Oreste Tarallo

Synthesis and Characterization of Novel Epoxy Geopolymer Hybrid Composites

The preparation and the characterization of novel geopolymer-based hybrid composites are reported. These materials have been prepared through an innovative synthetic approach, based on a co-reticulation in mild conditions of commercial epoxy based organic resins and a metakaolin-based geopolymer inorganic matrix. This synthetic strategy allows the obtainment of a homogeneous dispersion of the organic particles in the inorganic matrix, up to 25% in weight of the resin. The materials obtained present significantly enhanced compressive strengths and toughness with respect to the neat geopolymer, suggesting their wide utilization for structural applications. A preliminary characterization of the porous materials obtained by removing the organic phase from the hybrid composites by means of heat treatments is also reported. Possible applications of these materials in the field of water purification, filtration, or as lightweight insulating materials are envisaged.

A chiral co-crystalline form of poly(2,6-dimethyl-1,4-phenylene)oxide (PPO)

For an industrially relevant specialty polymer, poly(2,6-dimethyl-1,4-phenylene)oxide (PPO), for the first time, a crystalline structure is resolved. It is a co-crystalline structure of the polymer with a chiral guest molecule (α-pinene), exhibiting a 2/1 monomer-unit–guest molar ratio. The most relevant feature of this co-crystalline structure is its chirality. In fact, the unit cell includes all left- or right-handed polymer helices and (1S)-(−)- or (1R)-(+)-α-pinene guest molecules, respectively. The induction of non-racemic macromolecular helicity in the co-crystalline structure, clearly confirmed by VCD measurements, leads to amplification of chirality. Guest extraction procedures from the PPO–α-pinene co-crystalline form produce optically inactive nanoporous-crystalline modifications, which present high sorption ability toward organic compounds.

Synthesis and Characterizations of Melamine-Based Epoxy Resins

A new, easy and cost-effective synthetic procedure for the preparation of thermosetting melamine-based epoxy resins is reported. By this innovative synthetic method, different kinds of resins can be obtained just by mixing the reagents in the presence of a catalyst without solvent and with mild curing conditions. Two types of resins were synthesized using melamine and a glycidyl derivative (resins I) or by adding a silane derivative (resin II). The resins were characterized by means of chemical-physical and thermal techniques. Experimental results show that all the prepared resins have a good thermal stability, but differ for their mechanical properties: resin I exhibits remarkable stiffness with a storage modulus value up to 830 MPa at room temperature, while lower storage moduli were found for resin II, indicating that the presence of silane groups could enhance the flexibility of these materials. The resins show a pot life higher than 30 min, which makes these resins good candidates for practical applications. The functionalization with silane terminations can be exploited in the formulation of hybrid organic-inorganic composite materials.

Dipolar guest orientation in polymer co-crystals and macroscopic films

The crystal structures of δ-clathrates of syndiotactic polystyrene (s-PS) with highly polar guest molecules (nitrobenzene, NB and p-nitroaniline, NA) have been defined, on the basis of X-ray diffraction and FTIR linear dichroism analyses. The s-PS/NB co-crystal presents a structure very similar to those of the δ-clathrates already described in the literature, i.e. monoclinic and with the guest molecular plane nearly perpendicular to the host helical axes. The s-PS/NA co-crystal presents a definitely different structure, i.e. triclinic and with guest molecular planes inclined with respect to the host helical axes. The definition of the co-crystalline structures has allowed to establish that the a⊥c// uniplanar orientation of the co-crystalline phase leads the guest dipoles roughly perpendicular to the film plane, i.e. to a dipole orientation suitable for poling processes. Films presenting a high degree of a⊥c// uniplanar orientation of the s-PS/NA co-crystalline phase have been obtained and characterized by X-ray diffraction measurements.

Innovative Fly Ash Geopolymer-Epoxy Composites: Preparation, Microstructure and Mechanical Properties

The preparation and characterization of composite materials based on geopolymers obtained from fly ash and epoxy resins are reported for the first time. These materials have been prepared through a synthetic method based on the concurrent reticulation of the organic and inorganic components that allows the formation of hydrogen bonding between the phases, ensuring a very high compatibility between them. These new composites show significantly improved mechanical properties if compared to neat geopolymers with the same composition and comparable performances in respect to analogous geopolymer-based composites obtained starting from more expensive raw material such as metakaolin. The positive combination of an easy synthetic approach with the use of industrial by-products has allowed producing novel low cost aluminosilicate binders that, thanks to their thixotropicity and good adhesion against materials commonly used in building constructions, could be used within the field of sustainable building.

Tailoring the properties of polypropylene in the polymerization reactor using polymeric nucleating agents as prepolymers on the Ziegler–Natta catalyst granule

Innovation of the Ziegler–Natta polymerization process for polymerization of propene that allows tailoring of the mechanical properties of isotactic polypropylene (iPP) directly in the polymerization stage is presented. The catalyst is modified by prepolymerization of trimethylallylsilane or vinylcyclohexane so that the catalyst particles are coated by a thin skin of poly(trimethylallylsilane) or poly(vinylcyclohexane) that will act as a nucleating agent for the crystallization of iPP. The presence of the nucleating agent accelerates the crystallization of iPP and affords crystallization of the α form even upon fast crystallization by quenching the melt, a condition that generally produces crystallization of the mesomorphic form. Crystals of the α form so obtained show a nodular morphology and the absence of the spherulitic superstructure. This novel iPP material is characterized by outstanding and unexpected properties of high mechanical strength and modulus and contemporarily high ductility, flexibility and good transparency due to the nodular morphology of the α form.