Polymers and Materials Science Quiz

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

• Provides relevant data necessary to solve problems and find answers based on the information in the slides.

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.

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.