Glue

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Several glues are used in penmaking. Each has strengths and weaknesses.


Cyanoacrylate (CA) also known as Superglue [edit]

CA is fast, clear or black and available many places.  It comes in thin, medium, thick, and gel forms.  A pump or aerosol spray accelerator will cause the glue to set almost instantly.

More than you ever wanted to know about CA's...[edit]


The basic CA molecules are all very similar. Most of what we use in finishing are ethyl cyanoacrylates. The low odor CA's are things like ethoxyethyl cyanoacylate. They are low odor because the basic molecule is a higher molecular weight, and so it is less volatile.

Manufacturers of CA adjust the viscosity of the CA glues by adding in polymethylmethacrylate (Plexiglas) in small amounts. The CA materials themselves have a very low viscosity, so the PMMA is used to tailor the glues for a variety of applications. Sometimes they also add in microscopically small silica particles. The effect of aging on the shelf is just like the effect of adding PMMA -- instead of adding PMMA intentionally, polycyanoacrylate forms in the CA liquid due to the residual moisture.

CA cures via a process known as anionic polymerization. The reaction is triggered by the presence of a weak base. Water is a weak base, and every surface has a small amount of water present. Low humidity conditions (like winter up north) will slow down the cure of a CA. Very small amounts of moisture are needed to initiate the cure -- the water is not "used up" in each step of the reaction. This also means that exposure to very low levels of water during storage will reduce the shelf life of the CA. On the shelf, the CA cures due to the presence of water. every time you squeeze a drop of CA out of the bottle, the bottle breaths in a small amount of air (containing moisture), and the shelf life diminishes. When the tip clogs, using a pin to open up the clog can introduce more watter into the bottle, diminishing shelf life further. Always immediately replace the cap on your CA -- there is some diffusion of air/moisture in and out of the bottle even just sitting there. The reduced temperature of a refrigerator slows the aging, but if you take a bottle of CA out of the refrigerator and use it while the CA is cold and leave the opened bottle sitting near the lathe, you run the risk of condensation occurring within the bottle just due to the diffusion described above. With cold CA, it is very important to replace the cap right away. The thickened, old CA may still work for bonding, or even as a finish. If thin has aged to medium or thick, I wouldn't use it. A slight increase in viscosity is no big deal -- it is just like adding more Plexiglas to the original CA material just like the manufacturers do.

I store my CA bottles inside of a glass jar, and I keep a desiccant (like those little bags of silica gel you find in newly purchased electronics) inside the jar as well to scavenge any residual moisture.

Because CA cure is base-catalyzed, sometimes we have problems with the CA curing on wood. Many wood surfaces are slightly acidic, so the CA may not cure well right away, and sometimes not at all. The acid on the surface of the wood neutralizes the base required to catalyze the CA polymerization. It is a good practice to wipe your blanks with acetone to remove any surface oils, and then wipe with an accelerator for the CA. The accelerators are typically amines, and amines are somewhat basic. It is the presence of the additional base that catalyzes the faster CA cure.

Uses for Cyanoacrylate(CA) Glue in pen making include:
[edit]

  • Gluing brass tubes into drilled blanks.
  • Gluing Segments or inlays and blanks together .
  • Binding powdered pigments or crushed stone into inlay groves.
  • Adding a protective finish.

Advantages of CA[edit]

  • Sets and cures quickly. Especially when used in combination with an accelerator.
  • Exceptional bonding strength.
  • Appropriate for use with a wide range of materials thus permitting the joining of dissimilar strata.
  • Available in a wide range of formulations and viscosities for various purposes.
  • Single part adhesive. No need for mixing.
  • Very hard and chemical resistant when cured.

Disadvatages of CA[edit]

  • CA emits a pungent vapor that is irritating to mucus membranes. Therefore adequate ventilation or the use of a respirator are indicated. For some individuals, the irritation is sufficient to preclude it's use altogether.
  • Low Heat resistance. CA can rapidly smoke, melt and / or burn skin. In pen making, this is often caused by friction.
  • Bonds quickly to skin and is difficult to remove.
  • Brittle. If the joined materials expand and contract at markedly different rates or directions, the bond may shear and break.
  • CA emits a pungent vapor that is irritating to mucus membranes. Therefore adequate ventilation or the use of a respirator are indicated. For some individuals, the irritation is sufficient to preclude it's use altogether.

Safety[edit]

  • Cyanoacrylate (CA) is combustible. Store in a cool, dry, well ventilated area away from heat sources. Optimal storage temperature is between 40 degrees and 80 degrees F or between 5 and 25 degrees C.
  • A chemical reaction occurs when CA comes in contact with water or alkaline substances. This causes the glue to heat rapidly and can result in burns to the skin if precautions aren't taken.
  • Individuals displaying symptoms of respiratory or eye irritation should leave the gluing area to a place with fresh air until the symptoms pass.


Polyurethane
[edit]

This is an expanding glue that expands by a foaming action during the curing process.  It forms a strong bond but can move or give if stress is applied to the glue.  This property makes it a good choice for materials that are brittle, hard, or prone to cracking or splitting.

Advantages
[edit]

  • Long open time
  • Suitable for a wide range of strata
  • Expands as it cures.  Foaming action expands to fill gaps
  • Single component glue.  Ready to use, no mixing required
  • Strong Bond


Disadvantages
[edit]

  • Very short shelf life after opening
  • Relatively expensive
  • Long curing time
  • Easy to overglue due to foaming action
  • Difficult to clean up smears or spills


Safety
[edit]

Slight risk of respiratory, eye and or skin irritation

If a sufficient quantity of Polyurethane glue is inhaled, it can irritate the the respiratory system.  There is also the possibility of allergic an reaction.  Therefore use in an area with adquate ventilation or wear a respiratory mask. 

The use of gloves is recommended.  Any glue that gets on the skin will be difficult to remove and wil leave a stain.

After opening, store the container in an inverted position to extend it's shelf life.


Epoxy
[edit]

Epoxy glues are the hardest of all the glues and form the highest bond strength.  Glues can have working times from 5 minutes to 1 hour, and curing times from  30 minutes to 24 hours.

Advantages
[edit]

  • Non-shrinking
  • Gap filling
  • Wide range of open and cure times
  • Takes color well which is useful when gluing tubes into acrylic blanks
  • No clamping requirement
  • Exceptional shear strength
  • Good shelf life
  • Resists chemicals

Disadvantages
[edit]

  • 2 part adhesive.  Requires resin and hardener to be measured and mixed.
  • Time consuming to use because of thorough mixing requirement
  • Messy
  • Viscous, resulting in thick glue lines

Safety
[edit]

Slight risk of skin, eye and respiratory irritation. 

Protect the skin when using.  Adequate ventilation or respiratory equipment should be used.


Solvent Glue[edit]

Recently solvent style glues have been mentioned as working for acrylic segmented blanks.  Rather than a mechanical join, this glue works by dissolving a thin portion of the joint with a solvent.  When the solvent evaporates, the joint is done.  It takes a while for this kind of joint to reach full strength.

www.delviesplastics.com/mm5/merchant.mvc