The effect of maleinized linseed oil as biobased plasticizer in poly (lactic acid)-based formulations

[EN] The use of maleinized linseed oil (MLO) as a potential biobased plasticizer for poly(lactic acid) (PLA) industrial formulations with improved toughness was evaluated. MLO content varied in the range 0-20 phr (parts by weight of MLO per hundred parts by weight of PLA). Mechanical, thermal and morphological characterizations were used to assess the potential of MLO as an environmentally friendly plasticizer for PLA formulations. Dynamic mechanical thermal analysis and differential scanning calorimetry revealed anoticeable decrease in the glass transition temperature of about 6.5 degrees C compared to neat PLA. In addition, the cold crystallization process was favoured with MLO content due to the increased chain mobility that the plasticizer provides. PLA toughness was markedly improved in formulations with 5 phr MLO, while maximum elongation at break was obtained for PLA formulations plasticized with MLO content in the range 15-20 phr. Scanning electron microscopy revealed evidence of plastic deformation. Nevertheless, phase separation was detected in plasticized PLA formulations with high MLO content (above 15-20 phr MLO), which had a negative effect on overall toughness. (C) 2017 Society of Chemical IndustryThis research was funded by the Ministry of Economy and Competitiveness - MINECO, ref. MAT2014-59242-C2-1-R. The authors also thank Conselleria d'Educacio, Cultura i Esport - Generalitat Valenciana, ref. GV/2014/008, for financial support. DG-G thanks the Spanish Ministry of Education, Culture and Sports for financial support through an FPU grant (FPU13/06011).Ferri, J.; Garcia-Garcia, D.; Montanes, N.; Fenollar, O.; Balart, R. (2017). The effect of maleinized linseed oil as biobased plasticizer in poly (lactic acid)-based formulations. Polymer International. 66(6):882-891. https://doi.org/10.1002/pi.5329S88289166

DNA Adenine Methylation Is Required to Replicate Both Vibrio cholerae Chromosomes Once per Cell Cycle

DNA adenine methylation is widely used to control many DNA transactions, including replication. In Escherichia coli, methylation serves to silence newly synthesized (hemimethylated) sister origins. SeqA, a protein that binds to hemimethylated DNA, mediates the silencing, and this is necessary to restrict replication to once per cell cycle. The methylation, however, is not essential for replication initiation per se but appeared so when the origins (oriI and oriII) of the two Vibrio cholerae chromosomes were used to drive plasmid replication in E. coli. Here we show that, as in the case of E. coli, methylation is not essential for oriI when it drives chromosomal replication and is needed for once-per-cell-cycle replication in a SeqA-dependent fashion. We found that oriII also needs SeqA for once-per-cell-cycle replication and, additionally, full methylation for efficient initiator binding. The requirement for initiator binding might suffice to make methylation an essential function in V. cholerae. The structure of oriII suggests that it originated from a plasmid, but unlike plasmids, oriII makes use of methylation for once-per-cell-cycle replication, the norm for chromosomal but not plasmid replication

Mechanical recycling of polylactide, upgrading trends and combination of valorization techniques

The upcoming introduction of polylactides in the fractions of polymer waste encourages technologists to ascertain its valorization at the best quality conditions. Mechanical recycling of PLA represents one of the most cost-effective methodologies, but the recycled materials are usually directed to downgraded applications, due to the inherent thermomechanical degradation affecting its mechanical, thermal and rheological performance. In this review, the current state of mechanical recycling of PLA is reported, with special emphasis on a multi-scale comparison among different studies. Additionally, the applications of physical and chemical upgrading strategies, as well as the chances to blend and/ or composite recycled PLA are considered. Moreover, the different valorization techniques that can be combined to optimize the value of PLA goods along its life cycle are discussed. Finally, a list of different opportunities to nurture the background of the mechanical recycling of PLA is proposed, in order to contribute to the correct waste management of PLA wastes

Large-vscale hydrogen production and storage technologies: Current status and future directions

