From the different 3D printing technologies, the photopolymerization process is very attractive. Indeed, photopolymerization can be used in combination with the stereolithography technique or Inkjet 3D printing to produce a solid object from the polymerization of a liquid resin in the irradiated area. In the present project, high performance photoinitiating systems for 3D printing resins will be developed. Important results were already obtained the last 18 months.
Task1 and Task2 according to the submitted project. <br />No special issue raised. <br />(see the associated document for a full description)
Methods and technologies used in Task 1 and 2:
Task 1: Design of New Type I and Type II photoinitiators for 3D printing (390-480 nm range)
The search for new Type I or Type II PIs is actually the aim of many research works. The photochemical/chemical reactivity as well as the amount of light absorbed by the photoinitiator PI in polymerization reactions constitute the key points for the design of high performance PI systems. Among others, one question is related to the possibility to red-shift the absorption and to increase the absorption intensity while keeping a high photochemical/chemical reactivity.
We have explored, in the present project, new family of initiators based on different cores or dyes decorated with different Type I or Type II photoinitiators. We expect to get, through a strong MO coupling (PI synthesized in the sub-task 1.1), push-pull effect (PI synthesized in the sub-task 1.2) or the introduction of thiophene rings (PI synthesized in the sub-task 1.2), a new chromophore that no longer resembles that of the core or the PI moiety (see preliminary results). These systems will be called Light Harvesting Organic PhotoInitiators (LHPIs).
Task 2: New radical chemistries for 3D printing
Current Type I and Type II photoinitiators mainly generate carbon centered radicals as polymerization initiating species. The search for more reactive initiating radicals centered on other elements (boryls, germyls, silyls …) can be an elegant way to drastically improve the reactivity of the photoinitiating systems. Actually, only few studies are based on this approach. Particularly, silyl, germyl and boryl radicals are from this point of view particularly optimized i.e. their addition rate constants onto (meth)acrylate double bond are in the 108 M-1s-1 range; this can be very a high advantage compared with the relatively “low” reactivity of carbon centered radicals (rate constants in 105 M-1s-1 range). This work has been divided in two sub-tasks.
important results were obtained with already two publications in high impact journal (see the associated document).
The development of high performance resins in the present project (initiating systems & monomers) will undoubtedly overcome this issue and constitute an outstanding breakthrough in the field of 3D printing, as currently, a lack of really efficient initiating systems for LED induced polymerizations is noted.
For the exploitation of the results of this study, Photon & Polymers (PnP – Industrial Partner) should check several aspects; the selected systems must be highly efficient for radical or cationic polymerization. These systems will be investigated for polymerization under industrial LED irradiation device (PnP set-ups). This industrial scale-up will be led with the evaluations of the constancy of the quality and performances obtained in Task 5. Task 5 will be carried out by Dr. Khalid Zahouily assisted by a PnP R&D engineer.
One of the objectives will be the deposit of patents (in common between Partners 1-3). For the academic Partners (Partners 1&2), the CNRS (in common between Partners 1 & 2) will be selected as the reference agency for the patent application; PnP will be the industrial Partner. The relative contributions of each partner will depend about their participations to the study for the class of molecules covered in the associated patent.
1) Carbazole Scaffold Based Photoinitiator/Photoredox Catalysts: Toward New High Performance Photoinitiating Systems and Application in LED Projector 3D Printing Resins
Assi Al Mousawi, Frederic Dumur, Patxi Garra, Joumana Toufaily, Tayssir Hamieh,
The field of 3D printing is a hot area and is actually claimed as a “revolution”. The aim of the present proposal is to develop, in collaboration with an industrial partner, new photosensitive resins specifically adapted for 3D printing. The present consortium (from both academia and industry) is based on internationally recognized groups for the different aspects of the project (synthesis of the photoinitiators PI, study of the chemical intermediates, polymerization, 3D printing …), who have joined in an effort to answer one of the societal challenges evidenced by the ANR (see below). This project is in perfect agreement with the present call "industrial revival" and still more particularly with the aspect "Matériaux et Procédés". Indeed, this project completely answers to the development of new tools and methods for the production or the study of new polymer products which can be conceived, prototyped and tested in short time and for a reduced cost. It also resorts to the section "Procédés économes et intensifiés" because of the potential use of low-energy photochemistry in polymer producing processes. In particular, the use of light emitting diodes (LEDs) to industry processes (such as 3D printing) offers tremendous potential to stimulate industrial renewal.
For 3D printers using polymers through the stereolithography or the inkjet 3D printing, the writing speed is actually the strongest limitation and the increase of the resin sensitivity is actually the crucial challenge. The use of Light Emitting Diodes LED@405 nm as the irradiation device corresponds actually to the reference in this technology as LEDs are characterized by intrinsic advantages (low energy consumption, very compact, safer than laser …). However, the current commercial photosensitive resins are based on UV Type I photoinitiators that are perfectly adapted for the classical UV-curing field using Hg lamp but clearly not to the 3D-printing area using a LED with an irradiation wavelength at 405 nm. Therefore, these photoinitiators, not really adapted to the irradiation wavelengths of the LED used in 3D printers (405 nm), lead to slow printing speeds.
In strong collaboration with an industrial partner (the SME: Photon & Polymers noted PnP), we will propose to drastically improve the photosensitivity of these resins through the development of new systems specifically adapted for this application. The great originality is the development of high performance photosensitive formulations, this will undoubtedly overcome this issue and constitute a breakthrough in the field of 3D LED printing. This project of how to improve the chemistry (e.g. the photosensitivity) of the resins for 3D printers will allow to the French academic and industrial community to play a key role in this emerging domain. The participation of an industrial partner with a strong background in this field is important for the success of the project but also offers a high potential of valorisation (a significant part of the PnP activity is already based on 3D printing but is expected to increase if new reactive resins are successfully developed).
In the present project, we will develop new photosensitive formulations (photoinitiating systems and monomers/oligomers) well adapted for 3D LED printing requiring specific conditions (irradiation wavelengths, light intensity, viscosity, writing speed ...) since the current formulations are not so well adapted. An almost complete lack of really efficient initiating systems for 3D LED printing can be noted.
For the first time, all the active component of the photosensitive resins will be developed for this specific application: both the initiating systems and the monomers/oligomers will be taken into account.
Monsieur Jacques Lalevée (Institut de Science des Matériaux de Mulhouse)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
PnP Photon’Polymer (PnP) SME
IS2M Institut de Science des Matériaux de Mulhouse
CNRS DR12_ICR Centre National de la Recherche Scientifique délégation Provence et Corse _ Institut de Chimie Radicalaire
Help of the ANR 401,277 euros
Beginning and duration of the scientific project: September 2015 - 48 Months