The core material used in the cladding for Grenfell Tower was not only highly flammable but also toxic.
This month marks three years since Grenfell Tower was engulfed in flames, killing 72 people. In the early hours of June 14th, 2017, a fire started in a kitchen on the fourth floor. Firefighters quickly put out the fire, but were oblivious to the flames which had escaped through the open window. In a matter of minutes the fire on the fourth floor had spread up to the eleventh floor.
A number of problems were linked to this tragedy – the miscommunication between the responders and call centres, the recent cuts endured by the fire departments but this article will focus on the structural failures.
Attention was quickly shifted onto the newly installed cladding, believed to be the source of the rapid spread. Refurbishment of the Tower had recently been completed. A new aluminium, rainproof cladding had been installed on the exterior, along with ill-fitted windows.
Aluminium composite material (ACM) was installed by Arconic’s. This consisted of two half millimetre sheets of aluminium separated by a core material, in this case polyethylene, or PE.
I’ve spent a significant time researching why PE was used? Was there an advantage in its synthesis? Or, does it all come down to money? Was there really no scientific benefit in using one material over another? Polyethylene wasn’t installed because nothing else was available. The science was there. The choice was there.
In an attempt to understand why this material was used, we will look more closely at what polyethylene is. Polyethylene is a succession of ethylene molecules (H2C=CH2). Its lightweight, malleable and affordable properties make it an appealing material. The world’s biggest source of plastic comes from this polymerization. Polyethylene is highly combustible. Once it has melted, it’s used as fuel to keep the fire alight.
The smoke of a fire is usually the cause of death, rather than the heat of the flames. Large fires produce high concentrations of carbon monoxide and hydrogen cyanide. In the case of Grenfell, an additional problem arose. The combustion of polyethylene yields acrolein, a toxic gas. A study found large quantities of polyethylene which smoulder in a constricted environment, like cladding, leads to deadly concentrations of acrolein.
In the case of a fire, victims are told to place a wet cloth over their mouths, to create a barrier and filter noxious particles. This can be helpful when evacuating, but the moisture won’t help fight the toxic fumes for long. Although this is a big concern with polyethylene, it is pointless to try and pinpoint which of these gases was the biggest contributor. All three are chemical asphyxiates.
Despite its popularity in industry, polyethylene comes with many drawbacks. The two other core materials available for the clad insulation in Grenfell Tower were non-flammable or fire retardants. They were also slightly more expensive. Polyethylene was found to be on the exterior of numerous high rises, public and private, dotted around the country. The lack of UK regulations allowed this material to be used and was a large contributor to the men, women and children who died that night. Grenfell is a tragic example of the consequences of low-cost and poor building standards.
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- D. B. Malpass, Introduction to Industrial Polyethylene : Properties, Catalysts, Processes, Wiley-Scrivener, Salem, Massachusetts, 2010.
- Andrew O’Hagan, London Review of Books, 2018,Vol. 40 No. 11.
- The Guardian, Robert Booth, 2020, ‘Grenfell cladding maker ‘knew it fell below safety standard’, https://www.theguardian.com/uk-news/2020/jan/27/grenfell-tower-inquiry-companies-passing-the-buck-on-responsibility
- The Guardian, Rob Davies, 2017, ‘Grenfell Tower: cladding material linked to fire pulled from sale worldwide’, https://www.theguardian.com/uk-news/2017/jun/26/grenfell-tower-cladding-linked-to-fire-pulled-from-sale-worldwide
- Chemistry World, Emma Stone, 2017, ‘Material lessons from Grenfell Tower fire’, https://www.chemistryworld.com/news/material-lessons-from-grenfell/3007695.article#/