Aliphatic hydrogen bonded oligomers and polymers from natural resources

Chemistry is by definition the science of matter, the science of the transformation of the substances and for this reason and also for practical issues derived from its technological applications, has interested the different populations since ancient times. The strong connection of this branch of science with the industrial world has promoted its interest in the development of new materials that could substitute or improve traditional and natural materials. Although this development has not always been a direct consequence of a well specified research or demand, (in fact many important discoveries are result of serendipity) periods can be distinguished during the history of the chemistry in which the different industrial processes or researches were born considering demands and requests of the moment. For example the Alkali industry, probably the first important chemical industrial process, can be considered as born to serve the textile industry, leading sector of the second industrial revolutions. This continuous adaptation also led to development of materials such as plastics and synthetic polymers directly correlated to petroleum industry. Synthetic polymers, initially introduced in order to substitute more expensive materials like natural fibers or traditional materials like wood, glass, and ceramics, were improved with different and better properties with respect to the natural materials. In particular, exploitation of chemistry to meet challenges in material science, a detailed understanding of structure-property relationship is essential to meet the ultimate properties. These materials are characterized by their simple chemical structure and therefore good thermal stability that makes them processable in the molten state and outperform the thermal degradation of many natural materials is essential. Nowadays the scarcity of oil resources and the environmental and political issues are encouraging the production of environmental friendly materials. A new request is once again influencing the chemistry world and new answers from polymer science are expected. Many different projects on bio-polymers have been carried out in the last decades in several different laboratories. A lot of interest is paid by petrochemical industry to bio-based materials with the intent of replacing exiting plastics. The industrial interest is from one side promoted by the possibility of achieving green image and from the other side is due to the possibility of minimizing the exploitation of oil resources. However, many bio-based plastics represent durable materials that cannot prevent one of the most important issues, the biocompostability. In this thesis we have explored the possibility of using alternative feedstock in order to produce plastics. We have focused our attention on bio based monomers and the application of such monomers as a powerful method of tailoring thermal and mechanical properties of interesting known materials. In particular the role of secondary interactions such as hydrogen bonds on the crystallization of new bio-based polyamides and the role of bio-based monomers in influencing the secondary interactions has been investigated. Among many materials that can be considered as a source of bio- based polymers or monomers we have also explored a new approach using water under specific pressure-temperature conditions to hydrolyze keratins that is a part of Chapter 2 in this thesis. Our observations are that under controlled hydrolysis conditions it is feasible to extract oligopeptides with well defined sequences of amino acids (LC-MS and HPLC) and re-synthesize them via Solid State Peptide Synthesis by attaching aliphatic and hydrogen bonding motifs to the synthesized oligopeptides in order to promote self assembling phenomena. New semi-crystalline polyamides and co-polyamides from bio-based sebacic acid (SA), 2,5-diamino-2,5-dideoxy-1,4;3,6-dianhydroiditol (diaminoisoidide, DAII) as well as from 1,4-diaminobutane (DAB), have been synthesized. These monomers can be derived from castor oil (SA), starch (DAII) and putrescine (DAB). Synthetic routes, involving interfacial polycondensation, solvent-free bulk polycondensation accomplished by Solid State Polymerization (SSP) after a prepolymerization in the melt are reported in Chapter 3 where the chemical structure of the synthesized bio based polyamides and copolyamides was proven using 2D NMR and FT-IR spectroscopy. Moreover the influence of DAII/DAB content on the crystal structure and melting points of the polyamides were investigated using wide-angle X-ray diffraction and DSC techniques. In chapter 4, FT-IR, CP/MAS NMR and WAXD are successfully employed for the analysis of the structural behavior and mobility of the polyamides and copolyamides with a different DAII/DAB content as function of temperature. The contribution of DAII causes a conformational disorder of the polyamides and thus influences the crystal structure and the properties of these materials. Transmission electron micrographs of crystals of bio-based polyamides and the respective electron diffraction patterns, coupled with XRD data and modeling experiments confirm the influence of DAII content on the crystal structure of these materials and also on the mechanical properties. The latter is confirmed by DMTA (chapter 5). Last chapter in the thesis highlights possible technological aspects in these bio-polymers

Garigliano nuclear power plant: seismic evaluation of the turbine building

The Italian Garigliano Nuclear Power Plant (NPP) started its energy production in 1963. At present it is in the decommissioning stage. In order to get a proper management of the radioactive waste that will be produced during the dismantling operations it has been considered convenient to convert the turbine building of the plant into a temporary waste repository. This decision posed a remarkable seismic safety assessment issue. As a matter of fact, the challenge was to extend, in satisfactory safety conditions, the use of an important facility that has reached the end of its designed lifetime and to have this extended use approved by nuclear safety agencies. In this context many tasks have been accomplished, of which the most important are: (a) a new appraisal of site seismic hazard; (b) the execution of many investigations and testing on the construction materials; (c) the set up of a detailed 3D finite element model including the explicit representation of foundation piles and soil; (d) consideration of soil structure kinematic and dynamic nteraction effects. This paper describes the adopted seismic safety assessment criteria which are based on a performance objectives design approach. While performance based design is the approach currently recommended by European Regulations to manage seismic risk and it is fully incorporated in the Italian code for conventional buildings, bridges and plants, NPP are not explicitly considered. Therefore it was necessary to delineate a consistent interpretation of prescribed rules in order to properly select the maximum and operating design earthquakes on one side and corresponding acceptable limit states on the other side. The paper further provides an outline of the numerical analyses carried out, of the main results obtained and of the principal retrofitting actions that will be realized