Designing Bottles: Perfume to Soda Pop

Bottle designs must consider the pressure of the liquid to be contained, the form factor and the aesthetics. In this episode we explore the engineering constraints in glass and plastic bottle design for thermoses, perfume and soda pop bottles.

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Transcript For This Video
Soda pop contains carbon dioxide gas in solution. If we shake the bottle or heat it that gas can come out of solution and create a huge amount of pressure. The bottle has to be designed to withstand that pressure. So the soda bottle is actually an example of a pressure vessel; a closed container specifically designed to hold liquids or gases at pressures higher than the outside (ambient÷ pressure. Have you ever wondered why you never see any square soda bottles? That¦s because pressure forces inside a bottle are always (normal÷ meaning they push perpendicular to the surfaces. Because of this normal force a pressure vessel will tend to want to balloon outward. A square-shaped bottle would have stress from the pressure pushing out that would be concentrated at the corners turning them into weak spots where the bottle would want to tear apart. Heat transfers from one object to another in three ways: = conduction = convection = Radiation Thermoses are designed to minimize the effects of these three forms of heat transfer. The basic design for a Thermos is a jar within another jar. A layer of poorly conducting or insulating material sits between the two jars to prevent heat loss through conduction. The space between the two jars is also airtight so heat can¦t escape through air convection. And, in some Thermoses, the interior surface also has a shiny, mirror-like finish that will reflect any heat radiation back into the liquid inside. Now not every bottle has to hold liquid under pressure or keep it at a high or low temperature. Sometimes all a bottle has to do is look good. A funky bottle design can go a long way in helping a product stand out from its competitors.