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In short

I'm looking for an acid that can solve a polyester, fiberglass composite. However it cannot damage steel.

First of all i like to say that i'm not a chemist. I work in a plastic moulding company. Let me sketch a background. We make bars out of a polyester strengthened by fiberglas. To make this we have the two materials beeing pulled through a heated steel pipe (the mould). The polyester melts around the fiberglass and forms a strong lightweight pole. However sometimes the pole breaks mid process and then there is a part that's stuck in the mould. Like in the picture

Part stuck in mould

It's very hard to remove the polyester/fiberglass bar from the mould, dare I say near impossible.

I was wondering if there is an acid that solves the polyester but makes no damage at all to the chrome steel mould.

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  • $\begingroup$ Look using the terms " solvent for. ..". It seems a hard task because you have a rod trapped in the mould. If the mould cannot be open it might takes years. .. $\endgroup$
    – Alchimista
    Mar 13 '19 at 14:53
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    $\begingroup$ Is it not possible to heat the mold above the melting point of the polyester, then PUSH out the stuck bar with a rod? $\endgroup$
    – jeffB
    Mar 13 '19 at 15:11
  • $\begingroup$ we tried drilling, melting, ... if there is an acid or solvent of polymer that doesn't damage the steel, i would make a system that circulates, the acid, maybe even heats it to speed up the process. If it works after weeks, i'll be happy with it, a year, or years might be a bit too long $\endgroup$
    – RubenDefour
    Mar 13 '19 at 15:24
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    $\begingroup$ @jeffB we tried pushing it hydraulically with a force of 800kg, hammering, and the rod is usually just too long, and has too much friction, we're talking about a mould of a length of 1m50, $\endgroup$
    – RubenDefour
    Mar 13 '19 at 15:26
  • $\begingroup$ Can't you pretreat the mould by coating it, say with PTFE? Or would this not help? $\endgroup$
    – Buck Thorn ♦
    Mar 13 '19 at 15:46

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