Search

Circular design and fabrication of PLA nanofiber filters from PLA wastes for effective oil decontamination and oil/water separation.

A process for sizing down and functionalizing commercial polylactide (PLA) resin is developed by alcoholysis with 1,4-butanediol (BDO) and propylene glycol (PG) to medium-sized PLA-based diols, with lower cost than a bottom-up synthesis process. These are subsequently used as polyols in preparing polyurethanes (PU) by reacting with 1,6-diisocyanatohexane (HDI). The PLA-based PU has an excellent elongation at break of 487%. The products are suitable as toughening agents for brittle PLA resin due to their highly elastic properties and high compatibility with PLA. The PU products are blended with PLA resin at various compositions, and their physical and mechanical properties and shape recovery are examined. The tensile tests showed enhancements in elongation at break up to 160% with low modulus. The fracture morphology and FTIR results confirm that the blends show strong interfacial interaction and adhesion between the PLA-based PU disperse phase and the PLA matrix. The PLA/PU blends exhibit a high shape recovery efficiency, and their recovery mechanisms are identified. These flexible PLA/PU blends are promising for various applications where bio-compatibility/degradability and high ductility are required, especially as filaments for 3D bio-printing.

Curable precursors for production of thermosetting (co)polyesters are developed based on poly(butylene adipate) (PBA), poly(ethylene terephthalate), and poly(lactic acid) (PLA). The precursors are prepared from methacrylation of their hydroxyl-terminated oligomers. These include commercial HO-capped PBA prepolymer (HO-PBA), and bis-2-hydroxyethyl terephthalate (BHET) and glycolized PLA (GPLA), which are obtained from glycolysis reactions of their post-consumer products and original resin. The optimal conditions for methacrylation of each prepolymer, i.e., molar ratios of prepolymer to methacrylic anhydride (MAAH), temperature and time, are examined. The most efficient conditions are 1:4/120 °C/3 h (HO-PBA), 1:2.5/120 °C/2 h (BHET), and 1:4/140 °C/3 h (GPLA), respectively. These conditions are justified, where the highest degree of substitution and double bond content are obtained without self-curing side reaction. The resulting methacrylated precursors from HO-PBA and BHET are isothermally cured faster than those of GPLA. Thermosetting copolyesters developed from binary mixtures of the precursors possess tunable thermal stability, and physical and mechanical properties. The degradable copolyesters can be applied in various applications, especially in packaging and agricultural fields.

Nanofibers of polylactide (PLA)/poly(vinylpyrrolidone) (PVP) blends, loaded with TiO2 nanoparticles, have been prepared by an electrospinning method. The electrospun fiber mats were characterized by ATR-FTIR, X-ray diffraction (XRD), SEM, EDX, and UV-visible spectroscopy to examine structures, functional groups, crystallinity, surface morphology, and UV absorptivity. It is clearly observed that TiO2 particles are embedded on the filaments. All PLA-based spun fibers are completely amorphous in nature. The surface morphology of those blended with PVP is smoother and more uniform than the corresponding samples without PVP. Neat PLA fibers show a UV absorption band at around 200 nm, whereas the fibers loaded with TiO2 nanoparticles show an additional absorption band covering the 200–380-nm region. Photo-degradation of the fiber samples are conducted in phosphate buffer solution (PBS) under UVA light. The results indicate that the PVP component dissolves into the PBS solution, and the PLA matrix degrades as a function of time. The fibers are then applied as a catalytic system for epoxidation of unsaturated sunflower oil (SFO), for use as additives or plasticizers for biopolymers, employing a performic acid oxidizing agent. The fibers, especially those containing PVP, can effectively enhance the epoxidation yield of oils with a slow rate of undesirable side reactions, which break ester bonds of triglycerides to generate free fatty acids.

