Incresing Tensile Strength of HDPE

We are manufacturing HDPE water pipes. We want to use HDPE pipes for Submersible Bore Wells. For this we want to increase the tensile Strength of HDPE pipes.

Please fetch me information about additives that can increase tensile strength of HDPE pipes.

with thanks,
Sachi

 

[Demon3]

Sure, put some filler in the PE. For example mica or glass fiber. See

http://www.matweb.com

for specific properties and suppliers of such materials.

 

[TCrawley]

Hi K.P.Sachidhanandhan,
I am using HDPE in one of my products, and we are using a 5% talc content, as recommended by the manufacturer. It took the HDPE from a semi soft state and made it closer in strength to ABS. My product has a snap fit design and the softer HDPE was just pulling apart. The 5% talc made an astounding difference. Check with the manufacturer of the raw material to get the specified percentage of talc to use in your project.
Good luck.

 

[Demon3]

Adding any filler will help modulus (chalk, talc, mica, glass fiber). Only the latter three will increase the tensile strength. Talc is on the borderline, a good very platy talc can help but some grades of talc are less platy and will actually decrease the tensile strength. Unfortunately, adding a filler will affect the other properties. In particular the impact resistance may drop by a large amount even for small filler additions. The more anisotropic a filler is the more it helps modulus and yield strength but the more it hurts impact resistance.

The large effect of talc noted by the previous poster is probably due to the fact that small amounts of fine talc can nucleate crystalisation of some polymers (PE, PP, nylon). That is probably why he saw a large effect for just a small amount of talc.

 

[VANSIL]

What about using wollastonite to help improve tensile properties? This mineral is needle-like in shape and has a long history with many PE's and engineering thermoplastics for improving overall mechanical strength.
There are several options as to types. If this is a consideration, I will be happy to make grade suggestions or have further dialogue.

 

[Demon3]

Yes, I didn't mention wollastonite but it will work as well, very similar to mica overall in performance except mica has the advantage of increasing strength in two directions in the material whereas wollastonite will only increase it in the direction of the fiber orientation. To get the full strength increase you will need to optimise the aspect ratio of the filler and try additives that promote adhesion between the filler and the matrix. Top suppliers include Nyco and RT Vanderbilt.

 

[patprimmer]

To increase the tensile strength in the direction of the axis of the pipe, glass fibre will be best.

To do it in the circumferential direction, mica will be best.

Wollastonite is a fair to good value for money reinforcement if moderate gains are acceptable. I think it gives gains in both directions, but somewhat more so in direction of flow.

The higher the aspect ratio of fibres and the longer they are in relation to wall thickness, the more they align in direction of flow, and therefore the more they reinforce the material in direction of flow at the expense of reinforcement in other planes.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dwightdixon]

If you want to get circumferencial as well as machine direction improvement in the properties of rigid pipe you might look into using a process developed and patented when I was at Baxter Healthcare. You could check to see if the patent has run out and you would not have to license it by checking the Patent office website.

It basically using a spining pin or bushing in the extrusion die to make the filler and polymer orient in a diagonal direction around the tube as it is extruded. Works good on flexible tube to increase kink resistance also. If you want more data send a personal message to me.

 

[Demon3]

Nice tip and good idea!