DLP 3D printing of materials with heterogeneous material properties

master's thesis

• Title (croatian): DLP 3D tisak materijala heterogenih mehaničkih svojstava
• Author: Nikola Šebalj
• Mentor: Elvira Vidović (mentor)
• Committee member: Elvira Vidović (predsjednik povjerenstva)
• Committee member: Domagoj Vrsaljko (član povjerenstva)
• Committee member: Vesna Ocelić Bulatović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2022-11-25, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

With additive manufacturing, it is now possible to repeatedly create 3D objects without the need for molds or heavy machining. In comparison with other additive manufacturing techniques, vat photopolymerization provides a fast and precise way of producing complex shapes and objects. Photopolymerization 3D printing uses light exposure to solidify a resin formulation and is typically limited to a single material. In recent years, researchers have focused on using multi-material 3D printing to manufacture objects with heterogeneous properties. A promising approach for vat photopolymerization 3D printing of multi-material objects is the use of orthogonal photoreactions to tailor the network properties. In this work, three different hybrid acrylate-epoxide systems were formulated to present the possibility of preparing dual-curable resins for 3D printing, and tuning their properties using dual-wavelength DLP 3D printing technology: a) DOM:ECC = 75:25, 25:75 b) Eb:ECC = 25:75 c) PEGDA:ECC = 50:50 The 3D printer used in this work, employs two different light engines, operating at 405 and 365 nm. At visible light irradiation, a radical photoinitiator was selectively activated, leading to the curing of the acrylate component. Upon UV light exposure, a radical curing as well as cationic ring opening process of the epoxide component was initiated, yielding an interpenetrating network (IPN) with higher crosslinking density and stiffness. For the quantitative conversion of the epoxide network, a thermal post-baking step was carried out at 120°C for 2 hours. The cure kinetics of prepared hybrid acrylate-epoxide resins were investigated using the FTIR spectroscopy and through the initial printing trials. Selective illumination with either light source should shift material properties between the soft acrylate and rather stiff epoxide network. This was verified for DOM:ECC and PEGDA:ECC systems, while the system Eb:ECC displayed thermal instability and inability to print wavelength selective materials. The system Eb:ECC was not subjected to further testing. Furthermore, to investigate mechanical behavior of the printed samples, dynamical mechanical analysis and tensile test were carried out.

Abstract (croatian)

Zahvaljujući aditivnoj proizvodnji, moguće je stvarati trodimenzionalne objekte bez potrebe za kalupima ili strojnom obradom. U usporedbi s drugim tehnikama aditivne proizvodnje, „fotopolimerizacija“ omogućuje brz i precizan način proizvodnje predmeta geometrijski složene građe. U procesu foto-polimerizacije dolazi do očvršćivanja smole pod utjecajem svjetlosti te je uglavnom ograničen samo na jedan materijal (jednu vrstu smole). No, posljednjih godina znatno je porastao interes za printanjem objekata koristeći više materijala (više različitih smola istovremeno). Na taj način mogli bi se printati predmeti heterogenih mehaničkih svojstava bez potrebe za fizičkom zamjenom posuda u printeru. Korištenje ortogonalnih foto-reakcija pokazalo se kao jedan od najefikasnijih rješenja navedenog problema. U ovom su radu formulirane tri hibridne akrilno-epoksidne smole kako bi se predstavila mogućnost pripreme smola podložnih dualnom-očvršćivanju, te mogućnost podešavanja njihovih mehaničkih svojstava koristeći DLP 3D printer s dvije valne duljine: a) DOM:ECC = 75:25, 25:75 b) Eb:ECC = 25:75 c) PEGDA:ECC = 50:50 3D printer, korišten u ovom radu, sadrži dvije različite lampe koje rade na valnim duljinama od 405 i 365 nm. Pod utjecajem vidljive svijetlosti, aktivira se radikalni foto-inicijator, što dovodi do polimerizacije akrilatne komponente. Uslijed izlaganja UV svjetlosti, uz radikalnu polimerizaciju, dolazi i do otvaranja epoksidnog prstena uslijed kationske inicijacije, pri čemu nastaje IPN (engl. interpenetrating network) s većom gustoćom umreženja te, samim time, i većom čvrstoćom strukture. Za kvantitativnu konverziju epoksidne mreže provedena je i termička obrada printanih uzoraka na temperaturi od 120 °C tijekom 2 sata. Kinetika polimerizacije pripremljenih hibridnih smola ispitana je FTIR spektroskopijom, te putem inicijalnih probnih tiskova. Selektivnim obasjavanjem određenom valnom duljinom očekuju se mehanička svojstva na prijelazu između meke akrilatne i čvrste epoksidne mreže. Ovo je potvrđeno za sustave DOM.ECC i PEGDA:ECC, dok je sustav Eb:ECC pokazao toplinsku nestabilnost i nemogućnost ispisa materijala čija mehanička svojstva ovise o valnoj duljini korištene svjetlosti. Stoga sustav Eb:ECC nije podvrgnut daljnjim ispitivanjima. S ciljem istraživanja mehaničkih svojstava printanih uzoraka, provedena je dinamička mehanička analiza te test naprezanje-istezanje.

• Keywords: DLP 3D printing; dual-curable resins; radical and cationic polymerization; acrylate and epoxide; mechanical properties
• Keywords (croatian): DLP 3D printanje; dualno-očvršćujuće smole; radikalna i kationska polimerizacija; akrilat i epoksid; mehanička svojstva
• Language: english
• URN:NBN: urn:nbn:hr:149:396680
• Study programme: Title: Chemical Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka kemijskog inženjerstva (magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2023-02-15 15:53:16