Frequently Ask Question About PE UHMW

8/3/2019 Frequently Ask Question About PE UHMW

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FREQUENTLY ASK QUESTION F.A.Q

ABOUT PEUHMW

What is UHMW PE ?

UHMW-PE stands for Ultra High Molecular Weight Polyethylene. It is

the highest quality polyethylene (PE) available, engineered for tough

jobs and a wide range of applications. It delivers savings in a number

of difficult applications. Ultra High Molecular Weight is the secret of this polymer's unique properties. Its high-density polyethylene resin

has a molecular weight range of 3 to 6 million, compared to 300,000

to 500,000 for high molecular weight (HMW) resins. That difference

is what ensures that this material is strong enough to withstand

abrasion and impact better than lower level poly products. UHMW-

PE's high molecular weight means it will not melt or flow as amolten liquid. Processing methods are therefore derived from those

of powder metal technology. UHMW-PE cannot be transformed and

molded by conventional plastic processing techniques (injection

molding, blow molding or thermoforming). Compression molding is

the most common conversion process used with this resin because

it produces a stronger, more consistent product.



Where is UHMW used ?

UHMW is a self-lubricating material which exhibits excellent wear

and abrasion properties as well as adding extremely high impact

strength. A few of the markets which would utilize these attributes

would be snowboard bottoms, package handling, packaging, foodprocessing and automotive.

What are the benefit of UHMW PE ?

The high molecular weight is what gives UHMW-PE a unique

combination of high impact strength efficient of friction and

abrasion resistance that outwears carbon steel 10 to 1 making it

more suitable for applications where lower molecular weightgrades fail.

How do you differentiate UHMW from HDPE ?

here are three tests you can perform:

Burn Test - light it with a match and smell the smoke. If it smells

like candle wax - that indicates polyethylene. UHMW does not drip

as readily as HDPE but it will drip.

Oven Test - place it in an aluminum dish in a 300 degree oven.

Regular HDPE will slump or melt but UHMW will not change size or

shape. However, it could warp or distort due to built in stresses.

Saw Test - When cut with a saw, regular HDPE gives sawdust or

filings while UHMW gives strings or nothing.



What is the temperature range of UHMW PE ?

UHMW-PE can operate continuously up to 180 degrees F and

intermittently at 200 degrees F with custom blends available to

enhance the temperature range up to 300 degrees F. UHMW-PE

can perform without degradation at extremely low temperatures

(-452 degrees F).

What are the heat characteristics of UHMW PE ?

The sustained high temperature use is 180 degrees F and the

intermittent use is 200 degrees F.

Does the UHMW PE degrade at the higher temperature ?

Not for short times but for longer times above 200 degrees F it

loses mechanical properties, abrasion and impact.

What chemicals effect of UHMW ? Water solutions are generally safe except highly oxidizing

chemicals such as bleach. Hydrocarbons such as gasoline,

kerosene, oil and grease cause swelling. Chlorinated solvents cause

swelling. Organic alcohols, ketones and acids have little effect.



How can you tell if a sample of UHMW contains regrind ?

It is hard to tell - maybe some black or other colored specks might

be present. The only way to determine is by a sand slurry test.

After that test, it would tend to feel stiffer or harder. There may be

some increase in modules. If the resin has been reprocessed many

times, abrasion and impact resistance can greatly affected.

How does the UHMW protect metal from wearing away ?

UHMW has the highest abrasion resistance of any thermoplastic

polymer. When used as a wear liner, UHMW will not cake or stick

to metal. It also offers excellent noise abatement in materialhandling applications.

It is necessary to grease or oil UHMW ?

No, UHMW is a self-lubricating polymer and requires no additional

lubrication.

How thick should UHMW liner be ?

The minimum UHMW thickness is usually 1/4". The liner should bethicker in impact areas and thinner in slide areas. Important notes:

UHMW cannot be firmly fastened to metals because of a large

difference in thermal expansion. UHMW expands five times as fast

as steel and three times as fast as aluminum and about the same

as wood but slightly more than concrete.



What is the best way to secure UHMW liner to metal ?

Fasteners are the best way to secure UHMW to metal. The UHMW

must be allowed to expand or float. Large flat head fasteners must

be used. Fastener shaft holes in UHMW must be oversized to allow

for sheet expansion and contraction.

Can UHMW be formed into a curved liner ?

Bending or folding sheet can be done efficiently above the melt

point - at 300 degrees °F. At that temperature, it shapes easily.

However, it must be fastened in the bent or folded position until

cooled.What are my installation options for UHMW ?

There are two methods of adhering - the use of pressure sensitive

systems (peel and stick) and allowing UHMW-PE to be bonded

using epoxy systems or contact cements. A traditional metal

mechanical fastening can also be used if preferred.

Can adhesives be use to secure UHMW liners ? Not for most applications. The reason is the large difference

between the coefficient of thermal expansion of metal and UHMW

puts high stresses on the bond if the bond encounters

temperature extremes.



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Frequently Ask Question About PE UHMW

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