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1.
PLA/LPCL/HPCL blends composed of poly(lactic acid) (PLA), low molecular weight poly(ε-caprolactone) (LPCL), and high molecular weight poly(ε-caprolactone) (HPCL) were prepared by melt blending for bioabsorbable filament sutures. The effects of blend composition and blending time on the ester interchange reaction by alcoholysis in the PLA/LPCL/HPCL blends were studied. Their thermal properties and the miscibility due to the ester interchange reaction were investigated by1H-NMR, DSC, X-ray, and UTM analyses. The hydroxyl group contents of LPCL in the blends decreased by the ester interchange reaction due to alcoholysis. Thus, the copolymer was formed by the ester interchange reaction at 220 °C for 30–60 minutes. The thermal properties of PLA/LPCL/HPCL blends such as melting temperature and heat of fusion decreased with increasing ester interchange reaction levels. However, the miscibility among the three polymers was improved greatly by ester interchange reaction. Tensile strength and modulus of PLA/LPCL/HPCL blend fibers increased with increasing HPCL content, while the elongation at break of the blend fibers increased with increasing LPCL content.  相似文献   

2.
Biodegradable block copolymers containing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly (ɛ-caprolactone) (PCL) units (PHCLs) with different contents of PCL block were synthesized successfully by using telechelic hydroxylated PHBV (PHBV-diol) with low molecular weight as a macroinitiator to initiate ring-opening bulk polymerization of ɛ-caprolactone (ɛ-CL). The chemical structure and molecular weight were characterized by 1H NMR, FTIR and GPC. The PHBV and PCL blocks in PHCLs were miscible in amorphous state, and formed separate crystalline phases with lower crystallinity than corresponding homopolymers, which was characterized by DSC and WAXD. The results of TGA showed that PHCLs underwent a two-step thermal degradation process. The thermal degradation process of PCL blocks was significantly different from PCL homopolymers. The activation energies of thermal degradation of PCL blocks calculated by Horowitz and Metzger method were much higher than that of each step of thermal degradation of PCL homopolymers.  相似文献   

3.
In the present study, nanofibrils of cellulose are extracted from waste jute fibers using high energy planetary ball milling process in wet condition. The rate of refinement of untreated fibers having non-cellulosic contents was found slower than treated fibers due to strong holding of fiber bundles by non-cellulosic contents. At the end of three hours of wet milling, untreated fibers were refined to the size of 850 nm and treated fibers were refined to the size of 443 nm. In the subsequent stage, composite films of poly lactic acid (PLA) were prepared by solvent casting with 3 wt% loading of untreated jute nanofibrils, treated jute nanofibrils and microcrystalline cellulose. The influence of non-cellulosic contents on mechanical properties of PLA films are investigated based on results of tensile test, dynamic mechanical analysis and differential scanning calorimetry. The maximum improvement was observed in case of treated jute nanofibril/PLA composite film where initial modulus and tensile strength increased by 207.69 % and 168.67 %, respectively as compared to neat PLA film. These improvements are attributed to the increased interaction of treated jute nanofibrils with PLA matrix due to their higher precentage of cellulosic contents and mechanically activated surface.  相似文献   

4.
Liquid crystalline (LC) poly(ethylene terephthalate-co-2(3)-chloro-1,4-phenylene terephthalate) (50/50, mole/mole) [PECPT] was synthesized and blended with polycarbonate (PC). LC properties of PECPT and thermal, morphological, and rheological behaviors of the PECPT/PC blend were studied. PECPT showed the nematic LC phase and much longer relaxation time than poly(ethylene terephthalate) (PET). The apparent melt viscosity of PECPT was one third of that of PET. An abrupt torque change was observed during the blending process due to the orientation of LC domains. For the blends containing 10∼30 wt% of PECPT, the complex viscosities were higher than that of PC. As PECPT content increases above 40 wt%, shear thinning was observed. The lowest complex viscosity was obtained at 40∼50 wt%. Transesterification of PECPT and PC was confirmed by the selective chemical degradation of carbonate groups in PC.  相似文献   

5.
In the work, N-methylmorpholine-N-oxide monohydrate (NMMO·H2O) was used as a solvent to solve bacterial cellulose (BC) and hydroxypropyl chitosan (HPCS) together, and regenerated bacterial cellulose (RBC)/HPCS blend as-spun fibers were prepared by blending BC with HPCS via wet-spinning in the Lyocell process. Structure and properties of the blend as-spun fibers were characterized by different techniques, together with the antibacterial activity of the blend as-spun fibers against Staphylococcus aureus. Results revealed that HPCS was mixed with BC very well. The blend as-spun fibers showed a rough and folded surface morphology and an interior pore structure on the cross-section. Compared with pure RBC as-spun fibers, the blend as-spun fibers had lower degree of crystallinity and thermal stability. Although extension at break of the blend as-spun fibers was lower than the pure RBC as-spun fibers, their tensile strength and modulus had been enhanced obviously. The blend as-spun fibers were also found to exhibit excellent antibacterial activities against S. aureus.  相似文献   

6.
Cellulose nanowhiskers were used to improve the performance of poly (lactic acid) (PLA). The nanocomposites mixed with three different molecular weight of poly (ethylene glycol) (PEG) were characterized by mechanical testing, thermal gravimetry and differential scanning calorimetry. The tensile test showed an increase in tensile strength and elongation at break with the addition of PEG to PLA/CNW nanocomposites, the thermal analysis results showed an increase of crystallization temperature (T c) and crystallization compatibility (larger crystallization and melting areas), which indicated that the cellulose nanowhiskers (CNW) and PEG or CNW alone should not be considered as nucleating agents for the PLA matrix; The CNW was homo-dispersed which contributed to decreasing mobility of polymer chain segments. The compatibility between hydrophobic PLA matrix and the hydrophilic CNW was improved by the addition of different molecular weight polymeric-PEG. The thermo gravimetric analysis indicated that the thermal stability of the different composites were reflected well in the region between 25 °C and 245 oC. The structure of the PLA/CNW/PEG composites was characterized by AFM, which showed that the CNW dispersed in the PLA matrix evenly.  相似文献   

7.
Siloxylated polypropylene fibers composed of polypropylene (PP) and aluminosiloxane (AS) were prepared by melt blending followed by spinning. The effects of blend compositions on the thermal behaviors, surface and tensile properties of PP/AS blend fibers were investigated by DSC, WAXD, SEM, static honestometer, etc. The heat of fusion of PP/AS blends decreased with increasing AS contents. In addition, the peak intensity of PP/AS blends in X-ray diffraction patterns decreased with increasing AS contents. It was observed that the silicone molecules exist and well distribute on the surface of siloxylated polypropylene fibers. From the results of the half-life period measurements, the anti-static properties of PP fibers siloxylated with AS was found to be significantly modified.  相似文献   

8.
Cassava bagasse is an inexpensive and broadly available waste byproduct from cassava starch production. It contains roughly 50% cassava starch along with mostly fiber and could be a valuable feedstock for various bioproducts. Cassava bagasse and cassava starch were used in this study to make fiber-reinforced thermoplastic starch (TPSB and TPSI, respectively). In addition, blends of poly (lactic acid) and TPSI (20%) and TPSB (5, 10, 15, 20%) were prepared as a means of producing low cost composite materials with good performance. The TPS and PLA blends were prepared by extrusion and their morphological, mechanical, spectral, and thermal properties were evaluated. The results showed the feasibility of obtaining thermoplastic starches from cassava bagasse. The presence of fiber in the bagasse acted as reinforcement in the TPS matrix and increased the maximum tensile strength (0.60 MPa) and the tensile modulus (41.6 MPa) compared to cassava starch TPS (0.40 and 2.04 MPa, respectively). As expected, blending TPS with PLA reduced the tensile strength (55.4 MPa) and modulus (2.4 GPa) of neat PLA. At higher TPSB content (20%) the maximum strength (19.9 MPa) and tensile modulus (1.7 GPa) were reduced about 64% and 32%, respectively, compared to the PLA matrix. In comparison, the tensile strength (16.7) and modulus (1.2 GPa) of PLA blends made with TPSI were reduced 70% and 51% respectively. The fiber from the cassava bagasse was considered a filler since no increase in tensile strength of PLA/TPS blends was observed. The TPSI (33.1%) had higher elongation to break compared to both TPSB (4.9%) and PLA (2.6%). The elongation to break increased from 2.6% to 14.5% by blending TPSI with PLA. In contrast, elongation to break decreased slightly by blending TPSB with PLA. Thermal analysis indicated there was some low level of interaction between PLA and TPS. In PLA/TPSB blends, the TPSB increased the crystallinity of the PLA component compared to neat PLA. The fiber component of TPSB appeared to have a nucleating effect favoring PLA crystallization.  相似文献   

9.
Nanocomposites of polyurethane (PU) and multi-walled carbon nanotubes (MWNTs) were prepared via in-situ polymerization of poly(ɛ-caprolactone)diol (PCL)-grafted-MWNTs, 4,4′-methylene bis(phenyl isocyanate), and 1,4-butanediol. The grafting of PCL onto MWNTs was confirmed by Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The nanocomposites showed more improved mechanical properties compared to conventional nanocomposites with the same MWNT loading. The thermo-responsive shape recovery as measured in a cyclic tensile test was observed to be approximately 80 % for in-situ nanocomposites, though it showed a reduced trend as the wt% of MWNTs increased. X-ray diffraction investigation also showed that the addition of MWNTs into the polyurethane increased the crystallinity. Scanning electron microscopy and TEM measurements showed better dispersion of MWNTs in the nanocomposites synthesized using in-situ method. Consequently, the presence of PCL-g-MWNTs made an important contribution to the enhancement of the mechanical and shape memory properties of polyurethane.  相似文献   

10.
The maximum strain experienced by the thinnest segment of a non-uniform fiber governs fiber breakage, yet this maximum strain can not be obtained from a normal single fiber test. Only the average strain of the whole fiber specimen can be obtained from a normal single fiber tensile test. This study has examined the relationship between the average strain, the maximum strain and the degree of fiber non-uniformity, expressed in coefficient of variation (CV) of fiber diameters along fiber length. The tensile strain of irregular fibers has been simulated using the finite element method (FEM). Using this method, average and maximum tensile strains of non-uniform fibers were calculated. The results indicate that for irregular fibers such as wool, there is an exponential relationship (i.e.ɛ ave ɛ max=ae −b CV ) between the ratio of average breaking strain and maximum breaking strain (ɛ ave ɛ max) and the along-fiber diameter variation (CV). The strain ratio decreases with the increase of the along-fiber diameter variation.  相似文献   

11.
This research evaluates the miscibility and performance of polypropylene (PP)/polybutylene succinate (PBS) and PP/polylactic acid (PLA) blend and natural-flour-filled, PP/PLA and PP/PBS blend bio-composites. The melting temperature (T m ) and glass transition temperature (T g ) of pure PP, PBS and PLA showed a single peak but differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) presented two peaks for the T m and T g of the PP/PBS and PP/PLA blends. These results indicated that the PP/PBS and PP/PLA blend systems existed as immiscible blends. These results were also confirmed by the scanning electron microscopy (SEM) micrographs of the tensile fracture surface of the PP/PBS and PP/ PLA blends. At a PP/PBS and PP/PLA blend ratio of 70/30, the tensile and flexural strengths of bamboo flour (BF)- and wood flour (WF)-filled, PP/PBS and PP/PLA blend bio-composites were similar to those of BF- and WF-filled, PP and PBS bio-composites. In addition, these strengths of maleic anhydride-grafted PP (MAPP)- and acrylic acid-grafted PP (AAPP)-treated, BF- and WF-filled, PP/PBS and PP/PLA blend bio-composites were higher than those of non-treated bio-composites.  相似文献   

12.
Dense membranes of Chitosan (CS)/Poly(vinyl alcohol) (PVA)/Poly(lactic acid) (PLA) blend were successfully fabricated using casting technique. The mechanical properties, moisture regain and water vapor permeability of polymer blend membranes were estimated by tensile test, moisture regain rate and dish method test respectively. The microstructures, morphology, chemical composition and thermal properties were also characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) respectively. Results indicated that there were interactions and good compatibility among CS, PLA and PVA. And the blend membranes have good breaking elongation and slightly decreased breaking strength, and show best moisture regain at the case of CS60 (the content of CS in the blends is 60 %). They also have excellent porous structure, which is beneficial to their air permeability and may also contribute to cell regeneration. With the adding of PVA content, the melting peaks of blend membranes reduce and gradually close to that of PVA, demonstrating that the regularity of CS molecular chain may be destroyed and hydrogen bonds of macromolecules in polymers were newly formed. As a result, solution blending of the three polymers could complement their disadvantages and significantly improve the membrane performance of a single polymer, thus promote the mechanical and biological properties of blend membrane.  相似文献   

