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Struggling to determine the difference between UHMWPE and HDPE Sheet

 

There are many myths, miscommunications and misconceptions surrounding HDPE and UHMWPE sheets within the Australian and New Zealand markets. Let's start by asking, do you know what grade of Polyethylene you currently use? HDPE CoPolymer, HDPE HomoPolymer, UHMWPE, Recycled UHMWPE (Regen), Pressed only UHMWPE or Pressed and Planed UHMWPE? Confused?

Each of these materials have unique properties that if not chosen correctly will cause significant detrimental impact on the life of the applications in which they are being used hence the importance of :
a) choosing the correct grade
b) ensuring that you are being sold the correct grade

This special edition Solutions newsletter will tear through the miscommunications and myths while drilling into the truth about these two brilliant and universal materials. It will also explain how to identify these materials both visually and through simple test methods that can be conducted using a 20 cent piece.

HDPE CoPolymer (Polystone P300 - Dotmar's trade name for HDPE)
Supplied by Rochling, the number one manufacturer in the world of Polyolefins, Polystone P300 is produced using a first grade, CoPolymer HDPE resin. This special grade resin within Polystone P300 exhibits properties that are far superior to HDPE HomoPolymer materials offered locally through some other distribution channels.

The outstanding properties exhibited by Rochling's CoPolymer HDPE provides peace of mind in terms of performance for :
- Design and manufacture of tanks and vessels for chemical storage applications
- Finished parts for food applications i.e. chopping boards (FDA compliant)
- Engineered applications in high impact environments
- Wear parts

Polystone PG100 (Pipe) HDPE
Polystone PG100 exhibits outstanding properties that deliver tangible benefits to the fabrication industry. Polystone PG100 (Pipe Grade) is approved for chemical engineering and tank building and meets the strict requirements set for pipe grade PE100. Offering peace of mind in terms of performance and safety, Polystone PG100 is the logical choice.

Why Polystone PG100 (Pipe Grade PE100):
 - 100% weld integrity with PE100 pipe
 - Exceptional weld strength
 - Degauge material from *P300 (PE80) and standard HDPE
 - Superior acid resistance
 - Weatherproof with exceptional UV stability
*Manufactured in accordance with PE80 guidelines
HDPE HomoPolymer
HDPE HomoPolymer sheet is a general purpose HDPE sheet manufactured from lower grade resins and more suitable for non engineering applications such as interior panelling of vehicles, ducting fan housings or protective mats and liners for utes/vans. This material is not recommended for chemical storage, high impact or high abrasion applications. HomoPolymer HDPE has high rigidly but very low crack and impact resistance when compared to HDPE CoPolymer (Polystone P300 and Polystone PG100).
UHMWPE (Polystone P7000, 8000 and Matrox - Dotmar's trade names for UHMWPE)
UHMWPE sheet is manufactured by pouring powder into a large mould (6000 x 2500mm mega press). A large press with a heated bed and top plate is then used to force the powder into sheet form. Ultra High Molecular Weight Polyethylene (UHMWPE) is the great all rounder in thermoplastics. It has extremely long molecular chains, with a molecular weight numbering in the millions, usually between 2 and 6 million.

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Rochling Polystone UHMWPE sheet and rod exhibits a molecular weight of 9.2 million which is significantly more than other commercial grades of UHMWPE available. This results in an extremely tough material that exhibits an impressive array of characteristics. A higher molecular weight of Polyethylene has a significant influence on important technical properties such as wear resistance.
To further convey the wear characteristics of the Polystone and Matrox range of UHMWPE sheet materials they are tested utilising the sand slurry test method. The general concept of the sand slurry abrasion test is to measure the mass of material loss utilising a mixture of course sand and water.
Rochling's range of 9.2 million molecular weight UHMWPE materials have a sand slurry value of 80 whilst other materials with a molecular weight of 5 million or less have a sand slurry value of 100. This means that the lower molecular weight material has up to 20% greater loss than that of the higher Rochling grades.
UHMWPE Pressed and Planed (Polystone P7000 range, Matrox)

uhmwpe_pandp.jpgPressed and Planed UHMWPE sheet offers significant advantages over a standard pressed UHMWPE sheet. The main characteristics of pressed and planed UHMWPE is its uniform tolerance of -0/+4mm up to a thickness of 200mm. Once the sheet has been allowed to cool following the pressing process, it is then planed to ensure that the correct thickness and tolerance is achieved depending on the size selected. A planed flat sheet with a small tolerance has less stress built up in the sheet, will not curl when machined correctly and has lower friction properties for sliding parts. Planing the UHMWPE sheet also allows the internal stress to be mostly removed providing a more stable material to work with. 

