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Freeze-Thaw and Age Resistant Plastic 2
- Thread starter oldstuff
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- #2
A bit more data might be useful.
We are at the "How long is a piece of string?" stage at the moment.
H
We are at the "How long is a piece of string?" stage at the moment.
H
- Thread starter
- #3
Don't mean to "string" anybody along, sorry. The only data I can think to add is that the finished piece will be a thin (~1/8") strip designed to hold a screw in zero to 100 degree (F) temperatures. My only considerations are long term structural performance and cost.
Product is currently fielded (but untested) in HDPE and PP, both unreinforced, but I think Acetal and/or fibers could perform better. I can find no test data on long-term exterior performance.
Product is currently fielded (but untested) in HDPE and PP, both unreinforced, but I think Acetal and/or fibers could perform better. I can find no test data on long-term exterior performance.
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patprimmer
New member
Acetal is very bad to UV and stabilisers improve it a lot to mediocre.
Glass filled PET or PBT might be worth a look, but it depends on a lot of factors not in evidence.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
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Glass filled PET or PBT might be worth a look, but it depends on a lot of factors not in evidence.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
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- #5
patprimmer
New member
Before I write a long novel about every property of every plastic just in case it is of interest, how about yoy outline in detail what you are doing.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
MikeHalloran
Mechanical
Oldstuff, you ask questions like an MBA.
I don't mean that as a compliment.
You haven't told us in what ways the current fielded product is unsatisfactory. Would you be here if it actually worked?
I'm failing to see how a 1/8" strip of plastic can 'hold a screw'.
I can't figure out what _you_ mean by 'structural performance'.
Mike Halloran
Pembroke Pines, FL, USA
I don't mean that as a compliment.
You haven't told us in what ways the current fielded product is unsatisfactory. Would you be here if it actually worked?
I'm failing to see how a 1/8" strip of plastic can 'hold a screw'.
I can't figure out what _you_ mean by 'structural performance'.
Mike Halloran
Pembroke Pines, FL, USA
- Thread starter
- #8
It's been awhile since I enjoyed the "tact" of non-civil engineers. Refreshing!
Plastic (HDPE and PP, mostly) is being sold in many construction products. These molded shapes, typically grids with a folded edge about 1/8" thick, hold metal fasteners and are subject to shear and freeze-thaw stresses over at least 50 years. I can find NO evidence of any testing to confirm their ability to perform in the long run and am asking first if these are is a better material to be trying to accomplish this.
Perhaps a simpler first question is, does anybody have information on the long-term freeze-thaw resistance of any plastic material?
Plastic (HDPE and PP, mostly) is being sold in many construction products. These molded shapes, typically grids with a folded edge about 1/8" thick, hold metal fasteners and are subject to shear and freeze-thaw stresses over at least 50 years. I can find NO evidence of any testing to confirm their ability to perform in the long run and am asking first if these are is a better material to be trying to accomplish this.
Perhaps a simpler first question is, does anybody have information on the long-term freeze-thaw resistance of any plastic material?
patprimmer
New member
If it absorbs no water, freeze thaw cannot be an issue unless you mean water entering between the plastic and what it is attached to.
I now very much doubt you are any kind of engineer.
Now you sound like a lawyer preparing a trumped up not suitable for purpose case.
HDPE and PP are cheap, easy to mould, tough and absorb no water. They are far strong and relatively easy to tear or cut.
Regards
Pat
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I now very much doubt you are any kind of engineer.
Now you sound like a lawyer preparing a trumped up not suitable for purpose case.
HDPE and PP are cheap, easy to mould, tough and absorb no water. They are far strong and relatively easy to tear or cut.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
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- #10
Hey, Pat, I'm just a Civil Engineer (licensed) trying to figure out the best plastic for use in a building material. What I've found so far is ZIP for age testing of anything. My thinking is that thousands of cycles of freeze-thaw, under load, will affect the length of time I can expect a plastic strip to hold a screw.
I'm not asking to be taught plastic. I'm trying to find somebody who might understand aging characteristics and what plastic / mix might be expected to resist deterioration the best.
I'm not asking to be taught plastic. I'm trying to find somebody who might understand aging characteristics and what plastic / mix might be expected to resist deterioration the best.
MikeHalloran
Mechanical
My Vulcan Mind Meld unit is in the shop.
I suspect Pat's is, too.
