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1.
The following article is the presentation attempt of cellulose hybrid chemical modification approach as a useful tool in improving the mechanical properties of plant fiber-filled polymer materials. The treatment process is a prolonged method of the cellulose maleinization and consists of two steps: 1. solvent exchange (altering fiber structure); 2. maleic anhydride (MA) chemical grafting (surface modification). Thanks to the incorporated treatment method, the created ethylene–norbornene copolymer composite specimen exhibited an improved performance, tensile strength at the level of (38.8 ± 0.8) MPa and (510 ± 20)% elongation at break, which is higher than for neat polymer matrix and could not be achieved in the case of regular MA treatment. Moreover, both the Payne effect and filler efficiency factor indicate a possibility of the fiber reinforcing nature that is not a common result. Additionally, the polymer matrix employed in this research is widely known for its excellent resistance to aqueous and polar organic media, good biocompatibility, and the ability to reproduce fine structures which makes it an interesting material regarding healthcare applications. Therefore, plant fiber-based polymer materials described in this research might be potentially applied in this area, e.g., medical devices, drug delivery, wearables, pharmaceutical blisters, and trays.  相似文献   

2.
Nanocellulose has gained increasing attention during the past decade, which is related to its unique properties and wide application. In this paper, nanocellulose samples were produced via hydrolysis with ionic liquids (1-ethyl-3-methylimidazole acetate (EmimOAc) and 1-allyl-3-methylimidazolium chloride (AmimCl)) from microcrystalline celluloses (Avicel and Whatman) subjected to enzymatic pretreatment. The obtained material was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The results showed that the nanocellulose had a regular and spherical structure with diameters of 30–40 nm and exhibited lower crystallinity and thermal stability than the material obtained after hydrolysis with Trichoderma reesei enzymes. However, the enzyme-pretreated Avicel had a particle size of about 200 nm and a cellulose II structure. A two-step process involving enzyme pretreatment and hydrolysis with ionic liquids resulted in the production of nanocellulose. Moreover, the particle size of nanocellulose and its structure depend on the ionic liquid used.  相似文献   

3.
The irradiation of pulp is of interest from different perspectives. Mainly it is required when a modification of cellulose is needed. Irradiation could bring many advantages, such as chemical savings and, therefore, cost savings and a reduction in environmental pollutants. In this account, pulp and dissociated celluloses were analyzed before and after irradiation by electron beaming. The focus of the analysis was the oxidation of hydroxyl groups to carbonyl and carboxyl groups in pulp and the degradation of cellulose causing a decrease in molar mass. For that purpose, the samples were labeled with a selective fluorescence marker and analyzed by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), refractive index (RI), and fluorescence detectors. Degradation of the analyzed substrates was the predominant result of the irradiation; however, in the microcrystalline samples, oxidized cellulose functionalities were introduced along the cellulose chain, making this substrate suitable for further chemical modification.  相似文献   

4.
Physicochemical characteristics of Hibiscus cannabinus (kenaf) fibers from Burkina Faso were studied using X-ray diffraction (XRD), infrared spectroscopy, thermal gravimetric analysis (TGA), chemical analysis and video microscopy. Kenaf fibers (3 cm long) were used to reinforce earth blocks, and the mechanical properties of reinforced blocks, with fiber contents ranging from 0.2 to 0.8 wt%, were investigated. The fibers were mainly composed of cellulose type I (70.4 wt%), hemicelluloses (18.9 wt%) and lignin (3 wt%) and were characterized by high tensile strength (1 ± 0.25 GPa) and Young’s modulus (136 ± 25 GPa), linked to their high cellulose content. The incorporation of short fibers of kenaf reduced the propagation of cracks in the blocks, through the good adherence of fibers to the clay matrix, and therefore improved their mechanical properties. Fiber incorporation was particularly beneficial for the bending strength of earth blocks because it reinforces these blocks after the failure of soil matrix observed for unreinforced blocks. Blocks reinforced with such fibers had a ductile tensile behavior that made them better building materials for masonry structures than unreinforced blocks.  相似文献   