Pressed and Planed UHMWPE sheet can be identified by the small arc type planing marks on both sides of the sheet as shown in the picture above. It is due to this planing process that Pressed and Planed UHMWPE sheet is often slightly more expensive than other unplaned grades.

Recycled UHMWPE (Regen)
regen.jpgRecycled UHMWPE often referred to as Regen is the lowest grade of UHMWPE available. Regen has a molecular weight of 4 million which has a significant negative impact on its sliding and abrasion performance. This material is generally an unplaned and poor quality UHMWPE sheet. Regen is not suitable for low friction sliding applications or food contact but is generally used in areas that do not require the unique properties of Pressed and Planed UHMWPE such as ship fenders and ship rubbing strips. Regen is easily identifiable by the multiple spec like colours shown within the sheet as shown in the picture above. If you suspect that the sheet that you are using is a Regen grade and not Pressed and Planed virgin grade, please contact the Dotmar sales staff in your region to assist with correct selection.
Pressed only UHMWPE
Whilst manufactured in the same way as Pressed and Planed sheet, Pressed sheet cannot achieve the low tolerance due to the removal of the planing process. Unplaned sheet can vary in thickness from -4/+10mm across the length of the sheet. This can mean that for a 100mm sheet, one side of the sheet may measure 96mm and the opposing end of the sheet 110mm. Unplaned UHMWPE sheet can create problems when machining due to the unflat surface and internal stresses that cause the sheet to curl. Pressed only UHMWPE sheet can be identified by the lack of small arc type planing marks on both sides of the sheet.  

Identifying HDPE over UHMWPE

To identify these two materials can be difficult but a simple test using a 20 cent coin is a great start.

Simply drag a 20 cent coin over the materials sheet surface. If the 20 cent coin digs into the material leaving a jagged indentation it's most likely HDPE (see below).
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If using the same 20 cent coin over the sheet surface the coin digs in but flows smoothly over the sheet, then this suggests that it's UHMWPE (see below).
uhmwpe1.jpg

If you would like assistance in the identification of your materials then please do not hesitate to contact a member of the Dotmar team in your region.


CoPolymer Polystone P300 HDPE Properties vs Standard HomoPolymer HDPE

Higher molecular weight resulting in superior impact resistance - virtually unbreakable

Superior environmental stress cracking resistance

Superior acid resistance (up to 20 times better)

Chemical tank design to known life, resulting in increased safety

Superior, long term material strength, coupled with exceptional weld strength

Exceptional UV stability optimised and proven over 30 years for Australian and New Zealand climatic conditions

Unsurpassed machinability - excellent material flatness with no warping

Wide operating temperature of -50 to +80 degrees Celsius with no brittleness

Greater resistance to staining in food applications

Excellent insulating properties  


New to the range -Polystone 7000 AST

Polystone 7000 AST is new to the UHMWPE Dotmar range. This material has a permanent anti-static action where the electrostatic surface charge is reduced. Dust is not attracted and no electrostatic discharge occurs.

The standard sheet sizes are:
3000 x 2000
3000 x 1000
2000 x 1000
Thickness: 3mm - 100mm

Special Properties:

Anti-static action

Reduction in dust accumulation

High wear resistance

High impact resistance

Typical areas of application:

Belt Guides

Sliding and Conveying Elements

Mining

Electrical and Electronic Industries

Chemical Industry

Find out more about this product by contacting the Dotmar sales team.


HDPE & UHMWPE Industries

HDPE and UHMWPE can be used in a variety of industries. 

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