Re: photoinitator discussion

[4Ddabbler]

The Univ. of Ill project was done as a demonstration and proof of
concept for teaching and illustrating photo initiated stereo
lithography's potential with a fairly simple user equipment setup and
not intended in anyway for use as a prodution or prototype producing
device. Not going to argue either but I was wanting to point out that
the cited experimental project was never intended to be used for a
commercial production system. Also there are a lot of other multi-
component photo initiator formulas that will work as well but in all
cases light penetration and the use of an active filtering method such
as a dye or colorant inclusion. No matter what Veloso claims or plans
to do his "secret formula" is not going to defy laws of physic or
chemistry. Properties of rigidity and brittleness can be changed by
types of ingredients and formulation ratios significantly. I am by no
means a professional chemist but fortunately have local access to one
who is a specialist in resin and polymer formulations. Getting back to
the point though that particular chemistry we are discussing was
chosen because it does work well with the abundance of blue and violet
light a typical projector bulb or lamp emits. The dye is usually
irrelevant to the properties of what the activated or cured resin or
monomer or polymer will yield other than coloration. I have no idea
what exactly Veloso's mix has in it but even if he is using one of the
"commercial standard" dyes it is still performing same functional
actions as the Sudan I as far as limiting or controlling light
wavelength selectivity and penetration.
I did some reading on Irgacure784 which is definitely a high
reactivity PI compound and is a rather ugly blaze orange. Quite likely
it would explain the ugly color of Veloso's resin mix as well as
effectively letting the cat out of the sack about his secret formula
as the Thiol-ene and Acrylate chemistry use of Bis(.eta.5-2,4-
cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)
titanium Irgacure784 is well documented in a multitude of formulations
and applications. It has a very strong activation reactivity to light
from mid band green to far violet visible light (545 to 395 nm etc...)
depending on exact composition of the other components of the "brew".
I have been looking at other materials or compounds due to the unique
blaze orange tint it sort of imbibes into whatever it is mixed. Since
it is a sort of particulate colloid when this stuff is added to a
resin mix it definitely would cause some sharp light transmission
effects changes. I guess it might be a good choice to build upon for
the 3D modeller and figures or figurines crowd since it has some braod
leeway about rigidity and flexure in proper formulation. The other
formula of the phenylbis and Sudan is better suited to most of the
applications I am interested in as the resin is merely being used as a
fixative or setting compound of sorts which is meant to be burned away
in a very high temperature furnace under near hard vacuum conditions
to leave the components it was used to support as a carrier and
deposition mask in situ. My intended use is not dependent on
flexibility, durability or long term structural rigidity since the
resin is to be obliterated or destroyed after it has served purpose as
a fixative and anchoring component.

[4Ddabbler]

I've been reading more in-depth about photo-initiators and
specifically Thiol-ene based chemistry and it seems almost dead
certain that the chemistry behind Veloso's orange resin cocktail is
Thiol-ene and Acrylate composition based. Not absolutely certain that
it has to be using Irgacure784 or other similar trademarked or
licensed chemical formulations though. There are literally thousands
and thousands of variations of chemical components to achieve a Thiol-
ene "click chemistry" reaction. I've been browsing many papers and
abstracts on this topic and am starting to get a decent handle on the
theory and practice. I had to postpone my chemistry discussions with
an expert last week and likely I'll be better prepared to get across
the goals and requirements for a pretty functional concoction without
wasting much time and resources when I can re-schedule another meeting
soon.

[4Ddabbler]

And with use of these PIs what are you using for the monomers to have
the PI radicalize and activate? The main reason I am studying the
chemistry from the whole view of the components and reactants and not
just an individual component is to reduce amount of trial and error
variations and expenditures. From documentation on Irgacure784 it is
typically sold as an additive powder to be added into a monomer or
resin cocktail and not as a pre mixed compound solution. Also 1 kg
much less 5 kg of pure Irgacure784 PI activator should be enough to
allow mixing a monomer brew of several dozens of liters of solution at
fairly intense concentrations. I have found several datasheets on
Irgacure 784 as well as several other PI compounds. I'll either figure
out whether to just post links or to attach files to thread shortly.
It is interesting to see the commercial flyers showing exactly what I
have already found out in my reading research about the 784
formulation in proper concentration being very susceptible to
activation in range of 395 to 540 nm as I have already mentioned.

[TJ.]

>
> Irgacure 819 based on 5 kg, price $85/kg
> vs
> Irgacure 784 based on 5 kg, price $1150/kg
>
------------------------------------------------
That is Crazy!!! Why such a big difference??

