Re: Machining Delrin at home (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Wed, 20 Jun 2007 10:19:35 EDT
From: Mddeming@xxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: Machining Delrin at home (fwd)

 
Hi Scott, All,
 
Thanks for the correction. I guess I fell into the trap of "If it's on line  
from a vendor, it must be true." Here's the  listing with the warning that  
caused the consternation:
 
_http://cgi.ebay.com/Acetal-Delrin-virgin-white-10mm-x3-375-x23-25-1-4_W0QQite
mZ200119562622QQihZ010QQcategoryZ61794QQrdZ1QQcmdZViewItem_ 
(http://cgi.ebay.com/Acetal-Delrin-virgin-white-10mm-x3-375-x23-25-1-4_W0QQitemZ200119562622QQih
Z010QQcategoryZ61794QQrdZ1QQcmdZViewItem) 
 
 
 If I spread uncorroborated misinformation, I apologize.
 
Matt D.
 

Matt -

It looks like someone at this plastics distributor is a  bit confused. 
Actually, this information is incorrect, both as to the  breakdown 
temperature and thermal decomposition products of Delrin (Delrin  is a DuPont 
Co. trademark for acetyl copolymer).

When heated above  230 degrees C (not 200 deg F) Delrin begins to release 
formaldehyde, not  ammonia. The odor of formaldehyde is very distinctive, and 
causes immediate  coughing and tear formation.

When burned in air, Delrin decomposes and  releases formaldehyde and various 
isocyanate compounds, all potentially  toxic. Luckily, during machining of 
Delrin, it's very hard to get it hot  enough to release formaldehyde unless 
you create great friction  by the  use of very dull cutting tools operated at 
high speed.

The only time  I have ever seen any evidence of thermal breakdown of  Delrin 
during  machining was by the use of a very dull router bit in a high speed 
router  (spindle speed 25,000 RPM).

The melting point of Delrin resins is around  350 deg F, and Dupont 
recommends that the molding temperature for Delrin  resins not exceed 446 deg 
F. So, it's probably not a good material for  spark-gap electrode holders
where anything contacting the Delrin would get  much hotter than about 300
deg F.

All the MSDS (Material Safety Data  Sheet) for DuPont plastics (including 
commonly used plastics like Delrin,  Lexan, Kevlar, etc) can be found on 
Dupont's website  at:
http://msds.dupont.com/NASApp/msds/Mediator?sec=searchSection&sub=searchInitia
l

Regards,
Scott  Hanson





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