Synthetic materials are made from petroleum oil and natural gas, chemically transformed into long chains of repeating molecular units called polymers. The process starts with raw fossil fuels, breaks them down into small reactive molecules called monomers, and then links those monomers together thousands of times over to create everything from plastic bags to nylon jackets to car tires. Petrochemical feedstock accounts for about 12% of global oil demand, and that share is growing.
From Crude Oil to Building Blocks
The journey begins at oil refineries and natural gas processing plants. Crude oil is distilled into lighter components, most importantly a liquid called naphtha (used heavily in Europe and China) and a gas called ethane (the primary feedstock in the United States and the Middle East). These are then “cracked,” meaning heated to extreme temperatures that break apart larger hydrocarbon molecules into smaller, simpler ones.
Those smaller molecules are the monomers: ethylene, propylene, butadiene, styrene, and others. Each one is a compact arrangement of carbon and hydrogen atoms (sometimes with chlorine, nitrogen, or oxygen mixed in) with a reactive spot that lets it bond to copies of itself. Think of monomers as individual beads. The chemical process that strings them into a long necklace is called polymerization, and the resulting chain is a polymer.
How Monomers Become Polymers
There are two main ways to link monomers into polymers. In addition polymerization, monomers simply snap together end to end, and every atom from the original molecules ends up in the final chain. Polyethylene, the world’s most common plastic, forms this way: thousands of ethylene molecules join into one continuous strand with nothing left over.
In condensation polymerization (also called step-growth), two different types of monomers alternate along the chain, and each time they link up they release a small byproduct, usually water. This is how polyester and nylon are made. Polyester forms through carbon-oxygen bonds, while nylon forms through carbon-nitrogen bonds, which is why they behave so differently despite being produced in a similar fashion.
Common Synthetic Plastics
Global plastic use hit roughly 464 million metric tons in 2020 and is projected to nearly double by 2050. The major families include polyethylene (grocery bags, bottles, food wrap), polypropylene (food containers, car bumpers), polystyrene (foam packaging, disposable cups), and PVC (pipes, vinyl flooring). Each one starts from a different monomer but follows the same principle: small carbon-based molecules linked into long, stable chains.
What gives each plastic its distinct properties isn’t just the monomer. Manufacturers add a wide range of chemical additives to tune the final product. The 14 major classes include plasticizers (which make rigid plastics flexible), flame retardants, UV absorbers (to prevent sun damage), antioxidants, colorants, fillers for added strength, foaming agents, and lubricants. A single plastic product can contain dozens of these additives, sometimes making up a significant percentage of its total weight.
Synthetic Fibers and Textiles
Polyester is the dominant fiber on Earth, making up 59% of total global fiber production. Cotton, by comparison, holds just 19%. The overwhelming majority of polyester, about 88%, is fossil-based.
Nylon is composed of carbon, hydrogen, nitrogen, and oxygen, arranged in units called polyamides. It was one of the first fully synthetic fibers and remains widely used in stockings, parachutes, and rope. Acrylic fibers come from a monomer called acrylonitrile and mimic the feel of wool, which is why they’re popular in sweaters and blankets. Each of these textiles is, at its core, a petroleum product reshaped at the molecular level.
Synthetic Rubbers and Elastomers
Natural rubber comes from tree sap, but most rubber today is synthetic, built from petrochemical monomers designed to stretch and snap back. The most widely used is styrene-butadiene rubber (SBR), made by combining styrene and butadiene. It’s the standard material in car and truck tires.
Neoprene is made from chloroprene, a monomer that resembles butadiene but swaps in a chlorine atom for one hydrogen. That single substitution gives neoprene its resistance to oil, heat, and weathering, which is why it shows up in wetsuits, industrial hoses, and laptop sleeves. Butyl rubber combines isobutylene and isoprene and holds air exceptionally well, making it ideal for inner tubes. Silicone rubber is structurally different from most synthetics because its backbone is made of alternating silicon and oxygen atoms rather than carbon chains, giving it stability across a wide temperature range.
Many synthetic rubbers need to be “vulcanized,” a process that uses sulfur or peroxides to create cross-links between polymer chains. These cross-links are what transform a soft, sticky material into something tough and elastic. Some newer thermoplastic elastomers skip vulcanization entirely, behaving like rubber at room temperature but melting and reshaping like plastic when heated.
Bio-Based Synthetic Materials
Not all synthetic materials come from fossil fuels. A growing category of bioplastics starts from renewable sources like corn starch, sugarcane, or vegetable oils. The process typically involves growing starch-rich plants, extracting and fermenting the starches with specialized enzymes, and converting the results into monomers that polymerize into plastic.
The most established example is polylactic acid (PLA). Its building block is lactic acid, a simple organic molecule produced by fermenting plant sugars. Lactic acid molecules are converted into a cyclic form called lactide, which then polymerizes into a rigid, transparent thermoplastic used in food packaging, 3D printing, and disposable cups. Another family, polyhydroxyalkanoates (PHAs), is produced directly inside bacteria that store carbon as intracellular granules when fed sugar or lipids. PHAs are fully biodegradable and come in short-chain and medium-chain varieties depending on how many carbon atoms sit in each repeating unit.
Despite their promise, bioplastics still represent a small fraction of overall production. The vast majority of synthetic materials remain petroleum-based.
Why Synthetic Materials Last So Long
The same strong carbon-carbon and carbon-heteroatom bonds that make synthetic polymers useful also make them extraordinarily persistent. In the environment, plastics degrade through a combination of UV light, oxygen exposure, physical abrasion, and microbial activity, but these processes work slowly. Sunlight and oxygen cause oxidation and chain scission, gradually breaking long polymer chains into shorter fragments. As the chains shorten, the material becomes brittle and cracks, eventually fragmenting into microplastics: particles smaller than five millimeters that enter soil, water, and food chains.
The chemical composition, appearance, and mechanical strength of the plastic all change during degradation, but full breakdown to basic molecules can take hundreds of years. This durability is precisely what makes synthetics so useful for construction, packaging, and clothing, and precisely what makes them so difficult to manage as waste.