What are crisp packets made from, specifically Tyrrells or Walkers. I am doing a school project on single use plastic crisp packets. I am finding it difficult to find information online.
I'm not familiar with the brands you name (they don't sell those where I live), but crisps bags are most commonly made from a combination of aluminium and one or more plastics like polypropylene and low-density polyethylene. This is also known as aluminium-plastic laminate, or metalized film
Many crisps bags have a thin aluminium inside-layer to keep light, oxygen and moisture out and thus increase the shelf life of the crisps. Aluminium tears quickly, so that's why the outside is usually made of one or more plastic layer. Unfortunately the plastic and aluminium are hard to separate and since the amount of used aluminium is so small, most recycling companies do not recycle crisps bags as it's not worthwhile economically.
There are also crisps bags that consists of multiple layers of plastic (so no aluminium), but they are much less common.
BTW this website says that
There is a growing trend among snack producers to add a Matte finish to these metalized polypropylene films. UK Premium snack brand Tyrell’s Crisps for example uses a Matte surface to create its nostalgic branding
This suggests that Tyrells crisps also have a metalized polypropylene film. However the article is from 2013 and I'm not sure if their packaging has changed since then.