When working with acrylic sheet, one of the things that we often need to do is
stick it together, and while some glues work on acrylic. Solvent bonding with
commercial acrylic cement is preferable but not necessarily available or
affordable. The Internet says a lot about acrylic bonding alternatives, for example
acetone and other homemade concoctions but there's no real definitive answer
about what works, what doesn't, what's better and what's worse. So, let's take a
closer look at how to bond acrylic sheet without acrylic cement.
This is Cosador, Johnathan here. Bonding acrylic to acrylic
or solvent welding acrylic is a process where acrylic is chemically melted
together, and a lot of things are said about solvent welding chemical
alternatives and how to make them, but what I've done is pick a heap of
chemicals off of the shelf at the hardware store and I'm going to test
them in comparison to a well-known commercial acrylic cement. Our control,
I'll call this well-known bonding agent number three, I found number three to be
expensive and ridiculously hard to get in Australia, number three bonds quick
and has a very strong bond. Before we get started, a lot of these chemicals are
dangerous so please look up the MSDS for your own safety.
Now, the chemicals that we're going to test. First up,
xylene, xylene is used for thinning paints and varnishes, it can be used in
place of toluene because of the similar chemical structure and toluene is known
to be a good solvent for acrylic. Methyl ethyl ketone or MEK. Off the shelf this
stuff is PVC priming fluid, it's used by plumbers to clean and
prime PVC before gluing, and it's well known to model builders for solvent
welding styrene and similar plastics. Lacquer thinner, lacquer thinner is very
similar to xylene and it's used for similar purposes, this product contains
toluene and MEK as its largest component. Acetone, now there's a lot of
controversy on this one, many say it's the way to solvent weld and there are
others that say that it just stresses the acrylic, and lastly, paint stripper
this seems like a strange one but it's been picked because it contains
dichloromethane which is the solvent that is used in many commercial solvent
welding products. The two main attributes of a good acrylic solvent weld are
clarity and strength, so I'll build a rig to test the strength of the bond and
I'll bond some pieces together to test the clarity and visual defects. So I best
jump on the computer and design some parts.
I'll cut off a piece by hand to fit the laser cutter
laser cutters are great for repeat parts but if you don't have one and you'd like
to know how to cut acrylic by hand please check out my other videos, I'll
leave a card on this video and a link in the description and even though I'm
using laser laser cutting isn't the only way and it's not necessarily better but
it's quick and it repeats almost exact cuts which is perfect for a testing
situation. Now all the cuts are made, I'm going to stick them all together
acrylic cements are usually dispensed from an applicator bottle with a syringe nozzle
and to get these by themselves can be expensive and not really viable
for testing purposes. So, I'll be using some one mL medical syringes and
25 gauge needles, I got these for next to nothing because they were out of date.
So, let's get started I'll peg it together, I'll apply the
solvent and I'll do this for each of the chemicals and once they're all done I
need to let them cure for 24 hours . Okay, it's been a little over 24 hours and all
these parts are ready for testing and inspection. First I'll be doing the
strength test, for this test I've designed two pieces, one that will
be screwed to the bench and one that will be pulled on by a hook. They have
been designed to be joined face to face to avoid edge cut imperfections, with
a joining edge of 5 mm by 40mm with the distance to the
force applied by the hook of 50mm. I get a piece of ply and
clamp it down to the work surface and screw the test pieces to it and I have
made a luggage scale camera rig, so we can see the force required to break the
bonded pieces. None of these solvent bonds have had time to reach full cure
but they will show enough evidence for testing purposes. First up the control
number 3, breaking at 5.74kg calculated that's 56.25 N.
Unfortunately the xylene broke while setting up for the test and due to the
weak forces exerted, I'll award it a nil score. The methyl ethyl ketone or MEK
breaking at 3.74kg calculated that's 36.65 N.
The lacquer thinner breaking at 0.49kg calculated that's 4.8N.
The acetone breaking at 3.14kg calculated that's 30.77N,
and the paint stripper breaking out 3.29kg calculated that's 32.24N.
That means structurally that the control did the best, followed by the mek, then the paint
stripper, then the acetone with the others that are chemically similar
falling to the bottom of the list. On to the clarity tests, with the control, apart
from visible workshop dust, it is completely transparent and where number
three is present it appears as if the two pieces were one. With the xylene, it
was transparent where it could weld the piece, however much of the xylene appears
to have evaporated through the edge of the joint, it's left some big fractures
in the acrylic and has cracked some of the edges that were previously stressed
by the laser. With the methyl ethyl ketone, it's clear and appears to have
left accentuated fractures where it had been stressed by the laser, however there
are no internal cracks. The result of the lacquer thinner is unfortunately much
the same as the xylene, with high evaporation and deep fractures. The
acetone, it was transparent where it could weld the piece, however it's left
some big fractures in the acrylic, and finally the paint stripper, some of the
paint stripper is clear but what I suspect to be the cellulose thickener
has left a white residue, however the paint stripper seemed to melt
the acrylic the best without stressing it. Apart from the control, the methyl
ethyl ketone seemed to do the best, so I'll sand and polish one of the edges
and have a side-by-side comparison with the control, the edge of the join sands
and polishes up quite well, and looking at them apart from a few
minor fractures on the methyl ethyl ketone they can barely be told apart. Now,
I'm not saying that MEK or methyl ethyl ketone is a replacement for proper acrylic
cement, but for a potentially lower-cost bonding agent that does not need to be
perfect, it can do the job. With those tests, I got some results that kind of
surprised me and made me realize that there's more that I want to look into
and maybe I need to make a part two, and if you found this interesting to please
like subscribe and turn on notifications and if you would like me to make
something else please drop a comment below and remember guys
break it till you make it!
and I'll see you next time.