Gloss Plastic Could Eliminate Auto Painting 320
customs writes "There is a new plastic out from GE that covers plastic surfaces with a really good sheen. It's more resistant to scratches and random chemicals compared to conventional paint. It's actually a .5 mm polymer called Sollx; the Segway was the first semi-mass-produced product to use it, it has slender two tone fenders. Kinda cool. Auto painting is the industries largest manufacturing expense, and this could be what they're looking for...as soon as the price comes down."
Old News (Score:3, Informative)
Re:Question for you all... (Score:2, Informative)
Don't hold your breath.. (Score:5, Informative)
When plastic comes down in price, then it will be here. The thing that I don't like about this is it seems that it has to be in place during the molding process. This would mean that if you were to ever scratch it, or something along those lines, you'd have to replace the entire piece. Unless they developed a patch kit for it, which seems like the patch would be weaker than the rest of the area because it wasn't present in the mold...
Of course, a plastic fender with this on it would probably be cheap because they have already reduced the cost of plastic below that of steal. The thermochromatic aspect of it would be cool though, but I'd prefer it to be uniform. I wouldn't want the rest of the car to be black and my hood to be red... that would just look weird.
How well will it stick in practice? (Score:5, Informative)
I got out of graduate school in 1999 and found myself in the market for a new car. I didn't shop around, I thought I knew what I wanted -- a new 2000 Saturn SC2, black. I found that dream car sitting on the lot, and bought it (well, a bank helped me).
So, here I am, 4 years later, the not-so-proud owner of a blackberry (purple in bright sunlight, black at night) Saturn, having learned so much about the downfalls of plastic. I'll never buy another Saturn. If I had it to do over again, I wouldn't have bought a Saturn in the first place. The sales pitch says this: when you get into an accident, plastic body panels are much easier to replace than metal ones. They don't say that every little ding and scrape you get (ever park next to an SUV that doesn't have enough repsect for drivers of smaller cars that they open their doors until they hit the next car over? Ever find a shopping cart resting against your car?) will leave you with a white mark. In a white car, that may not be bad, but when this car is all newly washed and shiney, it's got ugly white scratches on the sides and rear fender. For some reason, metal cars don't seem to have this problem as much.
Gloss plastic. In practice, does this mean that it'll stick as well as paint does to my plastic Saturn? Or will it have the staying power of paint on metal? I don't care about the press articles on it, I want to know what the field tests say in the hands of real people.
Re:Question for you all... (Score:4, Informative)
You could ask Saturn [saturn.com]. They have building cars that way for ~10 years.
how do you wax a piece of plastic? (Score:5, Informative)
And for the same reasons. It adds a sacrificial layer that erodes instead of the base material. Prevents oxidation.Provides a smoother surface (racing cars are waxed for this reason, the aero drag of a waxed car is measurably lower than an unwaxed one), and as result, entirely coincidentally, gives a glossy sheen that some people find attractive.
People already wax plastic all the time. Hell, I wax my Lexan R/C car bodies. Makes 'em look great.
KFG
Tips from the Grammar Nazi (Score:0, Informative)
This is a run-on sentence. Replace the comma with a semicolon or a period.
-
Replace with a period.
Maybe he'll pass some along for my wife and I.
Should read "for my wife and me." You wouldn't say "Maybe he'll pass some along for I" would you?
I hope that doesn't sound too greedy, does it?
Another run-on sentence. Replace the comma with a period. Alternatively, you could rephrase to "That doesn't sound too greedy, does it?"
I can dream, its not like my own stock options in my own company are going up...
Again, this is a run-on sentence. Replace the comma with a period or semicolon. Since you seem to misuse commas very frequently, allow me to refresh your memory of 4th grade English class. A comma is used to join a dependent clause to an independent clause. To join multiple indepdendent clauses, use a semicolon or seperate them into multiple sentences with a period.
Thank you for your attention to this important announcement.
for unibody based vehicles, it adds strength (Score:4, Informative)
Metal door skins and fenders are part of this overall structure. Even the windshield is part of the equation.
Of course if you switched to plastic ( as Saturn has done or the old fieros for example ) then you design around that...
Saw on TV commercials for this very thing recently, but they were touting lexan based panels..
You can try this experiment (Score:3, Informative)
You'll now find that you can simply peel the paint film from the paper backing. You will also now find that paint has no structural integrity whatsoever.
The primary function of painting metal is to prevent oxidation. Rust. It's secondary function is the purely cosmetic one of letting you change the color of the object. Note that the DeLoren, made of stainless steel, was not even available stock with paint on it.
