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Adhesives To a Packaging Company.
Transcript of Adhesives To a Packaging Company.
What are Adhesives used for?
Adhesives are used for to bonding of 2 different substrates together for the following:
Woodwork and Building (Cement and super glue).
Joining of metals and plastics
Joining of polystyrene and fabrics
Different Types of Adhesives
Physical and Chemical Curing Adhesives
The most important factor to consider, it determines whether the adhesive joint will perform efficiently
Chemical curing adhesives: materials that need a chemical reaction to change them from liquid to solid.
Physical curing adhesives: has a base polymer already formed but dissolved, therefore needing physical effects such as pressure or heat to cause the occurrence of adhesion.
How to identify which Adhesives suit your packaging company?
How to know what adhesives are best for your company.
Physical curing adhesives and their compounds.
Chemical curing adhesives and their compounds
Things to identify:
Examples of Chemical curing adhesives:
Epoxy, silicones, anaerobic and phenolic.
As discussed in physical curing adhesives:
ADDITIVES, FILLERS AND PIGMENTS
Fundamental units that structure polymers.
Monomers join together to make the polymer via addition and condensation polymerisation.
How do adhesives bond?
1. Phase Changes
using 3 steps:
3.Substrate surface suitability
3.Substrate Surface suitability
The conversion of one state to another.
All adhesives experience the phase change, from a liquid (the time the joint is made) to a solid (after cure when the joint has reached its final strength).
These are chemical compounds used in both physical and chemical curing adhesives.
They are added to the polymer to alter its qualities such as colour, strength and improve shelf life.
For example, Resin is added to increase stickiness of some adhesives
Examples of physical curing adhesives: Hotmelts, solvent based, contact adhesives and pressure sensitive adhesives.
A molecule made up of monomers chemically bonded together.
Used in adhesives as a synthetic bonding substance that is stronger, more flexible and has a greater impact on resistance compared to other adhesives
Polymers most commonly used in adhesives:
Polyvinyl acetate (used in glue), Epoxies (used in glue guns), Resins, Cyanoacrylate (used in super glue), Viscose (used in scotch tape).
Van Der Waals forces
Example of POLYMERS
Monomers attach to each other forming a long line of polymers
Weak attractions between molecules that have a possibility of not normally having positive or negative charges.
Molecules in a pressure sensitive adhesive show dipole moments
Dipole moments: some molecules where its protons and neutrons are not evenly spread and causes a moment where it will exhibit charges or polarities.
The dipole moments can induce a change in electron density in neighbouring polymers/molecules, influencing their polarity and hence causing dipole moments where neutrality previously existed
The rearrangement of bonds within monomers, so that they link with each other
Requires monomers to have 2 or more kinds of functional groups that are able to react with each other and it combines to form a small molecule, usually H2O.
Condensation polymerisation using Glucose to maltose as an example.
Adhesives. Adhesives and Sealents [Internet]. [cited 2014 September 20]. Available from: http://www.adhesives.org/adhesives-sealants/adhesives-sealants-overview/adhesive-technologies/chemically-curing
Awaja F, Gilbert M, Kelly G, Fox B, Pigram PJ. Adhesion of polymers. Progress in Polymer Science. 2009;34(9):948-68.
Chemistry Explained. Adhesives [Internet]. [cited 2014 September 30]. Available from: http://www.chemistryexplained.com/A-Ar/Adhesives.html
Owen B. Adhesives. 1998 [cited 2014 September 28]. Available from: http://nzic.org.nz/ChemProcesses/polymers/10H.pdf
Pollock J. (2014, September 28). Condensation Polymerisation; Glucose to Maltose. Available from: https:/ /www.youtube.com/watch?v=RwYobhHi1lE
QuickChem. (2014, September 30). Alkenes and Polymers . Available from: https://www.youtube.com/ watch?v=8fzKivlqgf0
Xu M, International Union of Pure and Applied Chemistry. Macromolecular Division. Progress in polymer science and technology. Weinheim ; Chichester: Wiley-VCH; 2003. 327 p. p.
Prepolymers are short, light polymer chains and are often used as adhesives in compounds such as polyurethane and unsaturated polyester adhesives
1. What are you packaging?
2. What materials (substrate) will you be using to pack these items such as cardboard or plastic etc?
3. Identify the adhesives most effective on the materials (substrate)
There are many adhesives out there, to find out what adhesives are best for your company, it is vital to identify the type of materials needed to bond together, therefore finding the most effective adhesive for your company.
For effective adhesion, 'wetting', the adhesive must completely cover the substrate.
It requires the surface tension of the adhesive to be less than the substrate.
Good wetting is reported to have a degree of less than 90, while higher than 90 degrees are considered partial or non wetting conditions.
If substrate is not suitable, it results in Insufficient adhesion/poor bonding
Apply Promoter to improve adhesion
Promoter either acts to strengthen bonding or 'roughen' surface so that adhesion is better
Introduction to Chemistry 100