Polymers

Cornstarch is an example of a polymer. Polymers are long strains of molecules that keep repeating and have different properties of the original single molecule group. A single section of a polymer is called a monomer. It resembles the simplest form of the repeating portion of the entire polymer. These polymers may get stretched when you make a mixture such as cornstarch and water. This mixture behaves a certain way. There are many theories on why this may occur. One theory is because the strands get tangled, making it hard for them to slide against each other. Stretched molecules would offer more resistance to movement, like the resistance of a stretched rubber band. However, this argument does explain why rapid motion (stirring, shaking, etc.) increases viscosity, which is the property of a fluid that offers resistance to flow.

Cornstarch and water is a non-Newtonian, organic fluid. Fluids can fall under different sub groups. They are either Non-Newtonian or Newtonian. They can also be either organic or non organic. NonNewtonian Fluids are a group of liquids that change viscosity when they are stirred, shaken, or otherwise agitated. Cornstarch and water acts differently depending on whether it is still or agitated. This kind of fluid is called a dilatant. It becomes more viscous (has a relatively high resistance to flow) when agitated or compressed. The viscosity of a non-Newtonian fluid is also dependent

on temperature. Cornstarch would decrease in viscosity if put in a boiling pot (it would become thinner). Examples of Newtonian fluids include motor oils, mineral oils, gasoline, kerosene, and most salt solutions in water.

The most popular explanation for the behavior of cornstarch and water is that when sitting still, the tiny grains of starch are surrounded by water. The surface tension of the water keeps it from completely flowing out of the spaces between the grains. The lubrication of water allows the granules to move freely. However, if the movement is abrupt (shaking, stirring, poking, slapping, etc.) the water is squeezed out from between the granules and the friction between them increases dramatically.

Other examples of polymers are present in our everyday lives. Water-resistant paints and varnishes derive from a family of synthetic polymers called acrylics. Polystyrene foam, or styrafoam, is used when making cartons to protect eggs, or making packing peanuts to cushion fragile objects for shipping. It insulates, so people put drinks in foam cups and coolers to keep the warm ones warm and the cold ones cold. Placed behind walls and ceilings in homes, polystyrene foam keeps the weather outside. Polyethylene is the plastic used to make two liter soda bottles. Polyethylene is melted, inserted into molds, and blown up like balloons to make containers for soft drinks, fruit juices, water, and milk. Polyvinyl chloride, (PVC), Is better known as vinyl. Easy to clean, waterproof, and resistant to corrosion, vinyl is used in car interiors, siding for homes, and in sewage pipes. The plastic nylon replaced the silk in hosiery in 1938. Many of the airborne troops in World War II floated to earth beneath nylon parachutes. Other synthetic fibers such as polyester made the fashions of the 1970s possible.

Polymers can also be found everywhere in nature. With