Polypropylene question: "high heat tolerance"

[kenny1999]

The following red highlight is quoted from a website

"
5. PP: polypropylene.

PP is used to make yogurt containers, deli food containers and winter clothing insulation. PP actually has a high heat tolerance and as such, does not seem to leach many of the chemicals other plastics do."

However, as far as I understand, the melting point of PP is usually only around 100-120 degree celsius. And PP made container is not suitable for microwave oven, in that case, why it is considered to be "high heat tolerance"

 

[DaveC426913]

Good point. One must wonder if that website is objective.

I do find similar mentions elsewhere, though they do not go into any explanation as to the rationale.

Here's one possible rationale:

"A major useful attribute about thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like polypropylene liquefy, which allows them to be easily injection molded and then subsequently recycled. By contrast, thermoset plastics can only be heated once (typically during the injection molding process)."

 

[Borek]

What about: easily gets soft, but doesn't decompose.

 

[kenny1999]

What about: easily gets soft, but doesn't decompose.

Does "Decompose" mean changing to some other substance of different chemical structure?

 

[kenny1999]

Good point. One must wonder if that website is objective.

I do find similar mentions elsewhere, though they do not go into any explanation as to the rationale.

Here's one possible rationale:

"A major useful attribute about thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like polypropylene liquefy, which allows them to be easily injection molded and then subsequently recycled. By contrast, thermoset plastics can only be heated once (typically during the injection molding process)."

Do you know what is the odor / smell coming from the new PP made container? Are they vapor form of PP or any other substances during manufacturing of the products?

 

[Borek]

Does "Decompose" mean changing to some other substance of different chemical structure?

https://en.wikipedia.org/wiki/Chemical_decomposition

In the case of polymers it can mean breaking the plastic back into the monomer.

 

[DaveC426913]

Does "Decompose" mean changing to some other substance of different chemical structure?

Yes. Not only does it not decompose, it doesn't even degrade significantly when reheated multiple times.

 

[BillTre]

Polypropylene is used for a lot of lab items that can be autoclaved (121 °C (250 °F)).
Ployethylene on the other hand has a lower melting point and does not survive autoclaving.

If it is just a mold release compound on the surface, it should wash off.
Plastisizers and unreacted chemical components leach out slowly from the interior of the plastic parts.