PROPERTIES OF MATERIALS
Mechanical Properties
1. Abrasion
Abrasion is the process of wearing away a material’s surface through mechanical action
of another material. It usually occurs when two surfaces form a strong contact against each
other which causes them to collide and scratch each other’s surface. A material’s resistance to
abrasion is called abrasion resistance.
The reason why we should be aware of the abrasion resistance of a material is because
it can help us select the appropriate material for specific applications. The quality of a material
with better abrasion resistance to abrasion are
● harder than other material so it can withstand scratching
● Has high toughness that can resist cracking and breaking
● Has a strong capability to withstand stresses and forces
● And good wear resistance to resist material lost due to rubbing
Example:
1. A common example which we typically see in our everyday lives is the abrasion caused
by the collision of a automobile’s tires and the ground. This occurrence is unavoidable
because in order to make a car run, the wheels should role and slide making contact
with the ground.
According to a study conducted by Sommer et. al on 2018, tire abrasion is a major source of
microplastic in the environment. The ambient aerosol particles on the road surface in Germany
and examined it. The result showed that 90% of the particles found in motorways and urban
highways are derived from the abrasion of tires. This contributes considerably to the pollution of
microplastics in our environment.
Therefore, tires with low rolling resistance are advisable to use because they require less
energy to move and has lower tire wear. This minimizes the release of microplastic particles. But
to be exact, consult with tire professional.
https://aaqr.org/articles/aaqr-18-03-oa-0099#:~:text=Our%20study%20documents%20that%20ti
re,unlikely%20in%20the%20near%20future.
2. Coatings applied to surfaces, such as paints, varnishes, or polymer coatings, provide
protection against abrasion. Understanding the abrasion resistance of these coatings is
crucial in applications like automotive finishes, architectural coatings, or industrial
equipment coatings. High abrasion resistance ensures that the coating maintains its
appearance and protective function over time.
2. Creep
Creep is the tendency of a solid material to move slowly or undergo irreversible
deformation when subjected into constal mechanical load and stress. It can happen as a result
of prolonged exposure to high-stress levels as the material sustains a load, however, even if the
applied stress is below its yield strength, creep can occur. Creep typically happens at elevated
temperature because long term heat exposure makes creep more severe as the materials
reaches closer to their melting point
To avoid creep:
● Lower the material’s operating temperature while using it
● Utilize substances with a high melting point.
● The constant load that the metal must withstand can be reduced as an alternative,
Example:
1. Creep in geotechnical materials or materials that are used in engineering projects
including retaining walls, tunnels, or deep excavation where sustained loads and
constant stress are applied to the surrounding ground. Soils and rock materials can also
exhibit creep.
In an article written by The Associated Press, an unfortunate accident in 2007 also known as
BIG DIG which is considered as the most expensive highway project of the US back then was
executed poorly making use of substandard materials which caused the death of one motorist.
Including of which is an epoxy anchor adhesive with poor creep resistance was made use which
means that it only has short term strength making it incapable of supporting loads over time. A
rider was crushed to death because of the improper use of material with low creep resistance.
This is the reason why we should be careful with the material that we should use especially in a
project where high or low loads of stress are usually occurring.
https://www.npr.org/templates/story/story.php?storyId=11852203
https://www.youtube.com/watch?v=DRVHn7bNjbI SABO SHOWING CREEP
2. Metals: Many metals, including steel, aluminum, and titanium alloys, can experience
creep at elevated temperatures. Creep in metals can be of concern in applications such
as high-temperature components in power plants, jet engines, or steam turbines. creep
can cause the blades to elongate, which can ultimately lead to the blade beginning to
damage or pierce the turbine casing.
3. Elasticity
Elasticity refers to the ability of a material to deform when subjected to an external force
and then return to its original shape and size when the force is removed.
Elastic Deformation: Elastic deformation is a temporary deformation that occurs when a
material is subjected to a force but returns to its original shape when the force is released.
Example:
1. Stretching a spring. When the force is applied to a spring, it undergoes elastic
deformation. This happens when the spring elongates or compresses in response to the
applied force, storing potential energy. When the force is gone, the stored energy is
released and the spring returns to its original shape and length. Trampoline
Plastic deformation: occurs when a material is subjected to a force that exceeds its elastic
limit, causing permanent deformation. Unlike elastic deformation, the material does not return to
its original shape once the force is removed. The atoms or molecules within the material
undergo rearrangement or sliding, leading to a change in the material's shape that persists even
after the force is released.
Example:
1. A piece of modeling clay. When you apply force to it and mold it into a particular shape,
the clay’s atoms undergo plastic deformation. Even after you remove your force, the clay
retains its new shape.
2. This can also happen with metals where applied force and stress to a metal exceeds
their yield strength causing permanent deformation. This process can be used in metal
forming where metals are formed using plastic deformation for example pipes, wires, and
etc. rolling steel used in furnitures
It's important to note that the elastic and plastic properties of materials can vary significantly.
Some materials exhibit a larger elastic range and can undergo substantial elastic deformation
before entering the plastic deformation region, while others may have a smaller elastic range
and quickly transition to plastic deformation. The ability to withstand plastic deformation without
fracture or failure is an important consideration in the design and selection of materials for
various applications.
4. Fatigue
Fatigue, in the context of material properties, refers to the progressive and localized
damage that occurs when a material is subjected to cyclic loading or repeated stress over an
extended period. Fatigue can lead to failure, even when the applied stress is below the
material's ultimate strength.
The materials experience alternating periods of stress which cause small cracks that
eventually lead to catastrophic failure over time.
