One of the folding boat enthusiasts (who shall remain nameless, except to say that he is Ralph Diaz) wrote in his book that plastic boats have a life of about eight years and then become brittle. Is this because of UV damage? Or other chemical breakdown? Does it afflict both straght chain and cross-linked polyethylene? I have my doubts about this assertion because I own a number of polyethylene objects that are over 20 years old and they are still flexible and like new. OTOH, polyethylene left in the sun does indeed fall apart pretty quick -- a problem that can be solved for kayaks by proper storage. Ken Cooperstein *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Ken Cooperstein wrote: > > One of the folding boat enthusiasts (who shall remain nameless, except > to say that he is Ralph Diaz) wrote in his book that plastic boats have > a life of about eight years and then become brittle. > > Is this because of UV damage? Or other chemical breakdown? Does it > afflict both straght chain and cross-linked polyethylene? Ken, I don't believe that I said quite what you indicate above. But that is okay as the question is a good discussion to bring up and I hope we get some knowledgeable feedback. Re plastic boats as discussed in my book: p. 7 "Their hulls become suspect after around 8 to 10 years of service, and at that point they can't be easily patched." And in a discussion of repairing boats in general p. 10 "Plastic hulls grow brittle and inflexible with time, so the pliable patch material has difficulty adhering properly. How well a plastic kayak has been stored and treated determines the age at which it becomes too old to patch. Some experts advise that beyond about five or six years, a plastic hull cannot take a reliable patch. If you have to repair a five or six year old plastic hull, they advise for safety sake that you relegate the boat to light use from there on." I based that on some things I have read and observed. The most telling was a discussion of repairing plastic boats in an old Sea Kayaker that indicated that after 6 years or so, the original material is to brittle to take a patch reliably. Also I have seen discussions on this over at r.b.p. that pretty much backs up the idea. I suggest that you, in addition to any feedback you might get here, do a web check to see what the word is in various places regarding this. One problem is that there are plastics and there are plastics. Some obviously will last longer than others. And plastics as used in boats has improved in the 15 years or so since plastic started to be used for sea kayaks. Also I suspect that size and style of boat may vary any prediction. A short whitewater boat would have less flex in it than a longer sea kayak and therefore less stresses in that regard. But it would get banged up more. The longevity was just one of the issues I raised about plastic. Another was that it is not quite indestructable as people might think. It oil cans easily and takes indents from car racks that may become permanent. Moreover, while you may think it is neat to drag a plastic boat over beach sand and parking lots, you will pay a price in terms of slivers that will slow the boat down on the water. Also it is quite heavy, length for length, with other materials used in kayaks. One of the raps against folding kayaks was that they weighed more than other boats. But if you look at the realistic weights in Sea Kayaker reviews (ignoring the advertised weight) you will see that the average single plastic sea kayak weighs in the 65 pound range where as the average single folding kayak is quite a bit less. Of course most fiberglass boats (except the British boats) weigh less. The same is true of double plastic boats vs. double folding kayaks. > > I have my doubts about this assertion because I own a number of > polyethylene objects that are over 20 years old and they are still > flexible and like new. OTOH, polyethylene left in the sun does indeed > fall apart pretty quick -- a problem that can be solved for kayaks by > proper storage. Yes, proper storage will prolong the life of a plastic boat as it would for any boat. However, since a plastic boat's advertised selling point is its toughness, owners tend to buy the hype and store them pourly, drag em on parking lots, bang em around rocks etc. Oh yeah, folding kayaks's life spans are pretty impressive. A good 25 years on the skins and well beyond that for frames. best regards, Nameless p.s. Despite being a folding kayaker I do rely on polyethylene in my paddling...my pee bottle. I have been monitoring its life cycle and, in any update of my book, I intend to recommend that any one using a plastic pee bottle plan to retire it after about six years for safety sake. :-) -- ----------------------------------------------------------------------- Ralph Diaz . . . Folding Kayaker newsletter PO Box 0754, New York, NY 10024 Tel: 212-724-5069; E-mail: rdiaz_at_ix.netcom.com "Where's your sea kayak?"