Earlier in the class we mentioned many applications of polymeric materials. If y

Question

Earlier in the class we mentioned many applications of polymeric materials. If you recall, one categorv in which polvmers plav a maior role are glues. Your task is to "develop a new glue" Don't worry you won't have to go to the lab and start mixing chemicals . All we are asking is to identify what class(es) of polymers do you think would be suitable for glues and why? Use both our (still limited) knowledgebase about the various classes of polymers and "common sense" to answer this question. Can you do that? If you don't know how to approach this problem, here are two hints that might help (a) Identify 5 properties that (in your opinion) each glue has to possess and then try to match" them to a class of polymer materials we talked about in the class (is this going to be an amorphous or crystalline polymer, charged or neutral, thermopolastic or thermoset material? Would rubbers be good? What would be its molecular weight and why? etc.) (b) Look up what types of polymers some glues are made of - you might have a bit of trouble locating the exact chemical formula because this information is very often proprietary ("this is how the big guys make big bucks"). but vou can learn something general that I hope vou will find useful

Explanation / Answer

A glue should have

a) High cohesive strength

b) Ability to withstand degradation on exposure to other chemicals

c) Wetting is a procedure that determines the diffusion of a liquid (adhesive) over a solid surface (substrate), creating an intimate contact between them. The air displacement caused by this physical attraction minimises the interfacial flaws. Good wettability of a surface is a prerequisite for a good adhesive bonding.

d) strength, flexibility, and the ability to spread and interact on an adherend surface

They all mostly amorphous materials.

Thermoplastics: Polyvinyl acetate, polyethylene, polypropylene, polyamides, polyesters, and cyanoacrylics.

Reason: They can be softened by heating without degradation and provide strong adherence at normal temperatures, soluble. Good weathering resistance, resilience, and abrasion strength Flame retarding Moderate resistance to petroleum-based fluids

Thermoset: Phenol formaldehyde, urea formaldehyde, epoxies, and polyurethanes.

Reason: They are heat resistant and insoluble, degrades at high temperatures. Excellent resilience Characteristics equal to, or similar to, those of natural rubber Tensile strength is slightly lower than the tensile strength of natural rubber.

Elastomers: Natural rubber, butadiene rubber, styrene-butadiene rubber, silicone, and neoprene.

Reason: They have both thermoset & thermoplastic. Good flexibility, high peeling capacity. Adhesion to metals and fabrics is good. However, they have high cost which is disadvantage. Poor resistance hydrocarbons and not used in petroleum industry. Styrene vulnerable to oxygen, ozone. Excellent physical properties including abrasion and low temperature resistance Poor resistance to petroleum-based fluids

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