首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 203 毫秒
1.
Natural polymer, chitosan was obtained from dried prawn shell waste through the preparation of chitin and was characterized. Thin film of chitosan was prepared by casting method from its 2% chitosan solution. Mechanical properties like tensile strength (TS), elongation at break (Eb) of chitosan film were studied. Five formulations were developed with 2-ethyl-2-hydroxy methyl-1,3-propandiol trimethacrylate (EHMPTMA), a trifunctional monomer and 2-ethylhexyl acrylate (EHA), a monofunctional monomer in the presence of photoinitiator Darocur-1664 (2%). The film was soaked in those monomer formulations in dissimilar soaking times and irradiated under UV-radiation at different radiation intensities for the improvement of the properties of chitosan film. The cured films were then subjected to various characterization tests like TS, Eb, polymer loading (PL), water absorbency, gel content etc. The formulation, containing 25% EHMPTMA and 73% EHA showed the best performance at 10th UV passes of UV radiation for 4 min soaking time.  相似文献   

2.
In this study, a novel magnetic Cr(VI) ion imprinted polymer (Cr(VI)-MIIP) was successfully synthesized and used as a selective sorbent for the adsorption of Cr(VI) ions from aqueous solution. It can be synthesized through the combination of an imprinting polymer and magnetic nanoparticles. The high selectivity achieved using MIIP is due to the specific recognition cavities for Cr(VI) ions created in Cr(VI)-MIIP. Also, the magnetic properties that could be obtained using magnetic nanoparticles, helps to separate adsorbent with an external magnetic field without either additional centrifugation or filtration procedures. The magnetic Fe3O4 nanoparticles (MNPs) were synthesized using an improved co-precipitation method and modified with tetraethylorthosilicate (TEOS) before imprinting. The magnetic Cr(VI) ion imprinted polymer was prepared through precipitation copolymerization of 4-vinylpyridine as the complexing monomer, 2-hydroxyethyl methacrylate as a co-monomer, the Cr6+ anion as a template, and ethylene glycol dimethacrylate (EGDMA) as a cross-linker in the presence of modified magnetite nanoparticles. This novel synthesized sorbent was characterized using different techniques. Batch adsorption experiments were performed to evaluate the adsorption conditions, selectivity, and reusability. The results showed that the maximum adsorption capacity was 39.3 mg g?1, which was observed at pH 3 and at 25?°C. The equilibrium time was 20 min, and the amount of adsorbent which gave the maximum adsorption capacity was 1.7 g L?1. Isotherm studies showed that the adsorption equilibrium data were fitted well with the Langmuir adsorption isotherm model and the theoretical maximum adsorption capacity was 44.86 mg g?1. The selectivity studies indicated that the synthesized sorbent had a high single selectivity sorption for the Cr(VI) ions in the presence of competing ions. Thermodynamic studies revealed that the adsorption process was exothermic (\(\Delta H\)?<?0) and spontaneous (\(\Delta G\)?<?0). In addition, the spent MIIP can be regenerated up to five cycles without a significant decrease in adsorption capacity.  相似文献   

3.
In order to further improve the physical properties of plywood surface that was pretreated with UV and Gamma radiation at different radiation intensities before photocuring. After pretreatment with radiation the plywood surface was coated with different prepared formulations containing epoxyacrylate (EA-1020) as an oligomer, difunctional monomers such as tripropylene glycol diacrylate (TPGDA), 2-hexadioldiacrylate (HDDA), Ethylene Glycol dimethacrylate (EGDMA) and trifunctional monomer trimethyl propen triacrylate (TMPTA) with photoinitiator Darocur 1664. Thin polymer films were prepared on glass plate with these formulated solutions and cured under UV radiation. Pendulum hardness (PH) and gel content of the film were studied for selecting the formulations as top coat and as base coat. The polished plywood surface was coated with selected formulation and cured under UV radiation. Various rheological properties of UV cured plywood surface such as pendulum hardness, scratch hardness, microgloss, adhesion strength, percentage chipped off area and abrasion resistance were studied.  相似文献   

