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1.
The jute yarn was grafted with acrylamide monomer (AA) under ultraviolet (UV) radiation to modify its mechanical and degradable properties. A number of AA solutions of different concentrations in methanol (MeOH) along with photoinitiator Irgacure 907 [2-methyl-1-(4-methylthiophenyl)-2-morpholinopropanone-1] were prepared. The monomer concentration and irradiation time were optimized. Jute yarn grafted with 30% AA under UV radiation for 60 min showed of the highest polymer loading (PL) value of 22% with a enhanced tensile strength (TS) value of 195% and elongation at break (Eb) value of 256% compared to untreated jute yarn. To further improve the properties of jute yarn, a number of additives (1%) such as urea, polyvinylpyrrolidone, urethane acrylate, and urethane diacrylate were used in the AA (30%) solution. Among all the additives used, urea significantly influenced the PL (27%), TS (230%), and Eb (264%) values of the treated jute yarns. Water uptake and the degradation properties of treated and untreated jute yarn caused by simulated weathering and in soil (25% water) were also studied. The rate of degradation of grafted sample is lower then that of untreated sample. DSC studies showed the thermal stability of the AA plus urea grafted sample.  相似文献   

2.
Jute yarns were grafted with a single impregnating monomer 1,6-hexanediol diacrylate (HDDA) in order to improve the physicomechanical properties. Jute yarns soaked for different soaking times (3, 5, 10, and 30 minutes) in HDDA+MeOH solutions at different proportions (1–10% HDDA in MeOH [v/v] along with photoinitiator Darocur-1664 [3%]) were cured under UV lamp at different UV radiation intensities (two, four, six, and eight passes). Concentration of monomer, soaking time, and intensity of UV radiation were optimized with extent of mechanical properties such as tensile strength, elongation at break, and modulus. Enhanced tensile strength (67%), modulus (108%), and polymer loading (11%) were achieved with 5% HDDA concentration, 5-minute soaking time, fourth pass of UV radiation. To further improve the mechanical properties, the jute yarns were pretreated with UV radiation (5, 10, 15, 30, and 50 passes) and treated with optimized monomer concentration (5%). UV-pretreated samples showed the enhanced properties. The tensile strength and modulus increase up to 84% and 132%, respectively, than that of virgin jute yarn. An experiment involving water absorption capacity shows that water uptake by treated samples was much lower than that of the untreated samples. During the weathering test, treated yarns exhibited less loss of mechanical properties than untreated yarns.  相似文献   

3.
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   

4.
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   

5.
This paper mainly focuses on the fabrication process of long fibre reinforced unidirectional thermoplastic composites made using both natural (untreated) treated jute yarns. Jute yarns were wound in layers onto a metallic frame. Polypropylene films were inserted between these layers and compression moulded to fabricate unidirectional jute/PP composite specimens. Static mechanical properties were evaluated from tensile three point bending tests. Pre- post-failure examination were carried out on the test specimens using optical scanning electron microscopy to analyse the test results and investigate the correlations between their impregnation state, processing conditions, mechanical performances and fracture morphologies. For the unidirectional jute/PP film-stacked composites, the results indicated that the processing condition at the moulding temperature of 160°C and moulding pressure of 2.0 MPa for 15 min was ideally suited to obtain optimized properties. Improved wettability of resin melts due to complete matrix fusion at this processing condition facilitated thorough impregnation with minimum microstructural imperfections (microvoids) being generated. Jute/PP composites that contained treated jute yarns have shown superiority in tensile bending properties. Jute yarns polished or coated with PVA/PP (polyvinyl alcohol/polypropylene) must have contributed positively to fibre/matrix interfacial interactions leading to matrix to fibre effective stress transfer, thereby improving their reinforcing effects. Tensile strength and modulus of PP resin increased by approximately 285% and 388%, respectively, due to 50 wt% reinforcement by natural jute yarns. Further improvements in strength and modulus were achieved by approximately 14% and 10%, respectively, when treated yarns were used . The maximum bending stress modulus of jute/PP composites containing untreated yarns were approximately 190% and 460% higher than those of the virgin PP materials, and bending properties were improved by further 11% and 23%, respectively, due to coating treatments on the yarn surface.  相似文献   

