Poly(ethylene oxide) (PEO) based materials are widely considered as promising candidates of polymer hosts in solid-state electrolytes for high energy density secondary lithium batteries. They have several specific advantages such as high safety, easy fabrication, low cost, high energy density, good electrochemical stability, and excellent compatibility with lithium salts. However, the typical linear PEO does not meet the production requirement because of its insufficient ionic conductivity due to the high crystallinity of the ethylene oxide (EO) chains, which can restrain the ionic transition due to the stiff structure especially at low temperature. Scientists have explored different approaches to reduce the crystallinity and hence to improve the ionic conductivity of PEO-based electrolytes, including blending, modifying and making PEO derivatives. This review is focused on surveying the recent developments and issues concerning PEO-based electrolytes for lithium-ion batteries.

Poly(ethylene oxide)-based electrolytes for lithium-ion batteries

Evolution of the bioplastics industry has changed directions dramatically since the early 1990s. The latest generation is moving toward durable bioplastics having high biobased content. The main objective is to replace “fossil carbon” with “renewable carbon”, a holistic strategy to mitigate climate change by minimizing the environmental impact of a product throughout its life cycle. Durable bioplastics is desired for multiuse long-term application in automotive, electronics and other industries. One necessary requirement for them is to be both tough and strong, yet the two attributes are often mutually exclusive. Does this mean a biobased and biodegradable polymer as polylactic acid (PLA) with its high strength but low toughness cannot be adopted for durable applications? Well, not exactly; this is where the concept of tailoring the properties of PLA to achieve stiffness–toughness balance along with acceptable heat resistance comes into play. In this perspective, we summarize the recent research progress ...

http://pubs.acs.org/doi/pdf/10.1021/acssuschemeng.6b00321

Perspective on Polylactic Acid (PLA) based Sustainable Materials for Durable Applications: Focus on Toughness and Heat Resistance

Polylactic acid (PLA), one of the well-known biodegradable polyesters, has been studied extensively for tissue engineering and drug delivery systems, and it was also used widely in human medicine. A new method to synthesize PLA (ring-opening polymerization), which allowed the economical production of a high molecular weight PLA polymer, broad- ened its applications, and this processing would be a potential substitute for petroleum-based products. This review described the principles of the polymerization reactions of PLA and, then, outlined the various materials properties affect- ing the performance of PLA polymer, such as rheological, mechanical, thermal, and barrier properties as well as the pro- cessing technologies which were used to fabricate products based on PLA. In addition, the biodegradation processes of products which were shaped from PLA were discussed and reviewed. The potential applications of PLA in the medical fields, such as tissue engineering, wound management, drugs delivery, and orthopedic devices, were also highlighted.

http://www.expresspolymlett.com/letolt.php?file=EPL-0005820&mi=c

Properties and medical applications of polylactic acid: A review

Polyaniline (PANi) based electrode materials for energy storage and conversion

Calcium carbonate nano and micro-particles have a large number of industrial applications due to their beneficial properties such as high porosity, high surface area to volume ratio, non-toxicity and biocompatibility towards bodily fluids. Consequently, there has been significant research to deliver easy ways of synthesising nano and micro-sized calcium carbonate particles at specific sizes, polymorphs and morphologies. A majority of their synthesis approaches are based on either the biomimetic or the CO2 bubbling methods. This review paper describes these methods, and the effects of experimental parameters such as additive types and concentration, pH, temperature, [Ca2+] : [CO32−] ratio, solvent ratio, mixing mode and agitation time on the properties of the particles produced. The current and potential uses of calcium carbonate particles in areas such as material filling, biomedical, environmental and the food industry have also been discussed.

Synthesis of micro and nano-sized calcium carbonate particles and their applications

The poly( L -lactic acid) (PLLA) filled with nanometer calcium carbonate (nano-CaCO3) composites were prepared by means of a twin-screw extruder in the present paper. The nano-CaCO3 surface was treated with stearate. The crystalline properties of PLLA/nano-CaCO3 composites were measured using a differential scanning calorimeter, to identify the influence of the nanometer particle content on the crystalline properties. The results showed that the crystallization onset temperature, crystallization temperature and crystallization end temperature as well as the crystalline degree of the composites were obvious higher than those of the unfilled PLLA resin when the particle weight fraction (ϕf) was 1%, then they varied slightly. While the crystallization temperature interval decreased slightly. The improvement of crystallinity degree might be attributed to the heterogeneous nucleation of the nano-CaCO3 in the matrix.

