I read in another blog that the European car manufacturers (e.g. Mercedes) use biodegradable plastic to "save" the environment. After a few years, while the car is still in service, the parts start to degrade all on their own. So even if they survive the stress and strain of daily life, they will still fail early.
Leave it to the Europeans to come up with a planned obsolescence scheme that makes the old American GM/GE plans look amateurish.
Of course, Ann, you are right. It depends, as you said, what type of plastic is being used and what is being made of the material. Gears! Now that boggles the mind...even metal gears wear quite easily if they're not made quite durably! Yes, that was definitely a corner that could have been cut a different way. Still, I do miss chrome bumpers and other external car parts made of sturdier materials!
@Ann: Material selection is important, but part design is another big factor. Engineers who are designing plastic parts need to understand the properties of plastic materials. Don't assume that they deform linearly. Don't assume that they won't creep at room temperature. Don't assume that they will respond the same to a quickly-applied load as to a slowly-applied load. Don't assume that the properties are the same in every direction. Don't assume that the properties on the datasheet apply to anything other than a test bar.
I continue to refer people to an article that appeared in Design News nine years ago by Joseph Ogando titled The Misunderstood Material. It is a very good explanation of what plastic material properties actually mean.
I meant the Jetta was now departed, not my husband. He's still alive and kicking, and now fixing his latest used car, a Honda. Which, BTW, had a similar door/window problem on the driver's side, but didn't take nearly as long. Much saner design.
The author's experience reminds me of our driver door/window odyssey on my husband's (now departed) 1997 VW Jetta. We took it apart slowly over time--several weeks--to figure out what needed replacing where. It took so dang long because there was so much stuff on top of so much other stuff, and meanwhile, he had to drive it to work every day and secure the door somehow. That meant putting it back together every time after each disassembly.
All plastic is by no means created equal when it comes to strength and durability. The problem comes when lesser materials are spec'ed that will do the job, but won't do it long enough. But there are some places it should not be used at all. One of my favorite little desk clocks is now trash because it was made with, get this, plastic gears! And crummy cheapo plastic, at that. Of all the dumb things to use almost any plastic for, gears must be at the top of the list. Kind of like the brass gears in my old pretty but now useless hand coffee grinder: an equally dumb idea.
Wow, what an experience--but it's all too familiar now with the rampant use of plastic parts in automobiles. I am old enough to remember the days of chrome bumpers that would stay intact if you just nudged a wall or another car's bumper--now we have plastic ones that crumble or dent at the smallest impact. (Yes, I know I shouldn't be running into things, but it happens!) Plastic is on one hand one of the handiest inventions ever and also one of the most evil, in my opinion anyway. Yes it made things cheaper and lighter, but it's also taken its toll on quality and the environment.
I have similar experience in my 1993 Suburban and of course my 1968 Pontiac (though the latter has very little plastic parts for operational items). I know plastic degrades over time. This is particularily true when exposed to UV. What gets me, is cars that are less than 10 years old and the plastic is breaking.
Back in the day (meaning when I was younger), I had a 1984 Oldsmobile with power seat. The motor for the seat was coupled to the track drive with a plastic coupler. The first time it broke, I thought maybe I was the fault as I am heavy and I probably was to much resistance for the coupler. $25 later and about 1 month it broke again! This time I asked the parts guy about it. He said they break all the time. This is a design feature! What? Yes, the plastic will break to prevent overloading the motor!
My point is, new cars are being built with more and more plastic to make them lighter for CAFE standards to be met. Service will evidently become part of the design feature. get out your wallet or plan on trading in the car every 5 to 10 years before the plastic gets brittle!
Although plastics make up only about 11% of all US municipal solid waste, many are actually more energy-dense than coal. Converting these non-recycled plastics into energy with existing technologies could reduce US coal consumption, as well as boost domestic energy reserves, says a new study.
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