Polymers and Materials Science Quiz

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Questions and Answers

What characteristic distinguishes thermoplastics from thermosetting polymers?

Thermoplastics have greater hardness than thermosetting polymers.

Thermoplastics become permanently hard upon heating.

Thermoplastics can be reheated without undergoing chemical change. (correct)

Thermoplastics maintain better dimensional stability under heat.

Which of the following is a property of thermosetting polymers?

They are more elastic than rubber.

They remain flexible upon heating.

They degrade when exposed to extreme heat. (correct)

They can be reshaped multiple times.

What is the primary purpose of vulcanization in elastomers?

To enhance strength and stiffness. (correct)

To improve their dimensional stability.

To lower their melting point.

To increase their elasticity.

How do thermosetting polymers typically compare to thermoplastics in terms of strength and hardness?

Thermosetting polymers are generally harder and stronger. Signup and view all the answers

What is a common application for elastomers due to their properties?

Flexible parts like seals and hoses. Signup and view all the answers

What does machinability refer to?

The ease with which a material can be cut Signup and view all the answers

Which property measures the amount of energy absorbed per unit volume within the elastic limit?

Resilience Signup and view all the answers

What occurs when a material is subjected to constant stress at high temperature for extended periods?

Creep Signup and view all the answers

Fatigue failure occurs at stresses below which specific point?

Yield point stress Signup and view all the answers

Which test is NOT commonly used to measure hardness in metals?

Tensile strength test Signup and view all the answers

Thermal conductivity is an example of which category of properties?

Thermal properties Signup and view all the answers

What property describes a metal's ability to resist wear and scratching?

Hardness Signup and view all the answers

Which of the following is NOT a thermal property of metals?

Dielectric strength Signup and view all the answers

Which synthetic material is primarily derived from natural substances such as oil and coal?

Synthetic materials Signup and view all the answers

What is the main use of naturally occurring latex in engineering applications?

Vehicle tyres Signup and view all the answers

Which material is known for its excellent weathering properties and is commonly used in laboratory equipment?

Glass Signup and view all the answers

What process is used to produce ceramics?

Baking clays at high temperatures Signup and view all the answers

Which substance is used as an alloying element and for making semiconductor devices?

Silicon Signup and view all the answers

What is the primary use of emery in industry?

As an abrasive Signup and view all the answers

Diamonds are commonly used for which engineering application?

Cutting tools for high speed operations Signup and view all the answers

Which type of materials do ceramics primarily consist of?

Both metallic and nonmetallic elements Signup and view all the answers

What is a primary benefit of heat treatment for materials?

Increases ductility while maintaining high strength Signup and view all the answers

Which property is NOT typically associated with abrasives?

Low density Signup and view all the answers

What is the main component of wrought iron?

At least 99.5% iron Signup and view all the answers

Which application is NOT typically associated with wrought iron?

Steel forgings Signup and view all the answers

What is the purpose of heat treatment in metal processing?

To change the properties for improved performance Signup and view all the answers

Why are non-ferrous metals rarely used in their pure forms?

They lack mechanical strength Signup and view all the answers

What reacts with the zinc in brass when exposed to a marine environment?

Sea salt Signup and view all the answers

Which of the following is a characteristic of thermoplastics?

They can be reheated and reshaped multiple times Signup and view all the answers

What element is most commonly used to produce aluminum?

Bauxite Signup and view all the answers

Which characteristic makes non-ferrous metals suitable for electrical applications?

Good electrical and thermal conductivity Signup and view all the answers

How does resting affect steel structures?

Reduces the steel's strength Signup and view all the answers

What is desincification of brass primarily caused by?

Prolonged exposure to sea water Signup and view all the answers

At what temperature does aluminum typically melt?

658°C Signup and view all the answers

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

Glass Signup and view all the answers

Which property of aluminum changes when mixed with small amounts of other alloys?

It becomes harder and more rigid Signup and view all the answers

What effect does ultraviolet light have on many types of plastics?