Example:
1. Aircraft wings - they are subjected to repeated cycles of loading and unloading during
flight. The cyclic stresses induced by the wing’s flexing and the varying aerodynamic
forces can lead to fatigue. Over time, the aircraft wings develop small cracks at the
concentrated points. If it is not detected and addressed by the mechanics, this could
result into a critical failure especially during mid flight.
According to an article written by Daniel Wong. On May 25, 2002, China Airlines Flight 611, a
Boeing 747, suffered a catastrophic in-flight breakup. The accident was caused by fatigue
cracks that had developed and grown undetected in the aircraft's structure. The investigation
concluded that improper repairs and inadequate inspections were contributing factors to the
failure. This resulted in the death of all 225 passengers on board.
It is important for proper inspection and maintenance for fatigue because we never really know
when they will happen. Understanding fatigue behavior is essential for designing reliable and
safe structures and components subjected to cyclic loading conditions.
https://simpleflying.com/china-airlines-flight-611-metal-fatigue-story/
5. Hardness
Hardness is a material property that measures its resistance to indentation, scratching,
or abrasion. It refers to the ability of a material to withstand localized deformation and resist
surface penetration by another object. Hardness is an essential characteristic in materials used
for various applications, including engineering, construction, manufacturing, and mining.
Example:
1. Alumina is a widely used ceramic material known for its excellent hardness and high
thermal conductivity. It is utilized in applications such as cutting tools, grinding media,
electrical insulators, and wear-resistant components.
2. Concrete, although not traditionally considered a ceramic, exhibits considerable
hardness. It is a composite material composed of aggregates (such as crushed stone or
gravel), cement, and water. Concrete is widely used in construction due to its durability,
strength, and ability to withstand compressive forces. It is normally used in basic
foundations, exterior surfaces, and floor construction.
Understanding the hardness of materials is crucial for selecting appropriate materials for specific
applications, assessing wear resistance, and evaluating their performance under load or
abrasive conditions.
6. Impact Strength
Impact strength is a measure of a material's ability to absorb energy when subjected to
sudden or dynamic loading, such as impacts or collisions. It quantifies a material's resistance to
fracture under high-speed and high-stress conditions. Materials with high impact strength can
withstand sudden applied forces without fracturing or breaking.
Example:
1. Polycarbonate is a thermoplastic known for its excellent impact strength. It exhibits high
toughness and can absorb energy without fracturing. Due to its impact resistance,
polycarbonate is commonly used in applications that require protection against impacts,
such as safety goggles, helmet visors, bulletproof windows, and protective covers.
Motorcycle helmet.
2. The material used in bulletproof vests or kevlar. Kevlar is a synthetic fiber known for its
high strength-to-weight ratio and excellent impact resistance. It is a brand name for a
type of aramid fiber developed by DuPont. Kevlar fibers are extremely strong and are
widely used in applications that require high tensile strength, impact resistance, and
durability. ​Kevlar fibers have a unique ability to absorb and disperse energy when
subjected to impact or sudden loads.
7. Plasticity and Brittleness
Plasticity refers to the ability of a material to undergo permanent deformation without fracturing
when subjected to external forces. Plastic materials exhibit the property of plasticity, meaning
they can be molded, shaped, or stretched under stress and retain their new shape after the
force is removed.
Example:
1. Polyethylene is a widely used thermoplastic that exhibits high plasticity. It can be easily
molded and reshaped when heated, making it suitable for applications such as plastic
bottles, pipes, packaging materials, and various consumer products.
2. Plastic wrap is an example of plasticity. After stretched—it stays stretched.
Brittleness refers to the tendency of a material to fracture or break when subjected to stress or
impact without significant deformation. Brittle materials are characterized by low ductility and
limited ability to absorb energy before failure.
Example:
1. Glass is brittle because it lacks a regular atomic structure and has strong bonds that
break easily under stress. It does not deform plastically like some other materials,
leading to sudden fractures when subjected to impact or stress.
2. Eggshells are also considered brittle. They are thin and composed primarily of calcium
carbonate. The brittleness of eggshells is due to their relatively rigid and fragile structure.
When subjected to external forces or impacts, eggshells are prone to cracking or
breaking rather than undergoing plastic deformation.
The selection of a material with appropriate impact strength depends on the specific application
requirements, desired performance characteristics, and environmental conditions it will be
subjected to.
8. Strength
Strength is a material property that refers to its ability to withstand applied forces or
loads without permanent deformation or failure. It is an essential characteristic for materials
used in structural, mechanical, and load-bearing applications. Strong materials are able to resist
heavy impacts, and are able to absorb and distribute large amounts of energy without breaking.
Example:
1. Steel is a widely used material known for its exceptional strength. It is an alloy of iron
and carbon, with small amounts of other elements added to enhance specific properties.
Steel exhibits high tensile strength (maximum stress before breaking), compressive
strength (resist direct pressure), and yield strength (maximum allowable load), making it
suitable for a wide range of applications.
According to a report conducted by Dr Rahil Alipour Dating back 550 B.C. the persian army, a
major superpower in that era, developed the first known steel in the world. The chromium steel
known today as tool steel which they used to establish the biggest Empire in the world or
Persian empire. Using chromium steel was used as their weapons and armors which gave them
an advantage over their enemies who are using bronze or stone weapons that are much weaker
than steel.
https://www.ucl.ac.uk/news/2020/sep/chromium-steel-was-first-made-ancient-persia#:~:text=Chr
omium%20steel%20%E2%80%93%20similar%20to%20what,new%20study%20led%20by%20
UCL.
Strength is a critical material property that determines the performance and reliability of various
structures and components. The choice of a material with appropriate strength is crucial for
ensuring safety, longevity, and efficient utilization in a wide range of engineering and
manufacturing applications.