Crystalline properties of poly(L-lactic acid) composites filled with nanometer calcium carbonate

The poor electronic conductivity and low lithium ion diffusion rate of a LiFePO4 cathode material are the two major obstacles for its commercial applications in the power lithium ion batteries. This article utilized an electroactive and ion conductive copolymer, polyaniline–poly(ethylene glycol) (PANI–PEG), to modify carbon-LiFePO4 (cLFP) by a facile in situ chemical copolymerization method. The structure and morphology of the cLFP/PANI–PEG composite were confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Compared with a cLFP/PANI composite, the cLFP/PANI–PEG composite exhibited a more uniform and full polymer coating layer. Furthermore, this cLFP/PANI–PEG cathode material exhibits excellent cyclic stability (95.7% capacity retention after 100 cycles at 0.1 C) and high rate capability (125.3 mA h g−1 at 5 C) as the PANI–PEG copolymer coating layer facilitated electron and ion transport within the electrode. Electrochemical impedance spectroscopy (EIS) proved that the lithium ion diffusion in the cLFP/PANI–PEG composite was increased significantly by one order of magnitude compared with cLFP, indicating its possibility to be served as a cathode material for high-performance lithium ion batteries.

PANI–PEG copolymer modified LiFePO4 as a cathode material for high-performance lithium ion batteries

In this study, a powder metallurgy processing technique combined with rapid microwave sintering was used to synthesise carbon nanotubes (CNTs) filled AZ61 magnesium alloy composites under ambient conditions, without recourse to any secondary process. In order to determine the appropriate amount of CNTs for taking full advantage of the AZ61/CNTs composite, a powder mixture of the CNTs, in varying volume fractions of 1–3%, and the AZ61 alloy was prepared through a mechanical milling process. The optimized milling intensity allowed for reducing the powder size for effective microwave absorption, and thus improved the dispersion of the CNTs in the Mg alloy matrix without reducing the structural integrity of CNTs. In addition to the incorporation of the CNTs with the dual role of mechanical reinforcement and microwave susceptor, microwave sintering was achieved in only 8 min by using a synergetic combination of graphite and silicon carbide as microwave susceptors in a microwave furnace. The sintered samples, whose porosity ranged between 4 and 6%, were characterised for microstructural, hardness, compressive and fracture properties. The results of hardness and compression tests indicated that these properties of all the composites were significantly improved compared to the monolithic samples. The highest microhardness value (∼105% increment) was recorded for the composite with 3.0% volume fraction of CNTs, while the composite sample with 1.0% volume fraction of CNTs had the highest ultimate compressive yield strength and 0.2% offset yield strength with approximate increments of 59% and 127%, respectively. The failure mechanisms of the composites as compared with the monolithic samples were discussed.

Rapid microwave sintering of carbon nanotube-filled AZ61 magnesium alloy composites

The flame retardant and mechanical properties of polypropylene (PP) composites filled with microencapsulated red phosphorus (MRP) and magnesium hydrate (Mg(OH) 2 )/aluminum hydrate (Al(OH) 3 ) were measured. It was found that the synergistic effects between the MRP and Mg(OH) 2 /Al(OH) 3 on the flame retardant and tensile properties of the composites were significant. The limit oxygen index and smoke density rank of the composites increased nonlinearly while the horizontal combustibility rate decreased nonlinearly with increasing the MRP weight fraction. The Young modulus and the tensile elongation at break increased while the tensile yield strength and tensile fracture strength decreased slightly with increasing the MRP weight fraction. Both the V-notched Izod and Charpy impact strength increased with increasing the MRP weight fraction. Moreover, the tensile yield strength of the composites estimated using an equation published previously was roughly close to the measured data.

Chi-Pong Tsui

Papers

Crystalline properties of poly(L-lactic acid) composites filled with nanometer calcium carbonate

PANI–PEG copolymer modified LiFePO4 as a cathode material for high-performance lithium ion batteries

Rapid microwave sintering of carbon nanotube-filled AZ61 magnesium alloy composites

Mechanical properties and flame-retardant of PP/MRP/Mg(OH)2/Al(OH)3 composites

Finite element analysis of polymer composites filled by interphase coated particles