IIRC the thing that makes BPA plastic yellow over time is the gradual oxidation of a fire-retardant chemical added to it. You can reverse this process with bleach+UV light, reducing the chemical back to its non-oxidized form (sort of like how you can use activated charcoal to absorb moisture from the air, and then bake it to re-activate it.) If your 30yo white plastic isn't yellow, that's because the manufacturer skimped on the fire-retardant and it's likely highly flammable.

No idea about why some plastics get sticky, though. I'd imagine it's the plastic's polymer literally breaking down, but it might also be some additive "sweating" out. Maybe it's the very same fire-retardant chemical. (Old yellowing hard plastics don't get sticky, but they don't tend to have plasticizers in them, so they need far less flame-retardant.)

Somebody told me a while back that Apple cables self-destruct when other cables don't because a while back Green Peace talked Apple into no longer using PVC for their cables. The replacement plastic is presumably better for the environment but is less durable (possibly negating any environmental benefits by increasing the amount of e-waste produced?)

I don't know how much truth there is to this theory though. It doesn't seem to explain the poor strain relief.

If that were the case, I’d expect that Apple would use it in their marketing. A more environmentally friendly cable could be a good selling point.

Oh, they do: https://www.apple.com/environment/our-approach/

I never knew that! From their "Integrating Toxicological Assessments in Material Selection for Apple Products" white paper:

"Removal of BFRs and PVC were challenging since alternatives were not readily available at the time. The largest obstacle was identifying a replacement to PVC in AC power cords, where strict safety standards favored PVC and created barriers to its elimination. Apple worked with multiple material suppliers and tested dozens of different formulations until the right combination of performance and safety were achieved with lower toxicological and ecological risk than PVC. Apple then had to persuade dozens of safety agencies around the world to allow it to certify the alternative materials. Millions of PVC-free power cords are in use today with Apple products."

https://www.apple.com/environment/pdf/Toxicology_in_Material...

> "Every Apple product is free of PVC and phthalates with the exception of AC power cords in India, Thailand, and South Korea, where we continue to seek government approval for our PVC and phthalates replacement."

Investigating magsafe cable durability in those countries might be a way to corroborate or refute the PVC theory, though I wouldn't know where to start.