Causes them to degrade and become brittle Signup and view all the answers

What is the primary element found in ferrous metals?

Iron Signup and view all the answers

Which property describes the ability of a material to resist deformation upon the application of magnetic fields?

Magnetic permeability Signup and view all the answers

What is the objective of alloying metals?

To enhance properties of the base material Signup and view all the answers

Which of the following is NOT an optical property of metals?

Corrosion resistance Signup and view all the answers

What type of metals are primarily used in high-strength applications at a low cost?

Ferrous metals Signup and view all the answers

Which property is characterized by the size of the grains in a metal?

Grain size Signup and view all the answers

What is meant by coercive force in magnetic materials?

The resistance to becoming demagnetized Signup and view all the answers

What is a common application of ferrous alloys?

Railway lines Signup and view all the answers

Study Notes

Engineering Materials

Engineering materials are the materials used in the construction of man-made structures and components.
Their primary function is to withstand applied loads without breaking or excessive deflection.
Major classifications include metals, polymers, ceramics, and composites.

Importance of Material Science & Engineering

Mechanical engineers seek high-temperature materials for more efficient gas turbines and jet engines, and wear-resistant materials for bearing manufacture.
Electrical engineers look for materials enabling faster electrical devices/machines with minimal power losses.
Aerospace and automotive engineers search for materials with a high strength-to-weight ratio.
Electronic engineers search for materials useful in fabricating and miniaturizing electronic devices.
Chemical engineers seek highly corrosion-resistant materials.
Civil engineers prioritize material performance and resistance to various stresses in structures.

Selection of Materials

The ideal material fulfills the desired objective at the lowest cost.
Factors to consider include material availability, suitability for working conditions, and cost.

Structure of Metals

An atom is the smallest unit of matter retaining an element's chemical properties.
Atoms combine to form molecules, which then interact to form solids, liquids, or gases.

Structure of an Atom

Atoms are composed of protons, electrons, and neutrons.
Protons (positive charge) and neutrons (no charge) are found in the nucleus.
Electrons (negative charge) orbit the nucleus.
Atomic properties vary based on the arrangement and number of these basic particles.

Atomic Number and Mass Number

Atomic number = number of protons in an element.
Mass number = number of protons + number of neutrons.
Number of electrons (neutral atom) = number of protons.
Number of neutrons = mass number - atomic number.

Quantum Numbers

Quantum numbers describe the distribution of electrons in an atom.
Principal quantum number (n) describes the principal electron shell and its size (larger n, further from the nucleus).
Angular quantum number (l) describes the shape of the electron orbital (0 = spherical, 1 = polar, 2 = cloverleaf, etc.).
Magnetic quantum number (ml) describes the number of orbitals and their orientation within a subshell within a range from -l to +l.

Electron Configurations

Electron configuration depicts the occupied orbitals of electrons in an atom.
Aufbau Principle dictates filling orbitals with the lowest energy levels first.
The order of increasing energy of orbitals is determined by following specific arrows in a diagram (e.g., 1s, 2s, 2p, 3s, 3p, 4s, 3d, etc.).

Pauli Exclusion Principle

No two electrons within an atom or molecule can possess the same four quantum numbers.
An orbital can accommodate a maximum of two electrons.
These electrons must have opposing spins (+1/2 and -1/2).

Hund's Rule

Each orbital in a sublevel is singly occupied before being doubly occupied.
Electrons in singly occupied orbitals have the same spin.

Chemical Bonding

Chemical compounds are formed from the joining of two or more atoms.
Chemical bonds are physical phenomena holding chemical substances together.
Bonds arise from electron sharing (covalent), electron transfer (ionic), or electrostatic forces.

Covalent Bonds

Covalent bonds involve electrons being shared between two atoms.
The shared electrons provide a stable noble gas configuration for each atom.

Ionic Bonds

Ionic bonds occur when there are large electronegativity differences between two atoms.
Valence electrons are transferred from a metal to a nonmetal atom.
The metal atom and nonmetal atom become oppositely charged ions, which attract each other, forming an ionic compound.