9. Wear
Wear refers to the progressive loss of material due to the interaction between two
surfaces in relative motion. It occurs when surfaces experience friction, abrasion, or erosion,
leading to the removal of material from one or both surfaces.
Wear can manifest in different forms, including adhesive wear (material transfer between
surfaces), abrasive wear (surface degradation due to hard particles or contaminants), and
erosive wear (erosion caused by fluid or solid particles impacting the surface).
Example:
1. Tungsten carbide-coated tools are widely used in applications that require superior wear
or impact resistance. The coating consists of tungsten carbide particles embedded in a
metallic matrix. Tungsten carbide is an extremely hard and wear-resistant material. Cast
iron, cutting edges of saws and drills, and penetrating cores of armour-piercing
projectiles
Understanding wear properties is important in selecting materials for applications that involve
contact, relative motion, and potential surface degradation. By utilizing materials with excellent
wear resistance, the durability and longevity of components and systems can be improved,
leading to reduced maintenance and enhanced performance in various industries.
Chemical Properties
Chemical properties of a material refer to its behavior and reactions when exposed to various
chemical substances or environments.
1. Corrosion
Corrosion is a chemical process that leads to the deterioration of materials due to
chemical reactions with their environment. It typically occurs when materials are exposed to
corrosive substances such as moisture, gases, acids, or alkaline solutions. Corrosion can result
in the degradation of material properties, including strength, appearance, and structural integrity.
Example:
1. Stainless steel is widely used in various applications, including kitchen utensils, industrial
equipment, architectural structures, and medical devices, where resistance to corrosion
is essential. Its ability to withstand exposure to moisture, acids, and alkaline solutions
without significant corrosion makes it a preferred choice in environments where other
materials might corrode or degrade.
It's important to note that the corrosive behavior of materials can vary depending on the specific
corrosive agent, concentration, temperature, and other environmental factors. Therefore,
selecting the appropriate material with the desired corrosion resistance properties is crucial for
ensuring the durability and reliability of structures, equipment, and components in corrosive
environments.
Electrical Properties
Electrical properties of a material describe its behavior and characteristics in the presence of
electric fields or when used as a conductor, insulator, or semiconductor. These properties
determine how a material interacts with electricity and are important in various electronic and
electrical applications.
1. Conductivity
Conductivity is a fundamental electrical property that describes a material's ability to conduct
electric current and heat. It is influenced by the presence of charge carriers (e.g., electrons or
ions) and their mobility within the material. Materials can exhibit varying levels of conductivity,
ranging from excellent conductors to poor conductors (insulators).
1. Electrical Conductivity: Electrical conductivity refers to the ability of a material to conduct
electric current carried by free electrons. Metals are excellent conductors of electricity due to the
presence of a large number of free electrons that can move easily through the material.
Example:
1. Copper (Cu) is a prime example of a highly conductive metal. It is widely used in
electrical wiring and circuits due to its exceptional electrical conductivity. Copper's high
conductivity ensures efficient transfer of electric current with minimal resistance,
resulting in less energy loss and heat generation.
2. Thermal Conductivity: Thermal conductivity refers to a material's ability to conduct heat. It
describes how well a material can transfer heat energy through conduction.
Example:
1. Silicon (Si) is an interesting example as it is not only a semiconductor but also has good
thermal conductivity. Silicon is commonly used in electronic devices such as transistors
and integrated circuits, where efficient heat dissipation is essential to maintain optimal
performance and prevent overheating.
3. Ionic Conductivity: Ionic conductivity relates to the movement of ions within a material. Ionic
conductors are materials that allow the flow of charged ions, typically in the liquid or solid-state.
Example:
1. Nafion is known for its exceptional ionic conductivity, particularly for protons (H+) in the
presence of moisture. Nafion's high ionic conductivity enables efficient transport of
protons, contributing to the generation of electrical energy in fuel cell systems. (Fuel cells
are electrochemical cells that convert chemical energy from a fuel)
Permeability refers to a material's ability to allow the flow of substances (such as liquids, gases,
or electromagnetic fields) through its structure. It is a property that characterizes the ease with
which a material can be penetrated by external elements
Magnetic Properties
1. Permeability
Permeability refers to a material's ability to allow the flow of substances (such as liquids,
gases, or electromagnetic fields) through its structure. It is a property that characterizes the
ease with which a material can be penetrated by external elements
Fluid Permeability: Fluid permeability is the measure of a material's ability to allow the flow of
liquids or gases through its pores or matrix.
Example:
1. Sand The porous nature of sand allows water or other fluids to pass through it easily.
This permeability property makes sand useful in applications such as water filtration and
oil extraction.
Magnetic Permeability: Magnetic permeability describes a material's ability to respond to an
external magnetic field by becoming magnetized or allowing magnetic lines of force to pass
through it.
Example:
1. Iron exhibits high magnetic permeability, making it suitable for applications such as
magnetic cores in transformers and electromagnets. Its ability to conduct magnetic flux
efficiently enables the creation and manipulation of magnetic fields in various devices.
The magnetic permeability of iron quantifies this response. It is a measure of how
easily a material can be magnetized by an external magnetic field. In the case of iron, its
high magnetic permeability allows it to attract and concentrate magnetic field lines,
making it useful for applications such as electromagnets, transformers, and magnetic
shielding.
Permeability properties are crucial in designing materials for specific purposes. For example, in
engineering and construction, materials with controlled permeability are utilized in applications
such as waterproofing, gas barriers, or ventilation systems. Similarly, understanding and
manipulating permeability allows for the development of specialized materials for filtration,
environmental remediation, and electromagnetic shielding.
2. Hysteresis
Hysteresis refers to the phenomenon where the material's response lags or deviates
when subjected to changing external conditions. It is observed in various properties such as
mechanical, electrical, magnetic, and thermal.