This is an accepted manuscript of an article published by Elsevier in International Journal of Hydrogen Energy on 13/11/2020, available online: https://doi.org/10.1016/j.ijhydene.2020.10.110 The accepted version of the publication may differ from the final published version.Over the past years, hydrogen has been identified as the most promising carrier of clean energy. In a world that aims to replace fossil fuels to mitigate greenhouse emissions and address other environmental concerns, hydrogen generation technologies have become a main player in the energy mix. Since hydrogen is the main working medium in fuel cells and hydrogen-based energy storage systems, integrating these systems with other renewable energy systems is becoming very feasible. For example, the coupling of wind or solar systems hydrogen fuel cells as secondary energy sources is proven to enhance grid stability and secure the reliable energy supply for all times. The current demand for clean energy is unprecedented, and it seems that hydrogen can meet such demand only when produced and stored in large quantities. This paper presents an overview of the main hydrogen production and storage technologies, along with their challenges. They are presented to help identify technologies that have sufficient potential for large-scale energy applications that rely on hydrogen. Producing hydrogen from water and fossil fuels and storing it in underground formations are the best large-scale production and storage technologies. However, the local conditions of a specific region play a key role in determining the most suited production and storage methods, and there might be a need to combine multiple strategies together to allow a significant large-scale production and storage of hydrogen.Published versio

Prediction of interfacial behaviour of single flax fibre bonded to various matrices by simulation of microdroplet test

The microdroplet test is commonly used to determine the apparent interfacial shear strength (IFSS) of fibre-reinforced microcomposites. A deeper analysis of the test outcome can provide meaningful information about the fibre/matrix interface behaviour if a predictive approach is adopted. In this study, this predictive approach was used to investigate the quality of interface for polymer drops bonded single flax fibre at the microscale. Microdroplets of five thermoplastics matrices were prepared with single flax fibres. Microbond test was performed to assess the force–displacement curves of the studied composite systems. In addition, a finite element (FE) modelling methodology was adopted to quantify the interfacial role by proposing an interfacial constitutive law including the debonding stage. The numerical sensitivity results reveal the leading role of the interfacial stiffness as well as the fibre–matrix separation displacement in triggering the debonding behaviour. In addition, the numerical responses show strong matching with experimental trends using the proposed interfacial model for a wide variety of fibre/matrix interactions. The identification of the mechanical behaviour of the considered composite system shows that the best performing system is flax fibre/PLA, allowing a maximum fibre–matrix separation of 156 µm and an interfacial stiffness of 47 GPa/mm. The worst performing system is flax fibre/PP, which has a limited fibre–matrix separation of 55 µm. This study concludes that the proposed numerical model is able to capture the interfacial shear behaviour of polymeric drops bonded to a single flax fibre, which allows its extension at the mesoscale for a given arrangement of flax fibres in the bio-based composites

Single and repeated impact behaviors of bio-sandwich structures consisting of thermoplastic face sheets and different balsa core thicknesses

This paper aims to investigate the single and repeated impact behaviors of bio-sandwich structures consisting of E-glass fiber - reinforced thermoplastic face sheets and balsa cores. Low velocity impact tests were performed using a drop-weight impact machine under a hemispherical impactor. Preliminary single low velocity impact loadings were applied to the bio-sandwich composites with different core thicknesses (namely 15 and 25 mm) so as to obtain the energy limits which were ranged from fully elastic level (10 J) to perforation energy level (80 J). Impact behaviors and damage mechanisms which occurred at both face sheets and internal parts of the balsa core were elucidated through the energy profile diagrams and force - deformation (F-D) curves under low velocity single impact loadings. Besides, low velocity repeated impact tests of the bio-sandwich structures were performed with the same impact energy levels. Repetitive impact behaviors were also investigated with F-D curves at some specific repeated impact numbers. Impact failures which occurred in the upside and bottom of composite structures were detected with digital camera. According to the experimental findings, it was concluded that the total number of impact loads under impact energy level of 10 J until perforation were 38 for the sandwich structures with 15 mm balsa core thickness while it was 98 for the sandwich structures with 25 mm balsa core thickness. Based upon the test results, the number of impacts for perforation (N-r) under smaller impact energies without testing was easily predicted with the derived equation in the form of E-i = aN(r)(b), where E-i represents the impact energy while a and b are the constants