Cyanoacrylates, A Brief Overview:

Cyanoacrylates, A Brief Overview:

Post by Steven D. Russel » Wed, 20 Dec 2000 02:00:46



Hello to the group,

There has been a recent thread on CA and I thought some of you may like
a bit of background information on CA and it properties.

Cyanoacrylates, A Brief Overview:

Monofunctional 2-cyanoacrylates were first patented in 1949, but the
first viable production process did not evolve until 1954. In the early
1950's, scientists at Eastman Kodak were working on thermal
polymerization and discovered the rapid room-temperature cure and
excellent adhesion properties of 2-cyanoacrylates, quite by accident.

While working on a freshly prepared monomer, the scientists discovered
that the glass prisms of the refractometer has become tightly bonded.
Extensive work thereafter, found that many different types of substrates
bonded in the same manner. Subsequently in 1958, Eastman 910 debued, the
first in a large family of 2-cyanoacrylate ester adhesives.

2-cyanoacrylates polymers spontaneously form (via an anionic/radical
mechanisms) when their liquid precursors, or monomers are placed between
two closely fitting surfaces. The great utility of these adhesives
arises from the electron-withdrawing character of the groups adjacent to
the polymerizable double bond.

The high reactivity (cure rate) and their polar nature, enables the
polymers to adhere quite tenaciously to a wide variety of substrates.
Low humidity and/or acidic groups on the substrate surface will slow or
inhibit the cure reaction. To extend the usable shelf life, free-radical
stabilizers such as quinones or hindered phenols are used.

Methyl, Ethyl, Butyl, Allyl and Methoxyethyl esters are available with
various setting characteristics and rheological properties. However, the
Methyl and Ethyl esters dominate the commercial industrial market. The
vinyl structure of 2-cyanoacrylates makes them prone to spontaneous
polymerization. The chain propagation can be initiated by ionic or
radical mechanisms.

The rate of polymerization depends on temperature, humidity, light and
the presence of accelerators, like peroxides or bases. In addition to
polymerization, 2-cyanoacrylates undergo reactions typical of vinyl
compounds, such as addition.

2-cyanoacrylates can be manufactured by many different methods. The base
monomers are too thin for convenient use, so thickeners, stabilizers or
property-modifying additives may be added. The viscosity's are available
from wicking grades (water thin) to thixotropic gels that range from
20,000 to 50,000 mPa*s for large gaps.

The acrid odour of 2-cyanoacrylates, can be effectively mitigated by the
substitution of an alkoxyalkyl ester side chain, for the normal alkyl
group. Products so modified, are practically odour free, but are
slightly less effective as adhesives.

The basic method to manufacture 2-cyanoacrylate esters involves
preparation via the Knoevenagel condensation reaction (the corresponding
alkyl cyanoacetate reacts with formaldehyde in the presence of a basic
catalyst, to form a low molecular weight polymer). The resulting polymer
slurry is acidified and the water is removed.

The polymer is then cracked and redistilled at high temperatures onto a
suitable stabilizer combination to prevent repolymerization. Protonic or
Lewis acids are typically used in combination with small amounts of a
free-radical stabilizer.

Although the methods and processes have continually changed and evolved
over the years, this is the standard method to manufacture these esters.
One recent and significant advancement in the manufacturing process is a
continuous process where the condensation is carried out in an extruder.
By-products are then removed in a degassing zone and the molten polymer
(mixed with stabilizers), is cracked to yield a raw monomer.

Recent advances have lead to flexible 2-cyanoacrylate formulas, which
remain somewhat flexible when cured. These types of esters are
particularly useful to turners when bonding dissimilar materials like
stone/metal and wood. The dissimilar expansion and contraction rates of
these materials, can cause subsequent failure of the bond when using
traditional cyanoacrylates that feature non-flexible, or brittle bonds.

If you would like to learn more about CA's, look for my extensive
article on 2-cyanoacrylate adhesives, which will be published in
"Woodturning" magazine early next year. Happy holidays and best wishes
for a safe and prosperous new year!

