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

Abstract: In this paper, we have studied the hot forming process of composites made by polylactic acid (PLA) and corn straw fiber. In order to obtain the composite cushioning material with ideal density and expansion ratio, the parameters of processing was optimized. It showed that the optimum condition as follows: the hot-press time was 5min, the pressure was 15MPa and the temperature was 200°C. The structure of the composite was characterized by FTIR.

Abstract: This research aimed to study the use of curcumin as a natural dye for dyeing poly(lactic acid) and poly(ethylene terephthalate) fabrics. The study found that curcumin was dyeable on PLA and PET, providing a brilliant yellow color on the fabric. Curcumin could build up very well on PLA, while lower build up was on PET. At the same applied concentration, higher color yield was observed on the dyed PLA fabric. To achieve the same visual color yield, a significantly lower concentration of curcumin was required for PLA as compared with PET. The color shade of curcumin-dyed PLA differed from the PET analogue. A bathochromic shift of the K/S curve was found when the substrate was changed from PLA to PET. The influence of polymer media on the spectroscopic properties of curcumin could be elucidated by measuring absorbance properties of curcumin in ethyl acetate and methyl benzoate, being representatives of PLA and PET, respectively. At the same concentration, curcumin solution in ethyl acetate exhibited higher absorbance than that in methyl benzoate, corresponding to the deeper shade obtained when dyed on PLA as compared with PET. Bathochromic shift of absorbance curve was also observed when the solvent was changed from ethyl acetate to methyl benzoate.

Abstract: In this paper polylactide (PLA) nanofibers were successfully prepared via electrospinning using low toxic 1,4-dioxane and acetone as co-solvents. The morphology of nanofibers was studied by scanning electron microscopy (SEM) at the different weight ratios of co-solvent, concentrations of spinning solution, electrostatic voltages and collecting distance. Results indicate that the finer and uniform nanofibers were electrospun from the concentration of the spinning solutions at 8 wt.%, 1,4-dioxane and acetone with ratio of 40/60 (w/w), the spinning voltage at 20kV, the collecting distance at 180 mm and the extruding speed at 5 mL/h.

Abstract: Activated montmorillonite(MMT) was modified by toluene diisocyanate(TDI) and TDI-montmorillonite(TDI-MMT) was prepared. The characterization of TDI-MMT was carried out by X-ray diffraction(XRD) and fourier transform infrared spectrometry (FT-IR). The results showed that TDI had been inserted to the interlayer of MMT and the interlayer spacing of MMT increased by 0.26nm. With stannous chloride as catalyst, the biodegradable polylactide acid/TDI-montmorillonite(PLA/TDI-MMT) nanocomposites were synthesized through ring-opening polymerization of lactide in the layer of TDI-MMT by in-situ polymerization. The structure and thermal stability of nanocomposites were investigated by XRD, FT-IR and thermogravimetry (TG). Exfoliated nanocomposites were obtained as shown by XRD results. FT-IR spectra confirmed that TDI-MMT participated in the ring-opening polymerization of lactide. TG analysis indicated the decomposition temperature of nanocomposites rose and the thermal stability was improved contrast to the neat PLA. The effect of the content of TDI-MMT on the molecular weight and thermal stability of nanocomposites was studied. With the increase of the proportion of TDI-MMT, the molecular weight of resultant nanocomposites decreased and the decomposition temperature rose at the range of experiment research.

Abstract: To improve the thermal behavior of cellulose diacetate, cellulose diacetate-graft-poly(lactic acid) copolymers (CDA-g-PLAs) were synthesized by ring-opening polymerization of L-lactide using stannous octoate (Sn(Oct)2) as catalyst. The molecular structure of the copolymer was characterized by FT-IR and 1H-NMR and the thermal properties were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG-DTA). The results showed that the product was grafted copolymer of cellulose diacetate-graft-poly(lactic acid) with different side-chain structure. The thermal processing properties of CDA-g-PLAs are remarkably improved with melting temperature(Tm) about 140°C which lower than that of CDA and decomposition temperature (Td) higher than 260°C.

