Class contents:1. MATERIALS AND RAW MATERIALS2. PROPERTIES OF MATERIALS3. CHOICE OF MATERIALS
TECHNICAL PRODUCTS are made with TECHNICALMATERIALS that are obtained from RAW MATERIALS.Example: The production of a sweater.RAW MATERIAL TECHNICAL MATERIAL TECHNOLOGICAL PRODUCT
1. Materials and raw materialsRaw materials:Substances that are extracted directly from nature and are transformed through physical and chemical processes into technological products.Raw materials that have been manufactured but still are not a commodity are considered technical materials or materials. ANIMALS TYPES PLANTS MINERALS
Technical MaterialsThose materials that are used directly in the production of technological products. They are obtained from raw materials.Among the most highly used materials:a) Wood: Obtained from the woody part of trees. It is used as a combustible, for making paper, furniture, construction and decorative elements, etc.b) Plastics: Obtained artificially from oil. Plastics are used to make tubes, toys, recepticles, electrical insulators, etc.c) Metals: Extracted from minerals that form rocks. Metals are used for structures and pieces of equipment, tools, welding, electronic components, furniture, etc.
d) Stone (including ceramics and glass). Extracted from rocks. Someexamples are marble, chalkboard, plaster, cement, and concrete.Normally, these are used as construction materials.e) Textiles. These materials are used in the form of string to makecloth/fabric. They can be natural or synthetic. Examples are wool, cotton,silk, nylon, etc.f) Composite materials and alloys. Sometimes we want to combine theproperties of various materials into one. For those, we use compositematerials. For example: red-brick, plywood, fiber-glass.Normally, metals are not used in pure state. Instead, they are mixedwith other metals to form alloys. Examples are bronze, brass and steel.
2. Properties of materialsEach material has their own properties:a) This differentiates them from the rest.b) Determines their use. 2.1. Physical properties 2.2. Mechanical properties 2.3. Chemical properties 2.4. Ecologic properties
2.1. Physical properties: Physical properties indicate how a material is and how it behaves when exposed to external stimuli like light, heat or electricity. a) Density b) Electrical, thermal or acoustic conductivity c) Optical properties d) Porosity
a) Density:The relation between the mass of a material and its volume.
b) Electrical, thermal and acoustic conductivity:The ability of materials to transmit or block electrical current, heat or sound. Insulators do not allow these to pass and conductors do allow them to pass.Thermal conductivity is associated with expansion and contraction (ability of materials to expand or contract their volume along with the temperature). Fusibility is when some materials change from solid to liquid when their temperature is increased.
c) Optical properties.Material’s ability to permit light are classified into:transparent, translucent, and opaque.d) Porosity.Some materials can absorb or release liquids or gases. Woodand ceramic materials are porous (they contain tiny holes calledpores).
2.2. Mechanical properties:Related to the behavior of material when external forces areapplied: a) Hardness b) Toughness / Brittleness c) Maleability d) Ductility e) Elasticity f) Plasticity g) Mechanical resistence
a) Hardness:Resistence of a materialfrom being scratchedMohs’ scale:10 diamond - 1 talc (lesshard).
b) Toughness/brittleness:The resistance to breaking that a material shows when hit bysomething. Brittleness is when a material breaks easily. tough brittle
c) Malleability:Allows a material to be spread into sheets.d) Ductility:Allows a material to be formed into filaments or wires. Slate Copper - tin
e) Elasticity:The property of material to return to their original form when the deforming force stops.f) Plasticity:The property of a material to deform permanently when a deforming force stops.
g) Mechanical resistance:The property of materials to withstand forces without breaking. The forces can be from tension, compression, bending, severing/shearing or torsion. Bending Tension - traction Compression Torsion
2.3. Chemical properties:Oxidation and corrosion:This happens when a mineral reacts with oxygen in the air orwater. The reddish-brown substance produced is called rust.
2.4. Ecological properties:Those properties related to the harmfulness of materials to theenvironment.a) Recyclability: The ability to reuse materials.b) Biodegrability: The ability of materials to naturally decompose over time into simpler substances.c) Toxicity: The harmful nature of materials to the environment or human beings.
More than 4,000 years to decompose More than 10020 days to decompose years to decompose
3. Selection of materialsTo choose a material, you must take into account certain factors: a) Price. b) Its properties: Resistance, hardness, flexibility, conductivity, etc… c) Production possibilities: the machines and tools that you can use and the ease of the work… d) Its ease of obtaining: the abundance of the material, its proximity to where it is needed… e) Its impact on the natural environment: if it pollutes, if it is biodegradable, etc…