--
Letting the chips fly...
Steven D. Russell
Eurowood Werks Woodturning Studio
The Woodlands, Texas

Website coming soon!

 
 
 

Cyanoacrylates, A Brief Overview:

Post by Richard Prest » Wed, 20 Dec 2000 09:01:37


Hi Steve,
I noted the comment about 'brittle bonds'. While not a surprise, or new news,
it came home to roost today. My wife handed me a box with the metal round
hinge. It had come apart after 6 years. I sure hope I didn't sell anything
significantly dependant upon the glue!

I hope you have the opportunity to deal with the flexible CSs.
Regards,
Richard

Quote:
>Hello to the group,

>There has been a recent thread on CA and I thought some of you may like
>a bit of background information on CA and it properties.

>Cyanoacrylates, A Brief Overview:

>Monofunctional 2-cyanoacrylates were first patented in 1949, but the
>first viable production process did not evolve until 1954. In the early
>1950's, scientists at Eastman Kodak were working on thermal
>polymerization and discovered the rapid room-temperature cure and
>excellent adhesion properties of 2-cyanoacrylates, quite by accident.

>While working on a freshly prepared monomer, the scientists discovered
>that the glass prisms of the refractometer has become tightly bonded.
>Extensive work thereafter, found that many different types of substrates
>bonded in the same manner. Subsequently in 1958, Eastman 910 debued, the
>first in a large family of 2-cyanoacrylate ester adhesives.

>2-cyanoacrylates polymers spontaneously form (via an anionic/radical
>mechanisms) when their liquid precursors, or monomers are placed between
>two closely fitting surfaces. The great utility of these adhesives
>arises from the electron-withdrawing character of the groups adjacent to
>the polymerizable double bond.

>The high reactivity (cure rate) and their polar nature, enables the
>polymers to adhere quite tenaciously to a wide variety of substrates.
>Low humidity and/or acidic groups on the substrate surface will slow or
>inhibit the cure reaction. To extend the usable shelf life, free-radical
>stabilizers such as quinones or hindered phenols are used.

>Methyl, Ethyl, Butyl, Allyl and Methoxyethyl esters are available with
>various setting characteristics and rheological properties. However, the
>Methyl and Ethyl esters dominate the commercial industrial market. The
>vinyl structure of 2-cyanoacrylates makes them prone to spontaneous
>polymerization. The chain propagation can be initiated by ionic or
>radical mechanisms.

>The rate of polymerization depends on temperature, humidity, light and
>the presence of accelerators, like peroxides or bases. In addition to
>polymerization, 2-cyanoacrylates undergo reactions typical of vinyl
>compounds, such as addition.

>2-cyanoacrylates can be manufactured by many different methods. The base
>monomers are too thin for convenient use, so thickeners, stabilizers or
>property-modifying additives may be added. The viscosity's are available
>from wicking grades (water thin) to thixotropic gels that range from
>20,000 to 50,000 mPa*s for large gaps.

>The acrid odour of 2-cyanoacrylates, can be effectively mitigated by the
>substitution of an alkoxyalkyl ester side chain, for the normal alkyl
>group. Products so modified, are practically odour free, but are
>slightly less effective as adhesives.

>The basic method to manufacture 2-cyanoacrylate esters involves
>preparation via the Knoevenagel condensation reaction (the corresponding
>alkyl cyanoacetate reacts with formaldehyde in the presence of a basic
>catalyst, to form a low molecular weight polymer). The resulting polymer
>slurry is acidified and the water is removed.

>The polymer is then cracked and redistilled at high temperatures onto a
>suitable stabilizer combination to prevent repolymerization. Protonic or
>Lewis acids are typically used in combination with small amounts of a
>free-radical stabilizer.

>Although the methods and processes have continually changed and evolved
>over the years, this is the standard method to manufacture these esters.
>One recent and significant advancement in the manufacturing process is a
>continuous process where the condensation is carried out in an extruder.
>By-products are then removed in a degassing zone and the molten polymer
>(mixed with stabilizers), is cracked to yield a raw monomer.