Example:
1. Hysteresis in Magnetic Materials such as iron or nickel, exhibit hysteresis in their
magnetization behavior. When a magnetic field is applied to these materials, their
magnetization increases until reaching saturation. However, when the magnetic field is
removed, the material retains some magnetization, known as residual magnetism. The
relationship between the magnetic field and magnetization forms a hysteresis loop.
Hysteresis in magnetic materials is caused by the realignment of magnetic domains and
energy losses during magnetization and demagnetization processes.
2. Rubber is a common example of a material that exhibits hysteresis in its mechanical
properties. When subjected to cyclic loading and unloading, such as in the case of
stretching and releasing a rubber band, hysteresis is observed. The stress-strain curve
during the loading phase differs from that during the unloading phase, indicating energy
dissipation within the material. The difference in the stress-strain curves is attributed to
internal friction, molecular rearrangements, and energy losses within the material's
structure.
Understanding hysteresis in material properties is important for various engineering and
scientific applications.By accounting for hysteresis effects, engineers and researchers can
design and optimize materials and systems to mitigate energy losses and improve overall
efficiency.
3. Coercive force
It refers to the strength of the magnetic field needed to remove or “erase” the magnetism
from a magnetic material. It represents how resistant a material is to losing its magnetization.
Example:
1. Neodymium Magnets: Neodymium magnets, also known as NdFeB magnets, are
widely used in various applications due to their high coercive force. They have excellent
magnetic properties and can retain their magnetization even in the presence of strong
opposing magnetic fields. Neodymium magnets are commonly used in electric motors,
and dentures.
Dentures: Tiny neodymium magnets can be used for attachments in corrective devices or for
holding together replacement dentures where several teeth are missing. Because of their
strength, even tiny neodymium magnets can be effective and when coated they have an
increased resistance to corrosion.
Electric motors rely upon a combination of an electromagnet and a permanent magnet, usually
a neodymium magnet to convert electric energy into mechanical energy. A generator is the
reverse, it converts mechanical energy into electric energy by moving a conductor through a
magnetic field.
Optical Properties
1. Color
Color is a visual property of materials that is determined by the way they interact with
and reflect light. It is an important aspect of material appearance and can be influenced by
various factors such as the composition, structure, and surface characteristics of the material.
Example:
1. Titanium dioxide is a white pigment commonly used in paints, coatings, and cosmetic
products. It reflects most wavelengths of light, giving it a bright white appearance. The
high reflectivity of titanium dioxide contributes to its widespread use as a white coloring
agent.
2. Ruby is a precious gemstone that exhibits a deep red color. The red color of ruby is
primarily due to the presence of the element chromium within the crystal structure. The
chromium impurities absorb certain wavelengths of light, resulting in the perception of a
rich red color.
a. Synthetic ruby crystals are used as gain media in solid-state lasers. The unique
optical properties of ruby, including its ability to emit intense red light when
stimulated by an external light source, make it suitable for laser applications.
The perception of color is subjective and can vary depending on lighting conditions and
individual interpretation. The study of color in materials is an important field, with applications in
fields such as art, design, manufacturing, and materials science.
2. Light transmission
Light transmission refers to the ability of a material to allow the passage of light through
its surface or body. It is an important property in various applications, including optics, windows,
optical fibers, and display technologies.
Example:
1. Glass is a widely used material known for its transparency and excellent light
transmission. It allows visible light to pass through with minimal absorption or scattering,
making it suitable for windows, lenses, and optical components.
The ability to transmit light efficiently and without significant distortion or absorption is crucial for
optimal performance in optical systems, displays, and other light-dependent technologies.
3. Refractive index
Refractive index is a fundamental property of materials that describes how light
propagates through a medium and is characterized by the ratio of the speed of light in a vacuum
to the speed of light in the material. It provides information about how light is bent or refracted
as it passes from one medium to another.
Refractive index plays a crucial role in various optical applications, including lenses,
prisms, fibers, and optical coatings.
Example:
1. Water is a commonly known material with a refractive index. The refractive index of
water varies slightly with wavelength, but typically it is around 1.33. When light passes
from air (with a refractive index of approximately 1) into water, it slows down due to the
higher refractive index of water. This causes the light to change direction or bend,
resulting in phenomena such as the apparent displacement of objects viewed through
water (e.g., a submerged object appearing closer to the surface than it actually is).
The degree of light bending or focusing is epxressed by refractive index which can affect a
material’s performance and functionality.
4. Reflectivity
Reflectivity is a material property that describes the ability of a surface to reflect light. It
quantifies the amount of light that is reflected back from a surface compared to the amount of
incident light. T
Example:
1. Mirrors are designed to have a high reflectivity, typically over 90%. When light falls on a
mirror, most of it is reflected back, resulting in a clear and sharp reflection of objects.
Reflectivity plays a crucial role in various applications, including optics, architecture, solar
energy, and photography.
Physical Properties
1. Bulk Density
Bulk density is a material property that measures the mass of a substance per unit
volume, typically expressed in kilograms per cubic meter (kg/m³) or grams per cubic centimeter
(g/cm³). It provides information about how densely packed the material is on a macroscopic
scale.
Bulk density quantifies how much mass is present in a given volume of material. It takes
into account both the solid material and any void spaces or pores present within it meaning it is
a density with void spaces. The bulk density is determined by dividing the mass of the
material by its corresponding volume. It is influenced by factors such as particle size, shape,
porosity, and compaction.
