Reinhard,
this is a tough one,maybe mylat(polyethylene
terephthalate)
??? according to my handy id book blue flame hard to ignite is some type
of pom (acetal,delrin) but that does not sound right.
a good source for future sleuthing is:
"simple methods for identification of plastics"
by dietrich braun
distributed in europe by carl hanser verlag
kolbergertr 22,d-8000 munchen 80
good luck!
robert