5.
This paper investigated the feasibility of enhancing the interface between lignocellulosic fibers and a polypropylene matrix via structure alteration of lignin at elevated temperatures. Alkali treatment can remove gum substances from lignocellulose fibers effectively at elevated temperatures but easily causes damages to fiber strength. In previous studies on directional delignification of lignocellulosic fibers, loss of fiber strength is avoided but condensation and degradation of lignin are accelerated. So far, few reports have been available on the effect of lignin structures on the interface between fibers and a matrix. In this study, jute fibers with different lignin structures are produced at 100 and 130 °C for reinforcing a polypropylene matrix. The interface between the fibers and matrix is analyzed. The result shows that decrease in aliphatic hydroxyl concentration by 9.5% at 130 °C from 3 to 5 h contributes to a 14.2% decrease in the surface energy of jute fibers. Meanwhile, the polydispersity index of lignin decreases from 1.21 to 1.15. Centralized distribution of lignin molecule-weight and reduction in fiber surface energy improves the interface between the fibers and matrix, which manifests as a 30.8% increase in the impact strength of the composites. Similar improvement is not observed in the composites reinforced with jute fibers at 100 °C, due to the absence of lignin-structure changes. This paper provides a new strategy to improve the interface between lignocellulose fibers and a hydrophobic matrix.  相似文献   

6.
A chopped ZrO2 fiber (ZrO2 (f)) reinforced CaO-based integral ceramic mold was successfully fabricated by stereolithography (SLA) and tert-butyl alcohol (TBA)-based gel-casting, and the effect of chopped ZrO2 (f) content on properties of the ceramic mold was investigated. The results show that the ZrO2 (f) content had a significant effect on the viscosity of CaO-based ceramic slurry, which directly affects the filling ability of slurry in complex structures of the integral mold. The tiny structures of the ceramic mold cannot be filled completely with a ZrO2 (f) content exceeding 3 vol %. The sample fabricated with 3 vol % fiber content showed a harmonious microstructure and exhibited an excellent comprehensive performance with 25 °C bending strength of 22.88 MPa, an 1200 °C bending strength of 15.74 MPa, a 1200 °C deflection of 0.86 mm, and a sintering shrinkage of 0.40%, which can meet the requirements of casting very well.  相似文献   

7.
A new type of Janus cellulose acetate (CA) fiber membrane was used to separate oil–water emulsions, which was prepared with plasma gas phase grafting by polymerizing octamethylcyclotetrasiloxane (D4) onto a CA fiber membrane prepared by centrifugal spinning. The Janus–CA fiber membrane was described in terms of chemical structure using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) analysis, energy dispersive X-ray spectroscopy (EDX) analysis and morphology by field emission scanning electron microscopy (FESEM). In this contribution, we examine the influence of spinning solution concentration, spinning speed and nozzle aperture on the centrifugal spinning process and the fiber morphology. Superhydrophobic/hydrophilic Janus–CA fiber membrane was used to separate water and 1,2-dibromoethane mixture and Toluene-in-water emulsion. Unidirectional water transfer Janus–CA fiber membrane was used to separate n-hexane and water mixture. The separation for the first-time interception rate was about 98.81%, 98.76% and 98.73%, respectively. Experimental results revealed that the Janus cellulose acetate (CA) fiber membrane gave a permeate flux of about 43.32, 331.72 and 275.27 L/(m2·h), respectively. The novel Janus–CA fiber membrane can potentially be used for sustainable W/O emulsion separation. We believe that this is a facile strategy for construction of filtration materials for practical oil–water separation.  相似文献   