KFG
Fieros and plastic (Score:2, Informative)
This is equally true of steel "skins" (Score:4, Informative)
It's not only perfectly possible to make a stressed skin plastic car, but the chassis of every Indy car and Grand Prix car is made entirely of stressed plastics. Because they are stronger, lighter and offer greater protection in a crash then steel,
The primary reason for using steel in the construction of production automobiles is manufacturing cost. Steel can be run down an assembely line in sheet form and *stamped* into complex structural shapes in fractions of a second.
Other materials have traditionally required skilled labor to form and more expesive machinery that takes longer to form a part than stamped steel.
Plus, your steel car rusts out in 10 years and they get to sell you a new one. Never underestimate the power of planned obsolesence. GM invented the overt philosophy.
KFG
Plastic cars are a pipe dream (Score:5, Informative)
Second, metal is stronger than plastics, up until you get into carbon fiber or similar carbon or aramid composites, which aren't plastics. They're composites. Even FRP (Fiber-reinforced plastic) which is somewhat common for air dams and such, it's floppy. You could make it hard but then it would be brittle.
Something that people tend to forget about cars is that unibody cars are a monocoque or semi-monocoque design. Most unibody cars are actually half monocoque, with a unibody rear, and then frame rails and underfenders just sort of sitting out in front of the car beyond that. The entire back skin of a unibody car is load-bearing, which is why it's a monocoque design. Stresses from spirited driving are transferred into the roof. This is why convertibles are floppy and require additional reinforcement.
There are some full-monocoque cars, like the older Opel GT. They don't really HAVE a classic frame, they're just built up where the suspension equipment bolts on. Of course the new classic example (since no one seems to know what an Opel GT is any more) is the McLaren F1, which everyone has heard of. That, however, is a carbon fiber full-monocoque design.
So metal is stronger than plastic, necessary in the car's design, and it will in almost every case look different than plastic even after painting. Plastic and metal require different primers, and the texture of the primer on a different material changes the way the car looks when it is painted. It can also be a challenge to get a primer for plastic and a primer for metal which won't interact differently with the paint you lay on top of it.
If you want a prime (oh I kill me) example of this phenomenon, examine a Pontiac Fiero. The Saturns with plastic doors aren't old enough to really see a color change, but of course that is due to fading which this stuff is supposed to not do. The Fieros, however, are painted with different paints depending on whether you're painting plastic or metal. It becomes very noticable on them as they age.
The final and perhaps most compelling reason to use metal is that it has the best failure mode out of all available materials. Plastic tends to shatter when you put enough force into the same part of it all at once. Steel, on the other hand, first work hardens when you flex it, making it stronger in the bent place. If you bend it beyond its elastic limit, anyway. If you continue to stress it it will distress (Crack) and then tear. However, with sheet steel, it mostly causes other areas to deform instead of tearing.
With steel, there is no damage which cannot be repaired. Pieces too badly damaged to straighten can be replaced to or near original specifications by removing a relatively small piece and fabricating a new piece of steel to fill the hole. This is true of any steel part of the car, from the body to the unibody to the frame. Plastic, on the other hand, usually has to be cured into a shape. Plastic bumper covers can be repaired (with some difficulty) but they are not load-bearing. They're just dressing. The only load they ever have to bear is atmospheric.
I should not have to remind you that this tendency to work-harden when pushed past the elastic limit and excellent failure mode is the technology behind "crumple zones" in cars. We know about how the stress is going to be transferred into other parts of the steel. Even cars which DO have plastic parts on the outside have metal parts right under them to deal with crashes. The upgraded version of crumple zone technology is used in NASCAR racing, and it's carbon fiber honeycombs built to fail in a predictable way, just like the crumple zones in a normal car - except of course the cells are smaller and more predictable. The bumpers are also upwards of $2000, which makes them impractical for street use.
Steel is cheap and good and can be easily repaired out in the real world. Plastics may make it possible, but they also possibly make repairs a big pain in the ass. You have to consider the difficulty of repair as well as initial construction.
Re:Materials science (Score:4, Informative)
Lexan is a bullet resistant plastic, similar to bullet proof glass but lighter, easier to mold, and more resistant to penetration. A few years ago, I made a skateboard out of the stuff just to have a clear skateboard. Now, it weighed in excess of 25 lbs. and was completely impractical but it looked good, and couldn't be shattered. I agree with you, the people who come up with these materials deserve to be compenstated fairly for their effort and hard work.
Re:Question for you all... (Score:5, Informative)
Not entirely true. Crumple zones are designed to absorb the energy of an impact rather than transmit it to the passengers.
This design was taken from high performance race cars (like Indy and F1, not so much NASCAR) where the cars appear to disintegrate upon impact.
