I remember back in the early 70s as plastics where really coming into common usage for everything there was a panic about them lasting forever.
Then in the 80s everything plastic was basically considered to be very short term life (in terms of the human lifespan). I had heard that most (all?) plastics had been modified to make them break down.
Why can't we get those "good" plastics from the 70s anymore, and did they ever really exist or was it all a big scare tactic?
Apparently they never existed. Science News had a good article in November about this very subject, and discusses the measures that some museums are taking to try to preserve the plastics in their collections.
Sunlight breaks most of them down, unless they are buried in a landfill.
jw
There's a big difference between the point where a plastic part is degraded to the point where it no longer functions as was intended, and the time when it can be indiscriminately discarded.
A sun-damaged plastic bag isn't much use for carrying stuff, but you wouldn't flush it down the toilet.
Current leanings are that it is a huge problem (plastics not really degrading). A couple of articles I found:
The "good" plastics are still around. They are properly called engineering resins. Delrin aka acetal, polycarbonates, teflon, nylon and acrylics like plexiglass are still widely used in quality products.
The plastics from the 70's and 80's is a big part of why it is tougher to restore a car from that era. The parts are there but the sun has taken it's toll. Steve
Dunno about nylon; back in the late 60s I worked in a test house. We had some nylon brake hoses for examination ( the curly airline between the tractor and the body of a truck). UV exposure had made them as brittle as a chocolate bar. So much for the good old stuff!
Plenty of Tufnol parts on my boats and friends boats that are still going strong and 40 years young :-) Many of them are good for another
40 years too. You can still get phenolic composites that are just as durable. OTOH there is a lot of plasticiser loaded cr@p out there in consumer products which wont last a year of normal use. Rigidity seems to go with durability. UV resistance is a whole other ball game.
I believe it. Nylon still works well for internal parts though.
I believe the basic principal is that if you want them to last forever you keep them out in the oxygen and sun and changing temperature, which makes them break down.
OTOH, if you want them to go away you bury them deep in a pile of garbage, where there's no oxygen, no sun, and the temperature is constant. There, with only some discoloration, they last forever.
My recycled washer fluid jug bins for good stuff are getting brittle and cracking even without exposure to sunlight. Gerry :-)} London, Canada
Nylon, can be revived by boiling in water. The old nylon model airplane propellers would regain flexibility after 20 minutes in boiling water.
Steve R.
They're better than ever. We now have things like LCP (liquid crystal polymers) and other high performance plastics that will keep decent mechanical properties at high temperatures. We have stuff like HIPS that is incredible good compared to your Dad's polystyrene-- comparable to ABS or PC.
I don't think planned self-destruction is used anywhere but in packaging materials (though packaging does consume a substantial fraction of all plastics manufactured). IIRC, automotive is behind both packaging and construction applications as a consumer of plastics.
About ten years ago I was working in a restoration shop on a 1904 Panhard, and we were discussing which contemporary cars might be extremely valuable in 80-90 years. We all agreed that plastics would be the killer, as you would have to make molds and cast it from polymers or something. Now I can see that "rapid prototyping" machines hold promise. Find the blueprint and you solve the hardest problem. My "valuable" car? The Yugo. There may be only one.
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