A polymer is a substance made of very large molecules, each built from many repeating units. Polymers include everything from the polystyrene in a disposable cup to the DNA and proteins in living cells. They form when many small molecules, called monomers, join together in a chemical reaction called polymerisation. The size of the resulting molecules is what gives polymers their characteristic properties: strength, toughness, flexibility, and the ability to be shaped and to hold that shape. Plastics are the polymers made for that last property, and this article covers the materials for polymer production, where they come from, and what that means for the products made from them.
Classification of Materials for Polymer Production
Polymers are too varied to fit one classification, so several are used side by side.
By origin:
- Natural polymers: cellulose, natural rubber, silk, wool, and starch
- Synthetic polymers: polyethylene, polypropylene, nylon, and the other plastics made from petrochemical or bio-based feedstocks
- Semi-synthetic polymers: natural polymers chemically modified, such as cellulose acetate and vulcanised rubber
By chain structure:
- Linear: long unbranched chains, as in high-density polyethylene, which pack closely and give strength and rigidity
- Branched: chains with side branches, as in low-density polyethylene, which pack less closely and give flexibility
- Cross-linked: chains bonded to each other in a three-dimensional network, as in thermosets and rubbers, which cannot be melted and reshaped
Types of Materials for Polymer Production
By the composition of the backbone chain, materials for polymer production are either organic, with a carbon backbone, which includes nearly all plastics, or inorganic, with a backbone of other elements, such as the silicon-oxygen chain of silicones.
Materials for Polymer Production
The materials for polymer production have changed more in a century than the other two material families did in millennia. Materials science has long been organised around three families, ceramics, metals, and polymers. The first two developed over millennia; polymers went from laboratory curiosity to the most produced material class on earth in under a century. Global plastics production reached 430.9 million tonnes in 2024, and the materials for polymer production behind that output are changing.
Petroleum and Natural Gas
Most materials for polymer production are still fossil feedstocks: naphtha from crude oil refining, and ethane and other natural gas liquids. These are “cracked” at high temperature into the basic monomers, ethylene and propylene above all, from which the major plastics are built. Plastics consume only around 6% of global oil and gas output, so feedstock supply is not a constraint, and the low cost of these monomers at scale is the reason plastics are cheap.
Where the feedstock comes from determines regional cost: the US and Middle East crack cheap ethane from gas, Europe and much of Asia crack naphtha from oil, and China also converts coal to olefins, which gives it a feedstock route no other major producer uses at scale. For a buyer, this is why resin prices track oil and gas prices, and why a factory’s resin quote can move between order and delivery. The economics of engineering thermoplastics and speciality polymers follow the same feedstock chain a step or two further along.
Bio-Based and Recycled Materials for Polymer Production
Two alternative materials for polymer production are growing quickly. Bio-based polymers use plant sugars, starches, or oils as the starting point; some, such as bio-polyethylene, are chemically identical to their fossil equivalents, while others, such as PLA, are new materials with their own properties. Recycled feedstocks come from mechanical recycling, which re-melts sorted plastic waste into pellets, and chemical recycling, which breaks waste plastic back down into monomers or oil. Circular plastics from recycled and bio-based sources passed 43.9 million tonnes in 2024, just over 10% of global output, and are the fastest-growing part of the industry (Plastics Europe, 2025). Recycled-content requirements in the EU and several US states now make this a specification question, not only a sustainability one.
Plastics as Materials for Polymer Production
“Plastic” and “polymer” are often used interchangeably, but they are not the same thing. Polymer describes the molecular structure; plastic describes a property, the ability to be shaped under heat or pressure and to hold that shape once the force is removed. Elastomers, by contrast, return to their original shape. Plastics are usually processed by melting and forming, through extrusion, injection molding, blow molding, or thermoforming. Plastic polymers fall into four groups.
- Thermoplastics soften when heated and harden when cooled, and the cycle can be repeated, which is what makes them recyclable and what makes injection molding and extrusion possible. Their chains are linear or branched and not cross-linked. Four monomers, ethylene, propylene, styrene, and vinyl chloride, account for around 90% of all thermoplastics produced. Polyethylene, polypropylene, PET, PVC, polystyrene, ABS, nylon, and polycarbonate are the thermoplastics a product designer chooses between most often, and resin selection is one of the first decisions in any plastic part design.
- Thermosets form a permanent three-dimensional cross-linked network when they cure, and once cured they cannot be melted again. Epoxy, phenolic, polyurethane, and silicone resins are common thermosets, used for adhesives, coatings, composite parts, and anything that has to hold up under heat. Their permanence is their strength and their limitation: a thermoset part cannot be reprocessed, so the design has to be right before it is molded.
- Elastomers are soft, compliant polymers that undergo large, reversible deformation, the property we call elasticity, which only long-chain polymers with light cross-linking can provide. Natural rubber, styrene-butadiene rubber, silicone, and thermoplastic elastomers such as TPE and TPU are the common ones. Synthetic rubber was developed at industrial scale during the Second World War, when Southeast Asian natural rubber supplies were cut off, and the emulsion polymerisation processes developed then are still the basis of the industry. Thermoplastic elastomers, which can be injection molded like a plastic but behave like a rubber, are now the default for soft-touch grips, seals, and overmolded parts in consumer products.
- Fibres are polymers drawn into structures far longer than they are wide. Fibre diameter is expressed in dtex, the mass in grams of 10,000 metres of the fibre; typical filament values run from 1 to 10 dtex, and one gram of a 1-dtex filament is over 8 kilometres long. Polyester, nylon, and polypropylene fibres are the synthetic fibres used at the largest scale, in textiles, ropes, and reinforcement.
What Materials for Polymer Production Mean for Your Product
For a brand developing a plastic product, the choice of materials for polymer production comes down to three questions: which resin gives the part the properties it needs, what that resin costs and how its price behaves, and whether the product needs recycled or bio-based content to sell in its target market. Each of those affects the mold design, the process, and the unit cost, and the cheapest resin is rarely the cheapest part. Working through those trade-offs before tooling is cut is what our plastics production package is for.