8.
This paper presents results of a study on the effect of filler size in the form of 15 wt% corn stalk (CS) fibers on the mechanical and thermomechanical properties of polylactide (PLA) matrix composites. In the test, polylactidic acid (PLA) is filled with four types of length of corn stalk fibers with a diameter of 1 mm, 1.6 mm, 2 mm and 4 mm. The composites were composed by single screw extrusion and then samples were prepared by injection molding. The mechanical properties of the composites were determined by static tensile test, static bending test and Charpy impact test while the thermo-mechanical properties were determined by dynamic mechanical thermal analysis (DMTA). The composite structures were also observed using X-ray microcomputed tomography and scanning electron microscopy. In the PLA/CS composites, as the filler fiber diameter increased, the degradation of mechanical properties relative to the matrix was observed including tensile strength (decrease 22.9–51.1%), bending strength (decrease 18.9–36.6%) and impact energy absorption (decrease 58.8–69.8%). On the basis of 3D images of the composite structures for the filler particles larger than 2 mm a weak dispersion with the filler was observed, which is reflected in a significant deterioration of the mechanical and thermomechanical properties of the composite. The best mechanical and thermomechanical properties were found in the composite with filler fiber of 1 mm diameter. Processing resulted in a more than 6-fold decrease in filler fiber length from 719 ± 190 µm, 893 ± 291 µm, 1073 ± 219 µm, and 1698 ± 636 µm for CS1, CS1.6, CS2, and CS4 fractions, respectively, to 104 ± 43 µm, 123 ± 60 µm, 173 ± 60 µm, and 227 ± 89 µm. The fabricated green composites with 1 to 2 mm corn stalk fiber filler are an alternative to traditional plastic based materials in some applications.  相似文献   

9.
This work aims to investigate the process of obtaining highly filled glass and carbon fiber composites. Composites were manufactured using previously obtained cellulose derived polyol, polymeric methylene diphenyl diisocyanate (pMDI). As a catalyst, dibutyltin dilaurate 95% and Dabco® 33-LV were used. It was found that the addition of carbon and glass fibers into the polymer matrix causes an increase in the mechanical properties such as impact and flexural strength, Young’s modulus, and hardness of the material. Moreover, the dynamic mechanical analysis (DMA) showed a significant increase in the material’s storage modulus and rigidity in a wide range of temperatures. The increase in glass transition of soft segments can be noticed due to the limitation of macromolecules mobility in the material. The thermogravimetric analysis showed a four step decomposition, with maximal degradation rate at TmaxII = 320–330 °C and TmaxIII = 395–405 °C, as well as a significant improvement of thermal stability. Analysis of the material structure using a scanning electron microscope showed the presence of material defects such as voids, fiber pull-outs, and agglomerates of both fibers.  相似文献   

10.
Large amounts of archaeological wood are often excavated during groundworks in cities and towns. Part of the unearthed artefacts is usually saved, conserved and then presented in museums. However, if the finding contains several similar objects, some of them could potentially be further employed for some other practical purposes. The research aimed to determine the mechanical performance of the remains of wooden water mains excavated at Bóżnicza street in Poznań, Poland and evaluate its potential usefulness for any practical purposes. First, wood density was determined along with its mechanical strength in compression. The density of archaeological wood identified as Scots pine was lower than contemporary pinewood (383 kg × m−3 vs. 572 kg × m−3); therefore, its mechanical properties in compression tests were also lower, as expected, making the wood unsuitable for any practical applications. However, the differences in modulus of elasticity and compressive strength were not justified by the differences in wood density. Further infrared spectroscopy and X-ray diffraction analyses revealed additional differences in chemical composition and cellulose crystallinity between archaeological and contemporary wood. The results indicated the decrease in carbohydrate content and cellulose crystallinity in degraded wood, which, in addition to wood density, apparently contribute to the deterioration in mechanical strength of archaeological wood. The case study of the excavated archaeological wooden pipes shows that they have historical value but are not useful for practical purposes. It also revealed that not only wood density but also its chemical composition and cellulose crystallinity level has a substantial impact on the wood mechanical properties, particularly in compression.  相似文献   