Abstract: Kenaf fiber was treated with alkaline to reduce lignin content and tested under Fourier transform infrared spectroscopy (FTIR). FTIR result showed that peak at 1146 cm-1 which is acetyl group of lignin was reduced in treated fiber while disappearing of carbonyl group in treated kenaf fiber at 1750cm-1 was significantly shown compared to untreated kenaf fiber. Treated fiber undergoes mechanical size decrement process by high pressure homogenizer with 500bar pressure and 60 passes. Transmission Electron microscopy (TEM) was used to determine size and distribution of fiber. Moreover, morphology of nanofiber was observed under scanning electron microscope (SEM). Nanofiber (3%, 5%, 8% and 10%) was mixed with PLA using internal mixer and then compressed with hot pressed to produce specimen for tensile test. Tensile strength and tensile modulus of nanocomposite with 10% of nanofiber increased by 30% and 85% respectively compared to pure PLA.

Abstract: The potential of using cellulose to reinforce the thermal stability of kenaf derived cellulose (KDC)/polylactic acid (PLA) composite was investigated in this study. The cellulose was derived from kenaf bast fibre which was chemically treated via chlorination and mercerisation processes. The composites with various loadings of cellulose (dry weight basis) ranging from 0% to 60% were produced by melt mixing and compression moulding. Dynamic mechanical properties namely storage modulus (E’), loss modulus (E”) and tan δ of the KDC/PLA composites and the commercial PLA were analysed and compared as a function of temperature. ESEM micrographs demonstrated that the mercerisation of kenaf fibres have successfully removed the lignin and hemicellulose, thus producing cellulose which can be observed by its rougher surface and greater size reduction than the raw fibre. The DMA results demonstrated that the storage modulus of 60% KDC/PLA composite is twice higher than the commercial PLA and the rest of the composites within a high temperature range (above 80°C). The glass transition temperatures (Tg) generated from the loss modulus curves exhibit that the peak of the loss modulus was shifted to higher temperature as the percentage of the cellulose loading was increased. These results show a better thermal stability of the composites when incorporated with the cellulose.

Abstract: This paper reported the interfacial shear strength (IFSS) between kenaf fibre (KF) and polylactic acid (PLA) matrix which was measured using microbond tests device. The value of IFSS obtained in PLA-KF is comparable to other polymer with natural fibre reinforcements. The properties of single kenaf fibre was determined from tensile tests and also described in this paper. From single kenaf fibre properties, various mechanical properties can be estimated for various applications.

Abstract: One best way to harness the petroleum-based solid wastes is to develop biodegradable materials. Among which, PLA is the most important one, because it is made from renewable plant. But Poly(lactic acid) (PLA) is brittle and low impact resistance. The cellulose nanowhiskers are about 5-40 nm in diameter and the length can be from 100 nm to several micrometers depending on the source of cellulose and the processing technology. The cellulose nanowhiskers can act as efficient reinforcement because of the high aspect ratios, important surface areas and high modulus. The celluloses nanowhiskers are hydrophilic because of the abundant exposed hydroxyl (-OH) groups and PLA is hydrophobic. So we added the low molecular weight polymeric-poly (ethylene glycol) (PEG) to improve compatibility between PLA matrix and the cellulose nanowhiskers. The PLA/cellulose nanowhiskers composites were prepared by casting solution. The tensile strength and the elongation rate of the composites improved 56.7% and 48% comparing with the PLA/cellulose whiskers composites. The thermo gravimetric analysis indicated that the thermal decomposition of PLA/cellulose nanowhiskers/PEG composites include only one stage. The pictures of SEM showed the fracture morphology of the different kind of the composites. The structure of the PLA/cellulose nanowhiskers/PEG composites were characterized by AFM, which showed that the cellulose nanowhiskers dispersed evenly in the PLA matrix.

Abstract: The modified rice straw fibers (MRSF) were prepared by suspension polymerization technique of butyl acrylate (BA) monomer and rice straw fibers (RSF) in water solution. FTIR test indicated that PBA was coated and absorbed on RSF.The biodegradable composites were prepared with the MRSF and poly(lactic acid) (PLA) by HAAKE rheometer. Mechanical properties showed that the tensile strength of PLA/MRSF composites were (W (%) =7.98%) increased by 6 MPa compared with blank sample. The possible reason was that the good interfacial adhesion between PLA and MRSF, which was demonstrated by SEM.