Engineering Applications of Polymers
50 Questions
3 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary property of elastomers that allows them to regain their original shape after deformation?

  • Elasticity (correct)
  • Amorphous structure
  • Chemical resistance
  • High tensile strength

Which of the following is NOT an application of the material described that provides electrical insulation?

  • Insulating material for high voltage cables
  • Cation-exchange resins
  • Bonds in grinding wheels
  • Inner tube for tires (correct)

Which property is a characteristic of Butyl Rubber?

  • Low abrasion resistance
  • Excellent resistance to oxidative aging (correct)
  • High gas permeability
  • High flexibility at low temperatures

What is the main disadvantage of Nitrile Rubber regarding its chemical resistance?

<p>Less resistance to alkalis (D)</p> Signup and view all the answers

Which synthetic rubber has high temperature stability and solvent resistance due to its chemical structure?

<p>Butyl Rubber (D)</p> Signup and view all the answers

What method is used to synthesize Nitrile Rubber?

<p>Emulsion Polymerization (D)</p> Signup and view all the answers

Which characteristic of elastomers is linked to the coiled nature of their molecular chains?

<p>Elasticity (C)</p> Signup and view all the answers

Which substance is used as a catalyst in the synthesis of Butyl Rubber?

<p>Anhydrous aluminium chloride (D)</p> Signup and view all the answers

What temperature range can this rubber withstand?

<p>-40 oC to 100 oC (C)</p> Signup and view all the answers

Which process involves heating rubber with sulphur to improve its strength?

<p>Vulcanization (A)</p> Signup and view all the answers

What is the primary purpose of compounding in rubber manufacturing?

<p>To mix raw rubber with other substances for specific properties (D)</p> Signup and view all the answers

Which of the following applications is NOT mentioned for the rubber?

<p>Insulation for wiring (D)</p> Signup and view all the answers

What are polymer composites commonly developed for?

<p>Military and aerospace applications (B)</p> Signup and view all the answers

Which characteristic is NOT desirable in an ideal structural material for the aircraft industry?

<p>High density (A)</p> Signup and view all the answers

What is the main purpose of curing in the context of elastomer materials?

<p>To create a stronger, more durable substance (B)</p> Signup and view all the answers

What is true about the properties of strong materials in relation to density and impact strength?

<p>Higher stiffness generally leads to poorer impact strength (C)</p> Signup and view all the answers

What is the primary method for obtaining polyglycolide?

<p>Ring-opening polymerization of glycolide (C)</p> Signup and view all the answers

Which catalyst is commonly used in the ring-opening polymerization of glycolide?

<p>Aluminium isopropoxide (B)</p> Signup and view all the answers

What characterizes the degradation of polyglycolide?

<p>It is characterized by hydrolytic instability (C)</p> Signup and view all the answers

What type of degradation process does polyglycolide undergo?

<p>Erosive degradation in two steps (A)</p> Signup and view all the answers

Which of the following is NOT a commercial application of biodegradable polymers?

<p>Non-biodegradable dental implants (A)</p> Signup and view all the answers

What is released during the degradation of polyglycolide?

<p>Glycolic acid (D)</p> Signup and view all the answers

How does glycolic acid affect the body after degradation?

<p>It enters the tricarboxylic acid cycle (B)</p> Signup and view all the answers

What is the primary role of the matrix in polymer composites?

<p>To bind the fibers and transmit external stress (D)</p> Signup and view all the answers

Which of the following statements about the degradation process of polyglycolide is true?

<p>The polymer chain dissolves after the crystalline regions collapse (A)</p> Signup and view all the answers

Which of the following statements about Kevlar is true?

<p>It can withstand temperatures up to 450 ⁰C (D)</p> Signup and view all the answers

What is the correct chemical process for preparing Kevlar?

<p>Polycondensation between 1,4-phenyl-diamine and 1,4-benzedicarbonyl chloride (B)</p> Signup and view all the answers

How does Kevlar behave at cryogenic temperatures?

