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a b s t r a c tHighly porous biocompatible composites made of polycaprolactone (PCL) and 45S5 Bioglass Ò (BG) were prepared by a solid-liquid phase separation method (SLPS). The composites were obtained with BG weight contents varying in the range 0-50%, using either dimethylcarbonate (DMC) or dioxane (DIOX) as solvent, and ethanol as extracting medium. The porosity of the scaffolds was estimated to be about 88-92%. Mechanical properties showed a dependence on the amount of BG in the composites, but also on the kind of solvent used for preparation, composites prepared with DIOX showing enhanced stress at deformation with respect to composites prepared with DMC (stress at 60% of deformation being as high as 214 ± 17 kPa for DIOX-prepared composites and 98 ± 24 kPa for DMC-prepared ones, with 50 wt/wt PCL % of glass), as well as higher elastic modulus (whose value was 251 ± 32 kPa for DIOX-prepared scaffolds and 156 ± 36 kPa for DMC-prepared ones, always with 50 wt/wt PCL % of glass). The ability of the composites to induce precipitation of hydroxyapatite was positively evaluated by means of immersion in simulated body fluid and the best results were achieved with high glass amounts (50 wt/wt PCL %). In vitro tests of cytotoxicity and osteoblast proliferation showed that, even if the scaffolds are to be considered non-cytotoxic, cells suffer from the scarce wettability of the composites.

Abstract. In this work we report on the microstructural and the mechanical characteristics of high density polyethylene (HDPE)-clay nanocomposites, with particular attention to the creep behaviour. The samples were prepared through melt compounding, using two high-density polyethylenes with different melt flow rate (MFR), two different organo-modified clays, and changing the relative amount of a polyethylene grafted with maleic anhydride (PEgMA) compatibilizer. The intercalation process is more effective as the matrix melt viscosity decreases (higher MFR), while the clay interlamellar spacing increases as the compatibilizer amount increases. The relative stiffness of the nanocomposites increases with the addition of clay, with a limited enhancement of the relative yield stress. The better intercalation obtained by the addition of the compatibilizer is not accompanied by a concurrent improvement of the tensile mechanical properties. The creep resistance is enhanced by the introduction of clay, with an appreciable dependence on both the polyethylene and the clay type.

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Abstract. Linear low-density polyethylene (LLDPE) based composites were prepared by melt compounding with 1, 2, 3 and 4 vol% of various kinds of amorphous silicon dioxide (SiO2) micro-and nanoparticles. Dynamic rheological tests in parallel plate configuration were conducted in order to detect the role of the filler morphology on the rheological behaviour of the resulting micro-and nanocomposites. A strong dependence of the rheological parameters from the filler surface area was highlighted, with a remarkable enhancement of the storage shear modulus (G′) and of the viscosity (η) in fumed silica nanocomposites and in precipitated silica microcomposites, while glass microbeads only marginally affected the rheological properties of the LLDPE matrix. This result was explained considering the formation of a network structure arising from particle-particle interactions due to hydrogen bonding between silanol groups. A detailed analysis of the solid like behaviour for the filled samples at low frequencies was conducted by fitting viscosity data with a new model, based on a modification of the original De Kee-Turcotte expression performed in order to reach a better modelling of the high-frequency region.

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Fabrics of basalt (BFs), E-glass (GFs), and carbon (CFs) fibers with the same areal density were used to prepare epoxy-based laminates. The BF laminates presented elastic moduli and strength values higher than those of the corresponding GF laminates, with tensile strength values near to that of CF laminates. Investigation of the behavior under fatigue conditions indicated superior performances of BF laminates with respect to the corresponding GF composites, with an improved capability of sustaining progressive damaging and slightly higher damping properties. As far as the fatigue behavior is concerned, BFs may therefore represent a valid substitute of GFs in structural composites.