13.
N-methylmorpholine-N-oxide (NMMO) is used widely in the manufacturing of man-made cellulose fibers and functional lyocell fibers due to its environment-friendly advantage. Although chitosan is known as a natural antibacterial polymer it has poor solubility in neutral to basic medium and the antibacterial activity is shown only in acidic medium. Chitosan’s poor solubility in NMMO is the disadvantage for the production of antibacterial lyocell fibers. This paper investigates a more “NMMO soluble” derivative of chitosan, 2-(2-aminoethoxy) ethyl chitosan (AECS). AECS has greatly improved solubility in NMMO hydrate, and stronger antibacterial activity than chitosan. AECS was introduced to modify the lyocell fiber spun in a co-solution of cellulose and AECS in NMMO hydrate. The physical properties and antibacterial activity of the fibers were examined and the results indicated that the modified lyocell fiber, containing more than 2 wt% of AECS, exhibits good antibacterial activity against E. coli and slightly decreased tensile strength compared with unmodified fibers.  相似文献   

14.
Braided silk sutures were coated using a combination of poly(ε-caprolactone) (PCL) and sulfamethoxazole trimethroprim (SMZ) to investigate their antimicrobial performance. SMZ (2500 μg/ml) was combined with different PCL concentrations, i.e., 2.5 %, 5 %, 7.5 %, and 10 % (w/v). Antimicrobial test results showed that SMZ and PCL-treated silk sutures exhibited increasing antimicrobial efficacy against Gram-negative (Escherichia coli) and -positive bacteria (Staphylococcus aureus) with increasing PCL concentrations. The tensile and knot strength of sutures coated with 10 % PCL were significantly higher than those of sutures coated with 7.5 %, 5 %, and 2.5 % PCL. Treatment with PCL exhibited a positive effect on drug release from the sutures. Significant traits of antibacterial activity were observed up to 4 days after instalment of 10 % PCL-coated silk sutures. Under a scanning electron microscope, untreated silk sutures showed a surface heavily coated with bacteria, whereas treated sutures showed a smooth surface without bacteria. The results of this study indicate that SMZ combined with high concentrations of PCL may afford a suitable antibacterial coating agent for braided silk sutures.  相似文献   

15.
The flame-retardant poly(lactic acid) (FR-PLA) fibers with different contents of modified α-zirconium phosphate (α-ZrP) and polysulfonyldiphenylene phenyl phosphonate (OP) were prepared by melt spinning. The organic modification of α-ZrP was characterized by Fourier transform infrared spectroscopy, wide angle X-ray diffraction, and thermo gravimetric analysis. The limiting oxygen index, vertical burning test, and cone calorimeter test were used to investigate the synergistic effect of OP/α-ZrP on flame-retardant property of FR-PLA, the test results suggested that the combustion of PLA fibers was efficiently inhibited by OP/α-ZrP. The results of scanning electron microscopy, Raman spectrum, and X-ray photoelectron spectroscopy indicated that the flame-retardant mechanism of OP/α-ZrP mainly depended on condensed phase. The tensile strength and morphology of FR-PLA fibers with OP/α-ZrP were better than those of fibers treated only with OP, demonstrating that α-ZrP could significantly improve the mechanical property of FR-PLA fibers.  相似文献   

16.
The viscosity effect of matrix polymer on melt exfoliation behavior of an organoclay in poly(ε-caprolactone) (PCL) was investigated. The viscosity of matrix polymer was controlled by changing the molecular weight of poly(ε-caprolactone), the processing temperature, and the rotor speed of a mini-molder. Applied shear stress facilitates the diffusion of polymer chains into the gallery of silicate layers by breaking silicate agglomerates down into smaller primary particles. When the viscosity of PCL is lower, silicate agglomerates are not perfectly broken into smaller primary particles. At higher viscosity, all of silicate agglomerates are broken down into primary particles, and finally into smaller nano-scale building blocks. It was also found that the degree of exfoliation of silicate layers is dependent upon not only the viscosity of matrix but thermodynamic variables.  相似文献   