Nanofibers of poly(L-lactide-co-DL-Lactide) (PDLLAx) copolymers with DL-lactate (DLLA) contents of 0, 2.5, 7.5, and 50%, which exhibit strong structure/properties correlation, were fabricated by electrospinning. Effect of the copolymer structure and electrospinning conditions on morphology and properties of the fibers were examined by SEM, DSC, XRD, and tensile measurements. Bead-free fibers of PDLLAx prepared from a DMF/CHCl3 mixed solvent are roughly 10-times smaller in size (600–800 nm), with lower degree of surface porosity, compared to those of CHCl3. When CHCl3 is employed, an increase in size (2.4–5.5 μm) and surface porosity (0–45%) with relative humidity value is observed in crystallizable copolymers, whereas an amorphous copolymer shows a reverse trend. Thermal properties and chain arrangements of the electrospun fibers are critically affected by DLLA content of the copolymers and electrospinning conditions, as a result from interplay between intermolecular and intramolecular hydrogen bonding. Contents of crystalline domains and “physical crosslinks” generated from DL lactate segments are proposed as the origin of this phenomenon. Fiber mats of PDLLA with 50% DLLA content show a large improvement in all aspects of mechanical properties, which are suitable for various biomedical applications. POLYM. ENG. SCI., 54:472–480, 2014. © 2013 Society of Plastics Engineers

Curable precursors are prepared from chemical recycling of degradable polylactic acid (PLA) for development of aliphatic polyester thermoset materials. PLA resin (NatureWork 4042D) was de-polymerized via glycolysis under various conditions to produce PLA glycolysates (GlyPLAs), whose chain-ends mainly consist of hydroxyl groups with $$\bar{M}_{n}$$ ranging from 3,600 to 17,000 g/mol. Unsaturated double bonds (DB) were introduced into GlyPLA structures by end-capping with methacrylic anhydride to generate curable LA-precursors. The end-capping efficiency is strongly dependent on the molecular weight of GlyPLAs, where smaller-sized glycolysates produce LA-precursors with higher DB content. Curing behaviors of the precursors are thoroughly examined. DSC and FTIR results show that curing reactions at 140 °C are completed after 2 h for all samples. Results on gel fraction indicate that LA-precursor with $$\bar{M}_{n}$$ ~ 3,600 g/mol is the most effective candidate for producing network products with high crosslink density.

A series of 0-3 composites of lead zirconate titanate (PZT) and nylon77 was prepared with PZT volume fractions between 0.1 and 0.6 using the combined method of solvent casting and hot pressing. Depending upon the volume fraction of PZT, the relative permittivities of the composites were found to be in the range of 200–2000 when measured at the highest practically possible temperature of 200°C. As PZT volume fraction increases, both the relative permittivity and the piezoelectric constant d33 increase. The best combination of electrical properties and flexibility was obtained in 0.5 PZT volume fraction composites. At this composition, the remanent polarization Pr of composites was up to 1000 mC/m2 at the applied electric field of 40 MV/m and it increased with an increase in temperature. The highest piezoelectric strain coefficient d33 was obtained at 17 pC/N in 0.6 PZT volume fraction composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Naproxen (NPX) drug-loaded magnetic nanoparticles (MNPs) have been prepared in a one-step process utilizing a biocompatible polylactide-grafted-chitosan copolymer. The copolymer serves both as a NPX drug carrier as well as a polymeric surfactant for the synthesis of MNPs without the use of any additional surfactant. Highly stable MNPs with high magnetization in the form of maghemite (γ-Fe2O3) are prepared in aqueous media. Effects of preparation conditions on structures and properties of the copolymer-coated and drug-loaded MNPs are investigated by employing particle size and zeta potential measurements, transmission electron microscopy, vibrating sample magnetometer, X-ray diffraction, Fourier-transform infrared, nuclear magnetic resonance, and confocal Raman spectroscopy. The results show that average particle size (150–300 nm), coating efficiency, and coating structures of the resulting MNPs materials are strongly dependent on MNP/copolymer and MNP/NPX ratios in feed. It is also observed that NPX acts as co-surfactant in the drug-loading process, resulting in different encapsulating structures with the variation in the MNP/copolymer and MNP/NPX ratios. Properties of the MNPs materials can be further optimized for use in specific biomedical applications.