which manufacturer uses the strongest plastic?

thats a tough one. Just because a manufacturer buys a good plastic does not mean they process it well, and it could come out crap - as it often does.

Even though I work for Dragorossi, I have no problem saying that Prijon and Eskimo have the strongest plastic. Pure strength - all other issues aside, they come out on top.

The flip side to this is, the process they use make it very difficult to mold good shapes. even simple thing like a cockpit rim that doesn't leak, or break, or make your skirt pop all the time is tough. The molds are expensive, so the designs are usually out-dated, and even when the designs are brand new, the shapes are not as good as rotomolded boats due to the process. But they are strong, and thats what you asked.

Dragorossi has the next in line, for sure. While the impact (pure impact strength) is not quite as high as Prijon's HTP, the Dragorossi HDTP plastic is the toughest rotomolded plastic out there. This means we can mold complex shapes and have high impact. After that, most of the superlinears are very similar (in fact everyone from Dagger, to Riot, to Wave Sport etc all use the same plastic from the same supplier, though not all cook it as well). Crosslink is also strong, and in fact in pure impact tests, is probably similar to HDTP, but its nowhere near as stiff, so while the plastic is high impact, a wobbly flexing boat is not much good.

Hope this answers your question

Corran

There was a pretty long thread on this a while back, and basically ended up with people arguing over their favorites, the final outcome being that they are all pretty much made the same, it really just depends on how you treat them. One nice thing about Wavesport's plastic that may be true for other companies, i'm not quite sure, is that if you get a dent, you can put it out in the sun, and it will go back to its original shape, but the guty I bought my boat from used it in the ocean all the time without rinsing it, so now whenever I put in, I leave more plastic than there is at a britney spears concert.

Here is some great information on plastic:
Linear High Density PE is one type of plastic and companies use it almost exclusively. Prijon, Eskimo, and Jackson Kayak use different materials. Jackson Kayak uses Cross-linked High Density Polyethylene. to sum it up:

YOu can stretch it twice as far as the best linears with out breaking. It has the best wear characteristics (last longer before wearing thin) and has memory for when you bend it, it goes back to its original shape better.

here is what the experts say:

JUDGING PERFORMANCE OF A POLYETHYLENE PRODUCT
A brief discussion by Dr. A. Brent Strong, Lorin Farr Professor of Entrepreneurial TechnologyProfessor of Manufacturing Engineering TechnologyBrigham Young University (Originally prepared April 2000)

Summary of Criteria Used in Judging Performance of a Polyethylene Product
The overwhelming consideration in specification and final judgement on any product is performance in actual use. While other considerations such as processing ease and raw material cost are also important, these dim in importance if the part will not perform as required. Ultimately that performance can only be judged by monitoring the part in actual service, under real conditions. Some applications, such as storage tanks, require that the part perform flawlessly for very long periods, often many years. Therefore, laboratory tests have been developed to give indications of long-term performance. These laboratory tests should be used in combination with actual performance data as it becomes available, and with an understanding of the molecular behavior of polymers so that the nature of failure and survival can be understood and improved. Therefore, the basic nature of polymers, laboratory data, and real performance experience, will all be examined so that these criteria can be combined in judging and predicting the performances of both various polyethylene products. General

Understanding of Polymers
Polyethylene is a polymer – a material composed of many long molecules that are highly entangled about each other. The molecules of polyethylene are made of a backbone or chain of carbon atoms with hydrogen atoms attached to each carbon on the backbone. Occasionally short carbon and hydrogen branches can also be attached to some of the backbone carbons. This material, the first type of polyethylene made, is called branched polyethylene. If only a moderate number of branches are present and the branches are relatively short, the polyethylene molecule is called linear polyethylene – reflecting the general domination of the linear backbone. If the branches are even scarcer, the material is called high-density polyethylene (HDPE) because the molecules form extensive crystalline regions and that increases the density The physical and mechanical properties of polyethylene are overwhelmingly dominated by the interactions or intermingling between the polymer chains. Generally, the greater the interactions, the better the properties. This is understood by realizing that as the polymer chains interact, they are separated less easily, thus making it more difficult for cracks to form between them; the force needed to pull them apart is increased, thus increasing strength and stiffness; and their ability to dissipate impact energies is improved, thus increasing toughness. Other properties are increased as well. Therefore, to improve performance, polymer resin manufacturers and molders have consistently worked to increase the amount of interactions between the chains. One method to increase chain interactions is to increase the length of the chain or, in other words, the molecular weight, which simply increases the amount of entanglement between polymers. Early polymer performance was adversely affected by the inability of polymer manufacturers to achieve high molecular weights. Gradually that problem was solved but then it became apparent that if the molecular weight was increased too high, the polymer could not be processed well. As a result, a compromise was made between property performance and processing capability. For many products, that compromise was acceptable. However, for applications where long term performance is critical, such as storage tanks, insulation for electrical and telephone wires, tubing and pipes for irrigation, and many others, the compromise invited a serious problem. Long-term exposure to the environment often resulted in massive cracking and total product failure. The problem was simply that the polymer chains did not have the amount of interaction required to give long-term performance. The problem (dilemma) was to increase polymer interactions while maintaining processing capabilities.