11.
The paper assesses the influence of the heat flux on spruce wood (Picea abies L.) behavior. The heat flux was performed at 15, 20, 25, and 30 kW·m−2. The fire-technical properties, such as the mass burning rate, charring thickness, charring rate, as well as the chemical composition (contents of the extractives, lignin, cellulose, holocellulose), of wood were determined. The highest burning rate of spruce wood of 0.32%·s−1 was reached at the heat flux of 30 kW·m−2. The charring rate ranged from 1.004 mm·min−1 (15 kW·m−2) to 2.016 mm·min−1 (30 kW·m−2). The proposed model of the charring process of spruce wood in time and appropriate thickness as a selected parameter is applicable in validation of the results of computer fire models in the design of fire protection of wooden buildings. The decrease in the holocellulose content mostly caused by the degradation of hemicelluloses was observed during thermal loading. The biggest decrease in hemicelluloses (24.94%) was recorded in samples loaded at 30 kW·m−2. The contents of cellulose increased due to the structural changes (carbonization and crosslinking), the content of lignin increased as well due to its higher thermal stability compared to saccharides, as well as the resulting lignin condensation.  相似文献   

12.

Background

In this study, we have aimed to evaluate the correlation between echocardiographic parameters that test systolic and diastolic function together.

Method

The study population was divided into two groups according to Vp. Group-1 (n = 103) represented the control group (Vp > 50 cm/s) and group-2 (n = 86) represented patients with systolic and diastolic dysfunctions together (Vp ≤ 50 cm/s). The echocardiographic parameters that evaluate systolic and diastolic function together, such as the Tei and the Sürücü indices, were compared between the groups.

Results

In group-2, the Tei index was higher (p = 0.001) and the Sürücü index was lower (p < 0.001). We also showed that the Tei and Sürücü indices were significantly and negatively correlated. That is, as the Sürücü index decreases, the Tei index increases (p = 0.001).

Conclusion

Vp is an index more affected by diastolic parameters but rarely by systolic parameters because it is measured at diastolic period. The Tei index, on the other hand, is affected by preload variables and needs two different heart cycles for calculation. The Modified Tei index, however, has limited diagnostic value because of high inter-observer variability. In this study, the usability of the Sürücü index is shown in comparison with other indices used for this purpose. Considering that it is less affected by preload variables, can be calculated over a single heart cycle, and has the ability to test variables of both systolic and diastolic periods unlike Vp. We postulate that the Sürücü index is more usable and reliable.  相似文献   

13.
Although amlodipine is recommended as the first‐line therapy for the treatment of hypertension, its use is limited by its potential side effects. S‐amlodipine is expected to be able to minimize side effects of amlodipine with a similar antihypertensive effect by removing the malicious R‐chiral form. However, sustainable blood pressure control with S‐amlodipine has not been well established yet. The purpose of the current study was to evaluate ambulatory blood pressure (ABP) profiles before and after a 12‐week treatment of S‐amlodipine. Patients received once‐daily S‐amlodipine 2.5 or 5 mg. ABP during 24 hr and office blood pressure were measured at baseline and after the 12‐week treatment. Primary endpoints were changes of systolic and diastolic 24 hr ABP. After 12‐week S‐amlodipine treatment, mean systolic ABP (‐15.1 ± 16.2 mmHg, p < .001) and diastolic ABP (‐8.9 ± 9.8 mmHg, p < .001) were decreased significantly. Both daytime and night‐time mean systolic BP and diastolic BP were also significantly decreased after the 12‐week treatment. Global trough‐to‐peak ratio and smoothness index after 12‐week S‐amlodipine treatment were .75 and .79 for SBP and .65 and .61 for DBP, respectively. Age ≥65 years (hazard ratio [HR]: 3.13; 95% confidence interval [CI]: 1.67–14.3) and nonalcohol drinking (HR: 3.09; 95% CI: 1.34–7.17) were independent clinical factors for target ABP achievement. Adverse drug reactions (ADR) were developed in 16 (6.4%) patients, including two (.8%) cases of peripheral edema. In conclusion, this study demonstrated the efficacy and safety of S‐amlodipine in patients with uncontrolled essential hypertension.  相似文献   