4.
The addition of plasticizers to biopolymer films is a good method for improving their physicochemical properties. The aim of this study was to evaluate the effect of chitosan (CHI) blended with two hydrophilic plasticizers glycerol (GLY) and sorbitol (SOR), at two concentrations (20 and 40 wt%) on their mechanical, thermal, barrier, structural, morphological and antimicrobial properties. The chitosan was prepared through the alkaline deacetylation of chitin obtained from fermented lactic from shrimp heads. The obtained chitosan had a degree of deacetylation (DA) of 84 ± 2.7 and a molecular weight of 136 kDa, which indicated that a good film had formed. The films composed of CHI and GLY (20 wt%) exhibited the best mechanical properties compared to the neat chitosan film. The percentage of elongation at break increase to over 700 % in the films that contained 40 % GLY, and these films also exhibited the highest values for the water vapor transmission rate (WVTR) of 79.6 ± 1.9 g m2 h?1 and a yellow color (b o  = 17.9 ± 2.0) compared to the neat chitosan films (b o  = 8.8 ± 0.8). For the structural properties, the Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analyses revealed an interaction in the acetamide group and changes in the crystallinity of plasticized films. The scanning electron micrographs revealed that all formulations of the chitosan films were smooth, and that they did not contain aggregations, pores or microphase separation. The thermal analysis using differential scanning calorimetry (DSC) revealed a glass transition temperature (Tg) of 130 °C for neat chitosan film, but the addition of SOR or GLY elicited a decrease in the temperature of the peak (120 °C). In addition, the antimicrobial activity of the chitosan films was evaluated against Listeria monocytogenes, and reached a reduction of 2 log after 24 h. The plasticizer concentration of 20 % GLY is sufficient for obtaining flexible chitosan films with good mechanical properties, and it could serve as an alternative as a packaging material to reduce environmental problems associated with synthetic packaging films.  相似文献   

5.
Thin films of gelatin were prepared by casting. Then the films were photocured and the mechanical properties were studied. The tensile strength of UV cured gelatin films showed about 10% enhancement than that of raw gelatin films. Minor amount of urea (1–5%) was used as additive in aqueous gelatin solution and films were prepared using same technique. Four formulations were prepared in methanol with 2-ethylhexyl acrylate in the presence of photoinitiator (darocur-1664). The films were soaked in the prepared formulations and then cured under UV radiation at different intensities (5–25 passes). Percentage of urea, monomer concentration, soaking time and radiation intensities were optimized with the extent of polymer loading, TS and elongation at break of the photocured film. The films containing 2% urea, cured with 3% EHA for 3 min at 15th UV pass showed the highest mechanical properties. A significant improvement of TS (31%) occurred when EHA (3%) was incorporated.  相似文献   

6.
Poly(lactic acid) (PLA) is a biodegradable polymer that exhibits high elastic modulus, high mechanical strength, and feasible processability. However, high cost and fragility hinder the application of PLA in food packaging. Therefore, this study aimed to develop flexible PLA/acetate and PLA/chitosan films with improved thermal and mechanical properties without the addition of a plasticizer and additive to yield extruder compositions with melt temperatures above those of acetate and chitosan. PLA blends with 10, 20, and 30 wt% of chitosan or cellulose acetate were processed in a twin-screw extruder, and grain pellets were then pressed to form films. PLA/acetate films showed an increase of 30 °C in initial degradation temperature and an increase of 3.9 % in elongation at break. On the other hand, PLA/chitosan films showed improvements in mechanical properties as an increase of 4.7 % in elongation at break. PLA/chitosan film which presented the greatest increase in elongation at break proved to be the best candidate for application in packaging.  相似文献   