>Recent advances have lead to flexible 2-cyanoacrylate formulas, which
>remain somewhat flexible when cured. These types of esters are
>particularly useful to turners when bonding dissimilar materials like
>stone/metal and wood. The dissimilar expansion and contraction rates of
>these materials, can cause subsequent failure of the bond when using
>traditional cyanoacrylates that feature non-flexible, or brittle bonds.

>If you would like to learn more about CA's, look for my extensive
>article on 2-cyanoacrylate adhesives, which will be published in
>"Woodturning" magazine early next year. Happy holidays and best wishes
>for a safe and prosperous new year!

>--
>Letting the chips fly...
>Steven D. Russell
>Eurowood Werks Woodturning Studio
>The Woodlands, Texas

>Website coming soon!


 
 
 

Cyanoacrylates, A Brief Overview:

Post by Steven D. Russel » Thu, 21 Dec 2000 00:41:52


Hello Richard,

I can relate to that! When I first began my inlaying endeavours, I
tested (yes, I seem to test every ***y thing) various adhesives for
inlaying polished stone agates and precious metals...

All of the 2-cyanoacrylate tested samples failed, some very easily.
Since most of my timber stock for these items are ***s, I added an
Acetone wash to the timber surface where the CA would be applied...
better by far, but all of the test samples still failed. Some of these
stones have extremely polished surfaces and the CA just could not make
an acceptable bond.

Epoxy worked well, but it was/is a pain to use at times. Not to mention
the lingering acrid odour. I do use Epoxy at times now, but it is
reserved for "difficult" situations where its particular properties are
needed. I eventually settled upon adhesives that remained flexible when
they were cured. In all of the test samples when the flex adhesive was
used, there were no failures, none, nada, zilch!

Because CA is so popular, some turners use it for almost everything.
Unfortunately, there are many situations where CA's are far from the
best choice to use. This is especially true when you are working with
dissimilar materials, that experience different expansion and
contraction rates when compared to timber. Take care and all the best to
you and yours!

--
Letting the chips fly...
Steven D. Russell
Eurowood Werks Woodturning Studio
The Woodlands, Texas

Website coming soon!

Quote:

> Hi Steve,
> I noted the comment about 'brittle bonds'. While not a surprise, or new news,
> it came home to roost today. My wife handed me a box with the metal round
> hinge. It had come apart after 6 years. I sure hope I didn't sell anything
> significantly dependant upon the glue!

> I hope you have the opportunity to deal with the flexible CSs.
> Regards,
> Richard

 
 
 

Cyanoacrylates, A Brief Overview:

Post by ChromeDom » Thu, 21 Dec 2000 01:28:53


Quote:

> needed. I eventually settled upon adhesives that remained flexible when
> they were cured. In all of the test samples when the flex adhesive was
> used, there were no failures, none, nada, zilch!

A quick list of those adhesives?  Please.

Gene

 
 
 

Cyanoacrylates, A Brief Overview:

Post by Steven D. Russel » Sat, 23 Dec 2000 21:48:29


Hello,

Sorry for the late reply, I have been out of town quite a bit of late.
One of my favourite adhesives for bonding stone to wood, or wood to
metal is a product called E-6000. It is available from lapidary
suppliers, craft stockists, jewellery and findings stockists and Craft
Supplies USA, in Provo.

If the substrate is an *** timber, I incorporate a solvent wash into
the assembly protocol. Both the mating surfaces receive this solvent
wash before the adhesive is applied. After the solvent has evaporated, I
apply the adhesive. The solvent wash removes any of the natural timber
oils/extractives, or dusts/debris that may be lingering on the intended
mating surfaces.

The E-6000 adhesive has a strong odour, so make sure you have a well
ventilated area and wear a proper respirator, with an organic vapour
cartridge. The respirator is also required during the solvent wash
phase. If you have any questions, please do not hesitate to contact me.
Best wishes for a safe and happy holiday season.