PS
I have also wondered instead off using a "spectrum" blocker what if we
use an Aluminum powder like they use in spraypaint as a actual
physical blocker ,A silver metal like model would also look really
cool too!.
My reasoning behind it is this.The light would enter the first few
microns by scatering between the flakes and finally just die out.

[Jon Watson]

Just curious but wouldn't it be difficult to keep the metallic
particles suspended uniformly in the resin? I have a friend that casts
with aluminum-based resins but personally don't know much about them.
It seems the aluminum particles would settle to the bottom, especially
when the resin is just sitting in the tray for hours during a build. I
could be wrong.

[4Ddabbler]

depends on viscosity and molecular weight of the resin components as
well as the particle size as beyond certain threshold electrostatic
potentials and other influencing factors can actually help levitate
particles in the fluid suspension... also many desirable metals can be
added in some form of active chemical compound that allows them to be
homogeneous in solution till the click chemistry reaction caused by
the photo-initiator takes place

[TJ.]

Speaking of Photo Initiators, ,Mine just landed from Sigma:
I figured I'll give Prof. Fang's mix a first shot when I startup the
printer,(At least just to eliminate one variable at startup).


103624-25Gram SUDAN I (C.I. 12055) 16.40 USD
1 ............................ 16.40 USD
511447-10Gram PHENYLBIS(2,4,6-TRIMETHYLBENZOYL)PHOSPH& 36.10 USD
1......... 36.10 USD
246816-500Gram 1,6-HEXANEDIOL DIACRYLATE, TECH., 80% 70.50 USD
1 ......... 70.50 USD

--------------------------------------------------------------------------------

Sub-Total: 123.00 USD
(Sudan I is still on backorder.)

After these its Cytec's concoction and after
that....huuuuhhhh.....hhmmmm ...by then hopefully you guys will give
me some good news with one of your concoction recipies. =...lol..
Happy brewing
TJ.

[4Ddabbler]

Read some more research papers on irgacure784 and 819. Have seen
several instances of incorporating both PIs into a brew batch to keep
radicalization levels elevated after 784 does its photo smog breakdown
and decay. Appears that the photolyse and photobleaching is more about
decomposition and decay of 784 and loss of PI effectiveness than any
other big issues in its use. As a noticeable byproduct it seems that
the accumulated crud of photosmog decay would start to hamper light
penetration and dispersion actions somewhat as well as adding cruddy
brown or amber hues to what it is in. This would make final cure part
look washed out or faded due to masking and obstructing light
transmission and reflection. Seems to describe the look and general
lack of luster or shine of output parts yield from Veloso's printing
bath to a tee now though. Quite likely he is using a combination of
784 and 819 or other similar more UV prominent activator PI in a
concerted reaction so that when 784 decays past viability there is
still enough 819 or other PI to keep radicalization going till cure
out completion. The blending of two different wavelength PIs also
helps somewhat in last layer next layer melding or adherence too plus
improving internal rigidity and strength with balanced formulation
amounts. Also the inclusion of a photoexciting dye or compound to amp
up activity based on selected wavelength of source emitter still bears
further consideration. Anyway I am going to look over couple of other
PIs that straddle the line on near UV to VL activation peaking and
then move onto the monomer and polymer base components studies in full
depth to resolve more about composition, texture, flexibility and
hardness combinations or results. After acrylate and related monomers
some concentration on metallization click activation depositor
chemistry as that is more to the core of my purpose in this whole mess
anyway.

[4Ddabbler]

Counting solely on your PI compound or activator as a light filtering
agent not good chemistry or engineering in my book. Use of a parameter
or performance selected pigment or dye colorant for filter purposes is
much more reliable methodology to achieve controlled light penetration
depth and exposure levels. Again I have no significant familiarity
with "standard" commercial offerings sold to rapid prototype
businesses or such so many of the "off-the-shelf-items" likely are
sold with some sort of a masking or filtering agents included and
matched properly by formulation and molar concentrations. When we
start playing with homemade or experimental recipes we are in
unfamiliar waters so planned use of filters agents by the book with
regards to soundly researched and formulation chemistry and math is
going to save lots of heartache and wasted dollars. Getting back to
the wearily over cited example of the U of Ill project study the
professor(s) and graduate students heading the development did their
math homework and used specific chemistry and equations to derive
formulations for both the monomer part components and the dye used for
the light filter agent. There are of course several other options for
dye agents if time is taken to evaluate their spectral absorption
properties and find the best match and balance between the light
wavelengths allowed or concentration upon verses those filtered or
attenuated. Similarly even if the monomer base they worked from is too
brittle or fragile to suit purposes of the planned development outcome
for this machine project design- the light filtering choices and
chemistry system can still be applied to other methyl-acrylate and
acrylates etc. for a formulation blend with better rigidity and
flexibility characteristics. After a little more ground level research
and information it will be time to do some applied chemistry and the
related mathematical figuring to proceed on or at least I'll be
feeling a lot better about spending some money for some materials to
stir together and brew with anyway.