Metallic Bonds

Metallic bonds involve shared electrons between many positive ions.
The electrons act as a "glue" giving the substance a definite structure.
Delocalized electrons are not associated with any specific atom and are free to move throughout the whole crystalline structure, forming a "sea of electrons"
The mobile electrons are responsible for the excellent thermal and electrical conductivity of metals.

Conductivity of Metals

Delocalized electrons in metals can rapidly transfer heat between atoms when the metal is heated.
Free electrons allow a rapid transfer of electrical current.
Collision of electrons with atoms and other electrons accelerates heat transfer.

Malleability and Ductility

Ductility is a material's ability to change shape under tensile stress (stretching) resulting in a wire-like shape.
Malleability is a material's capacity to change shape under compressive stress (hammering or rolling) resulting in a sheet-like shape.
Delocalized electrons allow the metal atoms to roll over one another, leading to malleability and ductility.

Physical Properties of Metals

Physical properties of metals include appearance, color, size, shape, weight, density, melting point, boiling point, freezing point, glass transition temperature, and permeability.

Mechanical Properties of Metals

Mechanical properties, including strength, stiffness, elasticity, plasticity, ductility, brittleness, malleability, toughness, resilience, creep, and hardness, describe how metals react under stress.
Strength – material's ability to withstand external forces without breaking or yielding
Stiffness – material's ability to resist deformation under stress
Elasticity – material's ability to return to its original shape when external forces are removed
Plasticity – material’s ability to become permanently deformed when forces are applied
Ductility – material's ability to be drawn into wires
Brittleness – material’s ability to break with little distortion
Malleability – material’s ability to be shaped into thin sheets
Toughness – material's ability to resist fracture
Machinability – ease with which a material can be cut
Resilience – amount of energy a material can absorb
Creep – slow, permanent deformation of a material under constant stress at high temperatures
Fatigue – failure of a material due to repeated stresses at stresses below the yield point
Hardness – resistance to wear, scratching, deformation and machinability.
Different tests used to measure metal hardness (Brinell, Rockwell, Vickers and Shore scleroscope tests)

Thermal Properties of Metals

Thermal properties describe a metal's reaction to heat. Examples include thermal conductivity, expansion coefficient, resistivity, thermal shock resistance, and thermal diffusivity.

Electrical Properties of Metals

Electrical properties describe a metal's reaction to electricity and include conductivity, resistivity, dielectric strength, thermoelectricity, superconductivity, and electric hysteresis.

Magnetic Properties of Metals

Magnetic properties describe the magnetism, examples include ferromagnetism, paramagnetism, diamagnetism, magnetic permeability, coercive force, Curie temperature, and magnetic hysteresis.

Chemical Properties of Metals

Chemical properties describe how metals react with other substances. Examples include reactivity, corrosion resistance, polymerization, composition, acidity, and alkalinity.

Optical Properties of Metals

Optical properties describe how metals react to light. Examples include reflectivity, refractivity, absorptivity, transparency, opaqueness, color, and luster.

Metallurgical Properties of Metals

Metallurgical properties describe how metals are processed and their structure. Examples include grain size, heat treatment, anisotropy, and hardenability.

Classification of Engineering Materials

Materials are categorized in general, based on common characteristics, nature of the material and their applications.
Major categories include metals (ferrous and non-ferrous), polymers(thermoplastics, thermosetting, and elastomers), ceramics (glasses, cements, clay products, refractories, and abrasives), which in turn have several subclasses.

Metals

Metals are the most used engineering materials.
Alloys are formed from combining metals with other metallic and/or non-metallic materials. Alloying improves base material properties.
Metal alloy compositions are described by the percentages of different alloying elements, measured by weight.

Ferrous Metals

Ferrous metals are metal and alloys that contain a high proportion of iron.
Strong, low-cost, and suitable for applications where weight is less important.
Example applications include bridges, large building structures, railway lines, and heavy-duty engine components.