--
Letting the chips fly...
Steven D. Russell
Eurowood Werks Woodturning Studio
The Woodlands, Texas

Website coming soon!

Quote:


> > needed. I eventually settled upon adhesives that remained flexible when
> > they were cured. In all of the test samples when the flex adhesive was
> > used, there were no failures, none, nada, zilch!

> A quick list of those adhesives?  Please.

> Gene

 
 
 

Cyanoacrylates, A Brief Overview:

Post by Markus Ellermei » Sun, 31 Dec 2000 05:12:08


On Tue, 19 Dec 2000 15:41:52 GMT, "Steven D. Russell"

Quote:

>Hello Richard,

>I can relate to that! When I first began my inlaying endeavours, I
>tested (yes, I seem to test every ***y thing) various adhesives for
>inlaying polished stone agates and precious metals...

>All of the 2-cyanoacrylate tested samples failed, some very easily.
>Since most of my timber stock for these items are ***s, I added an
>Acetone wash to the timber surface where the CA would be applied...
>better by far, but all of the test samples still failed. Some of these
>stones have extremely polished surfaces and the CA just could not make
>an acceptable bond.

Hello Steven,
Sometimes precious stones are "waxed" with liquid paraffin, especially
the soft ones like turquoise, lapis, malachite, sodalith (I've even
seen carved rubies that were manipulated this way). So it might be
worth trying to give them that acetone wash, too. The waxing, however,
is done using vacuum, so the stone is ***d. Best check with the
dealer.
Re precious metal, with silver there can be a firescale layer beneath
the outer surface which gives bad adhesion, as the bond between the
layers isn't too firm. The firescale forms when silver is annealed or
soldered with no protection by borates.
Sorry for answering late, but I haven't access to the net very often.
 
 
 

Cyanoacrylates, A Brief Overview:

Post by Steven D. Russel » Sun, 31 Dec 2000 18:23:16


Hello Markus,

I should have mentioned that my Acetone wash included the mating surface
of the stone/metal. It does help considerably, but typical brittle CA's
are not the best choice for an adhesive in these situations. In
addition, I lightly sand the mating surface of the metal to improve
adhesion.

Since I began inlaying stone, gemstones and precious metals, I have a
new respect for these materials and how they are produced. I have always
felt that the marriage of stone and wood was quite provocative... It is
a frequent marriage in my work, as it evolves into new and exciting
paths to explore. Good luck to you and thanks for the helpful
information. Take care and all the best to you and yours!
--
Letting the chips fly...
Steven D. Russell
Eurowood Werks Woodturning Studio
The Woodlands, Texas

Website coming soon!

Quote:

> On Tue, 19 Dec 2000 15:41:52 GMT, "Steven D. Russell"

> >Hello Richard,

> >I can relate to that! When I first began my inlaying endeavours, I
> >tested (yes, I seem to test every ***y thing) various adhesives for
> >inlaying polished stone agates and precious metals...

> >All of the 2-cyanoacrylate tested samples failed, some very easily.
> >Since most of my timber stock for these items are ***s, I added an
> >Acetone wash to the timber surface where the CA would be applied...
> >better by far, but all of the test samples still failed. Some of these
> >stones have extremely polished surfaces and the CA just could not make
> >an acceptable bond.

> Hello Steven,
> Sometimes precious stones are "waxed" with liquid paraffin, especially
> the soft ones like turquoise, lapis, malachite, sodalith (I've even
> seen carved rubies that were manipulated this way). So it might be
> worth trying to give them that acetone wash, too. The waxing, however,
> is done using vacuum, so the stone is ***d. Best check with the
> dealer.
> Re precious metal, with silver there can be a firescale layer beneath
> the outer surface which gives bad adhesion, as the bond between the
> layers isn't too firm. The firescale forms when silver is annealed or
> soldered with no protection by borates.
> Sorry for answering late, but I haven't access to the net very often.