7.
Chitosan films were prepared from dried prawn shell via chitin and then tensile properties like tensile strength (TS) and elongation at break (Eb) of the films were evaluated. Six formulations were developed using methyl methacylate (MMA) monomer and aliphatic urethane diacrylate oligomer (M-1200) in methanol along with photoinitator (Darocur-1664). Then the films were soaked in the formulations and irradiated under UV radiation at different doses for the improvement of physico-mechanical properties of chitosan films. The cured films were characterized by measuring TS, Eb, polymer loading (PL), water absorption and gel content properties. The formulation containing 43% MMA and 15% oligomer in methanol solution showed the best performance at 20th UV pass for 4 min soaking time.  相似文献   

8.
Shellac (SL) films were prepared by casting and were grafted with various acrylic monomers of different functionalities using gamma radiation. Different formulations of shellac with varying concentrations (3, 5 and 7%) of these acrylic monomers such as 2-hydroxyethyl methacrylate (HEMA), 2-ethylhexyl acrylate (EHA) and 1,4-butanediol diacrylate (BDDA) in methanol were prepared. The pure shellac and other treated films were then irradiated under gamma radiation (Co-60) at different doses (0.5–5 kGy) at a dose rate of 3.5 kGy/h where 1 Gy = 1 J/kg = 100 rads. The mechanical properties like tensile strength (TS) and elongation at break (Eb) of the prepared films were studied. The mechanical properties of the irradiated shellac films demonstrated superior values. Among the formulations, shellac grafted with BDDA (SL-g-BDDA) showed the highest TS and Eb values which were 543 and 168% higher than those of raw shellac films, respectively. The water uptake behavior of raw and treated films was also studied. The raw film showed 11% water uptake but HEMA containing film showed 67%. In the soil burial test, HEMA containing shellac film was rapidly degraded than other raw, EHA and BDDA grafted films. Thermal properties indicated that grafting of acrylic monomers decreased the melting temperature of the pure shellac films.  相似文献   

9.
A hydrophilic copolymer, ethylene–vinyl alcohol (EVOH), was incorporated into the poly(lactic acid) (PLA) matrix to improve the barrier property of PLA through twin-screw extrusion rather than the typical coextrusion process. A chain extender, poly[(ethylene)-co-(methyl acrylate)-co-(glycidyl methacrylate)] (PEMG), was used to reduce the probability of the thermal degradation of PLA during melt compounding. Biaxial stretching was used to enhance the microstructure and barrier property of PLA-PEMG/EVOH films. Experimentally, PEMG considerably reduced the probability of the thermal degradation of the PLA-PEMG sample. Biaxial stretching increased the tensile strength and decreased the value of elongation at break of the PLA-PEMG/EVOH80 (PLA/EVOH 100/80) film. Because of the efficient blending of PLA/EVOH in the twin-screw extruder, the dispersion of EVOH in the PLA matrix revealed homogeneous dispersion with a domain size of 1–5 μm. EVOH effectively improved the water vapour transmission rate (WVTR) of PLA through melt blending. Blending PLA-PEMG with EVOH substantially decreased the WVTR from 250 cc—20 μm/m2-day-atm for neat PLA to approximately 65 cc—20 μm/m2-day-atm for the PLA-PEMG/EVOH80 film, a decrease of approximately 74 % compared with neat PLA. Moreover, the WVTR decreased further from 65 cc—20 μm/m2-day-atm for the unstretched PLA-PEMG/EVOH80 film to 6.3 cc—20 μm/m2-day-atm for the film stretched at a stretch ratio of 3.5 × 3.5 and at 100 %/s, a decrease of approximately 90 % compared with neat PLA.  相似文献   