14.
Smoking not only is one of the most important risk factors of hypertension (HTN), but also alters the composition of gut microbiota (GM) in previous studies. Although dysbiosis of GM has been implicated in HTN, how GM alters in patients with HTN under smoking status is still not clear. This study aimed to explore the difference in intestinal microflora among smokers with HTN (S‐HTN), nonsmokers with HTN (NS‐HTN), and smokers without HTN (S‐CTR) and identify whether cigarette smoking led to disordered intestinal microbiota in patients with HTN. Metagenomic sequencing analysis of fecal specimens was conducted in nonsmokers without HTN (NS‐CTR, n = 9), S‐CTR (n = 9), NS‐HTN (n = 18), and S‐HTN (n = 23). Compared with S‐CTR or NS‐HTN, the GM in S‐HTN was disordered, with lower microbial α‐diversity and significant difference of β‐diversity on axes as compared to S‐CTR at genus and species level. The microbial enterotype in S‐HTN was inclined to Prevotella‐dominant type. Dramatic changes in the intestinal genera and species composition were observed in S‐HTN, including reduced enrichment of Phycisphaera and Clostridium asparagiforme. Moreover, the intestinal function altered in S‐HTN. Therefore, the findings of the present study revealed GM disorders in S‐HTN and clarified the role of smoking in impairing the intestinal microbiome in HTN. Tobacco control is particularly important for improving GM in patients with HTN, and might be beneficial in preventing future cardiovascular events.  相似文献   

15.
Date palm fiber (Phoenix dactylifera L.) is a natural biopolymer rich in lignocellulosic components. Its high cellulose content lends them to the extraction of tiny particles like microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC). These cellulose-derived small size particles can be used as an alternative biomaterial in wide fields of application due to their renewability and sustainability. In the present work, NCC (A) and NCC (B) were isolated from date palm MCC at 60 min and 90 min hydrolysis times, respectively. The isolated NCC product was subjected to characterization to study their properties differences. With the hydrolysis treatment, the yields of produced NCC could be attained at between 22% and 25%. The infrared-ray functional analysis also revealed the isolated NCC possessed a highly exposed cellulose compartment with minimized lignoresidues of lignin and hemicellulose. From morphology evaluation, the nanoparticles’ size was decreased gradually from NCC (A) (7.51 nm width, 139.91 nm length) to NCC (B) (4.34 nm width, 111.51 nm length) as a result of fragmentation into cellulose fibrils. The crystallinity index was found increasing from NCC (A) to NCC (B). With 90 min hydrolysis time, NCC (B) showed the highest crystallinity index of 71% due to its great cellulose rigidity. For thermal analysis, NCC (B) also exhibited stable heat resistance, in associating with its highly crystalline cellulose structure. In conclusion, the NCC isolated from date palm MCC would be a promising biomaterial for various applications such as biomedical and food packaging applications.  相似文献   

16.
The process of foaming poly(caprolactone)-based composites using supercritical carbon dioxide was analyzed. The impact of the conditions of the solid-foam production process on the process efficiency and properties of porous structures was investigated. The novel application of various types of porogens—hydroxyapatite, nanocellulose, carboxymethylcellulose, and graphene oxide—was tested in order to modify the properties and improve the quality of solid foams, increasing their usefulness in specialized practical applications. The study showed a significant influence of the foaming process conditions on the properties of solid foams. The optimal process parameters were determined to be pressure 18 MPa, temperature 70 °C, and time 1 h in order to obtain structures with appropriate properties for applications in biomedical engineering, and the most promising material for their production was selected: a composite containing 5% hydroxyapatite or 0.2% graphene oxide.  相似文献   

