Did you know that 2 revolutionary types of plastic were recently discovered when chemists made a stupid mistake?

Thermoset plastics are very strong and heat-resistant, therefore useful for constructing cars, planes and electrical equipment.

However they can’t be recycled, which is environmentally wasteful and expensive.

Here, chemists from California accidently forgot to add 1 of only 3 ingredients to a mixture, inadvertently creating 2 new plastics that can be recycled.

The first is extremely strong and heat-resistant, therefore useful for vehicle construction and electrical equipment.

The second is elastic and can repair itself if torn.

This is good news for the environment and might reduce the cost of plastics.

Do you want more information?

Background

Thermoset plastics used in construction of cars, planes and electrical equipment are very strong, stiff, durable and heat-resistant.

Their strength comes from chemical cross-linkers that bind polymer chains together.

They do not break down at high temperatures, making them useful for cars and electrical equipment.

This also means they can’t be broken down and recycled to make new plastics. Instead, they are thrown away, which is wasteful.

Here, 2 new types of plastic were developed that can be recycled.

Materials and Methods

Chemists from California were making plastic when they forgot to add one of only three ingredients. Instead, paraformaldehyde was mixed alone with either ODA (4,4’-oxydianiline) or PEG (polyethylene glycol). The resultant plastics were characterised using NMR and solid state infrared spectroscopy.

Results

When paraformaldehyde was mixed with ODA, it made a very strong, stiff, durable and heat-resistant plastic. Amongst the strongest of all thermoset plastics, making it suitable for cars and electrical equipment.

When paraformaldehyde was mixed with PEG, it formed elastic plastic that had self-healing properties (i.e. repair itself if torn).

Importantly, both types of plastic could be dissolved in acid (pH<2), returning the plastics to their original monomers for recycling.

Discussion

The ability to dissolve and recycle these plastics is good news for the environment (require less raw materials) and could even reduce costs of plastic goods.

Article

Recyclable, strong thermosets and organogels via paraformaldehyde condensation with diamines

Garcia et al., 2014 Science 344:732-5

Keywords

Plastic, monomer, polymer, polymerize, polymerization, thermoset, cross-link, organic, molecule, temperature, pH, self-healing

Subject

Science, chemistry, ST1-12MW, ACSSU018, ACSSU031, ST1-13MW, ST1-16P, ST2-13MW, ACSSU074, ST2-16P, ST3-6PW, ACSSU097, ST3-13MW, ST3-16P, SC4-11PW, ACSSU155, SC5-17CW, ACSSU187