Papers by Keyword: Poly(lactic acid) (PLA)

Abstract: This study investigated the synthesis and characterization of poly(lactic acid)-grafted natural rubber (PLA-g-NR) in molten state. The grafting was carried out in an internal mixer without and with the presence of tin octoate catalyst (TO). The grafting of lactide onto NR was carried out by using maleic anhydride (MA) as a linker. The FTIR and ¹H-NMR spectra revealed new peaks for the MA-grafted NR (NR-g-MA) and PLA indicating that MA was grafted onto NR and that LA was successfully polymerized into PLA. It was also found that MA grafted onto NR could assist as a linker for connecting PLA with NR via esterification reaction between hydroxyl group (OH) at the end chain of PLA and carboxylic group (COOH) from ring opening reaction of MA. Moreover, the decrease of residual LA peak in FTIR spectra suggested that the presence of TO catalyst in the reactive blend promoted higher degree of polymerization of PLA from ring opening reaction of LA.

Abstract: In this study, oligomer Joncryl^TM ADR was used to extend the chains and improve the mechanical properties. The chain extender multifunction epoxide was used with concentrations of 0.5 and 0.9 wt %. Pure and modified PLAs were characterized using DSC, MFI and FT-IR. The DSC results showed that Tg shifted to the high temperature and T_m increased slightly after chain extending. The MFI of the blends decreased with increasing the content of the CE which means the increase of molecular weight. The coupling between epoxy groups of CE and end groups of PLA was confirmed by FTIR tests. This coupling led to significant improvement in tensile strength and modulus.

Abstract: We precipitated Apatite Nucleus (AN) by raising pH of SBF. We mixed various concentration of AN in polylactic acid (PLA) and pressed by uniaxial press and cold isostatic press. We investigated the effect of AN concentration on bioactivity. We fabricated composite of PLA and AN configurating the shape by using 3D printer. The composite showed high bioactivity.

Abstract: Poly (L-lactic acid)/organically modified montmorillonite (PLLA/OMMT) nanocomposites were fabricated by a solution intercalation method. OMMT, modified with quaternary alkylammonium ion, was prepared by alkyltrialkoxysilane. The differential scanning calorimetry measurement revealed that the crystallization temperatures of PLLA/OMMT nanocomposites were at around 110 °C regardless of the existence of OMMT or the weight fraction of them. X-ray diffraction patterns suggested that the (001) diffraction was around 2θ = 2.5°. The TEM image showed variously expanded interlayer galleries of OMMT and partially exfoliated silicate layer unit in the matrix. Board-shaped specimens for mechanical property tests were fabricated by compression-molding at 190 °C (including 30 min annealing at 110 °C). The flexural modulus of the nanocomposites increased with increasing content of OMMT. Vickers hardness of the nanocomposites were almost same independent on weight fraction of OMMT.

Abstract: A biodegradable poly-lactic acid (PLA)/Sepiolite nanocomposite films were prepared by the thermo-compression and solvent-casting methods, and barrier properties (water-vapor and gas barrier) were evaluated. By introducing sepiolite into PLA, the properties of nanocomposite films improved until a certain amount (1.5% wt). By increasing sepiolite loading, nanoparticles tented to agglomerate and gas permeability (GP) decreased. According to the results, the nanocomposite films prepared by the thermo-compression method were more brittle but strong due to the formation of more crystals; while solvent-casted films were more ductile due to the presence of solvent, which may act as a plasticizer, as evidenced by the results of the GP.

Abstract: Poly (lactic acid) (PLA) blended with poly (butylene succinate) (PBS) were prepared by using twin screw extruder and injection molding machine at various contents of PBS from 0-15 wt%. The surface of titanium dioxide (TiO₂) nanoparticles was treated using aminopropyl trimethoxy silane (ATS) order to disperse them into the biopolymer blends. The mechanical and thermal properties of PLA/PBS/TiO₂ nanocomposites were investigated over a range of filler content 0-5 wt%. All samples with a wide range of TiO₂ addition exhibit the translucency. The surface morphology showed that the addition of PBS at 10 wt% was miscible with PLA while the other contents of PBS exhibited phase separation in the blends. Additionally, a uniform dispersion of filler in the matrix existed when the nanoparticles content was less than 3 wt%. The surface treated nanoparticles played an important role in mechanical and thermal properties of the nanocomposites because of its well dispersion and strong interfacial interaction between the nanoparticles and PLA/PBS matrix.

