copolymerA polymer made from more than one kind of monomer. A polymer of a single kind of monomer is a homopolymer. ABS plastic is a copolymer of three: acrylonitrile, butadiene and styrene.
cross-linkA bond that ties one long molecule to another. A moderate number of cross-links turns a gummy polymer into a springy one. A very large number makes it rigid.
macromoleculeA single molecule of very high molecular mass. Proteins, DNA and the molecules of polyethylene and nylon are all macromolecules.
monomerA small molecule that can link up with more like it. Ethylene is the monomer of polyethylene. Glucose, the most abundant natural monomer, links up into starch and cellulose.
natural polymerAny polymer made by a plant, animal or microbe. People were using wool, silk and natural rubber centuries before anyone made a plastic. Cellulose, the main part of wood and paper, is another.
nylonThe tough polymer of parachutes, rope and carpet. It was first sold in 1938 as toothbrush bristles, and nylon stockings reached stores across the United States in 1940. Its chains are joined by amide links, as the chains of a protein are.
Show all 36 terms (30 more)
Polymer basics, continued
plasticA moldable material composed chiefly of polymers. The name comes from the Greek plastikos, able to be shaped or molded. Most plastics are made from natural gas and petroleum, and about 40 percent goes into packaging.
polymerA substance made of long molecules of repeated units. Its name joins the Greek words for many and part. The word dates from 1833, though it then meant something different.
polymer chainThe main string of bonded atoms in a long molecule. It is also called the backbone. How easily the backbone bends shapes the properties of the whole material.
polymerizationThe reaction that joins small molecules end to end. In some polymerizations the units simply add on. In others, called condensation, each new link also gives off a small molecule such as water.
repeat unitThe piece that recurs along a chain, bead after bead. It is also called a mer, from the Greek meros, a part. A monomer is a separate molecule; a repeat unit is what it becomes once it is in the chain.
synthetic polymerAny polymer made by people and not by nature. The first plastic made from synthetic ingredients dates from 1907. Polyethylene, polyester and nylon are synthetic too.
Plastics and rubber 12
elastomerA polymer that stretches a long way and springs back. The name blends elastic and polymer, and it is often used to mean rubber. Its chains are held together by weak forces that let them stretch.
injection moldingShaping parts by forcing melted plastic into a mold. The plastic is heated in a barrel, pushed forward by a turning screw, and cools to the shape of the cavity.
plasticizerAn additive that makes a plastic softer and bendier. Plasticizers matter most to PVC, which is used in vinyl flooring and roofing once they are added.
polyesterA polymer whose units are joined by ester links. The best-known polyester is PET, the plastic of drink bottles. Recycled bottles are turned into new bottles and into fibers for clothing and carpets.
polyethyleneThe most common plastic, used for bags and films. Bottles, cups and jars are made of it too. High-density polyethylene, the plastic of milk jugs, carries the recycling number 2.
polypropyleneA rugged plastic of food tubs, ropes and carpets. It is a little harder than polyethylene and stands more heat, and microwave-safe containers are made of it. Only polyethylene is produced in larger amounts.
polystyreneA clear, brittle plastic, often puffed into foam. Solid, it is used for disposable cutlery and disc cases. As foam it makes packing peanuts and insulation.
polyvinyl chlorideThe plastic of water pipes and window frames; PVC. It is the third most widely produced plastic. Without plasticizers it is hard and brittle; with them it is soft enough to coat electrical cables.
siliconeA rubbery polymer built on silicon and oxygen. It is used in sealants, lubricants and cooking utensils. Silicone is often confused with silicon, the hard gray element used in computer chips.
thermoplasticA plastic that softens each time it is heated. Softened, it can be reshaped by injection molding or extrusion, and it hardens again as it cools. Polyethylene, polypropylene and polystyrene are thermoplastics.
thermosetA plastic that sets hard once and cannot be remelted. Curing builds cross-links between its chains, and the change cannot be undone. Because it cannot be reheated and formed again, it cannot be recycled the way a thermoplastic can.
vulcanizationHardening rubber by heating it with sulfur. The word first meant only this treatment of natural rubber, still the most common. It now also covers the hardening of synthetic rubbers by other means.
Natural polymers and waste 12
biodegradableOf a kind that living microbes can digest. Bacteria and fungi do the work. Vegetables may biodegrade within days, while some plastics take a very long time and meanwhile break into smaller and smaller pieces.
bioplasticA plastic whose raw material is renewable biomass. Corn starch and rice starch are two starting materials. A bioplastic is not always biodegradable.
celluloseThe stiff polymer that forms wood, paper and cotton. No organic polymer on Earth is more abundant. Cotton fiber is 90 percent cellulose and wood 40 to 50 percent.
chitinThe tough polymer of insect shells and fungus walls. Only cellulose is a more abundant polysaccharide in nature. Chitin also forms the shells of crabs and other crustaceans.
