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Questions and Answers
What is the primary monomer that forms natural rubber?
What is the primary monomer that forms natural rubber?
- Ethylene
- Butadiene
- 2-methyl-1,3-butadiene (correct)
- Polyisoprene
What is a key drawback of raw rubber related to temperature?
What is a key drawback of raw rubber related to temperature?
- It can withstand extreme cold without issues.
- It is brittle at room temperature.
- It becomes too hard at high temperatures.
- It becomes so soft at high temperatures. (correct)
What process significantly enhances the elasticity of rubber?
What process significantly enhances the elasticity of rubber?
- Polymerization
- Coagulation
- Vulcanization (correct)
- Hydrogenation
Who developed the vulcanization process for rubber?
Who developed the vulcanization process for rubber?
Which property makes raw rubber unsuitable for use with certain chemicals?
Which property makes raw rubber unsuitable for use with certain chemicals?
What is the purpose of compounding rubber?
What is the purpose of compounding rubber?
Which rubber composition may contain the highest percentage of sulphur?
Which rubber composition may contain the highest percentage of sulphur?
How much sulphur is typically found in tyre rubber?
How much sulphur is typically found in tyre rubber?
Which of the following is NOT a reason for compounding rubber?
Which of the following is NOT a reason for compounding rubber?
What type of rubber may need compounding for improved electrical insulation?
What type of rubber may need compounding for improved electrical insulation?
What is a common additive used in the compounding process of rubber?
What is a common additive used in the compounding process of rubber?
What characteristic can be modified through the compounding of rubber?
What characteristic can be modified through the compounding of rubber?
Which of these compounds is likely to increase the resilience of rubber?
Which of these compounds is likely to increase the resilience of rubber?
In rubber compounding, which of the following is primarily used for enhancing strength?
In rubber compounding, which of the following is primarily used for enhancing strength?
What is one key benefit of compounding rubber with specific additives?
What is one key benefit of compounding rubber with specific additives?
What is one classification of polymers based on their origin?
What is one classification of polymers based on their origin?
Which polymerization mechanism involves the formation of free radicals?
Which polymerization mechanism involves the formation of free radicals?
What does the term 'tacticity' refer to in polymers?
What does the term 'tacticity' refer to in polymers?
Which of the following is NOT a type of co-polymerization?
Which of the following is NOT a type of co-polymerization?
What is the glass transition temperature (Tg) affected by?
What is the glass transition temperature (Tg) affected by?
What is the primary distinction between low-density polyethylene (LDPE) and high-density polyethylene (HDPE)?
What is the primary distinction between low-density polyethylene (LDPE) and high-density polyethylene (HDPE)?
Which polymer is produced through condensation polymerization?
Which polymer is produced through condensation polymerization?
What is the primary purpose of vulcanization in natural rubber processing?
What is the primary purpose of vulcanization in natural rubber processing?
What is the formula for calculating the dispersity index (PDI)?
What is the formula for calculating the dispersity index (PDI)?
Which method is NOT used to determine the weight-average molecular mass (Mw)?
Which method is NOT used to determine the weight-average molecular mass (Mw)?
What is the number average molecular weight (Mn) for a polymer sample with 50 molecules of 10000, 35 of 12000, and 15 of 14000?
What is the number average molecular weight (Mn) for a polymer sample with 50 molecules of 10000, 35 of 12000, and 15 of 14000?
Which of the following properties is used to determine the number-average molecular mass (Mn)?
Which of the following properties is used to determine the number-average molecular mass (Mn)?
How is the degree of polymerization (DP) calculated if the molecular weight of the monomer is 1000 and Mn is 13000?
How is the degree of polymerization (DP) calculated if the molecular weight of the monomer is 1000 and Mn is 13000?
Which of the following best describes a property of TEFLON?
Which of the following best describes a property of TEFLON?
What applications are common for TEFLON?
What applications are common for TEFLON?
Which molecular weight formula is correct for the calculation of Mw?
Which molecular weight formula is correct for the calculation of Mw?
What is the main catalyst used in the manufacturing of HDPE via coordination polymerization?
What is the main catalyst used in the manufacturing of HDPE via coordination polymerization?
Which statement accurately describes the properties of HDPE compared to LDPE?
Which statement accurately describes the properties of HDPE compared to LDPE?
What is the primary type of polymerization involved in the formation of phenol-formaldehyde (PF) resins?
What is the primary type of polymerization involved in the formation of phenol-formaldehyde (PF) resins?
Which factor significantly influences the nature of the PF resin produced?
Which factor significantly influences the nature of the PF resin produced?
