Utilizzo industriale di cfrp (carbon fiber reinforced polymers) nanomodificati con nanofibre prodotte per elettrospinning

Attraverso questo studio sono state indagate le proprietà di compositi laminati in fibra di carbonio (CFRP) nano-modificati con nanofibre in Nylon 6.6, in termini di resistenza al danneggiamento da impatti a bassa velocità (con caratterizzazione Drop Weight at Low Velocity) e di smorzamento della vibrazione (con caratterizzazione a damping). Sono stati indagate due configurazioni di nanorinforzo differenti, confrontate con le prestazioni di provini vergini laminati tradizionalmente. Sono infine state operate delle analisi grafiche delle micrografie di campioni sezionati per trarre conclusioni di carattere tecnologico.

Novel materials for direct X-ray detectors based on semiconducting organic polymers

Conventional inorganic materials for x-ray radiation sensors suffer from several drawbacks, including their inability to cover large curved areas, me- chanical sti ffness, lack of tissue-equivalence and toxicity. Semiconducting organic polymers represent an alternative and have been employed as di- rect photoconversion material in organic diodes. In contrast to inorganic detector materials, polymers allow low-cost and large area fabrication by sol- vent based methods. In addition their processing is compliant with fexible low-temperature substrates. Flexible and large-area detectors are needed for dosimetry in medical radiotherapy and security applications. The objective of my thesis is to achieve optimized organic polymer diodes for fexible, di- rect x-ray detectors. To this end polymer diodes based on two different semi- conducting polymers, polyvinylcarbazole (PVK) and poly(9,9-dioctyluorene) (PFO) have been fabricated. The diodes show state-of-the-art rectifying be- haviour and hole transport mobilities comparable to reference materials. In order to improve the X-ray stopping power, high-Z nanoparticle Bi2O3 or WO3 where added to realize a polymer-nanoparticle composite with opti- mized properities. X-ray detector characterization resulted in sensitivties of up to 14 uC/Gy/cm2 for PVK when diodes were operated in reverse. Addition of nanoparticles could further improve the performance and a maximum sensitivy of 19 uC/Gy/cm2 was obtained for the PFO diodes. Compared to the pure PFO diode this corresponds to a five-fold increase and thus highlights the potentiality of nanoparticles for polymer detector design. In- terestingly the pure polymer diodes showed an order of magnitude increase in sensitivity when operated in forward regime. The increase was attributed to a different detection mechanism based on the modulation of the diodes conductivity.

Study and characterization of low molecular weight polymer solutions for application in lubricating oils

The aim of this thesis is to evaluate the possibility of using short linear polymer chains as additives in lubricating oil applications. Through previous works, it has been seen that they are particularly resistant to mechanical degradation, which is the main reason why lubricating oils need to be changed after a while. This is the main reason why they could be proposed as alternatives in the market. The results of this work have been split into two major phases: the first concentrated on characterizing a target product obtained through thermal degradation, starting from the original long chain parent polymer, and the second focused on the technological advancement of heat exchangers. Through the studies carried out, we’ve characterized our innovative polymers and the solutions made with them and base oil at different concentrations. The most promising result is that these short random coiled polymeric chains obey to a more general universal function which express the value of specific viscosity as function of a dimensionless quantity c/c*. For the design of the unit operation, several alternatives were proposed and these all shared the same final goal: cooling the polymer without the presence of oxygen to avoid oxidation and formation of unwanted substances. We’ve analyzed the main difficulties related to the presence of these highly viscous substances and, more importantly, how to deal with this situation (e.g. by considering radial static mixer or even more complex conformations).