Planetary Pros: Polyethylene is a lightweight and comparatively cheap radiation shielding material.
It’s pretty good shielding against galactic cosmic rays and solar particle events.
It has a high hydrogen content – and hydrogen atoms are really good at absorbing and dispersing radiation.
Polyethylene is also quite easy to make and mould, and is fairly tough, making it suitable for various parts of rocket designs. If all that wasn’t enough, it’s also non-toxic.
Cosmic Cons: While polyethylene is effective against low-energy radiation, it may not be as effective against high-energy radiation.
Also, polyethylene can wear out the more exposure it has to harmful rays, which can reduce its shielding effectiveness over time.
Thick polyethylene shielding may add weight and volume to the rocket, and the heavier the rocket, the lower the overall performance and fuel efficiency will be.