Ultrafast laser micro and nanotexturing are among the most active and promising fields of research that have recently boomed and can advance the plastics manufacturing industry. The integration of laser texturing in thermoplastic injection molding can enable the technical and environmental sustainability of the mass manufacturing of plastics products. Engineered mold surfaces have effects on the cavity filling performances and the replicated topography of the part. Parts with a reduced material intensity that embed a wider number of functionalities may offer new technological answers to the environmental issues, especially when combined with sustainable polymers. The application of ultrafast laser technology to the injection molding market is new and there are a wide number of open points related to the technologies’ integration. In this context, the design of mold surfaces represents the strategic juncture to boost processing innovations and new product functionalities. In this work, the generation of novel engineered mold surfaces was studied to enable novel polymer flows in the cavity, characterized by lower energy requirements. Specific textures have been designed and manufactured to meet the polymer process requirements. Regular micro and nano surface textures, surface thin coatings, and the combination of textures and coatings are obtained and introduced into the injection mold to modify the morphological, chemical, and thermal properties of the surface. Experimental campaigns were carried out to characterize the effects of the modifications onto the cavity filling and the replication performances of the process. Filling studies focus on the flow phenomena happening during the filling phase and aim at reducing the pressure drop yielded by the polymer to completely fill the cavity. Replication studies focus on the interactions that affect the mold surface morphology replica and aim to optimize the replication fidelity. In-line process monitoring and advanced characterization equipment have been implemented in the experimental investigations. The experimental results show that mold textures and surface coatings effectively reduce the pressure drop inside the mold cavity. The result has been translated in terms of material intensity reduction by calibrating a numerical model and modeling a case study with the proposed mold coating, obtaining a part volume reduction of 8%. The results of the experimental campaign on replication show that, depending on the replication grade of the mold micro- and nano-structures, the plastic parts can be functionalized, increasing the water contact angle. A process design tool for part functionalization was implemented through a multi-scale model predicting the replication of the mold texture. A numerical model solves the macro flow in the cavity and feeds the proposed analytical model for the micro polymer flow into the structures. The multi-scale model is sensitive to the variations of the polymer and process, with a maximum error of 8%. In general, the findings of this work can open new opportunities and markets for the laser texturing and injection molding sectors, providing tools for a more aware design of parts and molds towards the new market demands. Ultrafast laser-induced textures are specifically designed and manufactured for injection molding applications to introduce new functionalities as self-cleaning properties on injection molded parts in a cost-effective way. The multi-scale model resulted in a significant contribution to the understanding of the phenomena that control the injection molding process at the micro and nanoscale, providing tools for texture and process design. The efforts towards the modeling of the effect of coatings will allow for a more sustainable plastic part design, reducing their material intensity.
L’utilizzo di sorgenti laser ultraveloci per la micro e nano testurizzazione è uno tra i campi di ricerca più attivi e in costante crescita che può far progredire il settore dello stampaggio ad iniezione. L'integrazione della testurizzazione laser nello stampaggio può incrementare la sostenibilità tecnica e ambientale della produzione di massa di prodotti in plastica. Superfici stampo ingegnerizzate hanno effetti sulle prestazioni di riempimento della cavità e sulla topografia della parte stampata, riducendo il consumo di materiale specifico per il componente ed introducendo ulteriori funzionalità che possono offrire nuove risposte ai problemi ambientali, soprattutto quando combinate con polimeri sostenibili. La nuova applicazione della tecnologia laser allo stampaggio ha sollevato numerose opportunità e interrogativi. In questo contesto, la progettazione delle superfici degli stampi rappresenta la congiuntura strategica per potenziare le innovazioni di processo e le nuove funzionalità di prodotto. In questo lavoro, la generazione di tessiture per indurre nuovi flussi polimerici nella cavità è stata studiata per ottenere flussi da requisiti energetici inferiori, progettando e realizzando tessiture per il processo dei polimeri. Micro e nano tessiture regolari, rivestimenti superficiali e la loro combinazione sono state introdotte sullo stampo ad iniezione per modificare le proprietà morfologiche, chimiche e termiche della superficie. Le campagne sperimentali mirano a caratterizzare gli effetti sul riempimento della cavità e sulle prestazioni di replicazione del processo. Gli studi sul riempimento si concentrano sui fenomeni che si verificano durante il flusso per ridurre la caduta di pressione in cavità. Gli studi sulla capacità di replicazione del polimero si concentrano sulle interazioni avvengono in superficie per ottimizzare l’accuratezza nella replicazione. Durante le indagini sperimentali sono state implementate avanzate apparecchiature di caratterizzazione e di monitoraggio del processo in linea. I risultati sperimentali dimostrano che le strutture dello stampo e i rivestimenti superficiali riducono la caduta di pressione in cavità. Calibrando un modello numerico e modellando un caso