Ferrous Alloys

Ferrous alloys use iron as the base, and feature high versatility, ease of production, and high abundance of iron.
Main disadvantage of ferrous alloys is low corrosion resistance.

Carbon Steel

Carbon steel is typically a mixture of iron and carbon as the main alloying material.
Increasing carbon content generally leads to higher strength and hardness but lower ductility and weldability

Low-Carbon Steel

Low-carbon steel contains less than 0.30% carbon.
Characterized by low strength and high ductility.
Widely used for wire, structural shapes, machine parts, and sheet metal due to its weldability and low cost.

Medium-Carbon Steel

Medium-carbon steel has between 0.30% and 0.70% carbon.
Can be hardened by heat treatment, frequently used for axles, gears, shafts, and machine parts.

High-Carbon Steel

High-carbon steel (0.70% to 1.40% carbon) has higher strength than medium or low-carbon steels but lower ductility.
Widely used in applications requiring hardness and wear resistance, such as cutting tools, drills, knives, and springs

Low-Alloy Steel

Low-alloy steels usually contain less than 8% various alloying elements, typically offering higher strength and corrosion resistance compared to carbon steels.
Frequently used in tooling applications necessitating high hardness, wear resistance, and toughness.

Stainless Steel

Stainless steel has excellent corrosion resistance, attributed to a chromium content of at least 11% (12% or higher provides best results).
Stainless steel forms a protective chromium oxide layer that inhibits oxidation.

Cast Iron

Cast iron is a ferrous alloy with a high carbon content (usually greater than 2%).
Low melting temperature making it suitable for casting applications.
Has good compressive strength, but is very brittle and has poor weldability.
Varieties of cast iron (gray, ductile, white, malleable) exist, with differing properties.

Gray Cast Iron

Gray cast iron is the most common type of cast iron.
High compressive strength, low tensile strength, and low ductility.
The graphite in its structure acts as a lubricant which makes it good for parts needing sliding action.

Ductile Cast Iron (Nodular Cast Iron)

Ductile or nodular cast iron results from the addition of magnesium to gray cast iron, altering graphite structure to form nodules and improve ductility.
Offers a good balance of strength, ductility, and machinability.

White Cast Iron

White cast iron contains carbon in the form of carbide (cementite).
Extremely hard, with high tensile strength but low compressive strength.
Suitable for applications requiring wear resistance but needs grinding for shape.

Malleable Cast Iron

Malleable cast iron is created by heat treating white cast iron, improving ductility while maintaining the high strength of the material.
Used for intricate machine parts and applications where steel forgings are expensive because of good accuracy needed.

Wrought Iron

Wrought iron is the purest form of iron and contains 99.5% or higher.
Very tough, malleable, and ductile, resisting sudden shocks but not suitable for many high-stress uses.
Commonly used for structural purposes such as in chains, crane hooks, railway couplings, water and steam pipes.

Non-Ferrous Metals

Non-ferrous metals are all metals other than those that contain significant amounts of iron.
Used in high proportion to their exceptional properties in many applications.
These include, but are not limited to, corrosion resistance, very high electrical and thermal conductivity, and light weight.

Aluminum

Aluminum is a lightweight, corrosion-resistant metal, commonly employed in various industries due to its properties.
Pure aluminum is soft and weak on its own, thus alloyed to improve its properties.
Versatile material used for a variety of purposes, including aircraft, automobiles, food storage, and cooking utensils.

Aluminum Alloys

Aluminum alloys contain small amounts of other metals to improve mechanical properties.
Aluminum is often alloyed with copper, magnesium, manganese, silicon, or nickel to improve strength and/or corrosion resistance, or for high-temperature use in engines or parts exposed to high heat.

Nickel

Copper and Nickel alloys are frequently used for their exceptional properties in various manufacturing environments, most readily used for applications requiring excellent corrosion and heat resistance.