----"It's in the bag." ----------------------------------------------------------------------- *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Ken, Thomas Hobbs got the description of plastic boat life essentially correct in 1641. When compared to their fiberglass cousins, "The life of [plastic boats] is nasty, brutish and short." I don't know about all plastics but my AquaTerra Chinook age 7 years was definitely showing cracks in rounded areas and had always been stored indoors. Dave Kruger can give you the chemistry but one dramatic demo of the fragility of poly containers came years ago on a mountaineering expedition I'd organized on the Monarch Icecap in BC. We arranged for a bush plane to resupply us with an air drop after reaching the icecap plateau. The drop arrived more or less on time and in place but the results were an eye opener. We figured poly bottles and containers would be the most secure, flexible and impact resistant so we gathered our spare climbing bottles etc. and loaded them with rum, butter, honey, and and other gooey goodies. All the messy stuff was in 4-7 year old Nalgene bottles, Tupperware and other high-grade but somewhat aged poly containers. We also had some last minute additions -- 2/3 gallon of Coleman fuel in the can, canned fruit in a mailing tube, and canned meats. Everything was packed together in a multilayered semi-hard drop container, very tightly packed). We figured the tin would not make it but counted on the plastic. Wrong, wrong, wrong. *Every* poly container shattered upon impact. The butter and the run and the honey mixed nicely with my spare clothes and etc. You can imagine the mess. Upon examination, the poly containers looked like shards of glass -- splintered and cracked. The tin? Everything was fine! The Coleman fuel can distorted and stretched in shape, as did many of the other tin containers, but all remained intact. On subsequent climbing trips we used tin containers with much success and avoided any more poly unless it held nothing more vital than oats or toilet paper. So I don't know about boats, but poly bottles and boxes of a certain age, subjected to sudden shock, are not the best. RGM Ken Cooperstein wrote: > > One of the folding boat enthusiasts (who shall remain nameless, except > to say that he is Ralph Diaz) wrote in his book that plastic boats have > a life of about eight years and then become brittle. > > Is this because of UV damage? Or other chemical breakdown? Does it > afflict both straght chain and cross-linked polyethylene? > > I have my doubts about this assertion because I own a number of > polyethylene objects that are over 20 years old and they are still > flexible and like new. OTOH, polyethylene left in the sun does indeed > fall apart pretty quick -- a problem that can be solved for kayaks by > proper storage. > > Ken Cooperstein > > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** -- Richard G. Mitchell, Jr. Department of Sociology Oregon State University Corvallis, OR 97331 U.S.A. (541) 752-1323 phone/fax mitchelr_at_ucs.orst.edu *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
> So I don't know about boats, but poly bottles and boxes of a > certain age, subjected to sudden shock, are not the best. > > RGM Would the cold add to the brittleness Richard? -- gabriel l romeu http://members.aol.com/romeug studio furniture http://members.aol.com/romeugp paintings, photos, prints, etc. http://members.xoom.com/gabrielR a daily photo journal *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Not much. The ambient air temp. at drop time was around 60 degrees F, the solar radiation off the snow pack was a brutal scorcher (we wore face masks, hats and gloves at all times to keep from getting burned) and the airplane was nice and warm. Unless we can imagine the package dramatically cooled while falling 7 or 8 seconds, then it was a room temp. impact. Just like your kitchen, and warmer than a boat in the water. RGM Gabriel L Romeu wrote: > > > So I don't know about boats, but poly bottles and boxes of a > > certain age, subjected to sudden shock, are not the best. > > > > RGM > > Would the cold add to the brittleness Richard? > -- > gabriel l romeu > http://members.aol.com/romeug studio furniture > http://members.aol.com/romeugp paintings, photos, prints, etc. > http://members.xoom.com/gabrielR a daily photo journal > > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** -- Richard G. Mitchell, Jr. Department of Sociology Oregon State University Corvallis, OR 97331 U.S.A. (541) 752-1323 phone/fax mitchelr_at_ucs.orst.edu *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Richard, I'm no scientist, but doesn't plastic get more brittle in extreme col? Could this have been a factor in the drop on an ice cap? Scott *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