Example:
1. Imagine you have two piles of wood chips, one made from larger, chunkier pieces and
the other made from smaller, finer pieces. Even if the volume of the two piles is the
same, you might notice that one pile feels heavier when you lift it. The pile that feels
heavier has a higher bulk density. The difference in bulk density between the two piles of
wood chips can be attributed to how the chips are packed together. In the pile with
larger, chunkier pieces, there are more air spaces between the chips, resulting in a lower
bulk density. In contrast, the pile with smaller, finer pieces has fewer air spaces and is
more densely packed, leading to a higher bulk density.
2. Sand is a granular material composed of small particles of minerals or rock fragments.
The bulk density of sand can vary depending on factors such as the type of sand, its
moisture content, and compaction. Typically, dry sand has a bulk density ranging from
1,400 to 1,600 kg/m³. This means that for a given volume of sand, its mass would fall
within that range.
Construction: Bulk density is considered when designing concrete mixtures, as it affects the
strength, workability, and durability of the material. Mining and
Minerals: Bulk density is crucial in the handling and transportation of minerals, ores, and bulk
solids. It helps determine the capacity of storage containers, hoppers, and conveyor systems.
Agriculture: Bulk density is relevant in soil science and agricultural practices. It provides
insights into soil fertility, porosity, water retention, and root growth.
2. Chemical Resistance
Chemical resistance is a material property that refers to a material's ability to withstand
the effects of exposure to various chemicals without undergoing significant degradation,
damage, or alteration. It is an important consideration in applications where materials come into
contact with aggressive substances (acidic, alkali, gases, and salt solution).
Example:
1. Polypropylene (PP) in chemical storage tanks. Polypropylene is a thermoplastic polymer
that exhibits excellent chemical resistance to a wide range of acids, bases, solvents, and
other chemicals. It is resistant to corrosion and degradation, even when exposed to
aggressive substances such as sulfuric acid, hydrochloric acid, or sodium hydroxide.
2. stainless steel in corrosive environments. Stainless steel, specifically grades such as
316L or 904L, demonstrates high resistance to corrosion from various chemicals,
including acids, alkalis, and chlorides. This makes it suitable for applications in chemical
processing plants, pharmaceuticals, and marine environments.
Chemical resistance is essential in many industries and applications, including chemical
manufacturing, pharmaceuticals, automotive, aerospace, and electronics. It ensures the
durability, safety, and performance of materials in contact with aggressive substances.
3. Coefficient of softening
The reduction factor or softening factor represents the ratio of the compressive strength
of a material when saturated with water to its dry compressive strength. It quantifies the degree
of strength loss that occurs due to water saturation. The reduction factor can vary depending on
the specific material and its properties.
Example:
1. Concrete typically experiences a reduction in compressive strength when saturated with
water due to the weakening of the cementitious matrix. The reduction factor for concrete
can range from around 0.6 to 0.8, indicating a significant decrease in strength when
saturated.
It's important to note that the reduction factor or softening factor is specific to each material and
may vary based on factors such as the water-cement ratio, porosity, and the presence of
additives or reinforcing materials.
4. Density
Density is a fundamental material property that refers to the mass of a substance per
unit volume. It quantifies how much matter is packed into a given space.
Density represents the compactness or concentration of mass within a material. It is
calculated by dividing the mass of a substance by its corresponding volume. The density of a
material remains constant regardless of the size or shape of the sample.
Example:
1. Iron has a high density, typically around 7.8 g/cm³. This means that a cubic centimeter of
iron weighs 7.8 grams. The high density of iron contributes to its heavy and solid
characteristics, making it suitable for structural applications in construction, machinery,
and transportation.
2. Styrofoam, also known as expanded polystyrene (EPS), has a low density of around
0.03 g/cm³. This low density is due to its porous structure, which is filled with air pockets.
Styrofoam's low density makes it lightweight and buoyant, making it useful for insulation,
packaging materials, and floatation devices
Density is a crucial property in various fields, including engineering, chemistry, materials
science, and geology. It impacts properties such as buoyancy, strength-to-weight ratio, and
transportation efficiency.
5. Density Index
Density index is a measure that indicates how much of a material’s volume is occupied
by solid matter. It is calculated by diving the bulk density of the material (density with void
spaces) by its true density (density with no void spaces)
Example:
1. Powdered materials: in industries such as pharmaceuticals or food processing, the
density index can be relevant for powered materials. For example, comparing the bulk
density (measured by filing a container with the powder) and the true density (measured
by eliminating air voids) can provide insights into the flow properties and packaging
efficiency of the powder
2. Porous Materials: the density index is also applicable to materials with porous
structures such as foam, ceramic, or porous metals. By coimparing the bulk density
(measured with pores) and true density (measure with no pores or void spaces), the
density index can indicate the level of porosity and the material’s ability to absorb or
release fluids.
3. Consider a foam material with a bulk density of 0.3 g/cm³ and a density of the solid foam
material itself is 0.6 g/cm³. Using the formula for density index, we can calculate: Density
Index = Bulk Density / Density of Solid Material = 0.3 g/cm³ / 0.6 g/cm³ = 0.5. In this
example, the density index of the foam material is 0.5, indicating that 50% of its volume
is occupied by solid material, while the remaining 50% consists of air or voids.
6. Durability
Durability is a material property that refers to the ability of a material to withstand various
environmental conditions, stresses, and wear over time without significant degradation or loss of
functionality. It encompasses factors such as mechanical strength, chemical resistance, thermal
stability, and resistance to wear, fatigue, or corrosion.
A durable material can maintain its intended function and structural integrity even when
exposed to harsh conditions or prolonged use. It is resistant to degradation, deterioration, or
failure caused by environmental factors, mechanical stress, or chemical exposure.