DNAA twin-chain polymer that holds genetic instructions. Its two chains of nucleotides coil around each other in a double helix.
microplasticA plastic fragment under five millimeters in length. Some come from larger litter that breaks apart. Others, called microbeads, were made tiny on purpose for some cleansers and toothpastes.
natural rubberA bouncy polymer made of isoprene by certain trees. It is collected as latex, a milky fluid tapped from cuts in the bark of the rubber tree. Thailand, Malaysia, Indonesia and Cambodia are leading producers.
proteinA natural polymer whose monomers are amino acids. The genetic code spells out 20 standard amino acids. Keratin, the material of hair, nails, feathers and horns, is a protein.
recyclingCollecting waste and remaking it into useful goods. Most plastic recycling is mechanical: the waste is sorted by color and polymer type, melted and reformed. Of the plastic waste produced up to 2015, only 9 percent had been recycled.
resin identification codeThe number in a triangle on a plastic item. The triangle and its number were introduced in 1988 to help sort plastic waste for recycling.
silkThe fine fiber taken from a silkworm's cocoon. The fiber is mostly a protein called fibroin. Spiders make silk as well.
starchThe glucose polymer packed into potatoes and grains. Plants make it to store energy. No carbohydrate is eaten in larger amounts around the world: wheat, potatoes, corn and rice all hold a great deal of it.
How this list was compiled: Term list chosen for this site on 2026-10-12. Each meaning is written in our own words and was checked that day against the article on the term in the English Wikipedia (https://en.wikipedia.org/), whose text is under the Creative Commons Attribution-ShareAlike license: Polymer, Monomer, Polymerization, Macromolecule, Polymer backbone, Repeat unit, Biopolymer, Plastic, Bakelite, Nylon, Peptide bond, Cross-link, Copolymer, Thermoplastic, Thermosetting polymer, Elastomer, Vulcanization, Polyethylene, Polypropylene, Polystyrene, Polyvinyl chloride, Polyester, Polyethylene terephthalate, Silicone, Plasticizer, Injection moulding, Cellulose, Starch, Protein, Keratin, DNA, Natural rubber, Silk, Chitin, Biodegradation, Biodegradable polymer, Plastic recycling, Microplastics, Bioplastic, Resin identification code and Hermann Staudinger. Polymers and monomers, natural and synthetic polymers, plastics, and thermosetting and thermosoftening plastics were checked a second time against BBC Bitesize (https://www.bbc.co.uk/bitesize/articles/ztt6trd, Polymers, and the guides Polymers at https://www.bbc.co.uk/bitesize/guides/zrstng8/revision/1 and https://www.bbc.co.uk/bitesize/guides/ztr7b82/revision/1); microplastics and microbeads against the National Ocean Service of the National Oceanic and Atmospheric Administration (https://oceanservice.noaa.gov/facts/microplastics.html, What are microplastics?); the 1953 prize against the Nobel Prize site (https://www.nobelprize.org/prizes/chemistry/1953/summary/). The fact after each meaning is from the same pages. Licence: own work
How it works
This polymer vocabulary worksheet lists monomer, polymer chain, plastic, nylon, cross-link, natural polymer, synthetic polymer and five more terms down the left, with their meanings in another order down the right. An answer key prints as the last page.
Read the full guide
Plastics and rubber
Set opens on Polymer basics. The second set has thermoplastic, thermoset, elastomer, vulcanization, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyester, silicone, plasticizer and injection molding.
Natural polymers and waste
The third set has cellulose, starch, protein, DNA, natural rubber, silk, chitin, biodegradable, recycling, microplastic, bioplastic and resin identification code.
Reduce, reuse, landfill and compost are terms on the recycling vocabulary worksheet.
Questions and answers
Are all polymers plastics?
No. Plastics are synthetic polymers, but living things make polymers too. The starch in a potato, the cellulose in paper and the DNA in a cell are all polymers, and none of them is a plastic.
What do the numbers on plastic mean?
The number inside the triangle names the plastic an item is made of: 1 is PET, the plastic of drink bottles, and 2 is high-density polyethylene. It does not say whether the item can be recycled.
Who discovered polymers?
Hermann Staudinger proposed in 1920 that polymers are very large molecules whose atoms are joined by ordinary chemical bonds. He was awarded the 1953 Nobel Prize in Chemistry for his discoveries in macromolecular chemistry.