PLA composites: From production to properties

A facile approach for coating red fluoride phosphors with a moisture-resistant alkyl phosphate layer with a thickness of 50–100 nm is reported. K2SiF6:Mn4+ particles were prepared by co-precipitation and then coated by esterification of P2O5 with alcohols (methanol, ethanol, and isopropanol). This route was adopted to encapsulate the prepared phosphors using transition-metal ions as cross-linkers between the alkyl phosphate moieties. The coated phosphor particles exhibited a high water tolerance and retained approximately 87 % of their initial external quantum efficiency after aging under high-humidity (85 %) and high-temperature (85 °C) conditions for one month. Warm white-light-emitting diodes that consisted of blue InGaN chips, the prepared K2SiF6:Mn4+ phosphors, and either yellow Y3Al5O12:Ce3+ phosphors or green β-SiAlON: Eu2+ phosphors showed excellent color rendition.

Waterproof Alkyl Phosphate Coated Fluoride Phosphors for Optoelectronic Materials

Poly(lactic acid) (PLA) is regarded as one of the most promising biobased and biodegradable polymers due its various advantages including high mechanical strength, easy processability, high melting temperature, renewability, biodegradability, and biocompatibility. However, the inherent brittleness significantly restricts its wide application. Therefore, toughening PLA has attracted more and more attention and various materials have been used to blend with PLA for toughening. Considering the fact that the use of petroleum-based species to toughen PLA would partially sacrifice the sustainability, various renewable polymers have recently been employed to toughen PLA. A series of important achievements have been obtained but not reviewed. This article aims to review progress in toughening PLA with renewable polymers. The toughening theories and compatibilization strategies are also briefly introduced.

Progress in Toughening Poly(Lactic Acid) with Renewable Polymers

In recent years, there has been a growing interest in the study of particle swarm optimization (PSO) in dynamic environments. This paper presents a new PSO model, called PSO with composite particles (PSO-CP), to address dynamic optimization problems. PSO-CP partitions the swarm into a set of composite particles based on their similarity using a “worst first” principle. Inspired by the composite particle phenomenon in physics, the elementary members in each composite particle interact via a velocity-anisotropic reflection scheme to integrate valuable information for effectively and rapidly finding the promising optima in the search space. Each composite particle maintains the diversity by a scattering operator. In addition, an integral movement strategy is introduced to promote the swarm diversity. Experiments on a typical dynamic test benchmark problem provide a guideline for setting the involved parameters and show that PSO-CP is efficient in comparison with several state-of-the-art PSO algorithms for dynamic optimization problems.

/pdf/particle-swarm-optimization-with-composite-particles-in-3yvos11m6j.pdf

Particle Swarm Optimization With Composite Particles in Dynamic Environments

Thermal, mechanical and rheological properties of polylactide toughened by expoxidized natural rubber

Natural rubber grafted with poly(butyl acrylate) (NR-g-PBA) in an attempt to toughen polylactide (PLA) was prepared by grafting butyl acrylate onto natural rubber (NR) through emulsion polymerization. The purified NR-g-PBA was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. NR-g-PBA/PLA blend and NR/PLA blend were prepared with a Haake internal melt mixer. The morphology and mechanical properties of the blends were investigated as a function of rubber content. Observations by scanning electron microscopy showed that the spherical-particle-dispersed phase appearing in the NR/PLA blend was not found in the NR-g-PBA/PLA blend, which showed that NR grafted with PBA is compatible with PLA, and accounted for the efficient toughening effect on PLA. The elongation at break and the impact strength were significantly improved with an increase in NR-g-PBA content. The thermal stability of PLA decreased when blended with NR but was retained with NR-g-PBA. Copyright © 2011 Society of Chemical Industry

Toughening of polylactide with natural rubber grafted with poly(butyl acrylate)

Poly(N-isopropylacrylamide-co-acrylic acid) (poly(NIPAM-co-AA)) microgels with different copolymer compositions were prepared through soap-free emulsion polymerization at 80°C, and 2, 2'-azobisisobutyronitrile (AIBN) was used as initiator. Scanning electron microscope (SEM) characterization shows that the prepared microgels are regular and smooth and not easy to distort. Result of 1 H-NMR characterization shows that with increasing of the initial concentration of AA (AA in feed), the AA content in polymer chains increases. The thermal response of microgels latex was investigated by UV-3010 spectrophometer through detecting the transmittance of the latex at different temperature in the range of 190-900 nm. The thermal response of the poly(NIPAM-co-AA) microgels was tested by dynamic light scattering (DLS). The results show that with the increase of AA content in polymer chains, the low critical solution temperature (LCST) of microgels latex first decreases and then increases. Still, with increasing of AA in poly(NIPAM-co-AA) microgels, the LCST of microgels first increases and then decreases. The basic reasons causing the changes of LCST of microgels latex and microgels are interpreted clearly in this article from the perspective of hydrogen bonding interaction.