Example:
1. Titanium is highly durable and has excellent corrosion resistance. It is commonly used in
aerospace, marine, and chemical industries. Titanium alloys have high
strength-to-weight ratios, making them suitable for applications that require both
durability and lightness. (airplane bodies, missiles, fan blades, boosters, engine
compartments, jet engine parts, surgical instruments, artificial joints, dental implants)
2. Reinforced concrete is a composite material consisting of concrete and reinforcement,
typically steel bars or fibers. Reinforced concrete exhibits excellent durability due to its
resistance to a range of environmental factors, including moisture, chemicals, and
temperature fluctuations.
3. Stainless steel is an example of a highly durable material. It exhibits excellent resistance
to corrosion, making it suitable for applications in harsh environments or where exposure
to moisture, chemicals, or high temperatures is expected. Stainless steel's durability
allows it to maintain its mechanical strength and appearance over an extended period,
making it widely used in industries such as construction, automotive, aerospace, and
food processing.
Durability is a key consideration in material selection for infrastructure projects, where long
service life and minimal maintenance are desired. Materials with high durability can significantly
reduce the lifecycle costs associated with repairs, replacements, and maintenance, while
ensuring the safety and reliability of structures.
7. Fire resistance
The property of a material to resist the action of high temperature without losing its
load-bearing capacity. Fire resistance is an important property for materials, especially in
applications where protection against fire is critical.
Example:
1. Gypsum board, also known as drywall or plasterboard, is widely used in construction for
its fire-resistant properties. It consists of a gypsum core sandwiched between paper
facings. Gypsum is inherently fire-resistant and acts as a barrier to the spread of flames
which minimizes its spread.
2. Refractory materials are designed to withstand high temperatures and are used in
applications such as furnaces, kilns, and fireplaces. They are typically made from
materials like fire clay, silica, alumina, or magnesia, which can withstand extreme heat
without significant deformation or damage.
It's important to note that fire resistance can vary depending on the specific material, thickness,
and construction techniques used. Additionally, fire resistance is often measured and classified
using industry standards and testing methods to ensure compliance with fire safety regulations.
8. Frost Resistance
Frost resistance is a critical property for water-saturated materials used in cold climates
or applications where freezing and thawing cycles occur. It helps the material to not have a
considerable decrease of mechanical strength and failure.
Example:
1. Asphalt, commonly used in road construction, can be modified to enhance its frost
resistance. The addition of polymers or other modifiers can improve the asphalt's
resistance to cracking and deformation caused by freezing and thawing cycles.
2. FRP materials, such as fiberglass or carbon fiber composites, are known for their
resistance to freezing and thawing. They are used in various applications, including
bridge decks and other structural elements, to provide durability and prevent damage
caused by frost action.
It's important to note that frost resistance can depend on factors like material composition,
porosity, and proper installation. Different materials may require specific treatment or
considerations to enhance their frost resistance.
9. Hygroscopicity
Hygroscopicity refers to the ability of a material to absorb and retain moisture from its
surroundings. It is an important property to consider, especially in applications where moisture
control is necessary.
Example:
1. Wood is a hygroscopic material, meaning it can absorb and release moisture depending
on the surrounding humidity. It expands and contracts with changes in moisture content,
which can impact its dimensional stability. Proper treatment and sealing of wood can
help minimize its hygroscopicity.
2. Cotton fibers have a high affinity for moisture, making them highly hygroscopic. This
property allows cotton fabrics to absorb and release moisture quickly, providing comfort
in various clothing and textile applications.
It's important to note that the hygroscopicity of a material can vary depending on factors such as
humidity levels, temperature, and the specific formulation or treatment of the material.
Understanding and managing the hygroscopic behavior of materials is crucial in applications
where moisture control is critical, such as in construction, textile manufacturing, and storage of
sensitive goods.
10. Porosity
Porosity is a property that describes the presence of void spaces or pores within a
material. It indicates the amount of empty space or air volume within the material's structure.
Porosity can affect various characteristics of materials, such as permeability, strength, and
insulation properties.
Example:
1. Aerogels are highly porous materials with extremely low densities. They are typically
composed of silica or other materials and have a high surface area. Aerogels are
excellent insulators and find applications in thermal insulation, soundproofing, and as
lightweight structural materials.
In the early 21st century, aerogel was employed in a very special role by NASA- to capture
space dust. Aerogel is being used in conjunction with the ‘Stardust’ mission, which aims to bring
back particles from space from beyond the Moon for the first time.
When the particle hits the aerogel, it will be traveling at speeds of up to 6 times that of a rifle
bullet, which means most substances would not be able to slow the dust down without heating
and thus alteration taking place. With aerogel, however, the dust buries itself into the porous
material and is gradually brought to a stop as it loses momentum.
https://www.azom.com/article.aspx?ArticleID=6499
2. Foams, such as polyurethane foam or polystyrene foam, are highly porous materials
composed of gas-filled cells within a solid matrix. They are used for insulation,
cushioning, and packaging applications due to their low density and thermal insulation
properties.
The porosity of a material affects its properties and performance in terms of strength,
permeability, insulation, and other relevant factors.
11. Refractoriness
Refractoriness refers to its ability to withstand high temperatures without significant
deformation, softening, or structural damage. It is an important characteristic for materials used
in high-temperature applications.
Example:
1. Refractory bricks are specifically designed to withstand high temperatures. They are
made from materials like fire clay, silica, alumina, or magnesia. Refractory bricks are
commonly used in the linings of furnaces, kilns, and other high-temperature industrial
applications.
2. Refractory metals, such as tungsten, molybdenum, tantalum, and niobium, have high
melting points and excellent resistance to heat and deformation. They are used in
applications where extreme temperatures are encountered, such as in aerospace,
nuclear, and high-temperature furnaces.
