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Polymers > Manufacturing Materials 2023 > Flashcards

Manufacturing Materials 2023 Flashcards

1
Q

Elastomers are characterized by all these properties EXCEPT one, identify it:

  • Electrical insulator
  • Thermal insulator
  • Abrasion and wear resistance
  • Very low density
  • Wide range of properties
  • They are recyclable
  • Ductility
A

They are recyclable

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2
Q

The melt temperature (Tm) in a semi crystalline polymer is lower than its glass transition (Tg).

True or False

A

False

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3
Q

Maximum service temperature (Tmax) is:

i) In which the material can work without oxidation, chemical changes and creep
ii) When the material goes from fragile to ductile behavior
iii) When I can apply classic design (working stresses below the elastic limit) or fracture mechanics design

A

i) In which the material can work without oxidation, chemical changes and creep

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4
Q

What does the thermal expansion coefficient measure?

  • the changes of proportionality per Kelvin grade
  • the changes of proportionality per degree of temperature
  • the changes of length by degree per temperature
  • the changes of length per Hooke grade
  • none of the above
A

the changes of length by degree per temperature

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5
Q

Polymers are good ________________ and __________________ insulators.

  • chemical
  • electrical
  • spatial
  • optical
  • thermal
A

Polymers are good electrical and thermal insulators.

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6
Q

Amorphous thermoplastic polymers tend to have greater chemical resistance than semi crystalline.

True or False

A

False

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7
Q

What kind of chemical bonds are found in thermoplastics?

  • just covalent bonding
  • ionic bondings
  • covalent & van der Waals
  • just van der Waals bondings

-metallic

A

van der Waals

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8
Q

___________________________ is defined as the speed at which heat is conducted through a material.

-Melt temperature

-Thermal expansion

-Thermal conductivity

-Caloric conductivity

-none of the above

A

-Thermal conductivity

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9
Q

Describe 4 advantages of plastics on metals

A

Examples: lower density (they are lighter), possibility of producing complex geometries with ease, electrical and thermal insulation, and cost efficiency in high volumes.

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10
Q

The covalent bond is characterized by being:

-Good electrical conductor

-Strongly directional

-Presents high ductility

A

Strongly directional

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11
Q

Amorphous polymers only have glass transition temperature, while semi crystalline polymers also exhibit a melt temperature.

True or False

A

True

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12
Q

Co-polymers can be:

  • Random, in block, or attached
  • spherulitic, lamellar and branched
  • Random, in block, or branched
  • none of the above
A

Random, in block, or branched

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13
Q

List all the organic elements that can be used to produce polymers.

A

Carbon
Hydrogen
Oxygen
Nitrogen
Silicone
Fluorine
Chlorine

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14
Q

Identify the five polymer families that make up 95% of the global market

-Acrylics, polyolefins, PVC, esters, acetals

-Polyolefins, PVC, polyurethanes, styrenics, and esters

-Acetals, polyamides, esters, PVC, styrenics

-Polyamides, esters, styrenics, polyolefins, acrylics

-with none of the above

A

Polyolefins, PVC, polyurethanes, styrenics, and esters

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15
Q

The glass transition temperature (Tg) in a polymer:

-is the maximum service temperature

-characterizes the transition from a solid to a liquid

-characterizes the transition from a true solid to a very viscous liquid

-measures the change in length by degree of temperature

-none of the above

A

-characterizes the transition from a true solid to a very viscous liquid

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16
Q

By the criteria of spatial ordering of the molecules in their structure, how are thermoplastic polymers classified?

  • elastomers, thermoplastics, thermoplastic elastomers
  • thermosets and thermoplastics
  • recyclable and crystalline
  • amorphous and semicrystalline
A
  • amorphous and crystalline
17
Q

Polyethylene terephthalate PET is an engineering polymer. From the characteristics that are presented below, there is one that DOES NOT correspond to this polymer, identify it.

  • It exhibits high transparency when cooling in amorphous state
  • It belongs to the acrylic family
  • It is an aromatic polyester
  • It is a semicrystalline polymer
A

It belongs to the acrylic family

18
Q

An oligomer is:

  • a small chain composed of less than 10 units
  • a polymer with regular repeat units
  • a chain with the average molecular mass
  • all are correct
A
  • all are correct
19
Q

Melt temperature (Tm) ______________

  • characterizes the transition from a true solid to a very viscous liquid
  • characterizes the transition from a solid to a true liquid
  • is the maximum service temperature
  • measures the change in length by temperature degree
A
  • characterizes the transition from a solid to a true liquid
20
Q

Due to its wide range of properties and low cost, the polyolefins family is one of the most used families of commodities worldwide.

