MATERIALS and their USES - general index AND examples of uses of materials, relating their properties to a particular application

Doc Brown's Chemistry GCSE/IGCSE/O level Revision Notes

 

A GENERAL SURVEY OF MATERIALS

Properties of materials and choosing a material for a particular use - this page


NANOCHEMISTRY

Part 1. General introduction to nanoscience, nanoparticles and commonly used terms explained

Part 2. NANOCHEMISTRY - an introduction and potential applications

Part 3. Uses of Nanoparticles of titanium(IV) oxide, fat and silver

Part 4. From fullerenes & bucky balls to carbon nanotubes

Part 5. Graphene and Fluorographene

Part 6. Cubic and hexagonal boron nitride BN

Part 7. Problems, issues and implications associated with using nanomaterials

Word-fill quiz "Aspects of nanochemistry"


SMART MATERIALS

Part 1 Chromogenic materials - Thermochromic, Photochromic & Electrochromic Materials

Part 2 Shape memory alloys e.g. Nitinol & Magnetic Shape Memory Alloys

Part 3 Shape memory polymers, pH and temperature sensitive-responsive polymers, Self-healing materials

Part 4 Lycra-Spandex

Part 5 High performance polymers like kevlar

Part 6 Gore-Tex, Thinsulate and Teflon-PTFE

Part 7 Piezoelectric effect/materials & Photomechanical materials

Part 8 Carbon fibres

Word-fill quiz "Designer Smart Materials"


Examples of how we use materials

Ceramics, polymers and composites are typical categories of materials used in everyday life, transport and industry.

Most of the glass we use is relatively cheap soda-lime glass, made by heating a mixture of sand, sodium carbonate and limestone (limestone chemistry, glass and ceramics). More expensive borosilicate glass, is made from sand and boron trioxide, and melts at higher temperatures than soda-lime glass - good for laboratory apparatus! Clay ceramics, including pottery and bricks, are made by shaping wet clay and then heating to a high temperature in a furnace.

The properties of polymers depend on what monomers they are made from and the conditions under which they are made. For example, low density (LD) and high density (HD) poly(ethene) are produced from ethene using different catalysts and reaction conditions (see thermosoftening addition polymer notes). These are thermosoftening polymers consisting of individual, tangled polymer chains and melt relatively easily when they are heated.  This contrasts with thermosetting polymers consist of polymer chains with cross-links between them and so they do not melt when they are heated (see thermosetting polymer notes).

Most composites are made of two materials, (i) a matrix or binder surrounding and binding together (ii) fibres or fragments of the other material, which is called the reinforcement. Examples of composites include

wood is a natural composite of cellulose fibres strongly held together by a polymer matrix chemically derived from cross-linked cellulose structures (similar in this respect to man-made thermosetting resin).

concrete mixture (aggregate of sand, gravel and cement) - the sand and gravel act as reinforcement, used for basement flooring and road surfaces, but the concrete can also be set with reinforced with steel rods embedded in it, widely used as a construction material

resin-fibreglass - the polymer monomer mixture polymerises via a catalyst and sets hard to form a hard strongly bonded material (thermosetting polymer) and the set resin reinforced by the glass fibres embedded in it, this is a very strong low density composite material, its used for car body work, boat hulls, sports equipment e.g. surfboards, skis,

some more technologically advanced composites are made from carbon fibres or carbon nanotubes instead of glass fibres, carbon fibre composites are based on a polymer matrix which are reinforced by carbon fibres or carbon nanotubes, these composites are very strong and of low density ('light'), they are quite costly to produce but are widely used in the aerospace industry, sports car bodies,

It is important to be able to compare the physical properties of glass and clay ceramics, polymers, composites and metals and explain how the properties of materials are related to their uses and select appropriate materials.

See also natural polymers, structure, function and uses


Properties and choosing a material for a particular use

Part 1. Natural and synthetic materials

Reminders: All materials are atoms of various elements and they may be pure elements, pure compounds or mixtures of elements and compounds.

For definitions and explanations with examples see Some important ideas and definitions in Chemistry.

This section is more about ideas and decision making than learning lots of facts.

Be able to explain why a material is best suited for a particular purpose based on its characteristic properties.


