4.2C Glass

4.2C Glass

Glass

·      Glass is primarily composed from silica sand (silicon dioxide) together with limestone (calcium carbonate) and Soda Ash (sodium carbonate) and small quantities of a few other chemicals.

Characteristics of glass

·      Transparency

Þ   Allows light to pass through thus allowing you to see the contents of a jar or through a window.

·      Colour

Þ   Colour can be designed by adding chemicals.

·      Strength

Þ   Low tensile strength but high compressive strength.

·      Brittleness

Þ   It has low impact strength and thus will shatter easily (low toughness)

·      Hardness

Þ   High hardness and won’t scratch readily.

·      Un-reactivity

Þ   Is chemically inert so leaching of acid based contents is not a problem.

·      Non-toxic

Þ   Due to its un-reactivity therefore suitable for food storage.

·      Non-porous

Þ   Thus will hold liquids or stop moisture seeping from outside.

·      Insulator

Applications of glass

Type Of Glass	Description	Applications
Soda Glass	This commercial glass and is the most commonly used. Has medium to low thermal shock in other words it will shatter going from cold to hot or the other way.	Window panes, glassware, drink bottles, etc
Borosilicate (Pyrex)	Commonly know as Pyrex. The chemical composition  of Soda Glass is altered by the addition of oxides which improve thermal conductivity.	Cookware, science equipment such as beakers, oven doors and anywhere where heat/cold are crucial to the design performance.
Toughened	Is heated up to the point of melting then blasted with cold air. This makes the outside is in compression and the slower cool interior is in tension. When it is impacted it shatters into little pieces rather than sharp shards.	Side windows of cars, shower glass or design contexts where there is a potential for impact.
Laminated	It is layers of glass and plastic sheets between them. When impacted the glass fragments are held in place. This prevents cracks from growing	Bullet proof glass, windscreens, bank teller windows,
Glass Fibre	Is very long strands of glass. Sometimes these are woven into mats and used as glass fibre reinforced plastic when combined with a resin (polymer).	Tent poles, fishing poles,  car panels, swimming pools.

Recovery and disposal of glass

·      Recycled glass is known as cullet, which is added to new raw materials to make new glass.

·      It reduces the energy required thus the costs in producing new glass.

·      When recycled the glass is separated into the same colours groups (due to chemical compounds) then are crushed.

·      Improves environmental concerns such as the extraction of raw materials, energy consumption and reduced pollution.

·      It is continuously recyclable.