To answer the question, "Was it cold on the "ice" cap?"... For folks not acquainted with summer time mountaineering on big icecaps in BC these are often hot places, sometimes excruciatingly so. It is highly unlikely that the plastic bottles, boxes etc. were at all cold when they shattered. The ambient air temp. at drop time was around 60 degrees F, the solar radiation off the snow pack was a brutal scorcher (we wore face masks, hats and gloves at all times to keep from getting burned) and the airplane was nice and warm. Unless we can imagine the package dramatically cooled while falling 7 or 8 seconds through 50-60 degree air, then it was a room temp. impact. Just like your kitchen and warmer than a boat in the water in the PNW much of the year. RGM *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Richard Mitchell wrote: > I don't know about all plastics but my AquaTerra Chinook age 7 > years was definitely showing cracks in rounded areas and had > always been stored indoors. Dave Kruger can give you the > chemistry but one dramatic demo of the fragility of poly > containers came years ago on a mountaineering expedition I'd > organized on the Monarch Icecap in BC. We arranged for a bush > plane to resupply us with an air drop after reaching the icecap > plateau. [snip] We figured the tin [steel, actually] > would not make it but counted on the plastic. Wrong, wrong, > wrong. *Every* poly container shattered upon impact. [snip] > The tin [steel]? Everything was fine! The Coleman fuel can > distorted and stretched in shape, as did many of the other tin > [steel] containers, but all remained intact. I was going to stay out of this, but Rich invoked my mantle. (Rich can be very persistently devious -- he extracted *all* my intellectual worth over the course of a week's queries on materials science -- and I thought I was on a don't-need-to-use-my-brain (relaxing) sea kayaking trip! Shoulda got a consulting fee.) Per previous posts, Rich's poly bottles probably were not cold enough for that to contribute significantly to their fragility. However, it is mistaken to think that poly bottles have to be below 32 F (what we regard as "cold") for the temperature to have that effect. Somebody with an honest materials science background would be better versed in this, but I'll give it a shot: 1. Every plastic has a "glass transition temperature," below which it functions like a crystalline material, and above which it is more flexible -- hence resistant to fracture. This temperature might be higher than 32 F for polyethylene, depending ... 2. The tendency toward crystallinity for a polyethylene sample is a function of its initial polymerization conditions, its plasticizer content, and its age. a. Plasticizers are small molecules incorporated into the polymer during manufacture -- they are thought to "lubricate" the meshing of polymer molecules. They diffuse out of the plastic over time. Maybe topical application of "replacements" can forestall this process, the basis for application of Armorall and similar products to rubber tires and vinyl dashboards. b. Initial polymerization conditions determine whether the polyethylene is "linear," "cross-linked," "high-density," or "low-density." Each type has its property profile, with cross-linked high density polyethylene usually the stiffest, and least flexible. (Inexpensive poly bottles are usually linear, low-density polyethylene.) Reasons for the differences? We don't want to go there ... this is a family-oriented list! <G> If anybody wants to know more about polymers, check out some of the links at this URL: http://pw2.netcom.com/~uncleal0/net2.htm (ignore Uncle Al's politics -- his knowledge of chemistry is, however, impeccable). c. Age. Yeah. This is probably the biggy. Just like our own collagenous tissues, practically every plastic stiffens with age. [This applies equally to epoxy/polyester/vinylester/you name it - based polymers, though epoxy seems to be more resistant than the others, *if UV damage is minimized.*] The main factor is probably gradual loss of the random arrangement of the polymer chains. As they pack more efficiently, they more closely resemble an ordered crystal. Thus, they become more "crystalline," and are much less resistant to breakage from mechanical shock. Loss of plasticizers and oxidation of the polyethylene contribute. Bottom line: all our boats are aging, with polyethylene boats perhaps having the shortest lifetime. Hank Hays, and others, however, can no doubt attest to the fragility of well-aged polyester layups, which use styrene as a copolymer adduct / plasticizing ingredient. Sorry for running on ... I'm an academic, folks, I can't help it! -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
