An Analysis of a Plastic Spoon
Aside from these posts, another of my everyday habits is visiting 7-Eleven. Japanese 7-Eleven’s are almost, but not entirely unlike their American counterparts. This perhaps betrays their bifurcated origins. However, it’s interesting that Seven & I holdings is probably the largest Japanese company that Americans interact with regularly, while likely unaware of the fact.
While my limited experience of American 7-Eleven’s has led me to believe they are best avoided, the Japanese 7-Eleven is a relatively pleasant experience. I often end up buying something to go with my coffee…
And dear reader… sometimes… while aware of the environmental consequences. I do not reject the proffered disposable spoon.
This article is about one such spoon.
The spoon weighs 1.75g and has no discernible markings other than “G16”. This seems to vary from spoon-to-spoon, and I suspect is a batch marking. The back of the spoon handle (shame it’s not a fork…) is ridged I assume to strengthen it:
With no other markings, I was curious to see if I could determine what kind of plastic was used. And, having recently acquired a UV-Vis spectrophotometer this seems like the ideal approach… My initial scans however produced rather unexpected results:
In general, materials absorb UV light. If you want to project or photograph images using UV light you need to spend significantly more money on fused silica optics. But all the above plots are showing negative absorbance in the UV range.
It tuned out that a previous owner had mis-assembled the spectrophotometer, switching the reference and detector photodiodes, and the instrument require further debugging and repair.
With the repair complete, spectra look far more sensible (top images show the full spectra, below zoomed in around the UV transition point):
Going by the literature the spectra looks largely as expected. With PP plastic showing a characteristic “hump” started around 290nm, and PET showing increasing absorbance from ~334nm.
The spoon however looks different than either of these, adsorbance starts increasing at ~300nm and there’s a characteristic hump in the visible range at ~700nm. Again, from the literature, this seems to suggest PC (Polycarbonate) plastic.
Some articles suggest that 1 tonne of polycarbonate production releases 1.1 tonnes of CO2 suggesting the production of my spoon releases ~2g of CO2. The average human seems to exhale roughly 1Kg of CO2. Which suggests that producing this spoon may emit far less CO2 than I suspected.
But in any case, I’ll be trying my best to reject disposable cutlery in the future…