Solving the Dilemma of Optimizing Polymer Length for Processing and for Properties

A breakthrough in polymer processing provided the solution to the dilemma. This breakthrough was to crosslink the polymer after the part had been formed. Crosslinking of polymers had been known for many years, as a technique to improve properties in thermoset polymers, but was always done during forming, never afterwards. The concept of forming a part and then crosslinking it was brilliant and highly successful. Crosslinking is simply the formation of bonds between the polymer chains. These bonds, equal in strength and stability to the principal bonds along the polymer backbone, tie the polymers together, thus dramatically increasing molecular weight. In fact, the length of the polymer chains and, therefore, the physical properties, are much better than can ever be achieved without crosslinking. Several methods were employed to crosslink the plastic after it was formed. One method was to use peroxides and crosslinking agents, much like the technology used in making high performance aerospace parts and fiberglass reinforced plastics. This method was especially well suited to parts made by rotational molding and casting. Another method was to crosslink using electron bombardment – a method especially well suited to parts made by extrusion, injection molding and blow molding. Both crosslinking methods have proven to be highly effective in preventing stress cracking, and have enhanced many other physical properties. The advantages of crosslinked polyethylene are evident in the plastic molding process called rotational molding or rotomolding. In this process a weighed amount of non-crosslinked resin powder (which contains the materials required for later crosslinking) is laced into a mold, the mold is closed and then rotated inside an oven. The powder coats the inside surfaces of the mold as the mold gets hot, fuses together, crosslinks, and then solidifies as the mold is cooled. The initial low molecular weight of the non-crosslinked resin is a great advantage during the early stages of processing to help the resin particles uniformly fill the mold, melt, and fuse together. Then, when the part is fully formed, the crosslinking occurs, thus building molecular weight and enhancing the physical and mechanical properties. The additives required for crosslinking and the longer processing time generally add cost to crosslinked parts. When using linear polyethylene, compromises must be made. With linear, it is not possible to have short polymers for processing and then long polymers in the final part because the molecular weight of the polymer does not change during processing. If the initial molecular weight is increased to achieve long-term performance, problems can be encountered in properly filling the mold, in achieving proper part definition, and in fusing the particles together so that no porosity is present. Although linear could, in theory, also be crosslinked, the nature of the resin has resisted effective crosslinking. One further problem with linear has recently been discovered. Linear is susceptible to degradation if held at high temperatures for extended periods, as might be the case if heated too long in rotomolding. Therefore, crosslinked polymers have been found to also be more forgiving in processing than linear. Recent advances using metallocene catalyst systems have resulted in improved properties for both crosslinked and linear resins, although the differences based on molecular weight are still present.

Product Performance Testing
The ranking of polyethylene products in key laboratory tests is just as would be expected from considerations of molecular weight and polymer interactions. Crosslinked parts are better than linear, and linear is better than no crosslinking at all. Crosslinked parts will resist environmental stress cracking more than 15 times longer when compared with linear and with non-crosslinked parts (>1000 hours versus 72 hours versus 47 hours in ASTM D-1693). Izod impact toughness is more than 5 times better in crosslinked parts when compared to linear (17.0 versus 3.3 ft-lb in ASTM D-265). The resistance to crack growth is 10 times better in crosslink than linear (>1000 hours versus <10 hours in ASTM F-1473). The actual, in use performances of crosslinked parts have been closely monitored for many years and, in
general, have confirmed the superiority of the product as indicted in laboratory testing. Therefore, when longterm performance is required, the insistence on using crosslinked resin is strongly recommended. Additional information on this subject can be obtained from the book Plastics: Materials and Processing, 2nd Edition, by A. Brent Strong, Prentice Hall Publishers, (2000).

Pretty interesting stuff. Shot for the info EJ. There are many companies making tanks, including here in SA, and therefore a fair amount of work and research has gone into it adn therefore info. As an engineer, I found this pretty interesting, although not entirely conclusive of course:

www.polyprocessing.com/pdf/technical/LPEvsXLPE_Report_1.pdf

Cross linked seems to be more ductile and linear more brittle. Is that correct?

I also note that the density of the resin can increase during the moulding process and I take this as a good thing. True?

I found this particularly interesting:

www.safetanks.com/molding.html

Seems that cross linked is the better way to go? Or am I wrong? What about the higher melting point of cross linked? More energy required to manufacture the product? Chemicals released during the process harmful to the environment and labourers?

But only one question needs to be answered. Why isn't everyone using cross linked? ;grin: It does seem like the better way to go.

would this cross linked stuff resist big gouges more than others as my dagger juice has got some pretty nasty gouges in it. I dont think dagger use cross link or am i wrong?

The nice thing with statistics, is that if you torture them long enough, they'll say anything.