6.
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   

7.
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   

8.
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   

9.
Present work deals with the surface modification of Cannabis indica fiber through benzoylation and graft copolymerization of acrylonitrile (AN) onto C. indica fibers under the influence of microwave radiations. The Benzoylation of C. indica fiber was carried out by treating raw fiber with varying concentrations of benzoyl chloride solution. Different reaction parameters for graft copolymerization, such as reaction time, initiator concentration, nitric acid concentration, pH and monomer concentration were optimized to get the maximum percentage of grafting (25.54%). A suitable mechanism to explain benzoylation and graft copolymerization has been also proposed. Raw C. indica fiber, graft copolymerized and benzoylated fibers were subjected to evaluation of some of their properties like swelling behavior, moisture absorbance and resistance towards chemicals. Cannabis indica fibers treated with 5% benzoyl chloride solution and AN graft copolymerized fibers have been found to show more resistant towards moisture, water and chemicals when compared with that of untreated fibers. Morphological, structural changes, thermal stability and crystallanity of raw, graft copolymerized and benzoylated fibers have also been studied by SEM, FTIR, TGA and XRD techniques. It has been observed that the crystallinity of fiber decreases but thermal stability increases on surface modification.  相似文献   

10.
The aim of the present study is to investigate mechanical and morphological properties of pineapple leaf fibres (PALF) reinforced phenolic composites and its comparison with kenaf fibre (KF)/phenolic composites. Mechanical properties (tensile, flexural and impact) of untreated and treated PALF phenolic composites at different fibre loading were investigated. Tensile, flexural and impact properties of PALF and kenaf/phenolic composites were analyzed as per ASTM standard. Morphological analysis of tensile fracture samples of composites was carried out by scanning electron microscopy. Obtained results indicated that treated PALF/phenolic composites at 50% PALF loading exhibited better tensile, flexural and impact properties as compared to other untreated PALF/phenolic composites. Treated kenaf/phenolic composites at 50% fibre loading showed better tensile, flexural and impact properties than untreated kenaf/phenolic composite. It is concluded that treated 50% fibre loading kenaf and PALF/phenolic composites showed better mechanical properties than untreated kenaf and PALF/phenolic composites due to good fibre/matrix interfacial bonding. Results obtained in this study will be used for the further study on hybridization of PALF and KF based phenolic composites.  相似文献   

11.
Fabrication of complex injection molded parts often involves the use of multiple gates. In such situations, polymer melts from different gates meld to form the molded part (weld line). This paper reports on the fabrication and characterization of the mechanical and morphological properties of short fiber reinforced jute/poly butylene succinate (PBS) biodegradable composites. The effect of a dual gated mold in the fabrication of welded specimens was a key focus of the investigation. It was observed that incorporation of jute fiber (10 wt%) conferred drastic changes on the stress–strain properties of the matrix as the elongation at break (EB), dropped from 160% in the matrix to just 10% in the composite. The tensile strength of the composite was lower than that of the matrix. However, it is noteworthy that the tensile modulus of the composite increased. Bending test also revealed that both bending strength and modulus increased with the incorporation of jute. Morphological studies of the tensile fracture surface using SEM revealed two types of failure mode. Ductile failure was indicated by plastic deformation at the initiation of fracture followed by brittle failure. The good interfacial bonding indicated between jute and PBS was attributed to positive interaction between the two polar polymers. A comparison of the non-weld and weld-line samples revealed that the weld-line composites have better mechanical integrity than the corresponding polymer matrix with weld line. The results also revealed that elongation at break and toughness are most sensitive to the presence of the weld-line whereas flexural properties are least sensitive.  相似文献   

12.
Vinyl acetate (VAc) monomer of different percentage was grafted onto the recycled polyethylene terephthalate (r-PET) films using gamma irradiation. The properties of these modified films were characterized by Fourier transform infrared spectroscopy (FTIR), mechanical properties testing (Tensile strength, Elongation at break), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The Tensile Strength (TS) of the modified PET film increased by 132.25?% to the highest value of 50.12 MPa at 15% VAc monomer concentration at 3 kGy gamma dose, while the elongation at break (EB) decreased by 31.83?%. FTIR was used to investigate the molecular interaction of the modified films. TGA revealed that curve of the modified PET film shifted toward higher temperature region by 95?°C, which is very close to that of PET film made from virgin flakes. The results indicate that modified PET films of better mechanical and thermal properties were successfully prepared using VAc monomer grafting by gamma irradiation technique.  相似文献   

13.
This work focused on the durability of short jute fiber reinforced poly(lactic acid) (PLA) composites in distilled water at different temperatures (23, 37.8 and 60 °C). Morphological, thermal and mechanical properties (tensile, flexural, and impact) of jute/PLA composites were investigated before and after aging. Different from traditional synthetic fiber reinforced polymer composites, the stability of jute/PLA composites in water was significantly influenced by hydrothermal temperature. The mechanical properties of the composites and molecular weight of PLA matrix declined quickly at 60 °C, however, this process was quite slower at temperatures of 23 and 37.8 °C. Impact properties of the composites were hardly decreased, but the tensile and flexural properties suffered a drop though to various degrees with three degradation stages at 23 and 37.8 °C. The poor interface of composites and the degradation of PLA matrix were the main damage mechanism induced by hydrothermal aging. Furthermore, considering the hydrolysis of PLA matrix, the cleavage of PLA molecular chain in different aging time was quantitatively investigated for the first time to illustrate hydrolysis degree of PLA matrix at different aging time.  相似文献   

