Synthetic Polymers

Polystyrene was first known in the 1800's as a laboratory curiosity. It first found limited use because of brittleness. It was later found that if the formula weight was kept to about 10⁶ amu, polystyrene became more flexible. It has hardness, brilliance and complete resistance against water and weak acids and bases.

In the form of a hard solid, it is used to make glasses, containers and appliance parts. If the more flexible solid is injected with gases while in the liquid state it will entrap the gas bubbles and produce the insulating foam that is used for foodware, coolers and packing material.

The reaction used to prepare polystyrene is called an addition polymerization reaction. Addition polymers are formed when the monomer starting materials are bonded together without the loss of any of the atoms of the monomer. Polystyrene is prepared by the addition polymerization of styrene. Polymers are generally named by placing a "poly" in front of the monomer name.

High density polyethylene (HDPE) is mostly linear and is stronger, stiffer, more heat resistant, more flexible at lower temperature and more chemical and UV resistant than los density polyethylene (LDPE). HDPE has a melting point of 130^oC and is used to manufacture kayaks, toys, gasoline tanks, electronic equipment cases and food containers. The higher melting point allows items made from HDPE to be washed in a dishwasher, which can melt items made from LDPE.  A special fiber made of HDPE is called Spectra. It is used to make surgical gloves because it is very resistant to cutting.

Teflon was discovered by accident in 1938 by Plunkett. He was preparing new freons to be used as refrigerants. When he was using a cylinder of one of these freons that he had prepared, he noticed that the flow stopped. Upon cutting open the cylinder he discovered a white powder. This white powder was found to be very inert to chemical attack and is now used to manufacture nonstick surfaces for cooking utensils. Gore-Tex is made of nylon material sandwiched over a stretched sheet of Teflon. The stretching creates pores in the sheet that will pass water vapor but not water droplets. Teflon is formed by an addition polymerization of tetrafluoroethene.

Polymethyl -cyanoacrylate (Eastman 910...Super Glue) undergoes polymerization due to oxygen acting as a free radical initiator. Strength of the glue is attributed to both ester and cyano interactions with the material that is being glued. Polymethyl -cyanoacrylate is formed by an addition polymerization reaction of methyl -cyanoacrylate.

Nylon is the accepted generic term for synthetic aliphatic amides.  An amide is the same grouping of atoms that was called a peptide bond in protein. Nylon 66 was first prepared by Carothers while working for DuPont in 1931. Nylon is exceptionally strong, elastic, abrasion resistant, lustrous, resistant to chemicals and oil, can be dyed or precolored and it has low water absorbency. Nylon 66 is the predominate nylon manufactured in the U.S. and is used in clothing, carpet, fishing leader, surgical sutures, parachutes and molded items.

Nylon is a condensation polymer.  Condensation polymers are formed when monomer units are bonded together with the loss of a small molecule such as water. 

The polyester poly(ethylene terphthalate) (PETE) was first produced by DuPont in 1953. As a fiber it is called Dacron and as a film it is called Mylar. Aluminized Mylar was used to make the Echo satellite, wine bags and balloons. When coated with magnetic particles, it is used to make audio and video tapes. As the fiber it is strong, resistant to stretching and shrinking, resistant to most chemicals, quick drying, wrinkle resistant and abrasion resistant. PETE is the plastic that is used for soft drink bottles. PETE is formed by a condensation polymerization of ethylene glycol and terphthalic acid.