Clearly, you have a mental picture of exactly what you are talking about.
We do not. You haven't given us a clue about the fastener size, or the loads, or the manner of loading. I am also confused by continued references to a 'strip' of plastic 'holding a screw', yet you ask about injection moldable materials, not normally supplied in sheet/strip form. A 1/8" thickness of plastic can 'hold' a machine screw of no more than ~1/16" diameter, installed in a threaded hole through the thickness of the plastic. Is that what you meant?
Yes, there is little long-term application data for plastics, for several reasons:
- Many of today's plastics haven't been in the market for 50 years, or even 20 years.
- Accelerated aging as a predictor of material performance is notoriously unreliable, especially for plastics.
- Environmental factors like chemical exposure have a much greater influence than does time.
- As Pat pointed out, freeze/thaw does not directly affect common nonporous plastics; whether _water_ freeze/thaw affects them depends on the geometry of the application.
- Literally acres of aging samples of paint, and I think plastics, were blown away by Hurricane Andrew. I don't think the testing company or the accumulated data survived, either.
How about providing a photograph of a representative/ competitive product?
Mike Halloran
Pembroke Pines, FL, USA
I suspect Pat's is, too.
Clearly, you have a mental picture of exactly what you are talking about.
We do not. You haven't given us a clue about the fastener size, or the loads, or the manner of loading. I am also confused by continued references to a 'strip' of plastic 'holding a screw', yet you ask about injection moldable materials, not normally supplied in sheet/strip form. A 1/8" thickness of plastic can 'hold' a machine screw of no more than ~1/16" diameter, installed in a threaded hole through the thickness of the plastic. Is that what you meant?
Yes, there is little long-term application data for plastics, for several reasons:
- Many of today's plastics haven't been in the market for 50 years, or even 20 years.
- Accelerated aging as a predictor of material performance is notoriously unreliable, especially for plastics.
- Environmental factors like chemical exposure have a much greater influence than does time.
- As Pat pointed out, freeze/thaw does not directly affect common nonporous plastics; whether _water_ freeze/thaw affects them depends on the geometry of the application.
- Literally acres of aging samples of paint, and I think plastics, were blown away by Hurricane Andrew. I don't think the testing company or the accumulated data survived, either.
How about providing a photograph of a representative/ competitive product?
Mike Halloran
Pembroke Pines, FL, USA
- Thread starter
- #12
Thanks, Mike. I built the Univision Network building in Miami and we lost our antennae dishes during Andrew. Did not realize a test center also went away.
There are quite a few plastic construction materials and I'm trying to choose products that will likely perform best over time. Current building code requirements typically call for an initial pull-out resistance test of a screw. I'm willing to pay for testing if I can ID the most promising materials AND can develop an appropriate test. What are chances that a 3,000-cycle (what we in the Midwest see in 50 years) freeze / thaw / wet / irradiate test, under load (3 lbs suspended from a screw fastener) will tell me what I need to know?
$100,000 for a test is nothing compared to the cost of material failure. But if there really is no way to establish reasonable confidence, it makes more sense to avoid plastic altogether.
There are quite a few plastic construction materials and I'm trying to choose products that will likely perform best over time. Current building code requirements typically call for an initial pull-out resistance test of a screw. I'm willing to pay for testing if I can ID the most promising materials AND can develop an appropriate test. What are chances that a 3,000-cycle (what we in the Midwest see in 50 years) freeze / thaw / wet / irradiate test, under load (3 lbs suspended from a screw fastener) will tell me what I need to know?
$100,000 for a test is nothing compared to the cost of material failure. But if there really is no way to establish reasonable confidence, it makes more sense to avoid plastic altogether.
Compositepro
Chemical
Interesting to see such "cultural" miscommunication. Freeze/thaw has no effect, per se, on a plastic material that has no water absorption. It is a big problem with structures exposed to freezing conditions. Many steel structures exposed to water can be destroyed by freeze/thaw stresses.
The answer to the original question isthat it isa matter of design and not materials. Plastics have more strain capability that steel so, in specific cases, may be more durable than steel. Generally not, though.
The answer to the original question isthat it isa matter of design and not materials. Plastics have more strain capability that steel so, in specific cases, may be more durable than steel. Generally not, though.
For a brief overview of age-related performance of plastics,
contact Ticona and ask if they would email you their document number "General TDM 11 3/06". There is a short section in there.