Dispersion of energy is one of the best protections a passenger can have. This is what an airbag does. The energy of the impact gets disapated into the air filled bag of large volume.
So, a rigid frame may help handling, but it does not help accidents from causing bodily damage.
Re:Can I get that car in a color besides ugly? (Score:2, Informative)
It has air condition, ESP, ABS, 4 airbags (2 as an extra), and although it is not cheap, it is VERY cost effective.
BTW, I have been driving at -25 C, and no, the body panels did not shatter when I slammed a door. It has rear wheel drive, which actually is more of a problem in winter.
Re:Question for you all... (Score:5, Informative)
You might be interested to know that the windshield ends up absorbing/transferring to the roof up to 40% of the forces in a collision. This is the real reason it is illegal to drive around with a cracked windshield, not visual issues. If it were a visual issue, it would be illegal to drive around with a dirty windshield.
You can build your sacrificial crumple zones inside the body (in the front, the part of the body which the fenders are bolted to are called underfenders) but then you're just going to add weight. The fact that the skin of the car is load-bearing and part of the crumple zone just means that you don't need to add as much crap specifically and ONLY for the purpose of crash absorption under the body.
Re:for unibody based vehicles, it adds strength (Score:4, Informative)
For those who don't know, what a monocoque design basically does is convert one kind of force into another. Strictly speaking a monocoque design uses the outer skin of the car as a structural piece, but consider the case of a car door. Stress is transferred into and out of the door through the hinges and the latch. In the case of (for example) a C4 corvette, if you open the door and jack up the car from the center or the ends you can cause permanent frame damage! The car is intended to rest on the wheels when at rest, or to have the doors closed at all other times. Jacking the car must be done either at the wheels or at the four appropriate places on the frame. AT THE SAME TIME. Jacking up a vette to change a tire is best done (by a AAA guy so you have someone to sue) with the doors closed. Realistically you won't damage the car just jacking up one wheel enough to change a tire, Chevrolet isn't THAT clueless. But close.
Anyway, what I'm getting across is that there's no big structural member in the door. All the force gets transmitted through the skin of the door. The pushing force gets spread through the end of the door, and reaches a crease. (Any intentional crease in a door is called a "fold line" - if it's 90 degrees which it usually is at such places, it's called a flange.) A fold/crease/flange is work-hardened, so it can handle more stress than unhardened parts of the skin. The stress is transmitted through the work-hardened flange and into the skin of the door. This serves to translate it from whatever kind of force it is, which would normally want to deform the (reinforced) flat plane of the door, into a shearing force (pay attention, this is the important part of a monocoque) which means that the stress is distributed throughout the sheet metal starting at the point at which the stress is transferred INTO the flat plane.
That is the entire basis of monocoque design in a nutshell. Obviously there's a lot more to it in practice but that's the theory. If you look at the suspension links on a japanese car you see most of them are just metal folded around a shape to provide this effect. You can see it in its simplest form in a piece of box or u-channel from the hardware store. Even a piece of pipe which you are trying to bend from the ends is resisting as a monocoque would. If you put your knee in the middle, you expose the weakness of a monocoque design, which is that stress put into the system from points other than intended load points tends to destroy the design. Monocoque designs only handle stresses for which they are designed.
Re:I was hoping they would wait. (Score:2, Informative)
Most high production fiberglass parts are manufactured by blowing the resin and glass mixture onto a mold. The color is typically applied either as a mixture in the resin or by coating the mold prior to applying the resin and glass. I believe all current automotive applications for fiberglass are painted though--mostly because of the non-glossy finish. It's all about picking the right material for the application.
Kevlar uses aramid fibers in place of the glass, but works along the same theory.
Re:Brush Painted Car? (Score:3, Informative)
Let's get our semantics right. All plastics are polymers. Not all polymers are what we would call "plastics" (e.g. DNA), but from an engineering perspective, virtually all polymers are interrelated.
Your example shows you don't know what your are talking about. Acrylic is a plastic. You can buy chunks of it from McMaster-Carr [mcmaster.com]. It is dissolved in a solvent and sprayed on for paint, but what do you think happens when the solvent dissolves? The acrylic re-deposits to form a film, but it is still fundamentally the same material that is used to make those clear tumblers [crateandbarrel.com] you can buy at Crate & Barrel.
Can you heat it up and cause the film to flow? Yes, but that just makes it a thermoplastic (as opposed to a thermoset). You could do the same thing with a polyethylene film. The difference with polyethylene is that the flow temperature is about 120C (250F), whereas Acrylic will flow at temperatures closer to 60C (150F).
All paint contains a lot of highly engineered polymers with adhesive properties. Thus, paint amounts to brush on (or spray on) plastic coatings.