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ENMF 417 Post Midterm > L14 Polymers > Flashcards

L14 Polymers Flashcards

1
Q

What is the word plastic in Greek and its meaning?

A

The word is Plastikos meaning ‘it can be molded and shaped’

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2
Q

Name characteristics of Plastic

A
  • Low density
  • Low strength
  • Low stiffness
  • Electrical and Thermal insulating properties
  • Good chemical resistance
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3
Q

What were early polymers made from?

A

Natural organic materials such as celloluse and the earliest synthetic polymer was phenol formaldehyde (aka Bakelife lol its Bakelite pussy) in 1906

Side note, he seemed to mention bakelite a lot in class

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4
Q

When did modern polymer technology begin and what was plastic produced from?

A
  • 1920s
  • Plastics began to be produced from petroleum products (ethylene)
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5
Q

“Mono” is single in monomer what is the word for part?

A

Part: Meros

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6
Q

What kind of bonds and atoms do polymers usually consist of?

A

Covalently bonded carbon and hydrogen atoms

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7
Q

How are monomers joined together to form polymers?

A

Through a polymerization process

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8
Q

Thermoplastics consist of these two types of polymers and thermosets consist of the other two type of polymers (ie four all together)

A
  • Thermoplastics
    • Linear polymers
    • Branched polymers
  • Thermosets
    • Crosslinking polymers
    • Networked polymers
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9
Q

Define Linear polymers

A

Linear bonding structure but are not linear or straight in shape

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10
Q

Define Branched polymers

A

Side branched structures attached to the main chain during synthesis resulting in higher strength but lower density

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11
Q

Define Crosslinked polymers

A

Individual chains are linked by adjacent chains via covalent bonds which provide strength and dimensional stability (as Balinh does for all of us)

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12
Q

Define Networked polymers

A

Have three active covalent bonds for improved strength

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13
Q

Polymers have the ability to obtain both “_____” and “_____” structures

A
  • “Crystalline”
  • “Amorphous”
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14
Q

As crystallinity increases, polymers become…

A
  • Stiffer
  • Harder
  • Less Ductile
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15
Q

Can 100% cyrstalline polymers be achieved

A

No… (insert Balinhs voice) like what

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16
Q

Pure amorphous structures can be “______”, (relating to optics) but what happens as crystallinity increases?

A
  • “Transparent”
  • Opaqueness increases
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17
Q

What is the glass transition temperature?

A
  • As temperature increases, amorphous polymers undergo a distinct change in mechanical properties
  • Low temp: hard, glassy, brittle material to high temp: rubbery, leathery material
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18
Q

What happens to the density as you heat beyond the glass transistion temp?

A

Density decreases (spec. volume increases)

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19
Q

What happens to the glass transition temp as crosslinking increases?

A

The point of glass transition becomes less well defined

20
Q

What kind of bonds determine the strength of thermoplastics?

A

Secondary bonds, such as VDW, hydrogen bonds, ionic bonds

21
Q

What happens as you heat a thermoplastic?

A

Secondary bonds are broken due to thermal induced vibrations which allow adjacent chains to move easily and be shaped

22
Q

For thermoplastics, once you heat and stuff, upon cooling, do you get the orignal hardness and strength back?

A

Yes, you do get it back; the process is reversible but thermal aging can occur which causes degradation

23
Q

What other name can be catorgorized as thermoplastic?

A

Viscoelastic materials

24
Q

For thermoplastics, what happens when you stretch it at a high strain rate with a constant load?

A

It continues to elongate over time: Creep

25
Q

Name four types of thermoplastics

A
  • Acetals
  • Acrylics
  • Polycarbonate
  • PVC
26
Q

Advantages of Acetal and applications

A
  • Good
    • Strength
    • Stiffness
    • Chemical Resistance
  • Applications
    • Bearings, Cams, Rollers
    • Delrin (The description is just for kicks)
      • Precision parts requiring high stiffness, low friction, good dimensional stability
27
Q

Properties of Acrylics and applications

A
  • Moderate Strength
  • Good optical properties
  • Applications
    • Lighted signs, Skylights
    • Plexiglass
      • Light weight, shatter resistance
28
Q

