Researchers at the Hebrew University of Jerusalem, in Israel, have developed highly-flexible biodegradable thermoplastic elastomers that can be tailored for different soft-tissue applic-ations. They synthesised and studied poly(ethy- lene oxide)/poly(L-lactic acid), or PEO/PLA), copolymers. These polymers are based on multiblock backbones that integrate flexible, ‘soft’ PEO segments with ‘hard’, biodegradable PLA blocks.
Differential scanning calorimetry (DSC) and X-ray analyses indicate that, depending on copolymer composition, amorphous matrices, as well as materials comprising one or two crystaline phases, can be synthesised. The PEO segment prevents crystallisation of shorter PLA blocks of 12 and 17 lactoyl units. Only when the PLA blocks are sufficiently long – about 36 lactoyl units – do they crystallise.
The amorphous PEO chains can be considered as molecular springs, while the crystalline PLA blocks form strong, nonconvalent, crosslinked domains. This phase-segregated morphology provides excellent mechanical properties. The ultimate tensile strength is as high as 30 Mpa, and elongation at break levels are well above 1 000%. Even when fully hydrated, the block copolymers exhibited significant strength of 8 Mpa to 9 Mpa.
Self-cleaning solar collectors China is growing. To help cope with the growing demand for energy by the general population and industry, China is looking more and more to regenerative energy resources as a solution. The country has already become the world’s largest manufacturer of thermal solar collectors. Most of the collectors are sold and installed within China. A small number of units is exported to Europe. In Germany, thermal solar collectors made in China account for about 20% of the market.
The largest Chinese manufacturer of solar collectors is the firm Himin, in Shandong. In order to improve the effectiveness of its solar collectors, the company has turned to the Fraunhofer Institute for Solar Energy Systems, in Freiburg, and the Fraunhofer Institute for Silicate Research, in W
Edited by: Karel Smrcka
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