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In this study, plasticization of polylactide (PLA) with PEG-PPG-PEG triblock copolymers was examined. Two different copolymers were utilized, with molecular weight of 1100 and 1900 g mol À1 , and with PEG contents of 10 and 50 wt %, respectively. A PPG plasticizer with molecular weight of 1000 g mol À1 , close to that of PPG block in the copolymers, was also used for comparison. Melt blends containing 10 and 15 wt % of the plasticizers were prepared. Thermal properties, mechanical properties, and structure of quenched and annealed films of the blends were studied. The crystallization driven phase separation occurred in all the annealed blends but led to different structures depending on the plasticizer used. Distinct inclusions of the plasticizer were visible under the scanning electron microscope only in PLA with PPG but not in the blends of PLA with the copolymers. The drawability of the plasticized systems was improved when compared with neat PLA. In the quenched and annealed blends, elongations at break at the level of 5 and 0.7, respectively, were reached.

Polylactide (PLA), a main representative of biodegradable and made from renewable resources polymers, is surprisingly brittle at ambient temperature. In this article it is investigated how to increase its toughness by a strategy called ''rubber toughening'' using poly(1,4cis-isoprene), a major component of natural rubber, which is immiscible with PLA, could be well dispersed in PLA matrix and is biodegradable. Immiscible blends of PLA with poly(1,4-cis-isoprene) were prepared by melt blending and their properties were studied and optimized. Incorporation of as low as 5 wt % of rubber increased the strain at break of compression molded film during uniaxial drawing, and also improved its tensile impact strength by 80%. The complex mechanism of plastic deformation in the blends leading to improvement of ductility and toughness was revealed. The rubbery particles initiated crazing at the early stages of deformation, as evidenced by transmission and scanning electron microscopy and also by small angle X-ray scattering. Crazing was immediately followed by cavitation inside rubber particles, which further promoted shear yielding of PLA. The sequence of those mechanisms was proven by microscopic investigation. All three elementary mechanisms acting in the sequence indicated are responsible for surprisingly efficient toughening of PLA by a major component of natural rubber.

In the paper, experimental operation of a wireless transmission link employing identical LEDs both as transmitter and receiver is demonstrated. The transmitted signal is a simple, two-level pulse amplitude modulation. Digital equalization at the receiver is applied to overcome the bandwidth limitation of the link. Transmission throughput exceeding 100 Mbit/s is reported, even if the receiving red LED operates in the photovoltaic mode.

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Hematopoietic stem cells (HSCs) are extremely useful in treating a wide range of diseases and have a variety of useful research applications. However, the routinely generated low in vitro concentrations of HSCs from current bioreactor manufacturing systems has been a hindrance to the full-scale application of these essential cellular materials. This has made the search for novel bioreactor systems for high-concentration HSC production a major research endeavour. This review addresses process challenges in relation to bioreactor development and optimisation for high-density HSC production under effective monitoring of essential culture parameters, such as pH, dissolved oxygen and nutrient uptake. It discusses different process strategies and bioreactor configurations for HSCs production from a commercial viability perspective, and also discusses recent advances in the field.