Different materials are selected based on the specific temperature requirements and conditions
of the application to ensure their suitability and durability at high temperatures.
12. Spalling Resistance
Spalling resistance is a material property that refers to its ability to resist the formation
and propagation of spalls or cracks when exposed to high temperatures, rapid temperature
changes, or thermal cycling. Spalling can occur when the outer surface of a material
deteriorates, flakes off, or breaks apart under thermal stress.
Examples:
1. High-temperature coatings - Some coatings, such as ceramic or refractory coatings, are
applied to the surface of materials to improve their spalling resistance. These coatings
provide a protective layer that can withstand high temperatures and thermal cycling,
reducing the likelihood of spalling.
2. Ceramic fiber insulation materials, such as blankets, modules, or boards, are used for
thermal insulation in high-temperature environments. They are designed to have low
thermal conductivity and good spalling resistance to withstand thermal cycling and
prevent spalling.
Proper material selection and design considerations, along with appropriate maintenance and
thermal management, play crucial roles in ensuring spalling resistance in high-temperature
environments.
13. Specific Heat
Specific heat is a material property that measures the amount of heat energy required to
raise the temperature of a unit mass of the material by one degree Celsius (or one Kelvin). It
represents the material's ability to store and release heat.
Example:
1. Different metals have varying specific heat values. Metals generally have lower specific
heat compared to water and are known for their good thermal conductivity.
a. Aluminum has a specific heat of approximately 0.9 J/g°C. It has a relatively low
specific heat compared to other metals, which means it requires less energy to
raise its temperature. Aluminum is widely used in various industries due to its
lightweight, high thermal conductivity, and good corrosion resistance.
b. Silver has a specific heat of about 0.24 J/g°C. It has the highest electrical and
thermal conductivity among all metals. Due to its excellent properties, silver finds
applications in electronics, jewelry, and various industrial uses.
Specific heat is an important consideration in various fields, including thermodynamics, heat
transfer, and engineering, as it influences the amount of heat energy required or released during
temperature changes.
14. Thermal Capacity
Thermal capacity, also known as heat capacity, is a material property that measures the
amount of heat energy required to raise the temperature of the entire mass of the material by
one degree Celsius (or one Kelvin). It represents the material's ability to store heat.
Examples:
1. Lead has a thermal capacity of approximately 0.13 J/g°C. It has a relatively low thermal
capacity compared to many other metals. Lead's low melting point and high density
make it useful in applications such as batteries, radiation shielding, and some soldering
applications. Lead's thermal capacity influences its ability to absorb and retain heat.
2. Iron has a thermal capacity of about 0.45 J/g°C. It is a common and widely used metal
due to its strength, malleability, and magnetic properties. Iron's thermal capacity is higher
than that of aluminum and copper, meaning it requires more heat energy to raise its
temperature. Iron is used in various applications, including construction, automotive, and
manufacturing.
Thermal capacity is an important consideration in various fields, including thermodynamics, heat
transfer, and engineering, as it affects the amount of heat energy required or released during
temperature changes.
15. Thermal Conductivity
Thermal conductivity is a material property that measures the ability of a material to
conduct heat. It represents how easily heat can transfer through the material. Higher thermal
conductivity indicates a better ability to conduct heat, while lower thermal conductivity implies
poorer heat conduction.
Example:
1. Fiberglass is an effective thermal insulator due to its low thermal conductivity. The
thermal conductivity of fiberglass typically ranges from 0.035 to 0.04 W/m·K, which
means it has a relatively low ability to conduct heat. This property makes fiberglass
suitable for applications where thermal insulation is required, such as building insulation,
heat shields, and HVAC systems. (It is also used in electrical insulation, circuit boards,
adn protective cover)
In summary, the thermal conductivity of a material is important because it impacts heat transfer,
energy efficiency, temperature regulation, structural integrity, and material selection.
Understanding and utilizing the thermal conductivity of materials is essential in a wide range of
industries and applications, from electronics and construction to manufacturing and energy
systems.
16. Water absorption
Water absorption is a material property that refers to the ability of a material to absorb
water. It quantifies the amount of water that a material can absorb when exposed to moisture or
submerged in water. The water absorption of a material is typically expressed as a percentage
of the material's weight or volume.
Example:
1. Ceramic tiles are known for their low water absorption properties. They have a glazed
surface that acts as a barrier to water absorption. The water absorption of ceramic tiles
is typically less than 0.5%, making them suitable for applications where water resistance
is important, such as bathrooms, kitchens, and swimming pools.
2. Natural fibers, such as cotton, wool, and hemp, can absorb water due to their porous
nature. The water absorption of natural fibers depends on factors like fiber composition,
structure, and surface treatments. Natural fibers can absorb water up to a certain extent,
which affects their mechanical properties and dimensional stability.
Manufacturers often provide water absorption specifications for materials to guide their
appropriate usage and to ensure they perform as intended in specific applications.
17. Water Permeability
Water permeability is a material property that measures the ability of a material to allow
water to pass through it. It is a measure of the material's resistance to the flow of water. A higher
water permeability indicates that water can pass through the material more easily, while a lower
permeability implies greater resistance to water flow.
Examples:
1. Geotextiles are permeable fabrics used in various civil engineering applications. They
are designed to have specific water permeability properties based on the intended
function. Some geotextiles are highly permeable, allowing water to flow through, while
others are designed to restrict water flow and provide filtration or drainage capabilities.
Geotextile allow the water to pass through and Carry soil particles to maintain the
stability of water through separation within the soil.
