. Short-chain fatty acid modified starch Pickering emulsions (SPEs) were characterized after emulsification and after 50 days of storage. The particle size distribution, microstructure, emulsion index, and stability were evaluated. An increase in starch concentration led to a decrease of emulsion droplet sizes. Quinoa starch has shown the capability of stabilizing Pickering emulsions in both the native and modified forms. The emulsifying capacity of SPEs was improved by increasing the chain length of SCFA. Modified quinoa starch with higher chain lengths (i.e. propionylated and butyrylated), at higher levels of modification, showed higher emulsion index (>71%) and stability over the entire 50 days storage. At optimized formulation, SCFA-starch particles have the potential in stabilizing emulsions for functional foods, pharmaceutical formulations, or industrial food applications.
    Matched MeSH terms: Rheology
  10. Characterization, Functional Properties, and Resistant Starch of Freshwater Macrophytes
    Syed FNN, Zakaria MH, Bujang JS, Christianus A
    Int J Food Sci, 2021;2021:8825970.
    PMID: 33553420 DOI: 10.1155/2021/8825970
    Several aquatic macrophytes such as Colocasia esculenta, Eleocharis dulcis, Nelumbo nucifera, Sagittaria sagittifolia, Trapa bispinosa, and Typha angustifolia possessed carbohydrate mainly in their storage and reproductive parts. Starch morphology, total starch, and amylose content of these six freshwater plant species were determined. Their functional properties, i.e., starch crystallinity, thermal properties, and rheological behaviour were assessed. Large starch granules were in N. nucifera rhizome (>15 μm), medium-sized was N. nucifera seed (8-18 μm), while the rest of the starches were small starch granules (<8 μm). Shapes of the starch granules varied from oval and irregular with centric hilum to elongated granules with the eccentric hilum. Eleocharis dulcis corm starch had significantly higher total starch content (90.87%), followed by corms of C. esculenta (82.35%) and S. sagittifolia (71.71%). Nelumbo nucifera seed starch had significantly higher amylose content (71.45%), followed by T. angustifolia pollen (36.47%). In comparison, the waxy starch was in N. nucifera rhizome (7.63%), T. bispinosa seed (8.83%), C. esculenta corm (10.61%), and T. angustifolia rhizome (13.51%). Higher resistant starch was observed mostly in rhizomes of N. nucifera (39.34%)>T. angustifolia (37.19%) and corm parts of E. dulcis (37.41%)>S. sagittifolia (35.09%) compared to seed and pollen starches. The XRD profiles of macrophytes starches displayed in all the corms and N. nucifera seed had A-type crystallinity. The T. bispinosa seed had CA-type, whereas the rest of the starches exhibited CB-type crystallinity. Waxy starches of C. esculenta corm had higher relative crystallinity (36.91%) and viscosity (46.2 mPa s) than regular starches. Based on thermal properties, high-amylose of N. nucifera seed and T. angustifolia pollen resulted in higher gelatinization enthalpy (19.93 and 18.66 J g-1, respectively). Starch properties showed equally good potential as commercial starches in starch-based food production based on their starch properties and functionality.
    Matched MeSH terms: Rheology
  11. Comparison of physicochemical and functional properties of duck feet and bovine gelatins
    Kuan YH, Nafchi AM, Huda N, Ariffin F, Karim AA
    J Sci Food Agric, 2017 Mar;97(5):1663-1671.
    PMID: 27465360 DOI: 10.1002/jsfa.7970
    BACKGROUND: Previous studies have indicated that duck feet are a rich source of gelatin extractable from avian sources. In this study, the physicochemical and functional properties of avian gelatin extracted from duck feet (DFG) with acetic acid were compared with those of commercial bovine gelatin (BG).

    RESULTS: The yield of DFG obtained in this study was 7.01 ± 0.31%. High-performance liquid chromatography analysis indicated that the imino acid content was slightly lower for DFG compared with BG (P < 0.05). Differences in molecular size and amino acids between DFG and BG were also observed. The isoelectric points of DFG and BG were at pH 8 and 5 respectively, and the overall protein solubility of BG was higher than that of DFG. Gels prepared from BG exhibited higher bloom strength, viscosity and clarity and were darker in colour compared with DFG gels (P < 0.05). The gelling and melting points of BG were 21.8 and 29.47 °C respectively, while those of DFG were 20.5 and 27.8 °C respectively. BG exhibited slightly better emulsifying and foaming properties compared with DFG.

    CONCLUSION: Although some differences between DFG and BG were observed, the disparities were small, which indicates that DFG could be exploited commercially as an alternative source of gelatin. © 2016 Society of Chemical Industry.

