I want to start my research work on nano reinforced polymer composites, for that i am choosing desktop SLA additive manufacturing process for preparing the component. My doubt is that, is it possible to cross link the photo polymer which is reinforced with nano particles. If it is possible, then how extent will it give better performance? If not possible, then what is the alternative method to reinforce photo polymer to get better performance? Please respond, your suggestions will helps me a lot to go in right direction.
Dear Borra N Dhanunjaya Rao , if your resins are reinforced with nanoparticles it shouldn´t be any problem with 3D SLA printer. You could print any object with sizes equal or bigger than the smallest of your nanoparticles.
SLA don´t use nozzles, so even dealing with anisotropic NP´s like nanofibers or nanosheets you shouldn´t face any clogging problem.
SLA has its own drawbacks too, like the need of support scaffolding (depending on the 3D piece´s shape and size), problems of oxigen inhibition (depending on the photopolymer used) and resolution of the 3D structures fabricated (often derived from the mask projector used). Luckily all these problems can be solved.
Performance of the nanocomposite would depend on the intended application and probably the best way to test this is by making experimental tests. I would try first with a simple object like a typical test probe or bar, for measure mechanical properties, for instance. It wouldn´t need to be made by 3D printing, at least as a first test you can check what happens with a slab of material fabricated by molding (if you are just testing composite´s performance before buying a 3D printer. Of course, if you already have a printer, make the test slab by printing).
Optical, electrical, chemical,etc performances can be tested also, it will depend on the pourpose of the 3D printed object.
Methods for reinforcing photopolymers will depend on the kind of polymer you have and the physical or/and chemical processes that happens on the polymer when exposed to the light you are using. Crosslinking is a common way to improve its mechanical properties and also makes them more resistant to solvents.
Hope it helps.
Hi Borra N Dhanunjaya Rao
With SLA 3D printer, you can print different types of resins loaded or not with nanor-einforcements, however you must consider some factors both technological and of the resin itself.
If you decide to load a photosensitive resin with nanoparticles, you should consider the considerable increase in the viscosity of the formulation. This can lead to problems and defects during the printing of objects since if the viscosity is too high, the resin may not cover the printing area between layers.
Another point to consider is the stability of the particles within the resin. If they are not very compatible, the particles can aggregate within the resin, creating a heterogeneous or poorly stable resin. If the nano-loaded resin is not stable (at least during the time of 3D printing), the parts cannot be printed with the desired shapes, might present very low printing definition or the part could be full of defects.
Also, even if the compatibility of the particles is quite good, it could happen that the particles 'precipitate' or decay towards the bottom of the resin, so you should also consider that the viscosity of the resin (pristine) is adequate for keep the particles in suspension during printing.
From a more chemical point of view, the nanoparticles (NPs) added into the resin can absorb part of the light in the SLA (or DLP) printing process, so the reactivity and polymerization kinetics of the resin decrease as the amount of NPs increase. A resin for 3D printing (or photopolymer) is composed typically of oligomers/monomers and photoinitiator. This last one absorbs the light during the printing process generating radicals, which react with the pre-polymer or monomers and thus promoting the polymerization reaction. If the light is absorbed by another entity, such as the particles within the resins, the reactivity of the resin decreases.
So you should find a compromise between the amount of particles that you add into the resin, the viscosity and stability of the liquid system, and the absorption of light during printing. By finding a balance between these aspects, in addition to others, you can successfully print nanocomposites.
I hope it has been useful to you.
Gustavo Gonzalez,
Thank you Gustavo for your valuable suggestions, yes what you told is exactly correct but in recent years also there are many SCI papers are there on nano reinforced photo polymer 3D printing by SLA. And they are telling that the properties are improved by some post curing methods and all, as SLA only prints to build a structure or 3D object it requires some post curing process. If it is the case will it work with post curing process like additional UV curing, thermal curing and all. Gustavo Gonzalez
Well yes, after the 3D printing step the parts are frequently subjected to post-curing processes (upon UV light or thermally, depending of the starting resin) to achieve the higher polymer conversion as possible, obtaining thus printed parts with improved characteristic such as mechanical properties among other.
The post-curing step might boost the features of your printed part according to the desired final properties and the looked-for application of them.
But in my opinion, before to think about the post-curing step, one must first evaluate if the nano-reinforced resin could be effectively processed by a SL-3D printer. Borra N Dhanunjaya Rao
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