End of Life Tires that are no longer sufficiently safe or efficient to be reused can be mainly recovered as material or energy. The recovery as material is difficult and requires specific treatments such as a grinding process leading to significant reduction of tire dimensions and a separation of metallic and textile materials. The ground tire rubber (GTR) can be widely reused in several applications. However, its introduction is more difficult in systems that have to withstand high dynamic stresses, even when it is added in low amount as a filler after a strong size reduction. In order to increase the compatibility with raw rubber, GTR must be devulcanized by breaking the three-dimensional crosslink network. Out of all existing reclaiming technologies, a supercritical fluid, an ultrasonic and a biological ones were chosen as object of the present thesis work. The choice was primarily carried out considering their impact on the environment and in particular their tendency to minimize the use of solvents, chemicals or energy. Supercritical carbon dioxide represents an ideal green solvent with respect to the traditional ones and it has been used as a reaction medium for the devulcanizing agent diphenyl disulfide. The ultrasonic devulcanization, was carried out in a co-rotating twin-screw extruder without involving any chemical, since ultrasounds can generate cavitation leading to the rupture of the three-dimensional network in the rubber matrix. The biological devulcanization involved Gordonia desulfuricans 213E strain that is able to metabolize the sulfur present in the rubber matrix without using any swelling or devulcanizing agent. The aim of the present thesis work is to investigate and optimize these devulcanization technologies by using the design of experiment approach, providing a comparison among the optimal conditions on a GTR.
Gli pneumatici a fine vita, non più utilizzabili in modo sicuro ed efficiente, possono essere recuperati come materiale o energia. Il recupero di materiale è complesso e richiede trattamenti specifici, quali la rimozione della struttura metallica e tessile e una riduzione delle dimensioni. Il granulato così ottenuto può essere ampiamente riutilizzato in svariate applicazioni, tuttavia è più difficile una sua aggiunta a sistemi che devono sopportare elevate sollecitazioni dinamiche, anche qualora venga utilizzato come riempitivo in basse quantità. Per aumentare la compatibilità con gomma vergine, il granulato deve essere devulcanizzato tramite un processo in grado di rompere il network tridimensionale. Tra tutte le tecnologie di devulcanizzazione conosciute, nel presente lavoro di tesi si è deciso di investigarne tre: una in fluido supercritico, una ad ultrasuoni ed una biologica. La scelta è stata effettuata considerando principalmente l'impatto sull'ambiente e in particolar modo la tendenza a minimizzare l'impiego di solventi, agenti chimici o energia. Nel primo caso, la CO2 supercritica è stata utilizzata come mezzo di reazione per l’agente devulcanizzante difenil disolfuro. La devulcanizzazione ad ultrasuoni è stata condotta in estrusore a doppia vite senza l’impiego di alcun composto chimico, poiché gli ultrasuoni possono generare cavitazioni che portano alla rottura della rete tridimensionale nella matrice gommosa. Nella devulcanizzazione biologica, si è sfruttata la capacità desolforante di Gordonia desulfuricans 213E senza l’impiego di alcun agente devulcanizzante. Lo scopo del presente lavoro di tesi è quello di indagare queste tre tecnologie di devulcanizzazione di un granulato da pneumatici utilizzando un approccio basato sul disegno sperimentale, in modo da ottenere informazioni sulle variabili significative, trovare le condizioni ottimali di processo e confrontarle tra loro.
(2015). Recycling of Tire Rubber: Investigation and Optimization of Green Devulcanization Technologies. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2015).
Recycling of Tire Rubber: Investigation and Optimization of Green Devulcanization Technologies
MANGILI, IVAN
2015
Abstract
End of Life Tires that are no longer sufficiently safe or efficient to be reused can be mainly recovered as material or energy. The recovery as material is difficult and requires specific treatments such as a grinding process leading to significant reduction of tire dimensions and a separation of metallic and textile materials. The ground tire rubber (GTR) can be widely reused in several applications. However, its introduction is more difficult in systems that have to withstand high dynamic stresses, even when it is added in low amount as a filler after a strong size reduction. In order to increase the compatibility with raw rubber, GTR must be devulcanized by breaking the three-dimensional crosslink network. Out of all existing reclaiming technologies, a supercritical fluid, an ultrasonic and a biological ones were chosen as object of the present thesis work. The choice was primarily carried out considering their impact on the environment and in particular their tendency to minimize the use of solvents, chemicals or energy. Supercritical carbon dioxide represents an ideal green solvent with respect to the traditional ones and it has been used as a reaction medium for the devulcanizing agent diphenyl disulfide. The ultrasonic devulcanization, was carried out in a co-rotating twin-screw extruder without involving any chemical, since ultrasounds can generate cavitation leading to the rupture of the three-dimensional network in the rubber matrix. The biological devulcanization involved Gordonia desulfuricans 213E strain that is able to metabolize the sulfur present in the rubber matrix without using any swelling or devulcanizing agent. The aim of the present thesis work is to investigate and optimize these devulcanization technologies by using the design of experiment approach, providing a comparison among the optimal conditions on a GTR.File | Dimensione | Formato | |
---|---|---|---|
phd_unimib_703891.pdf
Accesso Aperto
Descrizione: Tesi dottorato
Tipologia di allegato:
Doctoral thesis
Dimensione
4.92 MB
Formato
Adobe PDF
|
4.92 MB | Adobe PDF | Visualizza/Apri |
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.