<p>It maintains its strength (B)</p> Signup and view all the answers

What is a key characteristic of carbon fibers?

<p>They contain at least 90% carbon (B)</p> Signup and view all the answers

What unique property does Kevlar exhibit when exposed to ignition?

<p>It ignites but burning stops when the heat source is removed (D)</p> Signup and view all the answers

What is one application of Kevlar?

<p>Used in bulletproof vests (B)</p> Signup and view all the answers

What technique is used to determine the weight average molecular mass (Mw)?

<p>Light scattering and ultra centrifugation (D)</p> Signup and view all the answers

Which statement about the properties of polymer composites is true?

<p>The bonding forces between fibers and matrix primarily contribute to strength (D)</p> Signup and view all the answers

What is the formula for calculating number average molecular mass (Mn)?

<p>Mn = ∑ Ni Mi / ∑ Ni (B)</p> Signup and view all the answers

Which statement is true regarding the Poly Dispersity Index (PDI)?

<p>PDI is the ratio of Mw to Mn. (A)</p> Signup and view all the answers

What characterizes a monodisperse polymer?

<p>All molecules have the same molecular mass. (D)</p> Signup and view all the answers

What is the relationship between Mw and Mn for polymers?

<p>Mw is always greater than Mn. (B)</p> Signup and view all the answers

What does a higher Poly Dispersity Index (PDI) imply about a polymer?

<p>The polymer is heterogenous with a wider range of molecular masses. (B)</p> Signup and view all the answers

Which of the following properties is NOT used to determine number average molecular mass (Mn)?

<p>Light scattering (D)</p> Signup and view all the answers

Why is an average molecular mass calculated for polymers?

<p>Individual macromolecules have different degrees of polymerization. (A)</p> Signup and view all the answers

What happens to the glass transition temperature (Tg) of a polymer as its flexibility increases?

<p>Tg decreases due to higher segmental mobility. (A)</p> Signup and view all the answers

How do intermolecular forces influence the Tg of a polymer?

<p>Stronger intermolecular forces increase Tg due to restricted molecular mobility. (D)</p> Signup and view all the answers

What effect does branching have on the glass transition temperature (Tg) of a polymer?

<p>A small amount of branching reduces Tg, while a high degree of branching increases it. (D)</p> Signup and view all the answers

What is the effect of molecular weight on the glass transition temperature (Tg) up to 20,000?

<p>Tg increases with increasing molecular weight. (A)</p> Signup and view all the answers

What role do plasticizers play in relation to the glass transition temperature (Tg)?

<p>They decrease Tg by diluting intermolecular forces. (D)</p> Signup and view all the answers

Which polymer is likely to have the highest Tg value based on structural characteristics?

<p>Polystyrene with Tg of 100 °C. (B)</p> Signup and view all the answers

Which configuration of a polymer is considered to be the least symmetric?

<p>Atactic (B)</p> Signup and view all the answers

What is the effect of adding hydrogen bonding polar groups to a polymer chain?

<p>It increases Tg due to restricted molecular mobility. (C)</p> Signup and view all the answers

Signup and view all the answers

Signup and view all the answers

Flashcards

Vulcanization

The process of improving rubber strength by heating it with sulfur, creating durable cross-links in the polymer chains.

Compounding

The process of mixing raw rubber with other substances to give it desired properties, like flexibility or resistance.

Curing

A chemical reaction or physical action that makes a material harder, tougher, or more stable. Often involves creating a strong bond.

Composite material

A material made by combining two or more different components, resulting in a material with enhanced properties.

Signup and view all the flashcards

Stiffness

The ability of a material to resist bending or deformation under load.

Signup and view all the flashcards

Abrasion resistance

The ability of a material to resist scratching or wearing away.

Signup and view all the flashcards

Impact resistance

The ability of a material to resist impact forces without breaking.

