FROM MASTER CURVES FOR THE MECHANICAL REINFORCEMENT OF RUBBER BASED NANOCOMPOSITES TO LIGHTWEIGHT MATERIALS

sp2 carbon allotropes are efficient reinforcing fillers for rubber materials. CB is made by primary nanometric particles, fused together to form micron-size aggregates. Nanofillers bring individual nanometric particles into the polymer matrix: they have large surface area and hence large interfacial area with the polymer matrix. Nanofillers such as graphene related materials (GRM) and carbon nanotubes (CNT) have anisometric nature. Nanoplatelets and nanofibers achieve the largest values of interfacial area and can exhibit preferential orientation inside a matrix, leading to anisotropic properties. In this work, the reinforcing ability and the anisotropy of mechanical reinforcement of CB, CNT and GRM1 in rubber matrices such as poly(1,4-cis-isoprene) and poly(styrene-co-butadiene) was investigated. Correlation was studied between mechanical reinforcement and filler-polymer interfacial area (i.a.), defined as the product Ai·ρ·φ, where Ai is the surface area (assumed to be equal to BET surface area), ρ is the filler density and φ is the filler volume fraction2. Samples based on nanofillers were transversally isotropic: properties were very similar inside the sheet plane and very different in the orthogonal direction. The initial modulus in the direction orthogonal to the sheet plane, was taken as the index of mechanical reinforcement. It was observed that for i.a. value up to about 27 μm-1, experimental points due to CNT, CB, as well as to hybrid filler systems, lie on a sort of master curve. Thanks to the above mentioned master curves, composites were designed and prepared with lower density

sp2 carbon allotropes in elastomer matrix: from master curves for the mechanical reinforcement to lightweight materials

This work presents high surface area sp2 carbon allotropes as important tools to design and prepare lightweight materials. Composites were prepared based on either carbon black (CB) or carbon nanotubes (CNT) or hybrid CB/CNT filler systems, with either poly(1,4-cis-isoprene) or poly(styrene-co-butadiene) as the polymer matrix. A correlation was established between the specific interfacial area (i.a.), i.e. the surface made available by the filler per unit volume of composite, and the initial modulus of the composite (G′γmin), determined through dynamic mechanical shear tests. Experimental points could be fitted with a common line, a sort of master curve, up to about 30.2 and 9.8 mass% as CB and CNT content, respectively. The equation of such master curve allowed to correlate modulus and density of the composite. Thanks to the mastercurve, composites with the same modulus and lower density could be designed by substituting part of CB with lower amount of the carbon allotrope with larger surface area, CNT. This work establishes a quantitative correlation as a tool to design lightweight materials and paves the way for large scale application in polymer matrices of innovative sp2 carbon allotropes

Aspetti immunologici e clinici in bambini affetti da infezione stafilococcica

Gli Autori riportano i risultati di uno studio su alcuni parametri dell'immunità, condotto su bambini affetti da infezione da Stafilococco Aureo in forma primaria e secondaria. Discutono, quindi, del ruolo che tale germe avrebbe nel determinismo della malattia e nel condizionare particolari modalità di risposta immunologica in rapporto alla carica batterica e alle diverse fasi della infezione

Serinol derivatives for the sustainable vulcanization of diene elastomers

2-amino-1,3-propanediol (serinol) was used as the starting building block of synthetic pathways which led to the preparation of innovative chemicals, suitable as ingredients for rubber compounds. Serinol based reactions were performed in the frame of a sustainable process, in the absence of any solvent and catalyst, with aldehydes and ketones, such as: acetone, cinnamaldehyde and camphor. The synthesis of either imines or oxazolidines was obtained with high selectivity. Serinol, imine and oxazolidine derivatives of serinol were used as accelerator for the vulcanization of diene rubbers. They were proved to be efficient secondary accelerators in silica based compounds based on poly(styrene-co-butadiene), in place of diphenyl guanidine. Kinetics of vulcanization were investigated for natural rubber based compounds, in the absence of any filler. With respect to serinol, the imine derivatives were able to enhance the induction time of vulcanization and to afford a similar vulcanization rate

Hysteresis modeling and microstructural analysis of soft amorphous alloys

The dynamic Preisach model is applied to the study of Fe-based and Go-based amorphous alloys characterized by different microstructural conditions. It is shown that all static and dynamic hysteresis properties are correctly predicted by the dynamic Preisach model by associating with each material a structural parameter, lambda, which represents the linear dimension of the correlation regions providing coherent magnetization changes. The dependence of this correlation length on annealing treatments is compared with Kerr-effect domain observations and structural data obtained by differential scanning calorimetry. It is found that lambda has a role comparable to that of grain size in micro-crystalline alloys. In particular, it is shown that the linear relation holds, H-c = H-c0 + c/lambda, between the static coercive field H-c and 1/lambda, where the slope c depends on the magnetostriction constant of the material and the amount of quenched-in stresses, whits the offset H-c0 is connected to surface characteristics

Hysteresis modeling and microstructural analysis of soft amorphous alloys

The dynamic Preisach model is applied to the study of Fe-based and Co-based amorphous alloys, characterized by different microstructural conditions. It is shown that all static and dynamic hysteresis properties are correctly predicted by the dynamic Preisach model by associating with each material a structural parameter, λ, which represents the linear dimension of the correlation regions providing coherent magnetization changes. The dependence of this correlation length on annealing treatments is compared with Kerr-effect domain observations and structural data obtained by differential scanning calorimetry. It is found that λ has a role comparable to that of grain size in micro-crystalline alloys. In particular, it is shown that the linear relation holds, HC=Hc0 + c/λ, between the static coercive field Hc and 1/λ, where the slope c depends on the magnetostriction constant of the material and the amount of quenched-in stresses, while the offset Hc0 is connected to surface characteristics