Tech Design

• Plastics are a semi-synthetic (man-made) organic compounds derived from petroleum or natural gas.
• Plastics are typically polymers (long chain molecules) of hydrogen and carbon and may contain other substances to improve performance and/or reduce production costs.
• Polymers can be linear – a long chain, single file.
• Polymers can branch – main chain with side branches.
• There are two types of plastics: thermoplastics and thermosets.
• Thermoplastics are plastics that do not undergo chemical change in their composition when heated and so can be molded more than once – Polyethylene, polypropylene, polystyrene and more.
• Thermosets melt and take shape only once.
• Plastics are produced in large petroleum processing facilities.
• Oil and natural gas are put through a ‘cracking’ process to separate out hydrocarbon raw materials.
• The hydrocarbons are then processed to create monomers (short molecules).
• Monomers are then processed in large plants to create polymers (longer chains) and may be further processed to produce the finished raw plastic material.
• There are numerous different processes to create products from raw plastic, including: Injection molding, blow molding, vacuum forming, rotational molding and more.
• Plastic can be recycled however the process has several drawbacks: Sorting waste to ensure a clean recycle stream is labour intensive and costly.
• Plastic degrades each time it is heated or processed.
• Advantages of plastics include: Low cost, easy and inexpensive to process (finished products), impervious to water, can be formed in to almost unlimited shapes using many processes, can be recycled (however it is costly and degrades the plastic).
• Disadvantages of plastics include: Limited mechanical properties (hardness, strength, heat resistance), too costly when used for large items, does not decompose in the environment.
• Typical applications of plastics include: Food containers and beverage bottles, film packaging, bags, wraps etc., construction – window frames, pipes, gutters, flooring, automotive components, electronic equipment cases, toys, foam and other packaging, foam for seat cushions, beds, shoes and more, bullet proof ‘glass’ for security uses and equipment.
• Iron is the most common element on the planet earth.
• Pure iron is soft, however impurities harden iron and give it different properties.
• Iron is found on earth only in the form of an ore, combined with other elements such as oxygen or sulfur.
• Steel is an alloy (mixture of elements) that consists mostly of iron with 0.2% - 2.1% carbon.
• Carbon is the most common alloying element for iron, however others are used such as manganese, chromium, vanadium and tungsten.
• Varying the amount and type of alloying elements changes the properties of steel, such as hardness, ductility and tensile strength.
• There are more than 2,500 standard types of steel worldwide.
• One common type of steel was discovered by accident.
• Steel with at least 11% chromium forms a hard oxide layer on the metal surface, known as stainless steel.
• The process used to produce steel can also greatly affect the material properties.
• There are many types of heat treating processes available to steel, the most common are annealing, quenching and tempering.
• Internally steel has a crystal structure which can be controlled through heat treating.
• Annealing is the process of heating the steel to a sufficiently high temperature to soften the material.
• The type of alloy affects the amount of heat needed for annealing.
• Quenching and tempering involves heating the steel to a soft form, then quenching (cooling) it in water or oil.
• This rapid cooling, results in a hard and brittle structure.
• The steel is then tempered, which is a form of annealing.
• The tempering softens some of the material to make it more crack resistant.
• The earliest known production of steel is a piece of ironware excavated from an archaeological site and is about 4,000 years old.
• Advantages of steel include abundant supply, high strength, durability, recyclability, and cost-effectiveness.
• Disadvantages of steel include corrosion, cost, and maintenance.
• Steel is widely used in construction, appliances, vehicles, heavy equipment, and infrastructure.
• Metal is strong and malleable, meaning it can be formed.