10.
Chitosan nano-composite film crosslinked by citric acid and with glycerol as plasticizer and MgO as antibacterial agent was prepared by casting method. MgO nanoparticles were synthesized via calcination method in furnace at 500 °C for 4 h and characterized by X-ray diffraction and transmission electron microscope. The chitosan nano-composite film with composition chitosan/citric/glycerol/magnesium oxide (1 wt%:1 wt%:75 vol%:10 wt%) has high mechanical properties than other films. The effects of different irradiation doses on the mechanical, thermal and antibacterial activity were investigated. The tensile strength enhanced by increasing irradiation dose up to 10 kGy and the elongation negligible changed as irradiation dose increased. The thermal stability slightly increased up to dose 2.5 kGy then decreased with dose increment. The antimicrobial activity film was studied against white mulberry-borne bacterial pathogens either Gram positive or Gram negative bacteria and has positive impact of gamma irradiation on the antimicrobial activity. The use of the selected chitosan nano-composite film which irradiated by dose of 2.5 kGy and has magnesium oxide of average particle size 54.3 nm as new packaging materials found to improve storage quality and shelf-life of mulberry fruit.  相似文献   

11.
Biomax® is an aliphatic-aromatic polyester. The biodegradability of Biomax® was studied at 58 °C using a laboratory scale bioreactor. The bioreactor was inoculated with bacteria derived from compost and supplemented with powdered Biomax® and an additional energy source. After a period of acclimation, the microorganisms in the bioreactor were capable of metabolizing the major components of the polymer, i.e., TPA and ethylene glycol. TPA and ethylene glycol were detected in the bioreactor only when they were added. Degradation and disintegration of the powdered Biomax® was monitored by laser diffraction. The particle size distribution of the powdered polymer progressively shifted toward smaller sizes until the diameters of the polymer particles were indistinguishable from bacteria. The types of microbes in the bioreactor were determined by analyzing 16S rRNA gene sequences. The bacteria belonged to 35 different groups, and the majority of the bacteria appeared to represent new species.  相似文献   

12.
The individual and interactive effects of glycerol and chitosan concentrations on edible film properties were investigated using response surface methodology. The results of ANOVA indicated that all the independent variables exhibited significant effect on the film properties. Chitosan concentration had a positive effect on CO2 permeability and negative effect on O2 while the glycerol concentration had a positive effect on permeability to both gases. Regarding water vapor permeability, the chitosan concentration had a negative effect, whereas the glycerol had no influence. Moreover, both chitosan and glycerol concentration influenced the elongation at break point (%A), and only glycerol concentration had a significant effect on tensile strength. Optimization by desirability approach was carried out on the independent variables to get the optimum levels within the experimental conditions. It was found that 1.5 % of chitosan and 25 % of glycerol (wt/wt of chitosan) retarded respiration and showed a strong permeability to water vapor.  相似文献   

13.
The relationship between the chemical structure of poly(alkylene glycol)s (PAGs) and their biodegradability was studied using a set of polymeric fluids that included poly(ethylene glycol), poly(propylene glycol) (PPG), random copolymers of ethylene oxide (EO) and propylene oxide (PO) differing in the EO/PO ratio as well as PAGs capped with ether or acyl moieties. The PAGs that were tested had an average molecular weight (MW) in the range of 350–3,600 Da and differed in their polymer backbones by either linear (diol type) or branched (triol type) molecules. The ultimate biodegradability of the PAGs was determined according to ISO 14593 (CO2 headspace test) with a non-pre-exposed (as in OECD 310 test) and pre-exposed (adapted) inoculum. PAGs with the structure of PPG and copolymers of EO/PO of diol or triol structures with average molecular weights lower than 1,000 Da can be considered as readily biodegradable. Their ultimate biodegradation exceeds the limit of 60 % (according to the criteria of the OECD 310 test). PAGs with a copolymer structure and MW values ranging between 1,000 and 3,600 Da are not readily biodegradable, but they can be considered as those of inherent ultimate biodegradability. The increased EO content in PAG structures and the acylation of the terminal hydroxyl groups with carboxylic acids favourably influenced their biodegradability. Capped PAGs containing terminal ether groups appeared to be resistant to biodegradation.  相似文献   