I assume you are in the USA - latest details I have:
Ticona Engineering Polymers
Product Information Service
8040 Dixie Highway
Florence, KY 41042
USA
Tel.: +1-800-833-4882
Tel.: +1-859-372-3244
If they can't/will not oblige, contact me via website and we'll take it from there.
Cheers
Harry
contact Ticona and ask if they would email you their document number "General TDM 11 3/06". There is a short section in there.
I assume you are in the USA - latest details I have:
Ticona Engineering Polymers
Product Information Service
8040 Dixie Highway
Florence, KY 41042
USA
Tel.: +1-800-833-4882
Tel.: +1-859-372-3244
If they can't/will not oblige, contact me via website and we'll take it from there.
Cheers
Harry
Polyethylene water pipes must last over 50 years and survive freeze / thaw cycles. I would try that. It's cheap and injection moldable too.
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
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- #16
Yes, lawn sprinkler systems remain in the freeze zone (after draining in the fall) and have about a 20-year life (according to a manufacturer). They don't see the range of temps a plastic on the outside of a wall would see, however, nor do they experience the shear loads of a fastener under load. Polyethylene may (perhaps with some fiber reinforcing) prove the most promising solution. Thanks.
Don't add too much filler, it will make the plastic brittle and it will crack when you screw into it.
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Chris DeArmitt PhD FRSC CChem
Consultant to the plastics industry
Oldstuff:
Polythene (or to give it it's correct name, "polyethylene") has a problem with GF - it is difficult (to say the least) to get a bond between the PE and glass, which does indeed make the glass just a "filler", rather than an additional worthwhile property. PE is usually filled with talc or some other such mineral as it's cheaper than the base material. They do impart other properties which are only of minor import to your query. (Tin hat on - incoming...!)
H
Polythene (or to give it it's correct name, "polyethylene") has a problem with GF - it is difficult (to say the least) to get a bond between the PE and glass, which does indeed make the glass just a "filler", rather than an additional worthwhile property. PE is usually filled with talc or some other such mineral as it's cheaper than the base material. They do impart other properties which are only of minor import to your query. (Tin hat on - incoming...!)
H
patprimmer
New member
I am still not perfectly clear as to exactly what properties you require.
Will the plastic be moulded with threaded holes into which screws will be placed.
Will the plastic be moulded with plain holes into which self tapping screws will be placed, or will screws or nails be driven through the plastic into the structure.
Are you worried about ice forcing the plastics to pull the screws out.
Have you considered that plastics cold flow when under constant load.
Are you aware that the plastic generally has a much higher co-efficient of expansion of what it is probably attached to.
Different plastics are indicated for thread holding ability, creep resistance, cold impact strength, toughness, elongation at yield, flex modulus, tear resistance and even chemical resistance, all of which might be required depending on how you are using the fasteners and where the ice might form.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
Will the plastic be moulded with threaded holes into which screws will be placed.
Will the plastic be moulded with plain holes into which self tapping screws will be placed, or will screws or nails be driven through the plastic into the structure.
Are you worried about ice forcing the plastics to pull the screws out.
Have you considered that plastics cold flow when under constant load.
Are you aware that the plastic generally has a much higher co-efficient of expansion of what it is probably attached to.
Different plastics are indicated for thread holding ability, creep resistance, cold impact strength, toughness, elongation at yield, flex modulus, tear resistance and even chemical resistance, all of which might be required depending on how you are using the fasteners and where the ice might form.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
for site rules
- Thread starter
- #20
Screw holes will not be preformed, ice between components is not a concern, and the tolerances of the associated construction materials will not be a problem with differential thermal movement.
Long-term cold-flow and brittleness leading to rupture are my major worries. The former could be addressed by havinging a huge factor of safety, say 10 to 20. Brittleness I'm thinking could be countered by the right fiber. Filler, in general, is probably not a good idea. And I'd still like to test the response to the plastic to repeated freeze-thaw as there may be significant deterioration even with a very low amount of absorbed water.
Long-term cold-flow and brittleness leading to rupture are my major worries. The former could be addressed by havinging a huge factor of safety, say 10 to 20. Brittleness I'm thinking could be countered by the right fiber. Filler, in general, is probably not a good idea. And I'd still like to test the response to the plastic to repeated freeze-thaw as there may be significant deterioration even with a very low amount of absorbed water.
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