Abstract: Poly (lactic) acid (PLA)/poly (caprolactone) (PCL) blends nanofibers, with mean diameter about 600nm, were prepared by electrospinning. This research focused on the morphological and thermal properties of nanofibers made from PLA/PCL bends with different PCL content. The results showed that the addition of PCL could improve the morphology of the nanofibers. The film with blend fiber at PLA/PCL ratio of 80:20 is characterized with the smoothest surface and the highest orientation. The diameter distribution of blend fibers is wider than that of pure PLA. The glass-transition temperature of PLA for blend fiber is higher than that of pure PLA, and their melting temperature is lower than that of pure PLA. It can be used in biomedical field for degradable membrane, anti-adhesive film and medical equipment.

Abstract: Polylactic acid (PLA) is the most promising material in the biodegradable category. However, brittleness and poor thermal stability restrict its application. To overcome this limitation, PLA may be blended with other biodegradable materials to tailor its properties while maintain biodegradability. In this study a series of blends of PLA and poly (ε-caprolactone) (PCL) with various mass fractions were prepared by solution method and solvent casting. Films of each blend were formed when the solvent evaporated. Subsequently, tensile test samples were punched out of the film for testing and tensile testing, Fourier transform infrared spectrometry (FTIR), Differential scanning Calorimetry (DSC) and contact angle measurements were carried out. Since PCL is a ductile material, the two materials were blended together in an effort to improve the mechanical properties. However, on thermal analysis of the blends, two individual melting peaks were observed in the DSC thermograms. Furthermore, no significant shift in peaks was observed on the FTIR spectra, and clear droplets and boundaries between two components of the blend can be observed in morphology study, all indicated the immiscibility of PLA and PCL. Tensile test showed poor mechanical properties due to the poor adhesion of the two immiscible components of the blend, and the addition of PCL did not influence the wettability of the surface of the blends as there were no significant differences in contact angle measurements.

Abstract: Electrospun poly (lactic acid)/poly (lactic acid-co-lysine) (PLA/PLL) blend were prepared, and the structures including fibers, beads and microspheres and properties of electrospun material were characterized. Viscosity, conductivity and surface tension of electrospinning solution had critical effect on the structures of the electrospun blend. The optimization process conditions of PLA/PLL electrospun fibers, beads and microspheres were confirmed and the structures, thermal properties, crystal properties, and hydrophilicity were analyzed. The results showed that the average diameter of electrospun PLA/PLL fibers was less than that of PLA under the same spinning process, and the crystallinity of spun products was affected by solution concentration, pushing speed and spinning voltage. Accurate controlling of spinning product morphology can be achieved by adjusting the formulation of electrospinning solution and spinning process. The addition of PLL into PLA could improve the hydrophilicity of electrospun PLA/PLL products.

Abstract: Glycolyzed polylactic acid (GPLA)-cured epoxidized natural rubber (ENR) is developed for use as a toughening agent for PLA resin. GPLA is obtained from chemical recycling of PLA resin by a glycolysis reaction. GPLA-cured ENR is then prepared by the crosslinking reaction of ENR with GPLA in an internal mixer. Chemical structures of the cured products are characterized by solvent fractionation and thermogravimetric analysis (TGA). The cured ENR products are blended with PLA resin, by varying the cured ENR contents from 5 to 15% wt. Mechanical properties of the blends, and their toughening mechanisms are examined. The cured ENR materials has higher efficiency in improving toughness of PLA resin, compared to uncured ENR, likely due to their rubbery network nature and higher compatibility with the PLA matrix. The incorporation of 5% wt. GPLA-cured ENR also improves elongation at break with no adverse effect on tensile strength and modulus of PLA.