14.
This study investigated the dehydrochlorination of flexible polyvinyl chloride (PVC) containing 59.2% PVC, 29.7% dioctyl phthalate (DOP), and approximately 12% stabilizers. Flexible PVC was treated with NaOH/ethylene glycol (NaOH/EG) solutions at NaOH concentrations in the range 0.5–4 mol/l and was heated in a microwave heater at a temperature between 100° and 160°C for 0–30 min. All chlorides were completely eliminated by internal heating at 160°C using microwaves for 10 min in a 1 mol/l NaOH/EG solution, and the residue was made up of hydrocarbons. The weight loss rate reached a maximum of 74.7% at a temperature of 160°C. It was discovered that the use of microwaves significantly shortened the reaction time compared to using conventional electric heaters or other external heating systems and also allowed the use of lower concentrations of NaOH. Chemical Feedstock Recycling & Other Innovative Recycling Techniques 6  相似文献   

15.
Extraction and depolymerisation of chitin and chitosan from shrimp waste material was carried out using fish proteases aided process. A high deproteinization level (80 %) was recorded with an Enzyme/Substrate ratio of 10 U/mg. The demineralization of shrimp waste was completely achieved within 6 h at room temperature in HCl 1.25 M, and the residual content of calcium in chitin was below 0.01 %. The degree of N-acetylation, calculated from the 13C CP/MAS-NMR spectrum, was 85 %. The chitin obtained was converted to chitosan by N-deacetylation. X-ray diffraction patterns also indicated two characteristics crystalline peaks approximately at 10° and 20° (2θ). Chitosan was then evaluated in the treatment of unhairing effluents from the tanning industry. A result showed that chitosan as a coagulant has good performance in alkaline pH and at concentration of 0.5 g/L. Within these conditions, chitosan could decrease turbidity value, total suspended solids (89 % at 1.5 g/L), biological oxygen demand (33.3 % at 1.5 g/L) and chemical oxygen demand (58.7 % at 1.5 g/L).  相似文献   

16.
The crosslinking of chitosan with cyanoguanidine shows some advantages, such as the improved the stability in acid solutions and the decrease of adsorbent cost. In this work, cyanoguanidine-crosslinked chitosan and pure chitosan were prepared to apply in the adsorption of Food Yellow 4 (FY4) and Food Blue 2 (FB2), in single and binary systems. Effects of pH and deacetylation degree (DD) of chitosan in adsorption were evaluated. The adsorbents were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The kinetic data were analyzed by pseudo-first order, pseudo-second order and Avrami models. The conditions of pH 3 and DD 95% were the more suitable to reach the highest adsorption capacities in all experimental assays. Under these conditions, the adsorption capacities for FY4 were approximately of 392 and 200 mg g?1 and, for FB2 were approximately of 370 and 184 mg g?1, respectively, in the single and binary systems. The Avrami model was suitable to represent the kinetic curves in all conditions, and the highest adsorption capacities were found for FY4 in binary aqueous system, being for the pure chitosan of 229 mg g?1 and crosslinked chitosan of 218 mg g?1. The Langmuir and extended Langmuir models presented a good fit to the equilibrium data in both systems. It was found that, the chitosan crosslinked with cyanoguanidine improved the chemical stability of chitosan as adsorbent.  相似文献   

17.
In recent years there is a growing need in generating a biocompatible and cost effective porous scaffold for tissue engineering purposes. Therefore, this study focused on conversion of the shell waste of locally available crab variety P.pelagicus (Blue swimming crab) into the chitosan scaffold. As the poor mechanical strength of chitosan limits its usage in tissue engineering, it was blended with alginate. The scaffolds were prepared by the freeze gelation method which requires less time and minimum energy, with fewer residual solvent and easier to scale up. To the best of our knowledge there are no reports on scaffold preparation from the extracted chitosan, blended with alginate by freeze gelation method. The biological properties of chitosan-alginate scaffolds (Cts–Alg) were evaluated and compared with those of chitosan scaffolds. The prepared scaffolds were characterized by SEM, swelling property, in vitro enzymatic degradation, and hemo, biocompatibility properties. Chitosan-alginate scaffolds had an average pore size of 40 μm and tensile strength of 0.564 ± 0.0.018 % MPa. Its swelling ratio was 27.5 ± 0.28 %, with mass loss percentage of 10 ± 0.33 % after 4 weeks of degradation. It has exhibited good hemocompatible properties too. Mouse fibroblast 3T3 cells were able to adhere and proliferate well in the blended scaffold. All these results indicated that chitosan-alginate scaffold is a suitable alternative substitute for tissue engineering.  相似文献   

