Heating up plastic before its melting point -- could it be bad?

[kenny1999]

I am interested in a water heater found in consumer market, however, it's made of kind of plastic, I often "feel" that there must be some problem heating up something like plastic.

I understand that it should be tested and safe before putting into the market, however, I still wish to know - from the physics and science's point of view, what do you think? Could it change the molecular structure and release kind of toxic particles when a kind of plastic heated up to 100ºC but well below its melting point?

My English is not perfect. Wish you understand my questions and concern.

 

[.Scott]

Perhaps the most common of these is the Rheem. Here are the specs for it.
Uses a Polybutene water tank

Of course, any material used in the tank will interact with the water. A selling point of the plastic tank is that is has less interaction.

According to the specs, the tank has several layers: polyethylene on the outside, then polyurethane, then fiber glass, and finally a polybutene coating.

So it's the polybutene in contact with the water.
According to the MSDS it can cause "mild gastrointestinal discomfort". But that would be ingesting it in bulk.

Polybutenes are clear, bright, viscous liquids with boiling points of about 250C. Even the most viscous ones will get into the water. Here is a table: Polybutene products.

 

[kenny1999]

Perhaps the most common of these is the Rheem. Here are the specs for it.
Uses a Polybutene water tank

Of course, any material used in the tank will interact with the water. A selling point of the plastic tank is that is has less interaction.

According to the specs, the tank has several layers: polyethylene on the outside, then polyurethane, then fiber glass, and finally a polybutene coating.

So it's the polybutene in contact with the water.
According to the MSDS it can cause "mild gastrointestinal discomfort". But that would be ingesting it in bulk.

Polybutenes are clear, bright, viscous liquids with boiling points of about 250C. Even the most viscous ones will get into the water. Here is a table: Polybutene products.

In a conclusion, it's much safer to use a shiny stainless steel one instead right?

 

[.Scott]

Polybutene has been determined safe for cosmetics - including lip gloss.
It is "insoluble" or has "negligible" solubility in water - (depending on the source).

According to this report, it is "virtually non-toxic":
https://www.sciencedirect.com/topics/chemical-engineering/polybutene

I wouldn't worry about it. But there is no guarantee.