Signup and view all the flashcards

Corrosion resistance

The ability of a material to resist the effects of chemicals or environmental factors.

Signup and view all the flashcards

Glass Transition Temperature (Tg)

The temperature at which a polymer transitions from a rigid, glassy state to a more flexible, rubbery state.

Signup and view all the flashcards

Number-average molecular weight (Mn)

The average molecular weight of a polymer sample, calculated by considering the number of molecules of each molecular weight.

Signup and view all the flashcards

Flexibility's Effect on Tg

A higher degree of chain flexibility allows for greater segmental motion, resulting in a lower Tg.

Signup and view all the flashcards

Weight-average molecular weight (Mw)

The average molecular weight of a polymer sample, calculated by considering the weight fraction of each molecular weight.

Signup and view all the flashcards

Intermolecular Forces and Tg

Stronger intermolecular forces hinder segmental motion, leading to a higher Tg.

Signup and view all the flashcards

Polydispersity Index (PDI)

The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn). It indicates the homogeneity of polymer chain lengths.

Signup and view all the flashcards

Branching and Tg

A small degree of branching can increase free volume, thus lowering Tg. However, excessive branching restricts motion and raises Tg.

Signup and view all the flashcards

Monodisperse polymers

Polymers with molecules having the same or a narrow range of molecular masses. They are usually uniform in size and properties.

Signup and view all the flashcards

Molecular Weight and Tg

Increasing molecular weight up to 20,000 increases Tg due to increased entanglement and restricted movement. Beyond that, Tg remains relatively constant.

Signup and view all the flashcards

Polydisperse polymers

Polymers with molecules having a wide range of molecular masses. They have varying sizes and properties, leading to different behaviors.

Signup and view all the flashcards

Polymerization

The process of linking together small molecules, called monomers, to form long chains called polymers.

Signup and view all the flashcards

Plasticizer

A substance added to a polymer to increase its flexibility. Plasticizers weaken intermolecular forces, reducing Tg.

Signup and view all the flashcards

Stereoregularity and Tg

The arrangement of side groups along a polymer chain affects its symmetry and flexibility, influencing Tg. Isotactic (all groups on the same side) is most symmetric, then syndiotactic (alternating sides), then atactic (random placement).

Signup and view all the flashcards

Monomers

Small molecules that repeat to form large chains in a polymer.

Signup and view all the flashcards

Polydispersity Index (PDI)

The degree of variation in polymer chain lengths, often expressed as a ratio of weight-average to number-average molecular weight.

Signup and view all the flashcards

Polymers

Large molecules composed of repeating structural units linked together by covalent bonds.

Signup and view all the flashcards

Butyl Rubber

A synthetic polymer with excellent resistance to heat, abrasion, aging, chemicals, and polar solvents, often used for inner tubes, hoses, and insulation.

Signup and view all the flashcards

Butyl Rubber Synthesis

A process where a monomer, such as isobutylene, is combined with a small amount of isoprene in the presence of a catalyst to form a long chain polymer known as butyl rubber.

Signup and view all the flashcards

Elastomers

High molecular weight polymers that exhibit elastic properties, meaning they can stretch under stress and return to their original shape.

Signup and view all the flashcards

Nitrile Rubber (Buna-N or Europrene)

A synthetic rubber synthesized by the emulsion polymerization of butadiene and acrylonitrile, known for its resistance to oils, fats, and solvents.

Signup and view all the flashcards

Nitrile Rubber Synthesis

The process of combining butadiene and acrylonitrile in a water-based solution under controlled conditions to form nitrile rubber.

Signup and view all the flashcards

Amorphous Transparent Plastic

A transparent and amorphous plastic known for its good tensile strength, electrical insulation, and chemical resistance.

Signup and view all the flashcards

Elasticity

A material's ability to withstand stretching and return to its original shape after the stress is removed.

Signup and view all the flashcards

High Molecular Weight Polymers

A type of polymer with a high molecular weight that forms a long chain structure, often used for its strength, durability, and ability to be molded into different shapes.

Signup and view all the flashcards

What is the role of the matrix in a polymer composite?

The material surrounding and holding together the fibers in a composite material. It transmits stress to the fibers and protects them from damage.

Signup and view all the flashcards

What is Kevlar?

A type of synthetic fiber known for its high strength, toughness, and thermal stability. It is a polyamide, meaning it's made of repeating units of amide groups.

Signup and view all the flashcards

How is Kevlar prepared?

The process of preparing Kevlar involves the reaction of 1,4-phenyldiamine with 1,4-benzenedicarbonyl chloride. This reaction forms long chains of poly(para-phenylene terephthalamide) and produces hydrochloric acid as a byproduct.

Signup and view all the flashcards

What are the strength and stiffness properties of Kevlar?

Kevlar is approximately five times stronger than steel, meaning it can withstand significantly more force before breaking. It also possesses high modulus, which indicates its stiffness and resistance to bending.

Signup and view all the flashcards

What is carbon fiber?

Carbon fiber is a lightweight material with exceptional strength and stiffness. It's made of at least 90% carbon, formed through controlled pyrolysis of specific fibers. It's often used in composites with a lightweight matrix.

Signup and view all the flashcards

What is the special property of carbon fiber regarding heat?

Carbon fiber is highly resistant to heat and can withstand much higher temperatures compared to most other materials.

Signup and view all the flashcards

What are some applications of carbon fiber?

Carbon fiber is used in a variety of applications, including aerospace components, sporting goods like tennis rackets and bicycles, and even in some medical implants.

Signup and view all the flashcards

What are the advantages of carbon fiber?

Carbon fiber is known for its high strength-to-weight ratio, making it ideal for applications where weight is critical. It's also highly resistant to corrosion and fatigue, making it a durable material.

Signup and view all the flashcards

Biodegradable Polymer

A type of polymer that breaks down naturally in the body, often used in medical applications.

Signup and view all the flashcards

Glycolide

A cyclic diester of glycolic acid, used as the monomer in the synthesis of polyglycolide.

Signup and view all the flashcards

Polyglycolide

A synthetic biodegradable polymer made from glycolide, used in various medical applications.

Signup and view all the flashcards

Polyglycolide Degradation

The process of breaking down polyglycolide into its smaller components, glycolic acid.

Signup and view all the flashcards

Hydrolytic Degradation

The breakdown of a material due to the action of water molecules.

Signup and view all the flashcards

Erosive Degradation

The process of polyglycolide degradation that starts with water diffusing into the polymer and breaking down its ester bonds.

Signup and view all the flashcards

Glycolic Acid

The breakdown product of polyglycolide, a non-toxic compound that can be metabolized by the body.

Signup and view all the flashcards

Biodegradable Polymer Applications

Applications of biodegradable polymers in medicine, including sutures, dental devices, and tissue engineering scaffolds.

Signup and view all the flashcards

Study Notes

Polymers for Engineering Applications

  • Polymers are essential components of everyday items and have diverse industrial applications, including paints, adhesives, fibers, and elastomers.
  • Molecular weight is a crucial property, measured by number average (Mn) and weight average (Mw) molecular weights, with the polydispersity index (PDI) signifying the homogeneity of the polymer.
  • PDI is the ratio of mass average molecular weight (Mw) to number average molecular weight (Mn). Monodisperse polymers have a PDI of 1, while polydisperse polymers have a PDI greater than 1.
  • Polymers' properties are significantly influenced by glass transition temperature (Tg), flexibility, intermolecular forces, branching, and molecular weight.
  • Higher flexibility generally corresponds to lower Tg values.
  • Intermolecular forces, such as hydrogen bonding, increase Tg.
  • Branching decreases Tg, while cross-linking increases it.
  • Higher molecular weight generally corresponds to higher Tg values.
  • Plasticizers lower Tg, improving flexibility.
  • Stereoregularity of polymers affects their Tg values (isotactic > syndiotactic > atactic).
  • Tensile strength, density, and melt viscosity are important mechanical properties, influenced by molecular weight.
  • Crystallinity, degree of crystallinity, and stereo-regularity influence polymers' properties, such as melting point, solubility, and permeability.

Plastics

  • Plastics are organic materials characterized by high molecular weights, moldability with heat and pressure, and a catalyst.
  • They exhibit lightness, corrosion resistance, and thermal/electrical insulation.
  • Different types of plastics exhibit varying resilience to specific chemical attacks or solvents.
  • The degree of crystallinity significantly impacts the chemical resistance of a plastic.
  • Resins are crucial components of plastics and provide the basis for molding and shaping.

Polymethyl Methacrylate (PMMA)

  • PMMA is synthesized via suspension polymerization and is rigid with a high softening point (~130-140°C).
  • It displays good optical clarity, dimensional stability, and shape-forming properties, but has low resistance to hot acids and alkalis.
  • PMMA applications include lenses, windows, and transparent fixtures.

Urea-Formaldehyde (UF) Resins

  • UF resins are produced through the condensation of urea and formaldehyde, forming cross-linked polymers through curing.
  • They demonstrate good tensile strength, electrical insulation, chemical resistance (except organic solvents), and shape integrity.
  • UF resin applications include bonding agents in grinding wheels, cation exchange resins, and binders in composites.

Elastomers

  • Elastomers are high-molecular-weight polymers that exhibit significant elasticity and recover their initial shape when the stress is released.
  • Butyl rubber is made by mixing isobutylene with isoprene, utilizing a methyl chloride solvent and anhydrous aluminum chloride catalyst at 80°C.
  • Nitrile rubber synthesis involves emulsion polymerization of butadiene and acrylonitrile in the presence of a water solvent and H2O2, culminating in a vulcanized product.
  • Nitrile rubber possesses excellent resistance to heat, sunlight, oils, fats, and organic solvents, though it is less resistant to alkali.
  • Nitrile rubber applications include tires, hoses, and various industrial parts.

Polymer Composites

  • Composite materials are composed of two or more components (e.g., matrix and fiber), combined to enhance properties compared to individual materials.
  • Polymer composites typically utilize a strong fiber embedded within a matrix to improve strength and other properties in structural applications.
  • Materials often utilized in composite materials include glass, carbon fiber, and Kevlar.
  • Kevlar is a high-strength, high-modulus aromatic polyamide fiber.
  • Carbon fiber is a strength and light-weight material of carbon content exceeding 90% obtained through pyrolysis.
  • Applications of composites encompass military, aerospace, and construction sectors.

Conducting Polymers

  • Conducting polymers are organic polymers with delocalized pi-electron systems exhibiting electrical conductivity approaching that of metals.
  • Polyacetylene is synthesized by reacting acetylene over a Ziegler-Natta catalyst.
  • The conductive properties in these polymers can be enhanced through doping (oxidative or reductive).
  • Examples include polyacetylene, polypyrrole, and polyaniline.

Biodegradable Polymers

  • Biodegradable polymers undergo hydrolysis or enzymatic degradation, forming soluble products.
  • Polyglycolide (PGA) is a biodegradable polymer produced through ring-opening polymerization of glycolide.
  • Biodegradable polymers have applications in controlled drug delivery, tissue engineering, and temporary implants, due to their biocompatibility.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Polymers for Engineering Applications PDF

Description

This quiz explores the fundamental concepts of polymers and their engineering applications. Topics include molecular weight, the polydispersity index, and how properties like glass transition temperature and intermolecular forces affect polymer behavior. Test your knowledge of essential polymer science principles!

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser