Posts Tagged ‘polyethylene’

UHMWPE (Ultra-High Molecular Weight Polyethylene) often abbreviated as “UHMW” is one of the most popular and well known industrial plastics. UHMW is seen as a “Jack of All Trades” in many applications while being more available and less expensive than other plastic options. While this is true to a degree, UHMW has limitations that means it will not solve all problems in all situations. In fact, it has some properties which make it deficient and the “DIY” community should keep this in mind.

When to use UHMW:

UHMW excels at taking impact and it is virtually unbreakable, it’s also very slick and the colder the operating temperature is, the better it performs. This is why UHMW is so popular in applications such as toboggans or as rails on sleds: impact + cold + slickness are all important to the application, and it does really well in this application. UHMW is also easy to work with as it drills, saws, and lathes well. It functions as wear pads, sliding blocks, fenders, and in other impact absorbing applications.

When NOT to use UHMW:

The main application we here at Redwood Plastics see UHMW incorrectly used in is bearing applications. UHMW is a poor choice as a bearing for two reasons:

1.) it is difficult to machine to tight tolerances (+-) 0.02″ are the best you can usually hope for and

2.) UHMW has low load bearing capabilities (500-800PSI). In a DIY bearing application nylon or Tuffkast will be superior.

The issue with tolerances is important to hit home: UHMW is not a dimensionally stable material. Not just compared to metals but even compared to many other plastics. We regularly receive drawings and requests for UHMW parts where we cannot quote based off the requested tolerances (or have to get a written waiver for acceptable tolerances). This lack of dimensional stability extends to thermal expansion and contraction which is why it is so hard to guarantee tolerances: if the part is manufactured in 30 degree weather but used in 90 degree heat the dimensions of the UHMW will drastically change!

We hope this points you in the right direction if UHMW is or isn’t right for your project. But if you have questions, or might be wondering what an alternative material could be, please contact us and we’d be glad to help!

UHMW polyethylene has countless applications for the DIY community but as we head into winter there is one simple application that we have to highlight on this blog. That is the UHMW plow blade for snow plows. Let’s not over-complicate things: this is just a UHMW strip with some holes drilled in. But in order to get what you need, you need to know what to ask for! First of all know that the material you likely want is the reprocessed-black UHMW grade. While being less expensive than the natural grade, the cross-linking in its production actually improves wear properties. A nice bonus when you’re also saving some money.

You also need to know what thickness of blade you want. In general, the blades are almost always 1″, 1.5″ or 2″ thick with 1.5″ being the most common. If you don’t know what you need, pick 1.5″. Many plastic companies will pre-drill holes for you if you need them for a fee (usually about $80.00) but we would recommend you do not. Firstly to save money, secondly you need to remember that UHMW is not a dimensionally stable plastic. Changes in temperature may expand the blade from when the holes were drilled meaning by the time you get it – the holes don’t line up! To avoid disappointment we recommend you do the drilling if at all possible.

If you have questions about UHMW snow plow blades please contact us.

SAMSUNG

SAMSUNG

Plastic synthetic ice is an increasingly popular “do-it-yourselfer” project for hockey fans. The ice allows year round training regardless of weather conditions. This blog is supported by Redwood Plastics, a plastics distributor, and increasingly we’ve had “synthetic ice” inquiries that actually refer to two different applications. “True” synthetic ice is a skating surface and the application can take a couple forms. Primarily training arenas will have the player suspended by a harness while skating on a single sheet. Because synthetic ice requires about 20-30% more effort to skate on, this improves strength and conditioning. The other format is having a full rink of sheets essentially as a replacement for ice.

There are two types of plastic used for this. One is HDPE polyethylene that has additives to make it optimal for skating, this would be “true” purpose-manufactured synthetic ice. Secondly, white-virgin UHMW polyethylene sheet is used. The UHMW is slicker and stronger than the HDPE but, as you might expect, it’s more expensive to the tune of about 25% more. The issue you need to solve as a “diy’er” taking on this project is how to make your rink. The sheets are just that – flat sheets.

There’s no set hardware for the application, though synthetic ice specialists may be able to offer some help. Otherwise you’re on your own and you essentially need to find a way to put the sheets together, tightly, but without hardware or holes sticking about the surface of the sheet. Usually this means the sheets are placed in a cavity that holds the sheets together and prevents them from moving. For example, a frame made of 2×4 wood bolted into the ground along the perimeter. Do not listen to what you might hear on the internet: adhesives or glues for the sheets will not work!

The second reason people approach us as a distributor for synthetic ice is for a simple platform to shoot pucks off of (or at). In this case, the customer requests UHMW polyethylene or ‘synthetic ice’ but they don’t really need that. It’s “overkill”. Truth is, a cheap plastic sheet – HDPE puckboard – will work just fine in this application, taking a beating and still slick enough to shoot pucks off of (but not skate on). When you’re working on a synthetic ice project you really need to know what you’re looking for!

