Manufacturing Materials 2023 Flashcards
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
They are recyclable
The melt temperature (Tm) in a semi crystalline polymer is lower than its glass transition (Tg).
True or False
False
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
i) In which the material can work without oxidation, chemical changes and creep
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
the changes of length by degree per temperature
Polymers are good ________________ and __________________ insulators.
- chemical
- electrical
- spatial
- optical
- thermal
Polymers are good electrical and thermal insulators.
Amorphous thermoplastic polymers tend to have greater chemical resistance than semi crystalline.
True or False
False
What kind of chemical bonds are found in thermoplastics?
- just covalent bonding
- ionic bondings
- covalent & van der Waals
- just van der Waals bondings
-metallic
van der Waals
___________________________ 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
-Thermal conductivity
Describe 4 advantages of plastics on metals
Examples: lower density (they are lighter), possibility of producing complex geometries with ease, electrical and thermal insulation, and cost efficiency in high volumes.
The covalent bond is characterized by being:
-Good electrical conductor
-Strongly directional
-Presents high ductility
Strongly directional
Amorphous polymers only have glass transition temperature, while semi crystalline polymers also exhibit a melt temperature.
True or False
True
Co-polymers can be:
- Random, in block, or attached
- spherulitic, lamellar and branched
- Random, in block, or branched
- none of the above
Random, in block, or branched
List all the organic elements that can be used to produce polymers.
Carbon
Hydrogen
Oxygen
Nitrogen
Silicone
Fluorine
Chlorine
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
Polyolefins, PVC, polyurethanes, styrenics, and esters
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
-characterizes the transition from a true solid to a very viscous liquid
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
- amorphous and crystalline
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
It belongs to the acrylic family
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
- all are correct
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
- characterizes the transition from a solid to a true liquid
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
True
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
PVC (hallogens are flame retardants)
Regarding stereo regular addition polymers, which one can crystallize?
Isotactic polymers
Syndiotactic polymers
atactic polymers
multitactic polymers
Isotactic polymers
The degradation temperature of a polymer is the one at which covalent bondings are broken down.
True or False
True
Select the correct answer: The difference between a thermoset polymer and a thermoplastic polymer is:
- thermosets possess crosslinked chains
- thermoplastics possess crosslinked chains
- thermosets possess crosslinked chains
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.
- cap: PP with Tg of 10°C, body: PS with Tg of 100°C.
Regarding stereoregular addition polymers, which one will tend to be amorphous?
- Isotactic polymers
- Syndiotactic polymers
- atactic polymers
- multitactic polymers
Atactic polymers (random arrangement of stereochemistry along the polymer chain)
A major ingredient in chewing gum is the group of terpenoids, it is a resin.
True or False
False (synthetic rubbers [thermosets] are the main ingredient)
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.
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.
This plastic is both, biobased and biodegradable.
PET
bPP
PP
PLA
PCL
PLA
Elastomers are amorphous polymers existing above their glass transition temperatures.
True or False
True, they exist above their Tg.
Crosslinking elastomers is used to prevent viscous plastic deformation while retaining large elastic deformations, and vulcanization is the most common method.
True or False
True
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-
S-S-S-S-S-S-S-
What are the three types of stereoregular addition polymers?
-Isotactic
-Syndiotactic
-Atactic
-Multitactic
Isotactic
Syndiotactic
Atactic
Elastomers display a nonlinear elastic defomation.
True or False
True, define by Mooney-Rivlin cosntants
Name the 3 main polymerization stages
Initiation, Propagation, and Termination.
What is another name for Step-growth polymerization?
- polycondensation polymerization
- polyadditition
- crystallization
- polycondensation polymerization
During a fire test, this plastics sizzles:
- PET
- PS
- PMMA
- PLA
PMMA
Step-growth polymerization is also named polycondensation because a by-product such as water or another small molecule is produced.
True or False
True
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
By using fillers