What characteristic of novolacs is defined by the phenol to formaldehyde molar ratio?
What characteristic of novolacs is defined by the phenol to formaldehyde molar ratio?
Which of the following applications is NOT commonly associated with HDPE?
Which of the following applications is NOT commonly associated with HDPE?
Which feature of PF resins leads to their thermosetting nature?
Which feature of PF resins leads to their thermosetting nature?
What temperature can HDPE withstand continuously without deterioration?
What temperature can HDPE withstand continuously without deterioration?
Study Notes
Engineering Chemistry Course Details
- Course Name: Engineering Chemistry
- Course Code: CHY1001
- Lecture Series No: 1
- Credits: 4
- Mode of Delivery: Hybrid
Polymers
- Definition: Long chain molecules composed of repeating structural units called monomers.
- Classification:
- Origin: Natural (e.g., rubber, cellulose) and Synthetic (e.g., polyethylene, nylon)
- Thermal Behaviour: Thermoplastics (soften on heating and solidify on cooling) and Thermosets (become rigid on heating and cannot be remelted)
- Polymerization Reactions:
- Addition Polymerization: Monomers add to form a polymer without the loss of any atoms.
- Condensation Polymerization: Monomers combine with the loss of a small molecule, such as water.
- Co-polymerization: Two or more different monomers combine to form a polymer. Types:
- Alternating
- Random
- Block
- Graft
- Tacticity: Arrangement of substituent groups on polymer chains (Isotactic, Syndiotactic, Atactic)
- Functionality: Number of reactive sites on a monomer.
- Degree of Polymerization (DP): Average number of monomer units in a polymer chain.
- Molecular Weight:
- Number Average Molecular Weight (Mn): Calculated based on the number of molecules of each molecular weight.
- Weight Average Molecular Weight (Mw): Calculated based on the weight of molecules of each molecular weight
- Dispersity Index (PDI): Mw / Mn
- Determination of Mn: Colligative properties (lowering of vapor pressure, osmotic pressure, depression of freezing point, elevation of boiling point)
- Determination of Mw: Light scattering, ultra-centrifugal techniques
- Glass Transition Temperature (Tg): The temperature at which a polymer transitions from a rigid, glassy state to a rubbery, flexible state. Factors affecting Tg:
- Chain flexibility
- Intermolecular forces
- Molecular weight
- Polythene (LDPE & HDPE)
- Properties of LDPE: Lower density, flexible, easily processed, used in films, bags, packaging.
- Properties of HDPE: Higher density, stronger, more rigid, resistant to chemicals, used in bottles, pipes, containers.
- Nylon (6:6, 6, 6:10, 11):
- Properties: Strong, resistant to abrasion, good thermal stability, used in fibers, ropes, gears.
- PF Resins:
- Formation: Condensation polymerization, thermosetting polymers.
- Types: Novolacs and Resoles
- Properties: Linear, low molecular weight, soluble, fusible, prepolymers.
- Moulding Process: Branching and cross-linking forming highly cross-linked, insoluble, hard, rigid, infusible products.
- Natural Rubber:
- Monomer: Isoprene (2-methyl-1,3-butadiene)
- Properties: High tensile strength, good elasticity, impermeable to gases.
- Drawbacks: Soft at high temperatures, brittle at low temperatures, susceptible to oxidation and degradation.
- Vulcanization: Heating rubber with sulfur (or other vulcanizing agents) to increase elasticity and reduce plasticity.
Teflon (Polytetrafluoroethylene - PTFE)
- Properties: Extremely tough, high softening point, high chemical resistance, high density, waxy touch. It can be punched, machined, and drilled.
- Uses:
- Insulating materials (motors, transformers, cables, wires, fittings)
- Gaskets, packing, pump parts, tanks, chemical-carrying pipelines, tubing
- Coatings
- Non-lubricating bearings and non-sticking stop-cocks
Compounding of Rubber
- Definition: Mixing of raw rubber with other substances to impart specific properties.
- Purpose: Improve specific properties of rubber, such as strength, flexibility, and resistance to degradation.
HDPE (High Density Polyethylene)
- Properties: High strength-to-density ratio, high density, little branching, strong intermolecular forces, high tensile strength, hard, opaque, heat resistant.
- Applications:
- 3D printer filament
- Banners
- Bottle caps
- Chemical resistant piping systems
- Food storage containers
- Fuel tanks for vehicles
- Electrical and plumbing boxes
- Folding chairs and tables
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Description
Test your understanding of polymers in Engineering Chemistry. This quiz covers definitions, classifications, polymerization reactions, and characteristics of various types of polymers. Perfect for students of the CHY1001 course!
