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Questions and Answers
Which type of bonds hold monomers together into a chain or macromolecule?
Which type of bonds hold monomers together into a chain or macromolecule?
What is the primary characteristic of thermoset polymers?
What is the primary characteristic of thermoset polymers?
Which type of forces are created when atoms and molecules in polymers approach each other but do not result in electron sharing or transfer?
Which type of forces are created when atoms and molecules in polymers approach each other but do not result in electron sharing or transfer?
What is the process by which a polymer is formed known as?
What is the process by which a polymer is formed known as?
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Which classification of polymers can be melted and reformed into various shapes multiple times?
Which classification of polymers can be melted and reformed into various shapes multiple times?
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What type of bonds are rare in polymers but can be found in some cases?
What type of bonds are rare in polymers but can be found in some cases?
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What mainly determines the ability of a polymer to crystallize?
What mainly determines the ability of a polymer to crystallize?
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Which material is an example of a semicrystalline polymer?
Which material is an example of a semicrystalline polymer?
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What causes some important sources of polymer irregularity in terms of crystallinity?
What causes some important sources of polymer irregularity in terms of crystallinity?
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Which type of linear polymer can easily crystallize?
Which type of linear polymer can easily crystallize?
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Which factor does polymer morphology mainly depend on?
Which factor does polymer morphology mainly depend on?
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In terms of crystallinity, what is atactic PP considered to be?
In terms of crystallinity, what is atactic PP considered to be?
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What is the Ultimate Elongation of a material?
What is the Ultimate Elongation of a material?
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Which property is largely a result of the amorphous regions in a polymer?
Which property is largely a result of the amorphous regions in a polymer?
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How is the toughness of a polymer typically measured?
How is the toughness of a polymer typically measured?
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What does brittleness in materials refer to?
What does brittleness in materials refer to?
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Which characteristic decreases with increasing crystallinity and orientation in polymers?
Which characteristic decreases with increasing crystallinity and orientation in polymers?
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What does creep in materials refer to?
What does creep in materials refer to?
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What does impact strength measure in polymers?
What does impact strength measure in polymers?
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Which type of impact test is often used for plastic film samples?
Which type of impact test is often used for plastic film samples?
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How is impact strength determined in the dart drop impact test for plastic film?
How is impact strength determined in the dart drop impact test for plastic film?
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What aspect of polymers do thermal properties describe?
What aspect of polymers do thermal properties describe?
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What does the melting temperature (Tm) refer to in polymers?
What does the melting temperature (Tm) refer to in polymers?
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Which property is closely related to impact strength according to the text?
Which property is closely related to impact strength according to the text?
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What is the important determinant of the overall properties of a polymer?
What is the important determinant of the overall properties of a polymer?
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Which type of polymer structure generally yields a more compact arrangement of atoms?
Which type of polymer structure generally yields a more compact arrangement of atoms?
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What does functionality refer to in the context of polymerization?
What does functionality refer to in the context of polymerization?
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Which type of polymer is formed when the functionality of a monomer is 2?
Which type of polymer is formed when the functionality of a monomer is 2?
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Which type of polymers are formed from monomers with the structure CH2=CHX or CH2=CXY?
Which type of polymers are formed from monomers with the structure CH2=CHX or CH2=CXY?
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How are addition polymers mainly produced?
How are addition polymers mainly produced?
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Which type of molecule fragment contains an unpaired electron and is involved in free radical polymerization?
Which type of molecule fragment contains an unpaired electron and is involved in free radical polymerization?
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What happens during addition polymerization?
What happens during addition polymerization?
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Study Notes
Tensile Properties
- Elastic Limit: the maximum stress a material can experience without undergoing permanent deformation
- Ultimate Elongation: the maximum strain a material can bear before it ruptures/breaks
- Resilience: the ability of a material to absorb energy and then return to its original dimensions
- Resilience is a property largely of the amorphous regions in the polymer
- Resilience decreases with increasing crystallinity and orientation in the polymer
- Toughness: the energy a material can absorb before rupturing
- The toughness of a polymer can be measured by the area under the stress-strain curve
- Impact tests also measure toughness, where polymers are tested at high strain rates
- Brittleness: the inability of a material to experience a significant amount of strain without rupture
- Brittleness is often associated with a lack of toughness
- Creep: the tendency of a material to deform over time when subjected to a constant load
- Creep is a result of the viscoelastic nature of plastics, where molecules tend to slowly change their positions when subjected to extended stress, leading to significant deformation over time
Types of Polymers
- Examples of polymers: PE, PP, PVC, PTFE, PAN, PA, PMMA, PET
- Examples of copolymers: ABS, E/P, VC/VA, VC/VD, VC/E
Bonds in Polymers
- Primary bonds: hold monomers together into a chain or macromolecule
- Covalent bonds: formed by the sharing of a pair of electrons, common in polymers
- Ionic bonds: formed by the complete transfer of an electron from one atom to another, rare in polymers
- Secondary bonds: examples include hydrogen bonds and van der Waal's forces, which are intermolecular forces between chains or neighboring molecules
Classification of Polymers
- Thermoplastics: can be melted and formed into various shapes repeatedly, examples include PE, PP, PVC, and PS
- Thermosets: crosslinking of the polymer occurs, shape and dimensions are set permanently after the initial heating, examples include unsaturated polyester resin and epoxy resin
- Commodity plastics: high volumes, modest price, reasonable performance, examples include polyethylene, polypropylene, polystyrene, and poly(vinyl chloride)
- Engineering plastics: maintain mechanical properties above 100°C, higher price, and superior thermo-mechanical properties, examples include nylon, polyester, and polycarbonate
Polymerization
- Polymerization: the process by which a polymer is formed, involving a catalyst/initiator, solvent (optional), monomers, and secondary chemicals (optional)
- Polymerization reactor: a schematic representation of the polymerization reaction process, which is maintained under controlled temperature and pressure
Crystallinity of Polymers
- Crystallinity: the ability of a polymer to crystallize, determined by the regular placement of atoms in the chain
- Sources of polymer irregularity: stereochemical irregularity, copolymers with random placement of comonomers, and branching in polymeric structure
- Polymer morphology: the fine structure of plastic, including amorphous and crystalline regions, which can coexist in a polymer sample
- Examples of polymers: LDPE, HDPE, PET, and EVOH, which are semicrystalline, and general-purpose polystyrene, which is amorphous
Mechanical Properties of Polymers
- Impact strength: the ability of a polymer to resist fracture when exposed to sudden impact, closely related to toughness
- Impact strength is measured using different types of impact tests, including the dart drop impact test for plastic film
Thermal Properties of Polymers
- Thermal properties: the relationship between polymer properties and temperature
- Melting temperature (Tm): the temperature at which a polymeric material transitions from a solid to a liquid state
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Description
Test your knowledge on different types of polymers such as PVC, PTFE, and Nylon, along with examples of copolymers like ABS and E/P. Learn about primary bonds in polymers including covalent bonds that hold monomers together in a macromolecule.
