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Glue

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by

Gordon Hu

on 11 June 2014

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Transcript of Glue

Glue
Glue is an adhesive. Adhesive adhere different surfaces together
Is composed of polymers in some cases monomers in others.
The most well known types of glue also contain a solvent.
Theories of Glue
Mechanical Locking
Chemisorption
Involves the interactions of ionic, covalent and hydrogen bonds, the latter being responsible for the strong bonds between the adhesive and substrate.
The bonding sites therein are called active sites: small openings where molecules go through chemical reactions. This type of adhesion is much stronger than that specified in the standard absorption theory of adhesion as the covalent bonds that develop are much stronger than Van Der Waals forces.

History of Glue
Used in cave paints by Neanderthal ancestors in Lascaux, France.
200,000 BC ago: glued together spear stone flakes to wood
6,000 years ago, people used animal based glue to repair ceramics.
Native Americans and Mongols used glue to make bows and canoes.
What is Glue?
Adsorption Theory

Depends on the development of Van Der Waals forces between the glue and the substrate, which includes London dispersion force, dipole-dipole forces, and hydrogen bond forces.
Wettability is especially important here because IMF's only interact at close distances
Wettability is the ability of the glue to come into intimate contact with the substrate.
Adhesive in viscous liquid form fills into the voids or pores of the adherents, which upon hardening acts as a interlocking physical anchor for both surfaces, thus making a strong surface bond.
The strength of this type of bonding is dependent on the flow of matter because the adhesive needs to penetrate all the cracks and pores.
Thorough penetration of the glue into the pores is responsible for a strong adhesion, and thus a material like wood is ideal for mechanical interlocking as wood is highly porous and rough.
Electrostatic Theory
Electro-negativity is the tendency of an atom or a functional group to attract electrons. Due to the differences in electro-negativity of the adhesive and the substrate an attraction develops between the two. This theory applies largely in adhering to metal substrates where there are free-flowing electrons
Diffusion Theory
During adhesion, the glue polymer strands will diffuse into the substrate.
Diffusion: Adhesive polymer strands and the substrate polymer strands interact on a molecular level and essentially entangle themselves in each other.
The result of this entanglement is akin to a molecular ‘knot’ that ties the substrate and the adhesive as they are pressed together. In order for this to work, both the adhesive and adherent must be polymers.
Different Types of Glue
Natural Glue
PSA
Solvent- Based Glues
Wood Glue
Hot Melt Glue
UV Cured Glue
Wood Glue
Why Is Glue Important
Because whats simpler then sticking two objects together.
Our Experiment
How does Glue work
We don't know.
There are only Theories to explain how glue dries and adheres two objects together

There Are Some Things We Do Know...
Glue Bonds through forces that operate only in close contact (not only IMF'S)
As such it is important to maintain a "wet" surface
Depends on balance of adhesive and cohesive forces
Glue is very substrate specific
Free Radical Polymerization
Our Attempted Experiment
How Cool It Would Have Been
Our goal was to create a uv cured glue that overcame the drawbacks of traditional uv cured glue, that is by incorporating chemiluminescence to allow light to reach previously unreachable areas
We would have, in theory, been capable of placing two objects together and having them form a bond in seconds.
The name says it all, these are adhesives that form bonds when pressure is applied to them. That's just a fancy way for saying tape.
Natural glue is any glue made from materials found in nature, this can range from animal glue, made from mashed up animal parts, to beeswax.
Natural glues were the only glues in use until WWI
Today some natural glues are still used in specific fields like woodworking, were hide glue is used, and in the production of wooden instruments.

Solvent based glues are what we traditionally think of as "glue"
These glues consist of two components, Polymer, and solvent
Curing occurs upon evaporation of solvent
Is a special solvent based glue that is meant specifically for the wood substrate
Polyvinyl acetate is made from the polymerization of vinyl acetate
Polyvinyl acetate has the a general formula of C4H6O2n.

Hot melt Glues are specials in that they don't contain a solvent.
Work through intense heating of polymer until it reaches a liquid state
The most well known kind of hot melt glue, is a Hot Glue Gun
UV cured glue like Hot Melt glues do not contain a solvent, instead they contain a photo initiator
The photo initiator starts a chemical chain reaction when UV light shined on it.
This chain reaction cures the glue and allows it to harden
One large advantage of UV cured glues over others is the time it takes for the photo initiator to cure the glue.
Free radical polymerization is the chain reaction initiated by the photo initiator that cures the UV cured glue

Agenda
History of Glue
Theories of Glue
Different Types of Glue
Experiment 1
Video
Results 1
Experiment 2
Demo
Results 2
Conclusion

Testing
Video
Experiment 2
DEMO
Materials
2% Milk
Baking Soda
Vinegar
Coffee Filter
Results
Conclusion
Results Cont.
Results Cont.
Results
Today glues are used in a variety of ways. Glue has found applications in furniture construction, car assembly, medical equipment, and dentistry
All in all this research is only part way there to understanding the adhesion theories fully.
It should be noted that these are not the only theories of adhesion that come into play when gluing to substrates together, and it should not be discounted that there are possibly many different ways in which a substrate adheres to another through the gluing process.
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