18.
Chitosan was dissolved in 2?% aqueous acetic acid solution and the films were prepared by solution casting. Values of tensile strength (TS), tensile modulus (TM), elongation at break (Eb?%) and water vapor permeability (WVP) of the chitosan films were found to be 30?MPa, 450?MPa, 8?% and 4.7?g?mm/m2?day?kPa, respectively. Poly(caprolactone) (PCL) films were prepared from its granules by compression molding and the values of TS, TM, Eb and WVP were 14?MPa, 220?MPa, 70?% and 1.54?g?mm/m2?day?kPa, respectively. PCL was reinforced with chitosan films, and composite films were prepared by compression molding. Amount of chitosan in the composite films varied from 10 to 50?% (w/w). It was found that with the incorporation of chitosan films in PCL, both the values of TS and TM of composite films increased significantly. The highest mechanical properties were found at 50?% (w/w) of chitosan content. The Oxygen transmission rate (OTR) of composite film was found to decrease significantly than PCL films. Thermal properties of the composite were also improved as compared to PCL. The water uptake test of the composite also showed promising results with a good stability of composite films. The interface of the composite was investigated by scanning electron microscopy and showed good interfacial adhesion between PCL and chitosan films.  相似文献   

19.
The synthesis of microcellular porous polymers based on 2-hydroxyethyl methacrylate (HEMA) by free radical polymerisation of a continuous phase of high internal phase emulsion (HIPE) is reported. N,N’-methylene bisacrylamide (MBAA) and glutaraldehyde are used as crosslinking agents. GA is added to the monomer phase either during the emulsion preparation or post polymerisation crosslinking of HEMA is performed. The crosslinker influences the morphological structure of porous poly(HEMA) materials. In the case of using MBAA as the crosslinker, homogeneous polyHIPE structure is obtained, with average cavities diameter approximately 8 μm and interconnecting pore diameter approximately 3 μm. In the case of using GA in situ crosslinking a polyHIPE is obtained exhibiting cavities of diameter approximately 12 μm and interconnecting pores of approximately 3 μm. Post polymerisation crosslinking with GA influence the structural features resulting in a different morphology. Samples are characterised using FTIR spectroscopy, scanning electron microscopy, nitrogen adsorption and swelling behaviour measurements. Polymers are prepared in the form of monoliths and membranes.  相似文献   

20.
This research aimed to prepare the silver nanoparticles (AgNPs)-loaded antimicrobial wound dressing patch using ethyl cellulose as a matrix membrane and diethyl phthalate as a plasticizer. The polymer suspension was homogeneously mixed with plasticizer, and then added to the colloidal AgNPs suspension. This mixture was poured into Petri dish and subsequently dried in a hot air oven at 80?±?2 °C for 10 h. The minimum inhibition concentration of the colloidal AgNPs suspension was 2.5 µg/ml. The AgNPs-loaded antimicrobial wound dressing patch was evaluated for physical properties by differential scanning calorimeter, X-ray diffraction, scanning electron microscope, and in vitro study. The antimicrobial wound dressing patch did not exhibit any interaction between the matrix membrane and AgNPs. The AgNPs were evenly dispersed in the patch. The patch could control the release of silver at 102.98?±?4.11% over 12 h. Although the AgNPs-loaded antimicrobial wound dressing patches can be easily prepared by the simple method, in future studies antimicrobial wound dressing patch will be developed by employing different types of film forming agents.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号