Preparation and thermal response behavior of poly(N‐isopropylacrylamide‐co‐a crylic acid) microgels via soap‐free emulsion polymerization based on AIBN initiator

A novel method to prepare organic/inorganic composite particles, i.e. poly(methyl methacrylate)/CaCO3/SiO2
three-component composite particles, using emulsion polymerization of methyl methacrylate with sodium lauryl sulfate as a surfactant in an aqueous medium was reported. CaCO3/SiO2
two-component inorganic composite particles were obtained firstly by the reaction between Na2CO3 and CaCl2 in porous silica (submicrometer size) aqueous sol and the specific surface area of the particles was measured by the Brunauer–Emmett–Teller (BET) method. The results show that the BET specific surface area of the CaCO3/SiO2
composite particle is much smaller than that of the silica particle, indicating that CaCO3 particles were adsorbed by porous silica and that two-component inorganic composite particles were formed. Before copolymerization with methyl methacrylate, the inorganic composite particles were coated with a modifying agent through covalent attachment. The chemical structures of the poly(methyl methacrylate)/CaCO3/SiO2
composite particles obtained were characterized by Fourier transform IR spectroscopy and thermogravimetric analysis. The results show that the surface of the modified inorganic particles is grafted by the methyl methacrylate molecules and that the grafting percentage is about 15.2%.

Preparation of poly(methyl methacrylate)/CaCO 3 /SiO 2 composite particles via emulsion polymerization

Diblock copolymers of poly(L-lactide)-block-poly(methyl methacrylate) (PLLA-b-PMMA) were synthesized through a sequential two-step strategy, which combines ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP), using a bifunctional initiator, 2,2,2-trichloroethanol. The trichloro-terminated poly(L-lactide) (PLLA-Cl) with high molecular weight (Mn,GPC = 1–12 × 104 g/mol) was presynthesized through bulk ROP of L-lactide (L-LA), initiated by the hydroxyl group of the double-headed initiator, with tin(II) octoate (Sn(Oct)2) as catalyst. The second segment of the block copolymer was synthesized by the ATRP of methyl methacrylate (MMA), with PLLA-Cl as macroinitiator and CuCl/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) as catalyst, and dimethyl sulfoxide (DMSO) was chosen as reaction medium due to the poor solubility of the macroinitiator in conventional solvents at the reaction temperature. The trichloroethoxyl terminal group of the macroinitiator was confirmed by Fourier transform infrared spectroscopy (FTIR) and 1H-NMR spectroscopy. The comprehensive results from GPC, FTIR, 1H-NMR analysis indicate that diblock copolymers PLLA-b-PMMA (Mn,GPC = 5–13 × 104 g/mol) with desired molecular composition were obtained by changing the molar ratio of monomer/initiator. DSC, XRD, and TG analyses establish that the crystallization of copolymers is inhibited with the introduction of PMMA segment, which will be beneficial to ameliorating the brittleness, and furthermore, to improving the thermal performance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis and characterization of AB‐type copolymers poly(L‐lactide)‐block‐poly(methyl methacrylate) via a convenient route combining ROP and ATRP from a dual initiator

Poly(L-lactide) (PLLA) films were exposed to ultraviolet (UV) light (254 nm) and water bath of 60°C and 80°C. The limiting viscosity ([η]) of PLLA decreased from initial 187.4 dl/g to 42.2 dl/g after UV irradiation, and to 33.3 dl/g after soaking in 80°C water for 40 h, while the [η] of PLLA exposed to 60°C water remained at 115.6 dl/g after 40 h. Compared with the original PLLA, the degraded PLLA was bimodal in the GPC profile. FTIR analysis showed that the chain scission of PLLA acted by water molecules resulted in a C=C structure.

Long Jiang

Papers

Toughening of polylactide with natural rubber grafted with poly(butyl acrylate)

Preparation and thermal response behavior of poly(N‐isopropylacrylamide‐co‐a crylic acid) microgels via soap‐free emulsion polymerization based on AIBN initiator

Preparation of poly(methyl methacrylate)/CaCO 3 /SiO 2 composite particles via emulsion polymerization

Synthesis and characterization of AB‐type copolymers poly(L‐lactide)‐block‐poly(methyl methacrylate) via a convenient route combining ROP and ATRP from a dual initiator

Degradation of Poly(L-lactide) Films under Ultraviolet Irradiation and Water Bath