14.
To evaluate the potential of halloysite nanotubes (HNT) as nanofiller for polylactide (PLA), various nanocomposites have been successfully produced by melt-blending the polyester matrix with HNT (HNT(QM)). HNT were also surface treated by silanization reaction with 3-(Trimethoxysilyl) propyl methacrylate (TMSPM). The morphology, thermal, tensile and impact strength properties of the nanocomposites containing 3?C12?% HNT were evaluated and compared to those of pristine (unfilled) PLA. The nanocomposites were characterized by higher rigidity (with Young??s modulus increasing with HNT loading), higher tensile strength (about 70?MPa at 6?% HNT(QM)), whereas the elongation at break and impact strength did not decrease. As demonstrated under dynamic solicitation (DMA), melt-blending PLA with HNT led to enhancement of storage modulus (E??) and offers the possibility to use PLA in applications requiring higher temperatures of utilization. However, with few exceptions, TGA and DSC measurements did not reveal important changes of thermal parameters. The surface silanization treatment proved to improve the quality of the nanofiller dispersion even at higher loading. As a result, good thermal stability associated to high tensile strength, and noticeable increases in impact properties were recorded. Furthermore, enhanced nucleating ability and crystallization kinetics of the PLA matrix were revealed as specific characteristics.  相似文献   

15.
Elongation properties of extruded cornstarch were improved by blending with glycerol. Further blending of starch-glycerol with polyvinyl alcohol (PVOH) resulted in significant improvements in both tensile strength (TS) and elongation at break. Samples of starch-glycerol without PVOH equilibrated at 50% relative humidity had a TS of 1.8 MPa and elongation of 113%, whereas those containing PVOH had a TS and elongation of 4 MPa and 150%, respectively. Dynamic mechanical analysis (DMA) of starch-glycerol-PVOH blends showed that decreases in glass transition temperatures (T g values) were proportional to glycerol content. Scanning electron microscopy (SEM) of fractured surfaces revealed numerous cracks in starch-glycerol (80:20) samples. Cracks were absent in starch-glycerol (70:30) samples. In both blends, many starch granules were exposed at the surface. No exposed starch granules were visible in blends with added PVOH. Starch-glycerol samples incubated in compost lost up to 70% of their dry weight within 22 days. Addition of PVOH lowered both the rate and extent of biodegradation.  相似文献   

16.
Switchgrass (SG) stems with lengths up to 10 cm have been used as reinforcement to make lightweight composites with polypropylene (PP) webs. The long SG stems, with simple cut or split and without chemical treatment, were used directly in the composites. Utilizing SG stems for composites not only increases the values of SG but also provides a green, sustainable and biodegradable material for the composites industry. Lightweight composites are preferred, especially for automotive applications due to the potential saving in energy. In this research, the effects of manufacturing parameters on the properties of composites have been studied. Although the tensile properties of SG stem are significantly worse than jute fiber, SG stem with low bulk density is found to better reinforce the lightweight composites. Compared with the jute-PP composites of the same density (0.47 g/cm3), composites reinforced by the split SG stems have 56% higher flexural strength, 19% higher modulus of elasticity, 15% higher impact resistance, 63% higher Young’s modulus, 52% lower tensile strength, and similar sound absorption property. The SG-PP composites with optimized properties have the potential to be used for industrial applications such as the support layers in automotive interiors, office panels and ceiling tiles.  相似文献   

17.
Natural composites have been important materials system due to preservation of earth environments. Natural fibers such as jute, hemp, bagasse and so on are very good candidate of natural composites as reinforcements. On the other hand regarding matrix parts thermosetting polymer and thermoplastic polymer deriver form petrochemical products are not environmental friendly material, even if thermoplastic polymer can be recycled. In order to create fully environmental friendly material (FEFM) biodegradable polymer which can be deriver from natural resources is needed. Therefore poly(lactic acid) (PLA) polymer is very good material for the FEFM. In this paper jute fiber filled PLA resin (jute/PLA) composites was fabricated by injection moldings and mechanical properties were measured. It is believable that industries will have much attention to FEFM, so that injection molding was adopted to fabricate the composites. Long fiber pellet fabricated by pultrusion technique was adopted to prepare jute/PLA pellet. Because it is able to fabricate composite pellets with relative long length fibers for injection molding process, where, jute yarns were continuously pulled and coated with PLA resin. Here two kinds of PLA materials were used including the one with mold releasing agent and the other without it. After pass through a heated die whereby PLA resin impregnates into the jute yarns and sufficient cooling, the impregnated jute yarns were cut into pellets. Then jute/PLA pellets were fed into injection machine to make dumbbell shape specimens. In current study, the effects of temperature of PLA melting temperature i.e. impregnation temperature and the kinds of PLA were focused to get optimum molding condition. The volume fractions of jute fiber in pellet were measured by several measuring method including image analyzing, density measurement and dissolution methods. Additionally, thermal and mechanical properties were investigated. It is found that 250° is much suitable for jute/PLA long fiber pultrusion process because of its less heat degradation of jute, better impregnation, acceptable mechanical property and higher production efficiency. Additionally the jute fibers seem much effective to increase deflection temperature under load, tensile modulus and Izod strength.  相似文献   