17.
In this study, PLA/PC blends were prepared in order to investigate the effects of the addition of PC loading level into PLA matrix on the mechanical properties of these blends. After that, PLA/PC (70/30), which has the lowest tensile strength value, was selected as a control sample for the compatibilization study. Commercial styrene-acrylic multi-functional-epoxide oligomeric agent (SAmfE), styrene maleic anhydride copolymer (SMA), tetrasilanol phenyl polyhedral oligomeric silsesquioxane (T-POSS) and glycidyl isooctyl-polyhedral oligomeric silsesquioxane (G-POSS) were used as compatibilizers for PLA/PC blends. The variation of mechanical, thermal, structural and morphological properties were examined by conducting tensile tests, dynamic mechanical analyses, differential scanning calorimetry, Fourier Transform IR and scanning electron microscope analyses. Tensile test results showed that the tensile strength and elongation at break values of the PLA/PC blend compatibilized with SAmfE were higher than those of the other blends. DSC analyses revealed that Tg and Tm values of the blends were not significantly affected by compatibilizer but, degree of crystallinity was found to be sensitive to compatibilizer type. DMA results showed that the best mechanical properties were obtained for the PLA/PC/SAmfE blend. When all of the results evaluated, it was found that the SAmfE is the most effective compatibilizer among the using compatibilizer types for PLA/PC blends.  相似文献   

18.
Green composites from Pattawia pineapple leaf fiber (PALF) and poly(lactic acid) (PLA) were prepared. The mechanical method was chosen to extract PALF from fresh leaves due to this method gave high yield of fiber, short extraction time, and environmental friendly. Tensile and thermal properties, together with morphology of the fibers were disclosed. The fibers were conducted into a specified length of 1–3 mm and blended with PLA, using a twin screw extruder, with the PALF content of 10–50 wt%. Tensile testing, morphology investigation and thermogravimetric analysis were applied. Preliminary results showed that tensile modulus of the composites depended on PALF content. The tensile modulus and elongation at break of the composite containing 40 % PALF was about 48 %, and 111 % increase, respectively, compared with that of PLA. With addition of maleic anhydride coupling agent, such the composite showed the tensile modulus of 5.1 GPa, which was 34 % higher than that of the non-coupling agent composite, and about 104 % higher than that of PLA. Although the elongation at break of the composite containing 40 % PALF was found to dramatically increase by 111 %, the introduction of maleic anhydride in such the composite caused only 57 % increase in the elongation at break compared with that of PLA. Finally, a pilot product of square boxes was produced successfully from the proposed composite, by conventional injection molding process.  相似文献   

19.
PLA/PLA-g-ABS blends were prepared and evaluated for mechanical properties performance. Firstly, carboxylic acid functionalized ABS particles were synthesized by grafting polymethacrylic acid (PMAA) onto ABS particle surface using potassium persulfate as an initiator. The reaction was followed by FTIR analysis. The resultant carboxylated ABS was melt mixed with virgin PLA in an internal mixer to obtain PLA/PLA-g-ABS blends. The obtained PLA/PLA-g-ABS blends were subject to injection molding to obtain specimens for testing evaluation. It was found that impact resistance values significantly outperformed neat PLA by 60 %, 87 %, and 150 % for PLA/PLA-g-ABS 10 wt%, PLA/PLA-g-ABS 20 wt%, and PLA/PLA-g-ABS 30 wt%, respectively. A significant increase in impact strength was contributable to ABS rubber which exhibited even dispersion and good interfacial adhesion. The impact strength was dependent on the percent loading of PLAg-ABS; the more the PLA/PLA-g-ABS the higher the impact strength value. In a similar manner, tensile strength increases when loaded with PLA/PLA-g-ABS albeit at lesser effect. Considering the percent elongation, a massive increase in percent elongation was recorded in case of PLA/PLA-g-ABS 20 wt% and PLA/PLA-g-ABS 30 wt%, implying that these blends were extremely flexible and tough when compared to neat PLA, control, and PLA/PLA-g-ABS 10 wt%.  相似文献   

20.
Poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA)/poly(ethylene octene) grafted with glycidyl methacrylate (GPOE) were prepared by simple melt blending method at PDLA loadings from 1 to 5 wt%. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) demonstrated the formation of the stereocomplex in the blends. The addition of PDLA led to the increase of nucleation density from polarized microscope (POM) observations. Rheological measurements indicated that the blends exhibited a rheological fluid-solid transition and an enhanced elastic behavior in that ternary system as the PDLA loadings reached up to 5 wt%. By adding 1-2 wt% PDLA, the ternary system has better tensile and impact properties. Dynamic Mechanical Analysis (DMA) results showed that SC crystal formation and its effect on the enhancement of thermal stability at higher temperature. It is interesting that the enzymatic degradation rates have been enhanced clearly in the PLLA/PDLA/GPOE blends than in the PLLA/GPOE blend, which may be of great use and significance for the wider practical application of PLLA/GPOE blends.  相似文献   

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