Copper

Copper is a soft, malleable, ductile reddish-brown metal.
Good electrical conductivity, corrosion resistance, suitable for making electrical cables and wires.
Widely used in various applications from electric machinery to coins, cookware, and building materials.
Essential ingredient is many important alloys used in construction and industry.

Copper Alloys (Brass and Bronze)

Copper alloys like brass (copper and zinc) and bronze (copper and tin), exhibit unique properties depending on the specific proportions of copper and other alloying elements. Different compositions are tailored for specific functions or characteristics.
Brass and Bronze exhibit various mechanical, electrical, and other attributes which affect their practicality in manufacturing.

Gun metal

Gun metal is a copper alloy composed mainly of copper, tin, and zinc.
Specifically suited for casting applications.
This alloy is resistant to corrosion, strong, and possesses good fluidity.

Lead

Lead is a bluish-gray metal.
Low tenacity, is soft, and easily cut.
Used for making solders, lining for acid tanks, water pipes, and electrical coatings due to corrosion resistance and low cost.

Tin

Tin is a silvery-white metal, highly malleable and ductile.
Used in alloys, especially for solder, as protective coating for iron, and steel products, as well as moisture-proof packaging.

Zinc Base Alloys

Zinc base alloys are commonly used for die castings.
They are cast easily, possess moderate strength at fairly low temperatures, and have good corrosion resistance.
Frequently used in automotive components, high-production items (washers, burners, refrigerators, electronics).

Nickel Base Alloys

Various nickel-based alloys with diverse characteristics, each chosen for applications requiring particular features. Common nickel-based alloys such as Monel, K-Monel, Inconel, and Hastelloy, are known for strength, corrosion resistance, and high-temperature capabilities. Applications vary, from exhaust components and parts exposed to corrosive environments in manufacturing and construction and equipment working under high temperatures or exposed to corrosive environments.

Non-Metallic Materials

Non-metallic materials do not contain significant amounts of iron.
Includes synthetic materials such as polymers and ceramics.

Polymers

Polymers are long-chain molecules formed from repeating units.
Many useful materials are polymers, including plastics, rubbers, fibers, adhesives, and coatings.
Classified into thermoplastics, thermosetting polymers, and elastomers based on their responses to heat.

Thermoplastic Polymers

Thermoplastics soften and melt when heated and return to solid form when cooled.
Commonly used for injection molding, due to repeatable heating and cooling cycles.

Thermosetting Polymers

Thermosets harden permanently after initial heating.
They do not melt upon reheating and typically possess greater hardness, strength, and dimensional stability compared to thermoplastics, making them suitable for applications demanding high-temperature resistance.

Elastomers

Elastomers are highly elastic polymers similar to rubber.
Used for seals, adhesives, hoses, belts, and other flexible components.
Vulcanization, a process involving sulfur and heat treatment, yields cross-linking within the polymer structure, improving strength and stiffness.

Ceramics

Ceramics are solid compounds, possibly with metallic or non-metallic elements.
Include classes like glasses, cements, clay products, refractories, and abrasives, each characterized by unique traits like high temperature stability, brittleness, and corrosion resistance

Processing of Materials

Materials processing techniques, like hot working and cold working, affect material properties.
Processing methods such as casting, rolling, forging, welding, and machining, impact desired characteristics.

Environmental Reactions

Environmental reactions can degrade materials.
Factors like resting and dezincification of brass are influenced by exposure to specific elements affecting material properties.
Degradation of plastics from UV light is an example of environmental reaction-based degradation.

Engaging Activities

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Explanation of briefly Questions

Include concise explanations related to slides questions, addressing heat treatment's effect on metal movement, types of carbon steels and their characteristics, classification of cast irons, enumeration of aluminum alloys, identification of copper alloys, engineering material applications in civil engineering and importance of knowing material characteristics in civil engineering.

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Description

This quiz assesses your understanding of polymers, focusing on the distinctions between thermoplastics and thermosetting polymers, as well as the properties and applications of elastomers. Test your knowledge on manufacturing characteristics, mechanical properties, and thermal behavior of various materials.