18.
In the presented work, the effect of crosslinker geometry on the properties of PVA is reported. The aliphatic (suberic) and aromatic (terephthalic) dicarboxylic acids are used as crosslinker molecules. On the basis of tensile test and thermal properties, it is observed that crosslinking of PVA by suberic acid is more effective than terephthalic acid. The maximum strength measured in crosslinked samples is 32.5 MPa for suberic acid crosslinked PVA which is higher than that of neat PVA (22.6 MPa). Swelling study shows that 8 h crosslinked terephthalic acid (35% w/w) samples have a minimum of 5.4% of water uptake compared to neat PVA, which dissolves readily in water. DTGA shows that the decomposition temperature of crosslinked PVA is 345?°C while neat PVA has a decomposition temperature of 315?°C. FTIR spectroscopy confirms the formation of crosslink ester bond in crosslinked PVA. The crosslinked samples kept for bio-degradation show maximum degradation in terephthalic acid (15% w/w) crosslinked PVA.  相似文献   

19.
In this paper we studied the synthesis of biodegradable optically active poly(ester-imide)s containing different amino acid residues in the main chain. These pseudo-poly(amino acid)s were synthesized by polycondensation of N,N′-(pyromellitoyl)-bis-l-tyrosine dimethyl ester as a diphenolic monomer and two chiral trimellitic anhydride-derived diacid monomers containing s-valine and l-methionine. The direct polycondensation reaction of these diacids with aromatic diol was carried out in a system of tosyl chloride (TsCl), pyridine (Py) and N,N′-dimethylformamide (DMF) as a condensing agent. The structures and morphology of these polymers were studied by FT-IR, 1H-NMR, powder X-ray diffraction, field emission scanning electron microscopy (FE-SEM), specific rotation, elemental and thermogravimetric analysis (TGA) techniques. TGA profiles indicate that the resulting PEIs have a good thermal stability. Morphology probes showed these polymers were noncrystalline and nanostructured polymers. The monomers and prepared polymers were buried under the soil to study the sensitivity of the monomers and the obtained polymers to microbial degradation. The high microbial population and prominent dehydrogenase activity in the soil containing polymers showed that the synthesized polymers are biologically active and microbiologically biodegradable. Wheat seedling growth in the soil buried with synthetic polymers not only confirmed non-toxicity of polymers but also showed possibility of phyto-remediation in polymer-contaminated soils.  相似文献   

20.
A range of bio-nanocomposites were prepared by incorporation of organo modified montmorillonite nanoclay (OMMT) with or without use of aluminum hydroxide (Al(OH)3) within polylactic acid (PLA) solution. Furthermore, the solution was employed for modification of ligno-cellulosic (jute) fabric structural reinforcements. The successful incorporation of nanofillers within the host polymer, polylactic acid (PLA) was confirmed by Fourier-transform infrared spectroscopy (FT-IR). Water uptake and swelling behaviour studies revealed that the water uptake and swelling ratio of bio-composites reduced significantly as compared to pristine jute fabric, whereas upon incorporation of OMMT and Al(OH)3, the water barrier properties reduced even further in the developed bio-nanocomposites. The flexural strength of the bio-nanocomposites also showed improved mechanical and dimensional stability. Synergistic effects of OMMT and Al(OH)3 were observed in enhancing the aforementioned physico-mechanical properties. Scanning electron microscopy (SEM) studies revealed microstructural details of developed samples. Similarly, the thermo-gravimetric analysis and linear burning rate studies of Al(OH)treated bio-nanocomposite materials revealed enhanced thermal resistance and reduced flammability respectively compared to both pristine woven jute fabric and fabrics treated with PLA alone or those without Al(OH)3. From the above results it can safely be said that the bio-nanocomposite material can be a prospective candidate for development of flame retardant biopackaging.  相似文献   

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