Polymer Chemistry Overview
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Questions and Answers

What does toughness of a material quantify?

  • The maximum load a material can bear
  • The area under the stress-strain curve (correct)
  • The total deformation before breaking
  • The ratio of tensile force to material length

    • How does a strong material differ from a tough material?

  • Tough materials can resist breaking under load. (correct)
  • Strong materials are always flexible.
  • Toughness is unaffected by the material's strength.
  • Strong materials can deform significantly.

    • Which of the following materials is an example of a brittle material?

  • General purpose polystyrene (GPPS) (correct)
  • High impact polystyrene (HIPS)
  • Rubbery polymers
  • Polybutadiene

    • What characterizes a material described as rubber-toughened?

    <p>It is a blend of brittle and ductile materials.</p> Signup and view all the answers

    In the context of the stress-strain curve, what does strain represent?

    <p>The percentage change in length of the material</p> Signup and view all the answers

    What is the primary characteristic of a homopolymer?

    <p>All repeating units are of the same type.</p> Signup and view all the answers

    Which of the following is an example of a copolymer?

    <p>Styrene-butadiene rubber</p> Signup and view all the answers

    Which prefix in the word 'polymer' signifies 'many'?

    <p>poly</p> Signup and view all the answers

    What is the molar mass of the ethylene repeat unit in grams per mole?

    <p>28 g/mol</p> Signup and view all the answers

    Polymers can be classified based on their monomer composition into which two main categories?

    <p>Copolymers and homopolymers</p> Signup and view all the answers

    What is one common application of polyethylene?

    <p>Floor coverings</p> Signup and view all the answers

    What term describes a polymer made from two or more different types of repeating units?

    <p>Copolymers</p> Signup and view all the answers

    Which of the following is NOT a characteristic of a polymer's mass?

    <p>It is always constant regardless of the number of units.</p> Signup and view all the answers

    What type of polymers are formed through the dehydration-condensation reaction?

    <p>Condensation Polymers</p> Signup and view all the answers

    Which process is used to improve the properties of natural rubber?

    <p>Vulcanization</p> Signup and view all the answers

    Which polymer exhibits a structure made up of side-branch chains?

    <p>Polypropylene</p> Signup and view all the answers

    What is a characteristic of cross-linked polymers?

    <p>They cannot be easily stretched.</p> Signup and view all the answers

    Which of the following is a common addition polymer?

    <p>Polystyrene</p> Signup and view all the answers

    What initiates the reaction in free-radical polymerization of styrene?

    <p>A free radical (R)</p> Signup and view all the answers

    In terms of density, how do branched polymers compare to linear chain polymers?

    <p>Branched polymers have lower density.</p> Signup and view all the answers

    What best describes linear chain polymers?

    <p>They have molecules joined end to end in single chains.</p> Signup and view all the answers

    What defines tensile strength in relation to polymers?

    <p>The stress needed to break a sample</p> Signup and view all the answers

    Which property is used to describe the strain on a polymer sample at the point of breaking?

    <p>% Elongation-to-Break</p> Signup and view all the answers

    What is the unit of measurement for stress in polymers?

    <p>Pascal</p> Signup and view all the answers

    How does Young's Modulus behave in response to increasing strain in common polymers?

    <p>It often shows variability and is not linear</p> Signup and view all the answers

    Which statement is true regarding the % elongation-to-break of elastomers compared to fibers?

    <p>Fibers generally have a lower % elongation-to-break than elastomers</p> Signup and view all the answers

    Which factor is NOT significantly influential on the mechanical properties of polymers?

    <p>Physical dimensions of the sample</p> Signup and view all the answers

    What is the typical characteristic of Young's Modulus values for different materials?

    <p>Fibers exhibit higher values compared to elastomers</p> Signup and view all the answers

    Which of the following properties is generally highest in rigid materials such as metals?

    <p>Young's Modulus</p> Signup and view all the answers

    What characteristic differentiates thermoplastics from thermosets?

    <p>Thermoplastics can be reshaped by heating.</p> Signup and view all the answers

    Which of the following is a property of thermosetting plastics?

    <p>They do not soften with heating.</p> Signup and view all the answers

    What is a common application for thermoplastics?

    <p>Automobile bumpers</p> Signup and view all the answers

    What defines the structure of elastomers?

    <p>They can return to their original shape after stretching.</p> Signup and view all the answers

    Which of the following is NOT classified as a natural polymer?

    <p>Nylon</p> Signup and view all the answers

    What is the main difference between natural and synthetic polymers?

    <p>Synthetic polymers are created by chemical processes.</p> Signup and view all the answers

    Which of the following statements about natural rubber is accurate?

    <p>It is extracted from rubber trees as latex.</p> Signup and view all the answers

    Why are thermoplastics considered to be versatile in their applications?

    <p>They can be reformed multiple times by heating.</p> Signup and view all the answers

    Study Notes

    Polymer Chemistry

    • Polymers are large molecules made up of many repeating units called monomers.
    • Polymers can be classified by their monomer composition (homopolymers, copolymers), structure, and origin (natural, synthetic).

    Types of Polymers

    • Homopolymer: all repeating units are the same.
    • Copolymer: two or more different repeat units.
    • Linear Chain Polymers: repeat units are joined end to end in single chains - are flexible and have high density and tensile strength.
    • Branched Polymers: side-branch chains are connected to the main chain, leading to a lower density than linear polymers.
    • Cross-linked Polymers: adjacent linear chains are joined together by covalent bonds, resulting in tougher, less flexible materials with high melting points.

    Natural Polymers

    • Occur in nature and are also known as biopolymers (e.g., natural rubber, silk, cellulose, starch, proteins).

    Synthetic Polymers

    • Polymers synthesized in the lab, often have high sensitivity to strain rate, temperature, and chemical environments.

    Mechanical Properties of Polymers

    • These are important properties that distinguish polymers from small molecules.
    • Tensile Strength: the stress needed to break a sample. Higher strength means the polymer can withstand more force before breaking.
    • Elongation-to-Break: the strain on a sample when it breaks. Measured as a percentage, higher elongation means the polymer can stretch further before breaking.
    • Young's Modulus: the ratio of stress to strain, which is the slope of the stress-strain curve. A higher modulus means the material is stiffer and less deformable.

    Stress and Strain

    • Stress: force per unit area of a material (measured in Pa or N/m2).
    • Strain: extension per unit length (unitless, as it's a ratio).

    Toughness

    • Toughness is the area under the stress-strain curve.
    • Represents the energy required to fracture a material.
    • A tougher material can absorb more energy before breaking.

    Strength vs. Toughness

    • Strong Materials: can withstand high stress, but may break easily (brittle).
    • Tough Materials: can withstand both high stress and significant deformation before breaking.

    Examples

    • General Purpose Polystyrene (GPPS): brittle.
    • High Impact Polystyrene (HIPS): a blend of polystyrene and polybutadiene (rubbery polymer), making it tough.

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    Polymer Chemistry - Topic 6 (Slides) PDF

    Description

    Explore the fascinating world of polymer chemistry, focusing on the definitions and classifications of polymers. Learn about homopolymers, copolymers, and the distinctions between natural and synthetic polymers. This quiz will enhance your understanding of polymer structures and their applications.

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