Naturally occurring materials which have proved useful

Materials from plants e.g.

The timber from trees is used as a construction material and pulped to make paper.

The cotton to make clothing fabrics is grown in fields of the cotton plant.

Latex rubber is collected as a sticky fluid from rubber trees

Materials from animals e.g

Wool for clothing comes from shearing sheep.

Leather goods are made from the skin of cows.

Silk, a fine weaving material is obtained from silkworm larva.

To compliment, and in many cases supersede these naturally occurring materials, we humans have developed an enormous range of ...

Synthetic materials e.g.

The main advantage of man-made synthetic materials compared to natural materials is that you can design their properties to suit a particular use and develop a better product by chemically changing the structure of the material and how it is processed.

The extraction of metals from raw materials from the Earth's crust - ores are mined and processed to produce iron, copper, titanium, aluminium, which are converted into lots of different things and variety of properties enhanced by making alloys to suit specific technical needs.

Plastics - polymers with a huge range of properties and uses have been developed from the products of crude oil in the petrochemical industry e.g.

Synthetic fibres like nylon and polyester can replace silk, cotton, wool and they can be made strong but flexible/stretchy, waterproof ...

plastics don't rot like wood so can replace wooden window frames, they don't corrode like metals to can replace iron/lead piping and guttering,

synthetic rubber polymers replaces natural rubber (though car tyres are still made of natural rubber and other materials),

insulating thinsulate can replace wool,

synthetic pigments mixed with solvents and binding agents make hard wearing long lasting coatings, and have mainly replaced traditional paints made from mineral powders + egg yoke + linseed oil.


Part 2. Typical important physical properties of materials

Mainly physical characteristics here, but chemical character is very important too and it is the properties of a material that decide what it can be used for. So, knowledge of the properties of materials helps you to decide on the suitability of a material for a particular purpose i.e. what is best for the job! The effectiveness of a material is how good it is for the function its supposed comply with.

For properties like strength, stiffness and hardness, you would need to do a 'fair  test' of pieces of the same size material to get an accurate comparison e.g. a similar rectangular block.

Strength

The strength of a material is measure of how much it can resist a force applied to it.

You might measure the force to break a bar of the material, or what force is needed to permanently deform it, that is changing its shape without snapping it.

There are two types of strength values of importance, depending on how you apply the force to a material.

Tensile strength

This is how much a material can resist being pulled in tension until it breaks.

Ropes or chains on pulley systems for lifting objects or steel cables supporting the road of a suspension bridge, all need to have a high tensile strength or they would snap under the weight of the load!

Compressive strength

This is how much a material can be compressed ('pushed') before it gives way or squashed and permanently deformed.

Building construction materials like stone, bricks or concrete all have a high 'compression' strength which is needed to support the weight of the rest of the building they support.

Combination of tensile plus compression strength

Sometimes materials must be strong in both tension and compression e.g. cross-beams in roofs which get both pulled and compressed.

 

Stiffness

The stiffness of a material is a measure of how easily it bends when a force is applied to it, but without permanently deforming it i.e. the material springs back to its original shape. A very stiff material hardly bends when a force is supplied.

Materials like stone, brick and concrete are very inflexible, but blocks of most plastics and wood are flexible and will all bend to some extent without breaking. Rubber is one of the most flexible of materials and can be bent and stretched by quite some margin and still spring back to its original shape.

Note that the thickness of the material is important when considering 'stiffness'. Thin sheets of almost any solid can be bent so far without breaking e.g. strands of glass fibre, steel spring.

 

Hardness

The hardness of a material is a measure of difficult it is to cut into, so materials like diamond and granite are very hard and butter and sodium metals are soft materials and easily cut into.

Diamond is one of the hardest substance is know and is used to put a strong cutting edge on cutting tools and some industrial drills have diamond tipped tips. Diamonds are so hard that they can only be cut by other diamonds!

 

Density

The density of an object is a measure of the mass of an object in a particular volume.

Density = mass / volume and is usually measured in g/cm3  or  kg / m3

The density of water is 1.00 g/cm3, the plastics poly(ethene) and poly(propene) are 0.92 to 0.98 g/cm3 (hence they float on water polluting the surfaces of rivers, lakes and seas), nylon is 1.11 to 1.18 g/cm3, metals have a wide range of density e.g. sodium floats on water, but most metals sink in water (unless you shape them like a boat!).

