The whatsit point.

You could try vicat softening point (ASTM D1525) or deflection temperature under load (ASTM D648)

http://www.matweb.com/reference/deflection-temperature.aspx

Glass transition temperature.

I have the exact issue with PVC pipe. Suggestion on temp would be great. I was also looking at boring out the ID as Wall thickness was not an issue. Any suggestion would be great.

Pure organic substances have a "melting point" - an exact temperature at which they liquefy. This is used in chemical analysis. Polymers and plastics have a "softening Point" as the change is gradual. Some polymers have a memory - and although they can be distorted under temperature they try to return to their original shape when cooled some just stay put - as used in blow moulding. You need to establish if the plastic you are dealing with has a memory. If you need to shrink plastic tube onto another tube then some memory is useful. Heat the tube until it is soft enough then insert the other part in it. If you get a firm grip then it has shrink-wrapped itself on and you are in business - if it is loose then you are in trouble and will need a different plastic or a sealant.

Some clarity here.

We're talking about thermoplastics. Thermoplastics soften when heated and can be extruded or molded or vac-formed. The Tg of thermoplastics is not as easily defined as with a thermoset, both polymers.

All thermoplastics try to return to their relaxed state. All thermoplastics have memory.

If you vac-form a hemisphere using PVC, it will eventually return to the flat shape it had before it was heat formed. Heating it up will speed the process.

The same is true of extruded PVC pipe. You can heat and stretch it and get it in the ballpark, but depending on the environment, it will try to return to it's original configuration.

Cheers

Then how come plastic bottles keep their shape when cooled?

Because "normal" temperatures are not hot enough to cause the plastic to revert to it's pre-molded form.

NOW I AM COMPLETLY CONFUSED!!!

No need to shout.

Polymers can be divided into two groups, generally. Thermosets are the two part kind that you mix together. They harden by virtue of a chemical reaction between the two chemicals mixed. Heat speeds the curing process. Some of these compounds even make their own heat. Exothermic reaction. Some require heat. Endothermic, they're called. Thermosets don't melt if heated. They get softer, and once beyond their Tg will expand rapidly and loose strength. Once cured, they cannot be reused, as can thermoplastics.

Thermoplastics are solids that get soft when heated and can be molded. When heated again they can be remolded. Since no chemical crosslinking takes place(as with thermosets) their molecules are free to "slide" over each other, under pressure and heat and can be formed into useful objects, such as pop bottles. Heat the pop bottle enough and it will revert back to a flat mass.

Heat the bottle as much as you like you will get a mess - some plastics have a memory at certain temperatures - problem with acrylics in the paint world.

Back to the original - some substances do not have a melting point no abrupt change eg ice/water - they just get softer when you heat them they generally get more liquid as you heat them until they decompose.

Thermoplastics (as defined!) do not change viscosity with heat - no softening or melting point - they will just decompose. Off subject!

Sorry I don't shout - I am just a rotten typist !

Skelley,

Yup! That'll do it.

Keep it simple.

How many do you need to do? Do you need to automate it?

"droop" springs to mind.

Cheers,

Stu.

Hello Stueywright:

You say 'droop'?...........I have that problem all the time!

Take care.................

I think the point should be "Vicat Softening Point "or "Glass Temperature"(Tg)

But the Vicat Softening Points are different from material grades,so you should tell us what grade of polypropylene(e.g. PE-10GF Polyone ) is going to be used.

Nice job! I thought I even saw "the whatsit point" referred to in there.

LL

Sorry for showing up late.

I have a small book that gives reference data on PP blown film extrusion.

Three temps are given;

1. Crystallization, 110 °C
2. Melt, 200 °C
3. Frozen Line, 90 °C

I would start around the 160° mark by Corraussians link in post 1.