In this unit we will learn about plastics used for packaging.
This includes a brief history
of plastics, packaging plastics and their identifiers and properties, and how plastic packages are
8.1 Brief History of Plastics
The first synthetic plastic, a form of cellulose nitrate called Parkesine, was invented in
1838 by A. Parker and was presented at the Great International Exhibition in London. Parkesine
was developed to replace some natural materials, particularly ivory used for billiard balls.
During the late 1860s, J. Wesley Hyatt developed celluloid from a homogeneous
colloidal dispersion of cellulose nitrate and camphor, and in 1907, L. Baekeland developed
another synthetic plastic material, phenol formaldehyde, commonly known as Bakelite.
A natural polymer of significance was Gutta-percha, made from the sap of rubber trees.
It could be molded into shapes which would harden. This early form of "plastic" was used for
tool handles, and similar applications around the mid-1800s.
The exact nature of plastics, rubber, and similar natural materials was not known until
1920 when H. Staundinger proposed that all plastics, rubber, and materials such as cellulose
were macromolecules or "polymers". This explanation permitted the rational interpretation of
experiments and gave industrial chemists a firm guide for their work, consequently becoming
the spark for the development of many new polymer materials.
Since 1930, the growth in the number of polymers has been rapid. Low density
polyethylene (LDPE), polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC),
polymethyl methacrylate, polyvinylacetate (PVA) and Nylon 66, were all developed during the
1930s. During the 1940s, polytetrafluoroethylene, unsaturated polyesters, polyethylene (PE),
butyl rubber, Nylon 6, fluoropolymers, silicones, polyethylene terephthalate (PET), epoxies and
ABS resins were developed. Polypropylene (PP), polycarbonate (PC), ionomers, polyamides,
moldable elastomers, ethylene vinyl alcohol (EVOH), methalocene polymers and polyethylene
naphthalate have all been invented since the 1950s.
Applications were slow at first. One of the most significant early applications was the
use of polyethylene to waterproof wires and other components in RADAR, SONAR, and similar
equipment that was first used during WWII.
Polyethylene insulation was more effective than
earlier rubber based materials and greatly improved the reliability of the equipment. Since that
time, applications of plastic have exploded onto the commercial landscape.
In packaging, plastic containers have replaced many of the metal, glass, paper, or wood
packages that were formerly used for many products. Many new products have been
introduced that are made of plastic and/or have plastic packaging. Many of these products
would have been impossible to develop without plastic.
Today, more than 100 million tons of plastics are made each year, and thousands of