17.
In the last few years, the scientific community around the world has devoted a lot of attention to the search for the best methods of obtaining nanocellulose. In this work, nanocellulose was obtained in enzymatic reactions with strictly defined dispersion and structural parameters in order to use it as a filler for polymers. The controlled enzymatic hydrolysis of the polysaccharide was carried out in the presence of cellulolytic enzymes from microscopic fungi—Trichoderma reesei and Aspergillus sp. It has been shown that the efficiency of bioconversion of cellulose material depends on the type of enzymes used. The use of a complex of cellulases obtained from a fungus of the genus Trichoderma turned out to be an effective method of obtaining cellulose of nanometric dimensions with a very low polydispersity. The effect of cellulose enzymatic reactions was assessed using the technique of high-performance liquid chromatography coupled with a refractometric detector, X-ray diffraction, dynamic light scattering and Fourier transform infrared spectroscopy. In the second stage, polypropylene composites with nanometric cellulose were obtained by extrusion and injection. It was found by means of X-ray diffraction, hot stage optical microscopy and differential scanning calorimetry that nanocellulose had a significant effect on the supermolecular structure, nucleation activity and the course of phase transitions of the obtained polymer nanocomposites. Moreover, the obtained nanocomposites are characterized by very good strength properties. This paper describes for the first time that the obtained cellulose nanofillers with defined parameters can be used for the production of polymer composites with a strictly defined polymorphic structure, which in turn may influence future decision making about obtaining materials with controllable properties, e.g., high flexibility, enabling the thermoforming process of packaging.  相似文献   

18.
The chemical composition of 48 glass finds from Histria and Tomis, Romania, chiefly dated to the 1st–4th c. AD, was determined using prompt gamma activation analysis (PGAA) at the Budapest Neutron Centre (BNC). Most fragments have composition typical for the Roman naturally colored blue-green-yellow (RNCBGY) glass; Mn-colorless, Sb-colorless, and Sb–Mn colorless glass finds were evidenced, too. Several Foy Série 2.1 and Foy Série 3.2 glass fragments, as well as an HIMT and a plant ash glass sample, were identified in the studied assemblage. The archaeological evidence, the glass working waste items, and the samples with compositional patterns suggestive of recycling are proofs of the secondary glass working activities at Tomis during the Early Roman Empire period.  相似文献   

19.
The aim of this work is to design and optimize the process of functionalization of cellulose fibers by organosilane functional groups using low-pressure microwave plasma discharge with hexamethyldisiloxane (HMDSO) precursor in order to prepare a compatible hydrophobic filler for composites with nonpolar thermoplastic matrices. Particular attention was paid to the study of agglomeration of cellulose fibers in the mixture with polypropylene. In our contribution, the dependence of the surface wettability on used process gas and treatment time was investigated. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses were applied to characterize the surface morphology and chemical composition of the cellulose fibers. It was observed that the plasma treatment in oxygen process gas led to the functionalization of cellulose fibers by organosilane functional groups without degradation. In addition, the treated cellulose was highly hydrophobic with water contact angle up to 143°. The use of treated cellulose allowed to obtain a homogeneous mixture with polypropylene powder due to the significantly lower tendency of the functionalized cellulose fibers to agglomerate.  相似文献   

20.
Hydrolyzing the amorphous region while keeping the crystalline region unaltered is the key technology for producing nanocellulose. This study investigated if the dissolution properties of the amorphous region of microcrystalline cellulose can be enhanced in the presence of Fe3+ salt in acidic medium. The process parameters, including temperature, time and the concentration of metal chloride catalyst (FeCl3), were optimized by using the response surface methodology (RSM). The experimental observation demonstrated that temperature and time play vital roles in hydrolyzing the amorphous sections of cellulose. This would yield hydrocellulose with higher crystallinity. The factors that were varied for the production of hydrocellulose were the temperature (x1), time (x2) and FeCl3 catalyst concentration (x3). Responses were measured in terms of percentage of crystallinity (y1) and the yield (y2) of the prepared hydrocellulose. Relevant mathematical models were developed. Analysis of variance (ANOVA) was carried out to obtain the most significant factors influencing the responses of the percentage of crystallinity and yield. Under optimum conditions, the percentage of crystallinity and yield were 83.46% and 86.98% respectively, at 90.95 °C, 6 h, with a catalyst concentration of 1 M. The physiochemical characteristics of the prepared hydrocellulose were determined in terms of XRD, SEM, TGA and FTIR analyses. The addition of FeCl3 salt in acid hydrolyzing medium is a novel technique for substantially increasing crystallinity with a significant morphological change.  相似文献   

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