True or False

A

True

21
Q

This “commoditiy” polymer, being a member of the halogenated polymer family is self- extinguishing, it is widely used in electrical casings and switches.

PP
PPS
PS
PVC
PEEK

A

PVC (hallogens are flame retardants)

22
Q

Regarding stereo regular addition polymers, which one can crystallize?

Isotactic polymers

Syndiotactic polymers

atactic polymers

multitactic polymers

A

Isotactic polymers

23
Q

The degradation temperature of a polymer is the one at which covalent bondings are broken down.

True or False

A

True

24
Q

Select the correct answer: The difference between a thermoset polymer and a thermoplastic polymer is:

  • thermosets possess crosslinked chains
  • thermoplastics possess crosslinked chains
A
  • thermosets possess crosslinked chains
25
Q

To manufacture a Bic pen two types of materials are required. At room temperature the cap must have a rubbery behavior (flexible) while the body must remain stiff, even at the Sonora desert. Considering their corresponding glass transitions, choose the correct materials from the following list:

  • cap: PP with Tg of 10°C, body: PS with Tg of 100°C.
  • cap: PP with Tg of 10°C, body: PE with Tg of 120°C.
  • cap: PA with Tg of 50°C, body: PP with Tg of 10°C
  • cap: PS with Tg of 100°C, body: PMMA with Tg of 120°C.
A
  • cap: PP with Tg of 10°C, body: PS with Tg of 100°C.
26
Q

Regarding stereoregular addition polymers, which one will tend to be amorphous?

  • Isotactic polymers
  • Syndiotactic polymers
  • atactic polymers
  • multitactic polymers
A

Atactic polymers (random arrangement of stereochemistry along the polymer chain)

27
Q

A major ingredient in chewing gum is the group of terpenoids, it is a resin.

True or False

A

False (synthetic rubbers [thermosets] are the main ingredient)

28
Q

Establish the differences between biobased and biodegradable plastics and give an example of each of them, plus an example of a material with both characteristics.

A

Biobased: derived from renewable biomass, not necessarily biodegradable.
- Bio PP

Biodegradable: polymers capable of decomposing, not necessarily biobased, it can be derived from petroleum.
- Polycaprolactone

  • PLA is an example of both.
29
Q

This plastic is both, biobased and biodegradable.

PET

bPP

PP

PLA

PCL

A

PLA

30
Q

Elastomers are amorphous polymers existing above their glass transition temperatures.

True or False

A

True, they exist above their Tg.

31
Q

Crosslinking elastomers is used to prevent viscous plastic deformation while retaining large elastic deformations, and vulcanization is the most common method.

True or False

A

True

32
Q

One of these element strands is the most commonly used for vulcanization.

Si- Si-Si- Si- Si-

S-S-S-S-S-S-S-

H-H-H-H-H-H-H-

Cl-Cl-Cl-Cl-Cl-Cl-

A

S-S-S-S-S-S-S-

33
Q

What are the three types of stereoregular addition polymers?

-Isotactic

-Syndiotactic

-Atactic

-Multitactic

A

Isotactic
Syndiotactic
Atactic

34
Q

Elastomers display a nonlinear elastic defomation.

True or False

A

True, define by Mooney-Rivlin cosntants

35
Q

Name the 3 main polymerization stages

A

Initiation, Propagation, and Termination.

36
Q

What is another name for Step-growth polymerization?

  • polycondensation polymerization
  • polyadditition
  • crystallization
A
  • polycondensation polymerization
37
Q

During a fire test, this plastics sizzles:

  • PET
  • PS
  • PMMA
  • PLA
A

PMMA

38
Q

Step-growth polymerization is also named polycondensation because a by-product such as water or another small molecule is produced.

True or False

A

True

39
Q

How can the thermal and mechanical properties of a polymer system be improved?

  • By using additives
  • By using fillers
  • By increasing the proportion of longer chains
  • none of the above
A

By using fillers

Polymers (1 decks)

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