A plastic material is any of a wide range of synthetic or semi-synthetic organic solids that are moldable. Plastics are typically organic polymers of high molecular mass, but they often contain other substances. They are usually synthetic, most commonly derived from petrochemicals, but many are partially natural.
Most plastics contain organic polymers. The vast majority of these polymers are based on chains of carbon atoms alone or with oxygen, sulfur, or nitrogen as well. The backbone is that part of the chain on the main “path” linking a large number of repeat units together. To customize the properties of a plastic, different molecular groups “hang” from the backbone (usually they are “hung” as part of the monomers before the monomers are linked together to form the polymer chain). The structure of these “side chains” influence the properties of the polymer. This fine tuning of the properties of the polymer by repeating unit’s molecular structure has allowed plastics to become an indispensable part of the twenty-first century world.
Most plastics contain other organic or inorganic compounds blended in. The amount of additives ranges from zero percentage for polymers used to wrap foods to more than 50% for certain electronic applications. The average content of additives is 20% by weight of the polymer. Fillers improve performance and/or reduce production costs. Stabilizing additives include fire retardants to lower the flammability of the material. Many plastics contain fillers, relatively inert and inexpensive materials that make the product cheaper by weight. Typically fillers are mineral in origin, e.g., chalk.