For many contexts of construction like aircraft wings and fuselage you would like a like a low density ('lightweight') material hence the use of aluminium and titanium alloys rather than steel.

Densities of some metals in g/cm3: sodium 0.97, aluminium 2.70, titanium 4.54, iron (~steel) 7.87, gold 19.30

States of matter density: solid > liquid >>> gas. Solids and liquids have the highest densities because the particles are close together. Gases have very low densities because the molecules are so far apart as they fly around through mainly empty space!

 

Durability

Durability isn't something that is easily quantified, but you should expect any product to have a reasonable 'working life'. Phrases like 'hard wearing', 'weather resistant' are a bit vague, but they mean a lot to the consumer!

So, how long will the material of a product last? or should last?

You don't want clothing fabrics wearing away after a few months of wear, you expect the soles of you shoes to last a reasonable length of time.

You don't want a carrier bag to fall apart before your reach the car after leaving the supermarket!

You don't want the car tyres wearing away after just a few thousand miles!

 

Melting point

Very pure materials have quite sharp melting points where the solid becomes a liquid e.g. water 0oC, sodium chloride 801oC. However, many materials are a mixture of different materials e.g. metal alloys or a range of different sized molecules e.g. thermoplastics like poly(ethene), and in these cases the material tends to melt over a wider temperature range. In the case of polymers, they have a softening point and very gradually become a liquid over the next few tens of degrees rise in temperature.

 

A brief summary of widely used materials and their properties

(initial thoughts, still under development)

which you should be able to relate to their uses, and of course, where they are not used!

What a material can be used for is very dependant on its properties, though cost can be a significant factor too.

Property/material metals - alloys polymers - plastics glass, bricks and other ceramics composites
Hardness - strength - rigidity - brittleness usually strong and fairly rigid, but may need alloying with other metals to make them stronger, not brittle relatively soft and flexible without breaking, though thermosetting polymers (thermosets) or rigid PVC can be quite hard and brittle, very hard and rigid, not flexible, but brittle and easily shatter when struck -
Heat related properties usually high melting point relative low softening - melting points, thermosets may not melt but degrade at higher temperatures high melting point concrete has good thermal stability
Thermal (heat conductivity) very good usually a good thermal insulators good thermal insulator concrete is an insulator
Electrical conductivity very good usually a good electrical insulators good electrical insulator -
Density moderately (e.g. Al) to high density (e.g. Fe) low density moderate density low density if based on carbon
Malleability, ductility, can it be moulded malleable (easily pressed or beaten into shape), ductile (easily drawn out into wire) some polymers can be drawn out to form quite strong fibres, thermosoftening plastics are easily moulded when warmed wet clay can be moulded before firing in a furnace, but not afterwards! composites are malleable or ductile, can't be moulded, but resins can be cast in moulds
Durability to the environment (e.g. water, atmosphere) may need protection from corrosion which is relatively cheap low carbon steel, Aluminium has natural protective oxide layer, non-porous, water repellent surface bricks are porous to water, but glass is not porous and water-proof -
Miscellaneous properties attractive shiny surface, - - properties depend on the composition e.g. matrix, binder or reinforcement
Uses electrical wiring, cutlery, strong sheeting e.g. aircraft, ships, car bodies clothing, insulators in electrical appliances - -
Unsuitable uses! anything requiring electrical or heat insulation, anything that might corrode which could be replaced e.g. with plastic - - -
Property/material metals - alloys polymers - plastics glass, bricks and other ceramics composites

 


Case Study 1 Choosing the material for parts of a car

  • Each component in a car must be made of the most suitable material, but production costs must be taken into consideration too.

    • The bodywork is made out of steel which has high tensile strength but relatively thin sheets can be hammered or pressed into shape and sections welded or bolted together. Steel is readily protected from rusting by galvanising and layers of paint.

      • Aluminium is much less susceptible to corrosion and lighter (lower density), giving better fuel economy, but it is a more costly metal.

