Rubber ducks: made from rubber, right? Wrong! This infographic examines the chemical history of a rubber duck, from its origins using genuine rubber in the 1800s to its modern incarnation, made possible by polymers and plasticisers.
Rubber ducks didn’t begin their commercial lives in the bathtub, but as chew toys in the late 1800s. A chemical discovery made their manufacture possible: In 1839, Charles Goodyear discovered that mixing rubber with sulfur and heating it made the rubber stronger and more durable. You’ll likely recognise his name from Goodyear tyres, though the company that makes these was founded and named after Goodyear several decades after his death.
While tyres were the most lucrative consequence of his vulcanised rubber, it also enabled the manufacture of durable rubber toys, including rubber ducks. It wasn’t until the 1940s that the more familiar floating bath toy versions appeared, however. Hollow, floating rubber ducks became available around this time, but the rubber duck’s real moment came when sculptor Peter Ganine patented a floating duck made from a new material.
Scientists discovered polyvinyl chloride, or PVC for short, accidentally in the 1800s on more than one occasion. A hard and brittle plastic, PVC had little commercial use until it was mixed with softening plasticisers to make a much more moldable material. Ganine’s rubber duck was not made from rubber, but from plasticised PVC coloured with a bright yellow pigment. However, the rubber-related name remained – perhaps “vinyl duck” isn’t quite so catchy.
The plasticisers that make rubber ducks squishy have also seen change. The initial plasticisers that made using PVC possible were phthalates, esters of phthalic acid. These compounds were the undisputed plasticiser champions for many years, until concerns about their effects on health and the environment started building. Today, phthalates produced from alcohol compounds with 3-8 carbon atoms are considered toxic as they may disrupt human hormones and damage fertility, with some also harmful to the environment. The compounds of concern include phthalate plasticisers such as di(2-ethylhexyl) phthalate (DEHP), historically one of the most common plasticisers.
As of 2011, the EU banned all phthalates considered to have reproductive toxicity from use in children’s toys. Their use is also prohibited in many other countries. Consequently, manufacturers have had to find alternatives. Newer plasticisers include 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), terephthalates, citrates, and adipates.
Of course, the challenge in chemistry is that further scrutiny of replacement compounds can sometimes reveal similar concerns. DINCH, one of the most popular phthalate replacements, has been investigated for the potential for the compounds it breaks down into to affect human metabolic processes, with research continuing to determine whether or not this represents a risk to our health.
One thing that doesn’t look like it will change is the popularity of rubber ducks. Estimates suggest that over a billion rubber ducks are manufactured every year. As well as providing bathtime fun, they’ve also made their own contributions to science: in 1992, almost 29,000 plastic bath toys, including 7,200 rubber ducks, fell off a Pacific cargo ship and have since been used to map ocean currents based on where they’ve washed up.
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