Search results for "plastics"
showing 10 items of 2724 documents
RADIATION-CLEAVABLE MICROPARTICLE CHAPERONES FOR DURABILITY-CONTROLLED NANOCOMPOSITE BIOPLASTICS
2012
Polysaccharide micro/nanoparticles, incorporating stabilizers (natural antioxidants), prodegrading agents (such as enzymes or metal oxide nanoparticles) or other active ingredients, can be considered ideal chaperones to introduce various and heterogeneous substances into polysaccharide films in virtue of their structural affinity. The possibility of obtaining biodegradable and colloidally stable nanoparticles from xyloglucan has been here investigated. Xyloglucans are a major class of structural polysaccharides found in the primary cell walls of higher plants. They are particularly interesting raw materials for their excellent film forming properties, thermal stability and hydroxyl rich, hi…
Structural and Thermal Properties of Ethylene-Norbornene Copolymers Obtained Using Vanadium Homogeneous and SIL Catalysts
2020
The series of ethylene-norbornene (E-NB) copolymers was obtained using different vanadium homogeneous and supported ionic liquid (SIL) catalyst systems. The 13C and 1H NMR (carbon and proton nuclear magnetic resonance spectroscopy) together with differential scanning calorimetry (DSC) were applied to determine the composition of copolymers such as comonomer incorporation (CNB), monomer dispersity (MD), monomer reactivity ratio (re), sequence length of ethylene (le) and tetrad microblock distributions. The relation between the type of catalyst, reaction conditions and on the other hand, the copolymer microstructure, chain termination reaction analyzed by the type of unsaturation are discusse…
Photo-oxidation behaviour of polyethylene/polyamide 6 blends filled with organomodified clay: Improvement of the photo-resistance through morphology …
2010
Abstract The impact of small amounts of organomodified clay (OMMT) on the photo-degradation behaviour of two blends obtained by mixing either low-density polyethylene (LDPE) or high density polyethylene (HDPE) with polyamide 6 (PA6) (LDPE/PA6 and HDPE/PA6 75/25 wt-%) was studied. The complex photo-degradation behaviour was followed by monitoring the main physical–mechanical properties of the blends. In particular, mechanical and spectroscopic tests were performed in conditions of accelerated artificial aging. An accurate mechanical and morphological characterization was previously carried out. The presence of the OMMT promotes the unexpected formation of a co-continuous morphology for the H…
Morphology of nanocomposites from ethylene-acrylic acid copolymers
2005
AbstractNew nanocomposites have been prepared by melt-compounding from commercial ethylene-acrylic acid copolymers (EAA) of different molar mass, molecular structure (branched or linear) and AA concentration, and a Zn-ionomer, with three commercial clays containing different proportions of the same organic modifier (dimethyldi(hydrogenated tallow)ammonium ion). Their morphology has been preliminarily investigated by X-ray scattering and transmission electron microscopy. The nanocomposites showed disordered intercalated morphology, with an expansion of the average gallery height, which appears to depend quite strongly on the molecular architecture of the EAA, whereas the other investigated v…
UV-stabilisation of polystyrene-based nanocomposites provided by polyhedral oligomeric silsesquioxanes (POSS)
2012
Abstract The photo-ageing behaviour of Polyhedral Oligomeric SilSequioxane (POSS)-polystyrene (PS) nanocomposites has been investigated for the first time. POSS having different inorganic framework and pendant organic groups have been used in the PS nanocomposite preparation and the formulated films were subjected to accelerated weathering. Compared to pristine PS, the POSS-containing PS developed a lower level of carbonyl and hydroxyl groups as a function of the exposure time, indicating a significantly improved resistance of the nanocomposites to photo-degradation. The results suggest that all of the investigated POSS molecules play a protective role and may extend the in-use lifetime of …
Study of polyethylene nanocomposites with polyhedral oligomeric silsesquioxane nanofillers—from structural characteristics to mechanical properties a…
2017
High-density polyethylene (HDPE) and low-density polyethylene (LDPE) nanocomposites filled with octakis({alkyl}dimethylsiloxy)octasilsesquioxanes (POSS) were prepared by the melt blending method. The effects of the structure and the content of POSS nanofillers on free-volume properties and structural characteristics of nanocomposites were investigated by the positron annihilation lifetime spectroscopy (PALS) and X-ray diffraction methods: wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). Incorporation of POSS nanofillers into polyethylene matrices modified the arrangement of the polymer chains and affected the size and number of free-volume holes in nanocomposites.…
Incorporation of Silica Nanospherical Particles in Epoxy–Amine Crosslinked Materials II. Dynamic Mechanical Measurements of Epoxy Matrix-Silica Nanoc…
2009
The mechanical strengths of epoxy composites reinforced with silica nanospheres, unfunctionalised or functionalised with either amine or epoxy groups, increase up to a proportion of 5 wt.% of filler, as reflected in a study of the shear storage modulus carried out in dynamic mechanical analysis. This improvement is observed in both glassy and rubbery states, moderately affecting the glass transition temperature of the material. From this percentage of strengthening substance the mechanical properties begin to deteriorate, but keeping (up to 10 wt.% of strengthening material), a greater storage modulus in shear than that of the pristine epoxy resin. A trend can be discerned as the percentag…
Dynamic Mechanical Measurements of Epoxy Matrix-Silica Nanocomposites II
2009
The mechanical properties of epoxy-silica nanocomposites have been studied; the silica nanosphere fillers used were un-functionalised, functionalised with amine, with epoxy, or a mixture of both kinds. Dynamic mechanical analysis measurements revealed an increase in the shear storage modulus, for all samples with a filler content of 3–5%. Improvements were observed in the glassy and rubbery states, without affecting the glass transition temperature of the materials. Above these strengthening percentages, the mechanical properties began to deteriorate, but in all cases they remained superior to those of the pristine epoxy resin. For low strengthening percentages, samples reinforced with bot…
Morphology, flexural, and thermal properties of sepiolite modified epoxy resins with different curing agents
2006
A bisphenol A-based epoxy resin was modified with 5 wt% organically modified sepiolite (Pangel B40) and thermally cured using two different curing agents: an aliphatic diamine (Jeffamine D230, D230) and a cycloaliphatic diamine (3DCM). The morphology of the cured materials was established by scanning and transmission electron microscopy analysis. The thermal stability, thermo-mechanical properties, and flexural behaviour of the sepiolite-modified matrices were evaluated and compared with the corresponding neat matrix. The initial thermal decomposition temperature did not change with the addition of sepiolite. The flexural modulus of the epoxy matrix slightly increases by the incorporation o…
EVA-montmorillonite nanocomposites: effect of processing condition
2004
The aim of this study is to examine the effect of the compounding apparatus and of processing conditions on the properties of an organoclay-poly[ethylene-co-(vinyl acetate)] (EVA) nanocomposite. The filled materials were prepared using either a discontinuous batch mixer, a single screw extruder, a counter rotating intermeshing twin-screw compounder or a corotating intermeshing twin-screw extruder. The characterization of the obtained nanocomposites was performed by XRD, thermogravimetry, mechanical and rheological measurements. The study has shown the possibility of producing nanocomposites based on EVA and a commercial organoclay (Cloisite 15A) by several mixing equipments. In fact all the…