    Matched MeSH terms: Rheology
  12. Fulltext Effects of different drying methods on the rheological, functional and structural properties of chicken skin gelatin compared to bovine gelatin
    Rasli, H.I., Sarbon, N.M.
    International Food Research Journal, 2015;22(2):584-592.
    MyJurnal
    This study investigates effects from different drying methods (vacuum oven dried vs. freeze dried) on the rheological, functional and structural properties of chicken skin gelatin compared to bovine gelatin. Vacuum oven dried chicken skin samples showed a higher gelatin yield (12.86%) than freeze-dried samples (9.25%). The latter showed a higher melting temperature (32.64oC) and superior foaming capacity (176%) as well as foaming stability (166.67%). Vacuum oven dried samples demonstrated greater fat binding capacity (5.5 ml/g) and emulsion stability (55.79%). There were no significant differences (p >0.05) in emulsion and water holding capacity for three gelatins. Bovine gelatin did hold the lowest of all functional properties studied. A Fourier Transform Infrared (FTIR) spectrum analysis of chicken skin gelatin under both drying methods presented structures similar to those of bovine gelatin. Collectively, this findings indicated no significant differences (p >0.05) in rheological, functional and structural properties for chicken skin gelatins prepared by either drying method. Hence, to save costs and maintain gelatin quality, vacuum oven drying offers potential as an alternative means of production.
    Matched MeSH terms: Rheology
  13. Fulltext Rheological studies on the effect of different thickeners in texture-modified chicken rendang for individuals with dysphagia
    Abu Zarim N, Zainul Abidin S, Ariffin F
    J Food Sci Technol, 2018 Nov;55(11):4522-4529.
    PMID: 30333649 DOI: 10.1007/s13197-018-3386-5
    Texture-modified food has become an important strategy in managing dysphagia. Pureed food is proven to be the safest texture due to its high viscosity which can slow down the rate of the food bolus during swallowing. In this study, texture-modified chicken rendang was developed according to Texture C (smooth puree) as described by the Australian standard for texture-modified food. Samples were added with five different thickeners (sago starch, tapioca starch, modified corn starch, xanthan gum and carboxymethyl cellulose gum) at three different concentrations (10, 20 and 30% w/w). Their rheological effects were analyzed through dynamic and steady shear test. Results obtained reveals that samples contained xanthan gum have higher structure rigidity and shear thinning behaviour, while carboxymethyl cellulose gum provides the highest viscosity as well as yield stress than other samples. In terms of concentration, a strong dependence of structural rigidity and viscosity of all prepared samples with amount of thickeners added was observed. Overall, based on its rheological properties, the addition of carboxymethyl cellulose gum at 30% concentration was found to be the most suitable thickener, to be incorporated in the texture-modified chicken rendang. Selecting a suitable food thickener in developing food for individual with dysphagia plays an important role to ensure the right texture and consistency for their safe consumption.
    Matched MeSH terms: Rheology
  14. Fulltext Effects of Hybridized Organically Modified Montmorillonite and Cellulose Nanocrystals on Rheological Properties and Thermal Stability of K-Carrageenan Bio-Nanocomposite
    Zakuwan SZ, Ahmad I
    Nanomaterials (Basel), 2019 Oct 31;9(11).
    PMID: 31683602 DOI: 10.3390/nano9111547
    Herein, hybrid k-carrageenan bio-nanocomposite films were fabricated by using two types of nanofillers, organically modified montmorillonite (OMMT), and cellulose nanocrystals (CNCs). Hybrid bio-nanocomposite films were made by casting techniques employing 4 wt% of CNCs, OMMT, and hybridized CNCs/OMMT in a 1:1 ratio. The rheological and morphological properties and thermal stability of all composites were investigated using rotational rheometry, thermogravimetry analysis, differential scanning calorimetry, field emission scanning electron microscopy, and transmission electron microscopy (TEM). The results showed that the hybrid CNC/OMMT bio-nanocomposite exhibited significantly improved properties as compared to those for the bio-nanocomposites with single fillers due to the nanosize and homogenous nanofiller dispersion in the matrix. Rheological analysis of the hybrid bio-nanocomposite showed higher dynamic shear storage modulus and complex viscosity values when compared to those for the bio-nanocomposite with individual fillers. The TEM analysis of the hybridized CNC/OMMT bio-nanocomposite revealed that more particles were packed together in the CNC network, which restricted the matrix mobility. The heat resistance and thermal stability bio-nanocomposite k-carrageenan film enhanced rapidly with the addition of hybridized CNCs/OMMT to 275 °C. The hybridized CNCs/OMMT exhibited synergistic effects due to the good affinity through interfacial interactions, resulting in the improvement of the material properties.
    Matched MeSH terms: Rheology
  15. Development of biofilm-targeted antimicrobial wound dressing for the treatment of chronic wound infections
    Ng SF, Leow HL
    Drug Dev Ind Pharm, 2015;41(11):1902-9.
    PMID: 25758412 DOI: 10.3109/03639045.2015.1019888
    It has been established that microbial biofilms are largely responsible for the recalcitrance of many wound infections to conventional antibiotics. It was proposed that the efficacy of antibiotics could be optimized via the inhibition of bacterial biofilm growth in wounds. The combination of antibiofilm agent and antibiotics into a wound dressing may be a plausible strategy in wound infection management. Xylitol is an antibiofilm agent that has been shown to inhibit the biofilm formation. The purpose of this study was to develop an alginate film containing xylitol and gentamicin for the treatment of wound infection. Three films, i.e. blank alginate film (SA), alginate film with xylitol (F5) and alginate film with xylitol and gentamicin (AG), were prepared. The films were studied for their physical properties, swelling ratio, moisture absorption, moisture vapor transmission rate (MVTR), mechanical and rheology properties, drug content uniformity as well as in vitro drug release properties. Antimicrobial and antibiofilm in vitro studies on Staphylococcus aureus and Pseudomonas aeruginosa were also performed. The results showed that AG demonstrates superior mechanical properties, rheological properties and a higher MVTR compared with SA and F5. The drug flux of AG was higher than that of commercial gentamicin cream. Furthermore, antimicrobial studies showed that AG is effective against both S. aureus and P. aeruginosa, and the antibiofilm assays demonstrated that the combination was effective against biofilm bacteria. In summary, alginate films containing xylitol and gentamicin may potentially be used as new dressings for the treatment of wound infection.
    Matched MeSH terms: Rheology
  16. Effect of different stent configurations using Lattice Boltzmann method and particles image velocimetry on artery bifurcation aneurysm problem
    Mokhtar NH, Abas A, Razak NA, Hamid MNA, Teong SL
    J Theor Biol, 2017 11 21;433:73-84.
    PMID: 28844907 DOI: 10.1016/j.jtbi.2017.08.016
    Proper design of stent for application at specific aneurysm effect arteries could help to reduce the issues with thrombosis and aneurysm. In this paper, four types of stent configuration namely half-Y (6 mm), half-Y (4 mm), cross-bar, and full-Y configuration will implanted on real 3D artery bifurcation aneurysm effected arteries. Comparisons were then conducted based on the flow patterns after stent placement using both LBM-based solver and PIV experimental findings. According to the data obtained from all 4 stent designs, the flow profiles and the computed velocity from both methods were in agreement with each other. Both methods found that half-Y (6 mm) stent configuration is by far the best configuration in reducing the blood velocity at the vicinity of the aneurysm sac. The analysis also show that the half-Y (6 mm) stent configuration recorded the highest percentage of velocity reduction and managed to substantially reduce the pressure at the bifurcation region. This high flow velocity reduction through the use of half-Y stent could consequently promote the formation of thrombus thereby reducing the risk of rupture in the aneurysm sac.
    Matched MeSH terms: Rheology
  17. Fulltext Synthesis and characterization of polylactide/rice husk hydrochar composite
    Nizamuddin S, Jadhav A, Qureshi SS, Baloch HA, Siddiqui MTH, Mubarak NM, et al.
    Sci Rep, 2019 Apr 01;9(1):5445.
    PMID: 30931991 DOI: 10.1038/s41598-019-41960-1
    Polymer composites are fabricated by incorporating fillers into a polymer matrix. The intent for addition of fillers is to improve the physical, mechanical, chemical and rheological properties of the composite. This study reports on a unique polymer composite using hydrochar, synthesised by microwave-assisted hydrothermal carbonization of rice husk, as filler in polylactide matrix. The polylactide/hydrochar composites were fabricated by incorporating hydrochar in polylactide at 5%, 10%, 15% and 20 wt% by melt processing in a Haake rheomix at 170 °C. Both the neat polylactide and polylactide/hydrochar composite were characterized for mechanical, structural, thermal and rheological properties. The tensile modulus of polylactide/hydrochar composites was improved from 2.63 GPa (neat polylactide) to 3.16 GPa, 3.33 GPa, 3.54 GPa, and 4.24 GPa after blending with hydrochar at 5%, 10%, 15%, and 20%, respectively. Further, the incorporation of hydrochar had little effect on storage modulus (G') and loss modulus (G″). The findings of this study reported that addition of hydrochar improves some characteristics of polylactide composites suggesting the potential of hydrochar as filler for polymer/hydrochar composites.
    Matched MeSH terms: Rheology
  18. Rheological behavior of biodegradable N-succinyl chitosan-g-poly (acrylic acid) hydrogels and their applications as drug carrier and in vitro theophylline release
    Bashir S, Teo YY, Ramesh S, Ramesh K, Mushtaq MW
    Int J Biol Macromol, 2018 Oct 01;117:454-466.
    PMID: 29807081 DOI: 10.1016/j.ijbiomac.2018.05.182
    Novel pH sensitive N-succinyl chitosan-g-poly (acrylic acid) hydrogels were synthesized through free radical mechanism. Rheometer was used to observe the mechanical strength of the hydrogels. In vitro degradation was conducted in SIF (pH 7.4). The effect of concentration of monomers, initiator, and crosslinking agent and pH and ionic strength of NaCl, CaCl2, and AlCl3 on swelling of the hydrogels was observed. The results showed that equilibrium swelling ratio was highly influenced by concentration of monomers, initiator, and crosslinking agent concentration, and pH and salt solutions of NaCl, CaCl2, and AlCl3. The swelling kinetics revealed that swelling followed non-Fickian anomalous transport. Furthermore, theophylline loading (DL %) and encapsulation efficiency (EE %) of the hydrogels was in the range of 15.5 ± 0.15-22.8 ± 0.06% and 62 ± 0.15-91 ± 0.26%, respectively. The release of theophylline in physiological mediums was strongly influenced by the pH. The theophylline release was in the range of 51 ± 0.20-92 ± 0.12% in SIF and 7.4 ± 0.02-14.9 ± 0.03% in SGF (pH 1.2), respectively. The release data fitted well to Korsmeyer-Peppas model. The chemical activity of the theophylline suggested that drug maintained its chemical activity after release in vitro. The results suggest that synthesized hydrogels are excellent drug carriers.
    Matched MeSH terms: Rheology*
  19. Synthesis of kenaf cellulose carbamate and its smart electric stimuli-response
    Gan S, Piao SH, Choi HJ, Zakaria S, Chia CH
    Carbohydr Polym, 2016 Feb 10;137:693-700.
    PMID: 26686181 DOI: 10.1016/j.carbpol.2015.11.035
    Cellulose carbamate (CC) was produced from kenaf core pulp (KCP) via a microwave reactor-assisted method. The formation of CC was confirmed by Fourier transform infrared spectroscopy and nitrogen content analysis. The degree of substitution, zeta potential and size distribution of CC were also determined. The CC was characterized with scanning electron microscopy, X-ray diffraction and thermogravimetry analysis. The CC particles were then dispersed in silicone oil to prepare CC-based anhydrous electric stimuli-responsive electrorheological (ER) fluids. Rhelogical measurement was carried out using rotational rheometer with a high voltage generator in both steady and oscillatory shear modes to examine the effect of electric field strength on the ER characteristics. The results showed that the increase in electric field strength has enhanced the ER properties of CC-based ER fluid due to the chain formation induced by electric polarization among the particles.
    Matched MeSH terms: Rheology
  20. Fulltext Physicochemical characterization and thermodynamic studies of nanoemulsion-based transdermal delivery system for fullerene
    Ngan CL, Basri M, Tripathy M, Abedi Karjiban R, Abdul-Malek E
    ScientificWorldJournal, 2014;2014:219035.
    PMID: 25165736 DOI: 10.1155/2014/219035
    Fullerene nanoemulsions were formulated in palm kernel oil esters stabilized by low amount of mixed nonionic surfactants. Pseudoternary phase diagrams were established in the colloidal system of PKOEs/Tween 80 : Span 80/water incorporated with fullerene as antioxidant. Preformulation was subjected to combination of high and low energy emulsification methods and the physicochemical characteristics of fullerene nanoemulsions were analyzed using electroacoustic spectrometer. Oil-in-water (O/W) nanoemulsions with particle sizes in the range of 70-160 nm were formed. The rheological characteristics of colloidal systems exhibited shear thinning behavior which fitted well into the power law model. The effect of xanthan gum (0.2-1.0%, w/w) and beeswax (1-3%, w/w) in the estimation of thermodynamics was further studied. From the energetic parameters calculated for the viscous flow, a moderate energy barrier for transport process was observed. Thermodynamic study showed that the enthalpy was positive in all xanthan gum and beeswax concentrations indicating that the formation of nanoemulsions could be endothermic in nature. Fullerene nanoemulsions with 0.6% or higher xanthan gum content were found to be stable against creaming and flocculation when exposed to extreme environmental conditions.
    Matched MeSH terms: Rheology
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