Tag Archives: polymer

LEGO: Is it more than just a kids toy?

Posted on March 21, 2020 by | 4 comments

With everyone staying at home due to recent events, a common struggle is finding ways to pass the time. You remember having a box of LEGO bricks lying around, but you think to yourself “Building with LEGO? Nah, that’s just a kid’s toy!”. However, LEGO bricks are more than just a construction toy, they are also a technological marvel both in manufacturing and function.

The LEGO group first patented their iconic LEGO brick design in 1958 in Billund, Denmark. Modern LEGO bricks are made of ABS plastic, a copolymer of acrylonitrile, 1,3-butadiene and styrene, which is formed into its distinct brick-like shape using the injection molding process.  The molds are designed to produce LEGO pieces accurate to up to five-thousandth of a millimeter (0.005 mm), which is around half the thickness of a human hair. This results in a piece defect rate of 0.0018%. In other words, the LEGO manufacturing process produces 18 defective pieces out of every 1 million total pieces produced.

Left to right: Structures of styrene, acrylonitrile and 1,3-butadiene, the main components that make up the plastic used to make LEGO bricks. Source: Sigma-Aldrich

LEGO bricks have become an iconic construction toy due to the endless building possibilities they present. LEGO bricks are connected together through round nubs on top of the brick, known as studs, to tube-based cavities on the bottom of the brick. For instance, six LEGO bricks that are two studs wide by four studs long, commonly referred to as a 2×4 brick, can be combined in 915,103,765 unique ways. This number was determined computationally by mathematics professor  Søren Eilers from the University of Copenhagen in 2005.

(Photo credit: Mark Rubinchik)

Although a LEGO brick may seem like a simple piece of plastic, there is a lot more to it than meets the eye. Next time you’re looking for something to do, why not pull out some LEGO and see how many combinations you can make!

-Mark Rubinchik

4 Comments

Posted in Organic Chemistry, Uncategorized

Tagged , , , ,

Polyurethane – a chemical in your mattress

Posted on February 24, 2020 by | 2 comments

We are living in “the polymeric world”. What does it mean by the polymeric world? Look around you! We cannot keep away from the materials made up of polymers. Probably, the most common polymer exposed to our body would be a polyurethane, if you sleep on some sort of a comfortable mattress.

The use of polyurethanes

How does a mattress relate to a polyurethane?  The polyurethane is a cushioning material to produce a flexible and rigid foam. More than 50 % of polyurethanes are consumed to make the foams (Figure 1). In addition to the function of recovering an original shape, the rigidity in the range between a flexible rubber and a hard thermosetting plastic makes polyurethanes the best material for mattresses.


Figure 1. Uses of polyurethanes for various materials. Mainly, polyurethanes are used to produce foam materials. This figure is modified from the open source

The carbamate group and the backbone of polyurethanes

How could polyurethanes have rigid and flexible properties? The chemical structure of a polyurethane would explain its properties. The polyurethane is a block polymer produced from two monomers, a polyol and a diisocyanate. The reaction between hydroxyl and cyanate groups gives a rise to repeating carbamate groups in a long chain (Figure 2; left). The polar carbamate group can have intermolecular hydrogen bonding, resulting in the decrease of free volumes within a polymer system (Figure 2; right, Figure 3). Therefore, polyurethanes can have the rigid property associated with the carbamate group.

Figure 2. A chemical reaction of a diol and a diisocyanate to form a polyurethane (left). Intermolecular H-bonding of polyurethane chains (right).

Figure 3. A flexible polymer system due to a large free volume (left). A rigid polymer system due to a small free volume (right). Polyurethanes would resemble the small free volume system due to intermolecular hydrogen bonding.

The backbones of polyol and diisocyanate are also an important factor to control the flexibility of polyurethanes. The flexibility of a long hydrocarbon chain, which both or either the monomers can have, would be introduced intrinsically to the polymers. This implies that polyurethanes can be variously derivatized, switching the backbone of diols and diisocyanates.

-Young Cho

2 Comments

Posted in Organic Chemistry

Tagged ,