It is possible to search the net, and find information that would petty much support any plastic over any other, if you are willing to take the time, and then post that as fact. No matter what you're going to have opinion.

However, when looking at plastics, you have to look at MORE than pure impact. For example, flex of the kayak is just as important as its ability to resist impact. if it's flexy, then you're not going to have your boat paddle the way the designer intended. if the plastic is very strong, but limits the shapes that can be made, then the designer can;t design what he wants, even if the plastic is super stiff.

As I said, I paddle for Dragorossi, so take my bias as you like, but I think that you'll be hard pressed to find anyone that disputes the impact strength, and stiffness of Prijon/Eskimo plastic. It's simply stronger and stiffer, period, because the molding process thats used. However, this same process seriously limits shape that can be molded. Thats teh trade off.

Most manufacturers used to use Crosslink. All moved away from it. Cost is not the issue... crosslink is a few cents more for some colours, and a few cents less for others. It's harder on the molds, and back when we were making 10 000 kayaks out of one mold, this was an issue. Nowdays, you get 1000 to 3000 and the design is retired, so wear and tear is irrelevant. Crosslinks ability to return to its original shape after a serious distortion is slightly better than superlinear. So if you totally bend your kayaks around a tree and its a folded letter, then chances are that crosslink will have a better chance at returning to its shape with less dammage. But its going to be a minimal differance.

The real advantage of crosslink over superlinear (any superlinear) its its resistance to chemical degradation. Thats what its for. Making gas tanks for industrial machenary, or things like chemical tanks (pesticides) etc. its ability to resist chemical attack is significanly higer than superlinear. This is what its formulated for and used for. Another area where its used is any area where the plastic is subjected to excessive hear. As a thermosetting plastic, once its molded, it cannot be melted down, making it great for housing chemicals that are exposed to heat.

But kayaks are not exposed to these chemicals, or heat. The real advantages of crosslinka re thus totally lost on our application. However, crosslink is SIGNIFICANTLY less stiff than even the basic superlinears. And this IS an issue for kayaks. Kayaks need to be strong AND stiff. And pretty much every superlinear out there beats crosslink hands down with reguards stiffness.

I would agree with EJ that the impact resistance of crosslink is generally slightly higher (in application) than that of most superlinears. It's close enough however that how the plastic is cooked by the manufacturer is more significant than which plastic was chosen first.

If its any indication, Dragorossi has had less than a dozen returns (breakage) since 2004. Pretty much anyone you talk to who has one will rave about the impact resistance, and wear resistance of the plastic. Is it as good as Prijon. Honestly, no. Its not. But the other advantages our process has, combined with the really high impact and wear resistance, AND stiffness, pretty makes the HDTP the best overall, combined choice out there.

Pure stiffness and impact. Prijon/eskimo.

Pure resistance to chemical degredation. Crosslink

But for all of it, HDTP is pretty ahrd to beat, and the track record speaks for itself

Corran

I have boats made of bolth types of plastic. On the river when boat meets rock the closslink holds up way better.

Both types pf plastic? Thats a very broad, and misleading statement.

Corsslink and Shulmann Suplinear? Suplerlinear molded by whom? Riot? Dagger? Wave Sport. Who molded the plastic is far more important than which plastic we're talking about. Or are you talking about Robson (as I understand it they're using a less stiff superlinear than the others). Or Dag? Or HDTP made by Dragorossi. I'll take the pepsi challenge any day with HDTP against Crosslink for overall performance (stiffness, impact strength, wear combination).

Stack HDTP against anything but Prijon/Eskimo, and it'll come out on top. The advantage of HDTP over Eskimo/Prijon is the ability to mold better shapes even if I will always conceed their plastic is stronger for pure ability to resist a massive hit.

I molded crosslink boats for a decade. Crosslink is readily available to me now, for the same price as HDTP (or slightly less actually). I'll take HDTP over crosslink, and even prijon, because it makes a better overall kayak, all things considered.

On the other hand, if I ever go boating in a toxic sewer, I'll be sure to get a crosslink boat for that

Corran

While we're having this chat can someone tell me if the reason Jackson boats seem to be lighter than most boats is because of crosslink plastic or somthing else.

Thanks

Less outfitting basically. But with thier new outfitting they're not really any lighter than the DR with perfomance fittings...

anyway, making light boats is not that hard if you don't mind the hulls felxing .

Corran

What about the toxicity of the fumes when moulding cross linked?

I've paddled both and have to say cross-link is way more tougher and stiff (at least in my jackson, maybe because of the core compostie beam). I find linear to be very brittle and easy to break, but an advantage is it can be welded. Eskimo and Prijon's blow moulded stuff is good but way too heavy

Toxicity of Cross-link fumes?
www.jacksonkayak.com/upload/podcasts/podcast200705262.mp3
EJ says stuff in there about the fumes.

i have to say that jackson has a really bad plastic, but of course i mean michael )

cebela, do you realise you just revived a thread nearly 2 years old...just to make a (very sad) wise crack?