> > Sorry for running on ... I'm an academic, folks, I can't help it! > This is the type of 'running on' that keeps the net fascinating for me Dave. It is generous of you to take the time for such an informative post. Thank you. -- gabriel l romeu http://members.aol.com/romeug studio furniture http://members.aol.com/romeugp paintings, photos, prints, etc. http://members.xoom.com/gabrielR a daily photo journal *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Dave, Thanks for your explanation. I wonder if some other factors should be added. Thickness of the material. The walls of a polyethylene boat are of x thickness. That would likely mean that they would age a lot faster than say the half inch thick high density polyethylene cross ribs used in Feathecrafts. Length of the material in conjunction with how much it is subjected to flex. I sense that polyethylene white water boats (except for the hard knocks they get against rocks etc.) tend to last a bit longer than their sea kayak counterparts because of the differences in length and amount of flex. ralph diaz Dave Kruger wrote: > 2. The tendency toward crystallinity for a polyethylene sample is a > function of its initial polymerization conditions, its plasticizer content, > and its age. > > a. Plasticizers are small molecules incorporated into the polymer during > manufacture -- they are thought to "lubricate" the meshing of polymer > molecules. They diffuse out of the plastic over time. Maybe topical > application of "replacements" can forestall this process, the basis for > application of Armorall and similar products to rubber tires and vinyl > dashboards. > > b. Initial polymerization conditions determine whether the polyethylene is > "linear," "cross-linked," "high-density," or "low-density." Each type has > its property profile, with cross-linked high density polyethylene usually > the stiffest, and least flexible. (Inexpensive poly bottles are usually > linear, low-density polyethylene.) Reasons for the differences? We don't > want to go there ... this is a family-oriented list! <G> If anybody wants > to know more about polymers, check out some of the links at this URL: > http://pw2.netcom.com/~uncleal0/net2.htm (ignore Uncle Al's politics -- > his knowledge of chemistry is, however, impeccable). > > c. Age. Yeah. This is probably the biggy. Just like our own collagenous > tissues, practically every plastic stiffens with age. [This applies > equally to epoxy/polyester/vinylester/you name it - based polymers, though > epoxy seems to be more resistant than the others, *if UV damage is > minimized.*] The main factor is probably gradual loss of the random > arrangement of the polymer chains. As they pack more efficiently, they > more closely resemble an ordered crystal. Thus, they become more > "crystalline," and are much less resistant to breakage from mechanical > shock. Loss of plasticizers and oxidation of the polyethylene contribute. > > Bottom line: all our boats are aging, with polyethylene boats perhaps > having the shortest lifetime. Hank Hays, and others, however, can no doubt > attest to the fragility of well-aged polyester layups, which use styrene as > a copolymer adduct / plasticizing ingredient. -- ----------------------------------------------------------------------- Ralph Diaz . . . Folding Kayaker newsletter PO Box 0754, New York, NY 10024 Tel: 212-724-5069; E-mail: rdiaz_at_ix.netcom.com "Where's your sea kayak?"----"It's in the bag." ----------------------------------------------------------------------- *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
rdiaz_at_ix.netcom.com wrote: > [snip] > I wonder if some other factors should be added. > > Thickness of the material. The walls of a polyethylene boat are of x > thickness. That would likely mean that they would age a lot faster than > say the half inch thick high density polyethylene cross ribs used in > Feathecrafts. Yup. And, sea kayak hulls are normally thicker than the usual PE bottle's walls. > Length of the material in conjunction with how much it is subjected to > flex. I sense that polyethylene white water boats (except for the hard > knocks they get against rocks etc.) tend to last a bit longer than their > sea kayak counterparts because of the differences in length and amount > of flex. Both valid points, Ralph. I suspect thicker materials such as the Fcraft ribs will outlast you or me! (Are they polyethylene? I believe Folbot frames are a filled polycarbonate -- much more long-lasting than PE.) The plastic equivalent of "work hardening" in metals probably makes our longer craft have shorter lifetimes than the WW boats. I agree. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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