    • However aluminium alloys are strong and is still used for parts of the engine to reduce the overall weight of the car.

    • Windscreens and windows must be made of a transparent material and strong glass sheets are used.

    • Plastics are cheap to make of varied composition for a wide variety of uses even just in the context of building a modern car plastics are light, durable and can be dyed any colour, they can be flexible or rigid and so can be used for e.g. used for

      • for internal fittings e.g. dashboard cover - rigid,

      • flexible floor covers (can be rubber too),

      • rigid door coverings

      • rigid and transparent and coloured covers over headlights and brake lights

      • flexible insulating sheathing for all the electrical wiring.

    • Natural and synthetic fibres are used to make coloured flexible hard wearing fabrics for seat covers.


Case study 2 Well actually, lots on 'mini-cases' of 'suitability' to get you thinking as broadly as possible!

  • Rubber needs to be strong, soft and flexible to be used for car tyres. Vulcanisation with sulfur makes it tougher and hardwearing, so it lasts longer - an example of modifying the properties of a material by extra processing.

  • Cooking utensils for the kitchen need to be made of a strong, high melting, good heat conducting, not toxic (aluminum is not used now!) material like stainless steel or iron. Oven dishes are made of heat resistant (high melting) ceramic materials.

  • Children's toys must be made of a tough durable material (stiff & strong), that is non-toxic, hard-wearing (''play resistant'!) and of low density. Not surprisingly, thermosoftening plastics like poly(ethene) and poly(propene) are mass produced to fulfil our children's needs, and such plastics are easily moulded into an infinitely range of objects, which are readily brightly coloured with an array of pigments!

  • Clothing fabric needs to be made of hard wearing fibres like nylon or terylene with a high tensile strength, but it mustn't be stiff (must be very flexible) and in the case of children's clothing or nightwear it must be fire resistant - so the material must incorporate a flame retardant substance.

  • Many 'older' materials have been replaced by more 'modern' synthetic materials e.g.

    • Strong plastics like poly(propene) have replaced iron for drain-pipes and guttering. The plastic doesn't break easily like brittle iron AND they don't rust and corrode away in bad weather!

    • Some compact discs (CDs) were originally made using a layer of aluminium to digitally record the sound, but this was prone to slow corrosion, so after some time the sound quality of reproduction deteriorated. CDs are now made from a very tough, hard wearing and slightly flexible polycarbonate plastic that will NOT corrode! (being plastic!) ...

    • ... and while we are in the music business, very old records were made of a very brittle material that easily shattered and so few have survived, but modern 'vinyl records' are made from strong and slightly flexible PVC plastic [poly(chloroethene), old name polyvinyl chloride] which is far less likely to break, even if dropped!

  • Plastics - polymers have a wide variety of physical characteristics, they can be hard, strong, stiff (rigid), flexible, low or high density, soften easily on heating or quite heat resistant, some are easily moulded when softened on heating (thermosoftening, the casing of many objects in the home), others set really hard and are strong and don't melt (thermosets, worktops), strong fibres like nylon for outdoor clothing and rope fibres.

  • -


USEFUL EXTRA READING ON MATERIALS and their PROPERTIES

This page can't cover all the materials or contexts you may come across on your course or in the exam,

so, for more on the uses of materials where their use is related to their properties see ...


KS4 Science relating properties to uses of natural synthetic materials GCSE chemistry guide notes on relating properties to uses of natural synthetic materials for schools colleges academies science course tutors images pictures diagrams of apparatus for relating properties to uses of natural synthetic materials investigations word balanced symbol equations of relating properties to uses of natural synthetic materials science chemistry revision notes on relating properties to uses of natural synthetic materials revising the chemistry of relating properties to uses of natural synthetic materials help in chemical understanding of relating properties to uses of natural synthetic materials description of relating properties to uses of natural synthetic materials experiments for chemistry courses university courses in chemistry careers in chemistry jobs in the chemical industry laboratory assistant apprenticeships in chemistry technical internship in chemistry IGCSE chemistry relating properties to uses of natural synthetic materials USA US grade 8 grade 9 grade10 relating properties to uses of natural synthetic materials chemistry comparing the properties and uses of metals, polymers, composites, glass and ceramics

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