Woodturning and Woodworking Articles:

Cyanoacrylates, A Brief Overview:
By: Steven D. Russell
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 stabilisers 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, stabilisers 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 stabiliser combination to prevent repolymerization. Protonic or Lewis acids are typically used in combination with small amounts of a free-radical stabiliser.

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 stabilisers), 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.
 

Making Pens With Polyester Resin
By Clarrie Snell
Sydney Woodturners Guild
The pens may initially take a while to make, however the finished article is extremely durable with brilliant colours that are striking and pleasing to the eye.


Mixing Equipment
4 flexible plastic containers (bottom half of small round drink containers or drink cups).
6 Stirrers (old hacksaw blades, or wooden sticks).
Eye dropper.
Dessert spoon or measuring cup.

Safety
Wear eye protection during the mixing procedure. The Resin Hardener, MEKP, is a dangerous substance to handle. Safety goggles should be worn during handling, as loss of eyesight is possible if MEKP comes in contact with the eyes.
Read safety instructions before using this substance.
Wear face masks with filters to suit chemicals during the mixing procedure, machining and finishing.
Wear disposable gloves during mixing procedure.

Chemicals
Acetone for cleaning purposes.
Surf Board Resin (Finishing Resin GC3).
Resin Hardener (MEKP)
Resin colours to suit your taste.
Vaseline (petroleum Jelly).

Mold and release equipment
5 pieces 5/8 OD electrical conduit x 120mm long.
Timber moulding jig, to support conduits (see sketch 1).
Timber separation jig with metal drift (see sketch 2).

Preparation
Place small amount of Vaseline onto moulding jig timber pegs and conduit supports.
Locate conduits onto timber pegs.

Mixing Procedure
Place 1 dessertspoon of resin into 3 plastic containers.
Using 3 separate hacksaw blades, place a small amount of each colour into each of the 3 containers and stir thoroughly.
Place 9 dessert spoons of resin into the remaining small plastic container .
With another hacksaw blade, add white colour, slightly more quantity than for the smaller containers and stir thoroughly
Add 4 drops of MEKP Hardener to each of the 3 colour containers,. Stir thoroughly.
Add 36 drops of MEKP Hardener to the white colour container and stir thoroughly.
Pour the contents of the three-colour containers into the white colour container, one at a time, using a circular motion onto the surface of the white resin. DO NOT STIR COLOURS TOGETHER otherwise you will have one solid colour mix and not a colour pattern that you are trying to achieve.
With a clean hacksaw blade, gently pierce or push the colours into the white colour, just a few times, the more you pierce the more you mix the colours into the white base colour.
Gently pour mixture into conduits.
Curing of resin pen blanks may take about 4 hours, depending on temperature. Resin blanks will not stick to the conduits but will shrink away from the sides making it easy to push the blanks out of the conduits.
After the blanks have cured, support conduit in separation jig. Use a steel drift to remove resin blank from conduit, (sketch 2).

Machining
Cut resin blanks to 52mm long.
Set lathe speed to approximately 1200rpm for drilling, turning and finishing operations.
Place Jacob chuck into headstock and place half resin blank into chuck with about 20mm protruding.
Drill through with 6.9mm drill, clearing drill regularly to prevent resin blank from overheating. Note 7.0mm drill will drill oversize hole for the pen brass sleeve.
Repeat above step for other half of resin blank.
Glue brass sleeves into pen blanks, preferably with a 2 pack epoxy glue.
After glue has dried, face ends of resin blanks to suit length of pen brass sleeve.
Place pen blanks onto mandrel.
Rough turning/shaping may be carried out using a one-sided curved skew scraper, (see sketch 3), or by using 80 grit paper.
Turn pen to desired shape with pen clip end turned to 8.1 diameter.

Finishing
Use 240 wet and dry paper with water to remove all marks and imperfections.
Repeat above step using 400 wet and dry paper and water.
Finish polish using metal or car polish.
Repeat above step. The pen should now have a high gloss finish, if not repeat step 3.
Assemble pen.

This Month's Tip:

Critique for turned vessels. Here is what you should look for when buying wood turned art.

Remember that these are guides only and special circumstances are always possible for exceptions.

1. Shape. The shape must be pleasing to the eye. Shapes based on classic ancient pottery forms are a good bet but are not the final answer. Wood was part of a living organism and takes its form from nature - a turned vessel that uses the natural form of the wood is often the best shape BUT the needs of "making the most" out of an odd shaped chunk of wood can also detract the artist and create lopsided pieces.
2. Balance. This is partly the shape but if the proportions are off then the shape will be unbalanced.
3. Turning quality. This is best gauged by the wall thickness of the vessel which should be uniformly thick, though may be a little thicker at the base and the rim. (Potters often make the rim heavier for reinforcement - also good for turners to remember that.) Wood vessels should not be too thick either - 5 to 10 mm for medium size vessels. Wood that is too thick will check if it dries unevenly. See also machine marks below - good turners take the time to eliminate any marks left by the machining process. Rim decorations can add significantly to the overall appearance of a piece
4. Finish. This is a personal thing but I prefer more natural finishes that allow the wood texture to be felt - though the surface should be smooth as a baby's bottom. Definitely no sanding marks. High gloss may be fun for some items but mostly it looks and feels like plastic (which it is) but it ought to feel like the wood it really is. If the finish is a varnish then it must be absolutely smooth (and preferably matte, my personal preference).
5. Machine marks. Can you tell how the work was held on the lathe when it was turned? A vessel that shows no signs of its machine heritage is superior to one that does.
6. Material. What specie of wood is it? Is it common or rare? Is it a burl? (rare) Are there knots and other inclusions which enhance the appearance? Are there checks (cracks) in the wood? (Checks should be avoided but in some pieces they can add to the appearance, though rarely) Some burls are full of holes and bark inclusions but this is what makes the material interesting. Remember it is slight imperfections that enhance beauty. "The beauty spot" on the face of Marilyn Monroe for instance.
7. Function. What is the function of the vessel? If it is a practical item then it should be suitable for its intended use. How will you use it? It CAN be art.
8. Uniqueness. Is that a word? No two pieces of wooden ware will ever be exactly alike but some turnings are emphatically unique and as such they are simply beautiful to behold. But the above criteria must be met first.
9. Name. Is the woodturner well known? If you are investing in his name you may want to buy an item from an unknown (but accomplished) craftsperson/artist because the price is right and you are investing in his future fame. But check out the above criteria to know the artists' potential. An art collector once told me he would rather have some bad art from a famous artist than great art from an unknown artist.
10. This tip is written by John Williams of Canada

Learn More:

A  monthly trip to your local AAW chapter meeting will do you more good in the long run towards learning the correct way to turn than any other method