Search results for "blends"
showing 10 items of 67 documents
Characterization of a fiber reinforced semirigid liquid crystalline polymer
1997
In this work, samples of a semirigid Liquid crystalline polymer reinforced with carbon and glass fibers has been characterized. Semirigid liquid crystalline polymers (LCPs) show some advantages with respect to rigid LCPs: in particular lower processing temperatures, and better compatibility with flexible thermoplastics, but also some disadvantages: lower mechanical properties and poor thermomechanical resistance. Both properties can be improved by adding inorganic fillers. Although elastic modulus and tensile strength of the glass fiber filled LCP improve remarkably with increasing the filler content, the same properties for the carbon fiber-filled samples do not increase with increasing ti…
Effects of filler type and mixing method on the physical properties of a reinforced semirigid liquid crystal polymer
1996
Semirigid liquid crystalline polymers (LCPs) show some advantages with respect to rigid LCP: in particular lower processing temperatures, better compatibility with flexible thermoplastics, but also some disadvantages. Thermal resistance of rigid LCPs is much better and the maximum working temperature is, in general, very high. The thermomechanical properties can be improved by adding inorganic fillers. In this work processing, mechanical and thermomechanical properties of a filled semirigid liquid crystal copolyester are reported. Several inorganic fillers have been used in order to put in evidence the influence of shape and dimensions of the particles on the properties of the filled materi…
Tuning of biodegradation rate of PLLA scaffolds via blending with PLA
2009
Blends of Poly-L-Lactic Acid (PLLA) with Poly-Lactic Acid (PLA) in different proportions (95/5, 90/10, 80/20, 70/30 and 60/40) were utilized in order to realize biodegradable and biocompatible scaffolds for soft tissue engineering applications. The scaffolds were produced via thermally induced phase separation (TIPS) starting from ternary systems where dioxane was the solvent and water the non-solvent. Morphology was evaluated by Scanning Electron Microscopy (average pore size and interconnection). Foams’ apparent density was also evaluated (porosity ranges from 87% to 92%). Moreover an in vitro biodegradation test of scaffolds was set-up in order to verify the rate of degradation of the va…
The role of organoclay in promoting co-continuous morphology in high-density poly(ethylene)/poly(amide) 6 blends
2008
The effect of organically modified clay on the morphology, rheology and mechanical properties of high-density polyethylene (HDPE) and polyamide 6 (PA6) blends (HDPE/PA6 ¼ 75/25 parts) is studied. Virgin and filled blends were prepared by melt compounding the constituents using a twin-screw extruder. The influence of the organoclay on the morphology of the hybrid was deeply investigated by means of wide-angle X-ray diffractometry, transmission and scanning electron microscopies and quantitative extraction experiments. It has been found that the organoclay exclusively places inside the more hydrophilic polyamide phase during the melt compounding. The extrusion process promotes the formation o…
On the compatibilization of PET/HDPE blends through a new class of copolyesters
2000
Polyethyleneterephthalate (PET) and polyethylene are incompatible polymers and their blends show, in general, poor properties. Compatibilization is then a necessary step to obtain blends with good mechanical and barrier properties. In this work different compatibilizing agents were used, i.e. a maleic anhydride elastomer and some new products containing graft-copolymers having polyester segments grafted onto polyethylene backbone chains. Both the functionalized elastomer and the new products drastically improve the morphology and the ductility of the blend. In the case of the modified elastomer the compatibilizing action has been attributed to the formation of H-bonds whereas the copolymers…
E-beam curing of epoxy based blends in order to produce high performance composites
2007
In this work, blends of a difunctional epoxy monomer and a thermoplastic toughening agent are E-beam irradiated at two different dose rates and two different total absorbed doses. The influence of the processing conditions on the thermal properties and on the morphology of the obtained matrices has been investigated. In particular, it is shown how the increase of the dose rate causes an increase of the temperature during irradiation, thus inducing a simultaneous thermal and radiation curing. On the contrary, at low-dose rate the system mainly undergoes to radiation curing, thus making the cured material very sensible to a post-irradiation thermal treatment with a significant improvement of …
Polymeric scaffolds based on blends of poly-l-lactic acid (PLLA) with poly-d-l- lactic acid (PLA) prepared via thermally induced phase separation (TI…
2012
Porous scaffolds based on blends of high crystalline Poly-L-lactic acid (PLLA) with low crystalline poly-D-L-lactic acid (PLA) were prepared via Ther- mally Induced Phase Separation (TIPS), with the aim of exploring the possibility to control the degradation behaviour of the PLA-based scaffold, simultaneously pre- serving the morphological characteristics required for tissue engineering applica- tions. Porous foams with different PLLA/PLA weight ratios (from 95/5 to 60/40) were produced and characterised in terms of pore size, porosity, and thermal properties. The scaffolds present an open porosity, with average pore sizes ranging from 30 to 70 lm. Results showed that, when dealing with a P…
Gamma radiation of EVA-AA/MMA swollen systems to obtain mechanically improved blends
2002
In this work a "new" way to obtain "compatibilised" blends of rubber-glassy thermoplastic components is presented. Polyethylen-vinyl acetate acrylic acid terpolymer is swollen by methylmetacrylate and the system is irradiated through gamma rays in order to induce polymerisation of the monomer. Solubility and dynamic mechanical tests indicate the formation of a two phase system, even though in presence of strong interactions between the two components. Mechanical tensile behaviour is that of a ductile material with appreciable modulus values.
Time–carbonyl groups equivalence in photo-oxidative aging of virgin/recycled polymer blends
2004
AbstractThe photo-oxidation behaviour of polymers is strongly dependent on the initial amount of carbonyl groups along the chains. The growing use of recycled post-consumer polymers coming from products used outdoors and then photo-oxidised, both pure and blended with the same virgin polymer, gives rise to an unpredictable behaviour of weathering resistance of products made with these materials. The present work shows that the carbonyl group–exposure time curves can be shifted along the time axis to give a single generalised master plot. It is then possible to predict the formation of the new carbonyl groups by knowing only the initial amount of the same carbonyl groups. The same shift fact…