studio con il rivestimento dello stampo proposto, il risultato è stato tradotto in termini di riduzione dell'intensità del materiale, ottenendo una riduzione del volume del componente dell'8%. I risultati riguardo la replicazione mostrano che, in relazione all’accuratezza nella replicazione, le parti in plastica possono essere funzionalizzate, aumentando l'angolo di contatto con l'acqua. Uno strumento di progettazione del processo per funzionalizzare parti in plastica è stato implementato con un modello multi-scala che prevede il grado di replicazione, composto da un modello numerico che risolve il macro flusso in cavità e alimenta il modello analitico per il micro flusso del polimero nelle strutture, sviluppato in questo lavoro. Il modello multi-scala risulta sensibile alle variazioni del polimero e del processo, con un errore massimo dell'8%. I risultati di questo lavoro possono aprire nuove opportunità e mercati per i settori della testurizzazione laser e dello stampaggio, fornendo strumenti di progettazione più consapevole di parti e stampi verso le richieste del mercato. Le tessiture indotte dai laser ultraveloci per applicazioni di stampaggio a iniezione possono introdurre nuove funzionalità su parti stampate ad iniezione come proprietà autopulenti. Il modello multi-scala ha fornito un contributo significativo alla comprensione dei fenomeni che controllano il processo di stampaggio a iniezione su scala micro e nanometrica, fornendo strumenti per la progettazione del processo e delle strutture sullo stampo. Gli sforzi verso la modellazione dell'effetto dei rivestimenti consentiranno una progettazione di parti in plastica più sostenibili, riducendo il consumo di materiale specifico.
Effetto di superfici nanostrutturate sul flusso del polimero in stampi a iniezione per applicazioni industriali / Piccolo, Leonardo. - (2022 Mar 23).
Effetto di superfici nanostrutturate sul flusso del polimero in stampi a iniezione per applicazioni industriali
PICCOLO, LEONARDO
2022
Abstract
Ultrafast laser micro and nanotexturing are among the most active and promising fields of research that have recently boomed and can advance the plastics manufacturing industry. The integration of laser texturing in thermoplastic injection molding can enable the technical and environmental sustainability of the mass manufacturing of plastics products. Engineered mold surfaces have effects on the cavity filling performances and the replicated topography of the part. Parts with a reduced material intensity that embed a wider number of functionalities may offer new technological answers to the environmental issues, especially when combined with sustainable polymers. The application of ultrafast laser technology to the injection molding market is new and there are a wide number of open points related to the technologies’ integration. In this context, the design of mold surfaces represents the strategic juncture to boost processing innovations and new product functionalities. In this work, the generation of novel engineered mold surfaces was studied to enable novel polymer flows in the cavity, characterized by lower energy requirements. Specific textures have been designed and manufactured to meet the polymer process requirements. Regular micro and nano surface textures, surface thin coatings, and the combination of textures and coatings are obtained and introduced into the injection mold to modify the morphological, chemical, and thermal properties of the surface. Experimental campaigns were carried out to characterize the effects of the modifications onto the cavity filling and the replication performances of the process. Filling studies focus on the flow phenomena happening during the filling phase and aim at reducing the pressure drop yielded by the polymer to completely fill the cavity. Replication studies focus on the interactions that affect the mold surface morphology replica and aim to optimize the replication fidelity. In-line process monitoring and advanced characterization equipment have been implemented in the experimental investigations. The experimental results show that mold textures and surface coatings effectively reduce the pressure drop inside the mold cavity. The result has been translated in terms of material intensity reduction by calibrating a numerical model and modeling a case study with the proposed mold coating, obtaining a part volume reduction of 8%. The results of the experimental campaign on replication show that, depending on the replication grade of the mold micro- and nano-structures, the plastic parts can be functionalized, increasing the water contact angle. A process design tool for part functionalization was implemented through a multi-scale model predicting the replication of the mold texture. A numerical model solves the macro flow in the cavity and feeds the proposed analytical model for the micro polymer flow into the structures. The multi-scale model is sensitive to the variations of the polymer and process, with a maximum error of 8%. In general, the findings of this work can open new opportunities and markets for the laser texturing and injection molding sectors, providing tools for a more aware design of parts and molds towards the new market demands. Ultrafast laser-induced textures are specifically designed and manufactured for injection molding applications to introduce new functionalities as self-cleaning properties on injection molded parts in a cost-effective way. The multi-scale model resulted in a significant contribution to the understanding of the phenomena that control the injection molding process at the micro and nanoscale, providing tools for texture and process design. The efforts towards the modeling of the effect of coatings will allow for a more sustainable plastic part design, reducing their material intensity.File | Dimensione | Formato | |
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Tesi_Leonardo_Piccolo.pdf
Open Access dal 24/03/2023
Descrizione: Tesi_Leonardo_Piccolo
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