For more information contact us.

 

UHMW Toboggan Super Sled

Posted: December 2, 2014 in UHMW
Tags: , , ,

It’s winter and it’s cold through much of North America. But if you can’t beat the deep freeze you might as well have fun with it, right?

One of the most fun – and easiest – industrial plastic projects you can work on for winter is a UHMW toboggan. Snowmobiles and dog sledders know well the benefits of UHMW polyethylene for sled tracks. UHMW is economical compared to other industrial plastics and has a very low coefficient of friction combined with no water absorption. In short, it will make your sled glide smoothly over the snow and ice. In fact, UHMW is a cryogenic plastic meaning that its properties actually improve in cold temperatures. But while sledders bolt UHMW rails to the bottom of their metal rails an entire toboggan can actually be made out of UHMW.

It’s simple too, information is widely available on the internet. Essentially you need a sheet of UHMW (natural-white seems to be used the most) about 12″ x 120″ long and 1/4″ thick. This will set you back about $90.00. Next, you need some rope and some 1-2″ wide x 12″ long wood (to be orientated as spars across the UHMW strip) and finally, some flat ended bolts. You tap the wood for the bolts, affixing theme to that the head of the bolts touches the snow (there will be less friction that way). The rope is particularly important to bend the front of the toboggan to produce that signature curl…And that’s pretty much it. You just need some snow and you’re on your way!

Information, tips and instructions are widely available on the internet but here are a few pictures of how a successful design should look:

Toboggan_1

 

 

 

 

 

 

 

 

 

 

 

Toboggan_2

 

 

 

One underrated plastic for use by “do-it-yourselfers” is HDPE (high-density-polyethylene) puckboard. Puckboard is an economy-grade plastic sheet that is excellent for a number of projects. Puckboard is durable and aptly named, as it is the material used in ice hockey rinks. It can take impact from everyday life such as body contact and its smooth surface means the material is easy to clean. You will often see it installed in farms providing a low-maintenance wall covering. You may also see it used as a covering to protect walls from dogs in various kennels. The two colors you will most commonly available are white and black.

The material is easily fabricated using household tools. When cutting, a saw with high RPMs works best, most commonly a jigsaw – at least that seems to be the anecdotal consensus online. Table saws also run at high RPMs and as long as you have proper support for the sheets, they will cut accurately. It is common when cutting plastics for the edge to melt a little due to friction so keeping some medium to heavy grit sandpaper on hand to smooth the edges and to deburr, is a good idea.

Puckboard

Livestock pen in Alberta

Affixation to a wall or substrate should be done mechanically – meaning use bolts or screws. Polyethylene does not “glue” or work well with adhesives, and a 4′ x 8′ x 1/8″ sheet, even that thin, is still 40 lbs. When you do drill your holes, oversize them by 1/8″ to account for thermal expansion. Another thing to keep in mind is that white puckboard is not always UV-stable. Any reputable distributor you contact can tell you if theirs is or not. If not UV-protected, it will degrade in outdoor applications but may provide a short-term fix for a few years as long as occasional replacement is not an issue in the application.

Finally, let’s face it – when you’re working on a home project budget is a concern and industrial plastics can be pricey. But it is common to find full 4′ x 8′ puckboard sheets for less than $100.00 each even in remote areas. Distributors often keep it stocked due to its popularity, so the long lead times associated with other industrial plastics, is usually not a concern.

For more information contact Redwood Plastics.

 

 

 

 

 

This one is in honor of the never-ending North American winter of 2014. Yes, it’s almost spring, but does it feel that way?

UHMW (polyethylene) plastic is one of the most affordable and versatile of the mechanical/engineering plastics. Two of its properties are a very low coefficient of friction and zero moisture absorption. In fact, it is so slick it makes excellent synthetic ice for skating rinks. UHMW has been used for decades in arctic regions as sled rails; however, it works very well on recreational toboggans as well.

UHMW_SledThe toboggan pictured here was built by an enthusiast of the Boundary Waters Canoe Area Wilderness (BWCAW). This is a protected area in Minnesota, which (apparently) has some excellent sledding! The material used appears to be the black reprocessed UHMW.

However, a simpler option may exist, especially if your toboggan is metallic. 1/4″ or 3/8″ thick UHMW sheet comes in a standard 4′ x 10′ size. Ten feet is a significant length and it means a liner that you can affix to the bottom of the sled can be formed out of a single sheet. In the case of the toboggan pictured, the sled builder sold another length cut out of the same sheet to his friend.

If you have the correct tools, it is possible to counter sink holes in the bottom of the sheet and then affix with bolts to the existing frame of the toboggan. The additional slickness will make for one great ride!