The influence of pre-treatment of Spartium junceum L. fibres on the structure and mechanical properties of PLA biocomposites

Different chemical pre-treatments of Spartium junceum L. fibres using alkali (NaOH), nanoclay (MMT) and Citric acid (CA) with the aim of producing biodegradable composite material are discussed. As environmental requirements in processing technologies have been higher in recent years, the Polylactic acid (PLA) is used in this research as a matrix, due to its renewability, biodegradability and biocompatibility. Biocomposites are prepared by reinforcing PLA with randomly oriented, short Spartium junceum L. fibres in order to increase material strength. The effects of different pre-treatments of Spartium junceum L. fibres on the mechanical properties of final biocomposite material are examined. Fibre tenacity is studied using Vibroscop and Vibrodyn devices. Tensile strength of biocomposite material was measured on the universal electromechanical testing machine Instron 5584. The results indicate that biocomposites reinforced with fibres modified with MMT and CA show upgraded mechanical properties of the final composite material in comparison with the composite materials reinforced with referenced (nontreated) fibres. Infrared spectra of tested fibres and biocomposites were determined with Fourier transform infrared spectroscopy using Attenuated total reflection (FT-IR ATR) sampling technique and the influence of fibre modifications on the fibre/polymer interfacial bonding was investigated. The interface of Spartium/PLA composites was observed with scanning electron microscope (SEM) and it was clearly visible that biocomposites reinforced with fibres modified by MMT and CA showed better interaction of fibres and matrix.British Scholarship Trust; Croatian Science Foundatio

Une approche SVM-méta-heuristique pour laclassification : application à l'information médicale

108 p. : ill. ; 30 cmCe projet de doctorat porte sur la r esolution du problème de classifcation de donn ees médicales par une approche méta-heuristique combinée avec un classifcateur SVM. La classifcation de données est un problème important et complexe en data mining. Ce problème nécessite une approche d'optimisation pour sa réesolution efficace. Dans cette thèse, nous nous interessons a la sélection d'attributs par une approche m eta-heuristique, ce qui permettra de sélectionner un sous-ensemble d'attributs pertinents pour la phase de classifcation. Nous proposons plusieurs méthodes de sélection d'attributs, combinant des algorithmes méeta-heuristiques avec un séparateur la vaste marge (SVM)

Homochirality of beta-peptides: a significant biomimetic property of unnatural systems

Homochirality, an interesting phenomenon of life, is mainly an unresolved problem and was thought to be a property of living matter. Herein, we show that artificial beta-peptides have the tendency toward homochiral diastereoselective chain elongation. Chain-length-dependent stereochemical discrimination was investigated in the synthesis of foldamers with various side chains and secondary structures. It was found that there is a strong tendency toward the synthesis of homochiral oligomers. The size of the side chain drastically influenced the selectivity of the stereodiscriminative chain-elongation reaction. It is noteworthy that water as the co-solvent increases the selectivity. Such behavior is a novel fundamental biomimetic property of foldamers with a potential of future industrial application

Damage analysis of corroded pipelines reinforced by composite materials

AC

The thermal and thermomechanical behaviors of Spartium junceum flour reinforced polypropylene composites: effects of treatment and flour content

The effects of Spartium junceum (SJ) flour content, treatment time on the thermal and thermomechanical properties of polypropylene/Spartium junceum flour (PP/SJ) composites were studied. In order to improve the interfacial adhesion between the PP matrix and the SJ flour, SJ flour was treated with NaOH (2 wt%) for 8, 24 and 48 h at ambient temperature, respectively, and treated by vinyltrimethoxysilane (VTMS) (5 wt%). The results of thermogravimetric analysis (TGA) of SJ flour shows that the treatment improves the thermal stability of SJ flour. DSC analysis measurements illustrates that the addition of SJ flour increase the degree of crystallinity X, which indicate that the SJ flour plays a significant role in heterogeneous nucleating of PP matrix. The chemical treatments significantly affect the storage modulus of composite, where E′ increases for composites with treated flour in comparison to the untreated ones.Peer Reviewe

Rheological and mechanical properties of recycled poly(ethylene terephtalate)/high density polyethylene blends

Triphenylphosphite (TPP) has been used as a chain extender to regenerate polyethylene terephtalate (PET) and high density polyethylene (HDPE) wastes and to improve the properties of PET/HDPE system based on recycled materials. TPP incorporation in PET and HDPE showed a noticeable increase of the torque as a function of the mixing time and proved that the degradation reactions are considerably decreased. In the case of PET/ HDPE blends, the increase of the torque was strongly dependent on the composition of the homopolymers and on the time of mixing. TPP incorporation contributed to significant variations of the rheological and mechanical properties of the regenerated PET and HDPE and their blends