The Chemistry of Legos


Legos are a line of plastic construction toys that come in a wide range of colors, shapes, and sizes. They can come as blocks, people, dogs, tires, flags, and much more. There have been about 560 billion parts produced since Legos were first introduced to the public in 1949. Legos are used mainly by children, but are also used by some adults. They can also be used to construct many different structures ranging from cars to robots, fences to towers, or any other crazy thing you can imagine. Original Legos were made of a plastic called Cellulose Acetate (CA) up until 1963. In 1963, Lego began to manufacture their bricks with Acrylonitrile Butadiene Styrene (ABS), which is what the blocks are made of today. I chose to study the chemistry of Legos because I was curious what my favorite childhood toy was made out of. Legos have impacted my life by fueling my imagination as a child, which helped me to become more creative.

Composition of ...

ABS: the main plastic used in Legos today

  • Acrylonitrile-C8H8
  • Butadiene-C4H6
  • Styrene-C3H3N

CA: was the main plastic used in Legos until 1963

  • Cellulose Acetate-C76H14O49

Polycarbonate: makes up the stretchy parts such as rods, flags, and clips

  • 1/n(OC(OC6H4)2CMe)n+2C6H5OH

Delrin: a nylon variant, makes up the cloth and string like parts

  • CH2O

Main Chemicals, Compounds, Components

ABS: Acrylonitrile Butadiene Styrene (C8H8)(C4H6)(C3H3N) is a thermoplastic, made of Acrylonitrile, Butadiene, and Styrene monomers. A monomer is a molecule that is able to bond with other identical molecules to form a polymer. ABS can stand a tensile strength of 4300 psi, and has excellent resilience to Glycerine, inorganic salts, many acids, and most alcohols and hydrocarbons. In Legos, the Acrylonitrile provides the blocks with excellent heat resistance, the Butadiene provides good impact strength, and the Styrene provides the rigidity for the blocks.

CA: Cellulose Acetate C76H14O49 ,is the acetate ester of Cellulose. CA was used in the original lego blocks, but was replaced by ABS in the sixties in favor of its stability and improved colors. Cellulose is a naturally occurring polymer obtained from wood and cotton seed fibers.

Chemistry's Role

Butadiene is obtained from the C4 fraction of steam cracking (the process of breaking down saturated hydrocarbons into smaller, usually unsaturated hydrocarbons). Acrylonitrile is a synthetic monomer produced from Propylene (C3H6) and Ammonia (NH4). Styrene is a monomer made from the dehydration of the organic compound, ethylbenzene (C6H5CH2CH3). ABS can be made two different ways. The first way to make ABS is dissolving the polybutadiene in liquid acrylonitrile and styrene monomers, and then polymerizing the monomers. The second way to produce ABS is by first preparing the polybutadiene into a watery latex consistency, then the acrylonitrile and styrene are added and are copolymerized.

Background Research

To begin making Legos, you first start with ABS. The ABS is heated until a dough like consistency is achieved at 450 degrees fahrenheit. The ABS is then injected into the Lego molds, with pressures ranging from 25 to 150 tons.The blocks are then left to cool for 10 to 15 seconds. The bricks are then tested for a tolerance of up to two millimeters, to make sure the bricks stay intact. The average 2 by 2 brick weighs about 1.152 g, and can withstand up to 4,240 newtons. Legos are able to be assembled with most other Legos, by interlocking with one another. They can be constructed, taken apart, then reconstructed into something new.


History of legos

brief description of how they are made

facts about legos

production of ABS


chemical formulas for ABS

information about ABS

ABS’s resilience

Tensile strength

information on polycarbonate

polycarbonate formula

information on Delrin


brief information on Cellulose Acetate and history

formula for CA

information on steam cracking and definition

information on cellulose acetate

how CA is made

How to make ABS

Ethylbenzene chemical formula

Propylene chemical formula

Definition of a monomer

About the Author

Hailey Larsen is currently a junior at Senior High School. After graduating, Hailey plans on attending college at the University of Missoula. There she is planning on studying pre-physical therapy and sports medicine. She hopes to make her career as a physical therapist specializing in athletic injuries.