A segment of Global Village made me wonder. They were using recycled plastic bags as a replacement for cement in pavers. Take heated plastic bags and add sand, cool and the plastic binds the sand together into a mix that makes good pavers.
The made me wonder about using recycles plastic bags (usually polyethene) as a cheap source of high quality carbon fibres, better quality and cheaper than can be made from cotton because cotton is mostly cellulose carbohydrate rather than a hydrocarbon. I’d attach opposite ends of the plastic bags to a stretching frame, so the stretching during pyrolysis would align the individual molecules as much as possible to get extra uniaxial strength.
The heating could be done either anaerobically driving off hydrogen (i.e. pyrolysis) for later storage and use, or done with just enough air to turn the hydrogen to water without oxidising the carbon.
Perhaps the resulting carbon fibres would be somewhat sticky, which would help to increase the fibre-fibre bonding for greater total strength.
What do you think?