2. Polyvinyl Chloride (PVC) membranes are commonly used in roofing applications for their
excellent waterproofing properties. They are flexible, durable, and resistant to chemicals,
UV radiation, and weathering. PVC membranes are typically installed as single-ply
sheets and provide effective water barrier protection
Other Properties
Thermal Properties
1. Specific Heat - Alr explained
Specific heat is a material property that measures the amount of heat energy required to
raise the temperature of a unit mass of the material by one degree Celsius (or one Kelvin). It
represents the material's ability to store and release heat.
Example:
2. Different metals have varying specific heat values. Metals generally have lower specific
heat compared to water and are known for their good thermal conductivity.
a. Aluminum has a specific heat of approximately 0.9 J/g°C. It has a relatively low
specific heat compared to other metals, which means it requires less energy to
raise its temperature. Aluminum is widely used in various industries due to its
lightweight, high thermal conductivity, and good corrosion resistance.
b. Silver has a specific heat of about 0.24 J/g°C. It has the highest electrical and
thermal conductivity among all metals. Due to its excellent properties, silver finds
applications in electronics, jewelry, and various industrial uses.
Specific heat is an important consideration in various fields, including thermodynamics, heat
transfer, and engineering, as it influences the amount of heat energy required or released during
temperature changes.
2. Thermal Expansion
Thermal expansion is a material property that describes the tendency of a material to
change in size or volume in response to temperature changes. When a material is heated, its
atoms or molecules gain kinetic energy and vibrate more vigorously, causing the material to
expand. Conversely, when a material is cooled, its atoms or molecules lose energy and become
less active, resulting in contraction or shrinkage.
Example:
1. Brass is an alloy of copper and zinc and has a coefficient of thermal expansion similar to
that of copper, around 19 x 10^-6 per degree Celsius (μm/m°C). Brass is known for its
corrosion resistance, malleability, and aesthetic appeal, making it suitable for
applications such as fittings, decorative elements, and musical instruments.
2. Nickel has a relatively low coefficient of thermal expansion of approximately 13 x 10^-6
per degree Celsius (μm/m°C). Nickel and its alloys, such as Invar and Kovar, exhibit low
thermal expansion properties, making them suitable for applications where dimensional
stability
is
critical,
such
as
precision
instruments
and
electronic
components(nickel-cadmium batteries a).
Technological Properties
The properties of metal and alloys which have a bearing on their processing or
application. Castability, machinability, weldability, and workability are some of the significant
technological properties.
Technological properties of a material refer to its characteristics and behaviors
related to various manufacturing and processing methods.
Castability: Castability refers to a material's ability to be easily cast into complex shapes
through casting processes such as sand casting, investment casting, or die casting. Materials
with good castability have the ability to flow easily into molds, maintain their shape during
solidification, and exhibit minimal defects.
Example:
1. Polyurethane is a versatile polymer that exhibits excellent castability. It is often used in
the form of liquid resin that can be poured into molds to create a wide range of products.
Polyurethane's castability is attributed to its low viscosity and ability to flow into intricate
mold cavities. It also cures relatively quickly to form a solid, durable product.
Polyurethane casting is commonly employed in industries such as furniture
manufacturing, automotive parts, and prototyping.
Examples of materials with good castability include aluminum alloys, brass, and cast iron.
Machinability: Machinability refers to a material's ability to be effectively machined or shaped
by cutting processes such as turning, milling, drilling, or grinding. Materials with good
machinability exhibit characteristics such as low cutting forces, reduced tool wear, and the ability
to achieve precise dimensions and surface finishes.
Example:
1. Miild Steel: Mild steel, also known as low carbon steel, is a commonly machined
material. It offers good machinability due to its low hardness, excellent chip formation
characteristics, and ease of cutting. Mild steel is widely used in various industries for
machined parts, such as automotive components, structural elements, and machinery
parts.
Some examples of materials with good machinability include free-cutting steel, certain aluminum
alloys, and brass.
Weldability: Weldability refers to a material's ability to be welded or joined by various welding
processes, such as arc welding, gas welding, or resistance welding. Materials with good
weldability exhibit favorable characteristics for welding, such as compatible melting
temperatures, minimal formation of cracks or defects, and strong joint integrity.
Example:
1. Carbon Steel: Carbon steel is widely known for its excellent weldability. It is a commonly
used material in welding applications due to its relatively low carbon content and good
thermal conductivity. Carbon steel can be easily welded using various welding processes
such as shielded metal arc welding (SMAW), gas metal arc welding (GMAW), and
flux-cored arc welding (FCAW). It is commonly used in the construction industry for
welding structural components, pipelines, and machinery.
2. Stainless Steel: Stainless steel is another material that exhibits good weldability. Despite
being more challenging to weld than carbon steel due to its higher alloy content,
stainless steel can still be welded effectively with proper techniques. Different grades of
stainless steel have varying degrees of weldability, but in general, they offer good
resistance to heat and corrosion during the welding process. Stainless steel is widely
used in industries such as food processing, automotive, and chemical processing, where
weldability is a crucial factor.
Examples of materials with good weldability include mild steel, stainless steel, and certain
aluminum alloys.
Workability: Workability refers to a material's ability to be easily shaped, formed, or deformed
using mechanical processes such as rolling, forging, extrusion, or bending. Materials with good
workability exhibit characteristics such as high ductility, low tendency for cracking, and the ability
to be shaped without excessive force or energy.
Example:
1. Polyethylene is a thermoplastic polymer that offers excellent workability. It is highly
flexible, allowing for easy deformation and shaping. Polyethylene can be extruded,
molded, and thermoformed into various forms, such as sheets, pipes, and containers. Its
workability is attributed to its low melting point, which enables it to be easily melted and
reshaped multiple times without significant degradation.
2. Examples of materials with good workability include copper, aluminum, and low-carbon
steel.