Advantages of Polycarbonates

A
  • Versatile
  • Great impact resistance
  • Applications
    • Windshields, Safety helmets
    • Lexan
      • PC based resin with high impact resistance, dimensional stability, crystal clarity, high mechanical, optical, electrical and thermal properties
29
Q

Pros and cons of PVC plus applications

A
  • Inexpensive
  • Water resistant
  • Not suitable for high temperatures
  • Applications
    • Pipes, Conduits, Flexible hose
    • Tygon
      • Family of flexibile tubing with varying properties but generally chemically resistant
30
Q

How can you characterize a thermoset with regards to bonding?

A

Long chained molecules that are crosslinked in a 3D arrangement where the structure is essentially a single molecule with strong covalent bonds

31
Q

For thermosets, is the process of heating and cooling reversible?

A

the cross linking (curing) process is IRREVERSIBLE

32
Q

Unlike thermoplastics, a thermosets strength is not affected by…? What happens if the temperature is too high?

A
  • Thermosets are not affected by
    • Temperature
    • Rate of deformation
  • When the temp is too high, the polymer will begin to burn
33
Q

What are the advantages of thermosets over thermoplastics?

A
  • Better mechanical properties
  • Thermal properties
  • More dimensionally stable
34
Q

What are some examples of thermosets

A
  • Aminos
  • Phenolics
  • Polyesters
35
Q

Properties of Aminos and applications

A
  • Hard, Rigid
  • Resistant to abrasion and creep
  • Applications
    • Countertops, Housing appliances
    • Melamine (as before description is just for giggles)
      • is an organic base and fire retardant. Combined with formaldehyde creates durable plastic. Can be used for soundproof, cleaning products, insulation
36
Q

Advantages of Phenolics and applications

A
  • High resistance to heat, water, and chemicals
  • Applications
    • Handles, Knobs, Connectors
    • Bakelite
      • Early plastic known for electrical nonconductivity and heat resistance
37
Q

Properties of Polyesters and applications

A
  • Good mechanical and electrical properties
  • Generally used with Fibres or avaiable as casting resins
  • Applications
    • Clothing, Textiles, Swimming Pools, Boat
    • Cool Max
      • Moisture wicking fabrics
38
Q

Elastomers are also known as

A

Rubber

39
Q

What characterizes an elastomer?

A

Its ability to recover substantially in size and shape after the load has been removed

40
Q

4 Properties of Elastomers

A
  • Low glass transition temp
  • Low elastic modulus (because its not stiff)
  • Soft
  • Large deformation without rupture
41
Q

Elastomers have what kind of molecular structure (like linked, straight, etc)? What can be done to the structure for added strength?

A
  • Highly kinked (curled or twisted)
    • Can be crosslinked for added strength
42
Q

What are the advantages of a highly kinked structure in elastomers?

A
  • Good in vibration insulation
  • Non-skid surfaces
  • Abrasion resistance
43
Q

Define Vulcanization. Who was the first to Vulcanize?

A

Sulfur added at elevated temperature to crosslink the elastomer which enhances strength and the elastic modulus (I added details that weren’t on the slide)

**** CHARLES GOODYEAR WAS FIRST TO VULCANIZE****

Allen will ask this on final

44
Q

Name some common examples of Elastomers

A
  • Natural Rubber
  • Synthetic Rubber
  • Silicones
45
Q

Pros and Cons of Natural Rubber

A
  • latex based, good for high friction abrasive applications
  • low resistence to oil, heat, sunlight
46
Q

Synthetic Rubber has what advantage over natural rubber. Name some applications

A
  • Improved environmental resistances over natural rubber
  • Higher temp range
  • Tires, seals, belts (butyl, neoprene, which is the wet suits, and nitrile which is the blue doctor gloves)
47
Q

Silicone is an elastomer that trumps all rubbers in what? Name some applications

A
  • Beats all in temp range (588K) but is inferior in other properties
  • Seals, gaskets, thermal insulation

***Know this temperature Boys and Emma***

ENMF 417 Post Midterm (2 decks)

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