[TJ.]

Techartisan
I have to apologize , It was my fault by starting of with the
"aluminium Blocker" a few posts back.Sorry my mistake and I should
have put that under it's appropriate thread,Promise.... I'll be good
from now on.......lol.
Come on guys let us be patient here, I truly think this is going to
turn into a awesome forum, we are all on new territory and
experimentation.Let us all (me included) stick to the topics respect
each others opinions and threads.
Also tnx you for that formula,can't wait to get the printer going,and
try it all out.
Thank you all for your input so far,we truly appreciate that.
TJ.

[TJ.]

"Product Availability: 1 In Stock from MILWAUKEE 06/22/11 "

What is the name the company in MILWAUKEE that sell these ?
tj.

[Jon Watson]

Tj, That's from Sigma-Aldrich. Their shopping cart shows what & when
stuff is available and in stock. Sudan I is still back-ordered until
Aug. but hopefully someone finds an alternative UV blocker or dye to
use. I would really like to find an opaque dye/solution. If I could
make black or gray opaque parts, that is my ultimate goal.

[John]

Annother source of chemistry is Santa Cruz Biotechnology, Inc.
(scbt.com). They have 1,6-HEXANEDIOL DIACRYLATE, listed @ $65/500ml.
Also Sudan1. Their website does not show stock levels though.
Also I didn't see the Irgacure 819 listed

[TJ.]

Tnx John
good tip!... And also good prices..!
Sudan 1 is hard to find.
TJ.

[4Ddabbler]

Nice to see some life again here in the forums. The discussions
threads were seeming very near lifeless and abandoned for the better
portion of this month.
Acrylate, di-acrylates and methyl-acrylates for the prime component
resin base can be improvised at prices of maybe 1/2,1/3 or maybe 1/4
that of even the latest more reasonable prices quotations and at 2X or
3X 4X etc. larger volume yields as well. The PI component is still
looking to be the deal breaker on cost for most. I am hoping to soon
run into some good news and results in the area of creating or
improvising something that works as a PI for much more reasonable
prices than any standard commercial offerings soon. Most of these
outrageous prices are for the tradename/brandbame BS and relevant
marketing involvement license extras and so forth. I have launched
some ongoing small experiments and inquiries for hopefully arriving at
something better cost and performance speaking in the realm of
workable PI agents. I am still betting on a mixture or blend of
something with the same/similar chemicals components ingredients
equivalent as the commercial branded Irgacure 819 + 784 or another
brew made very similar that has two components optimized to activate
and accelerate cures at two different distinct limited spectral bands.

[4Ddabbler]

Something else in PI land....

Found this product during a lookabout web search session on PIs
earlier this evening. Is really interesting chemical and properties as
it is for a red light centric activation that would allow for a
significant bandwidth separation in line with the dual bandwidth stuff
I am concentrating on. >>>:

H-Nu_Blue 640/660 >>>

> http://www.sglinc.com/files/H-Nu-Blue.pdf
and product page link showing three VL spectral band optimized
formulations at three different peak activation/absorption wavelength
center points
> http://www.sglinc.com/photoin.htm

No idea price or availability or any other gotchas at the moment but
something to take a look at still. Would allow scanning with a multi-
wavelength laser and galvo systems for doing a 3D inside out build as
I mentioned some time back. Basically it also could be used in a
layer by layer or ply method such as things are being worked on as
well as the ultra rapid fast build concept for the future forward
concepts.

[thebluedirt]

Hi 4Dabbler:
what if any progress have you made in this area in the last 6 months? 

[Milan Augustin]

I tested HnU Irgacure-470 and 819th
HnU is too slow .... 50-60s.
Irgacure 819 .... 15-20s
I recommend using photoinitiator Irgacure. 

http://3dtisk.blogspot.com/

2012/4/11 thebluedirt <dave....@gmail.com>

[thebluedirt]

Thanks for the tips!

On Wednesday, April 11, 2012 12:14:56 PM UTC-4, ago wrote:

I tested HnU Irgacure-470 and 819th
HnU is too slow .... 50-60s.
Irgacure 819 .... 15-20s
I recommend using photoinitiator Irgacure. 

http://3dtisk.blogspot.com/

2012/4/11 thebluedirt

Hi 4Dabbler: