Start with the principle
Polyetherimide, or PEI, is an engineering thermoplastic with useful stiffness and elevated-temperature properties. A raw-resin data sheet describes a grade, sample and test method. It does not establish the operating limits of every finished frame.
A pair contains more than its frame resin
Lenses, coatings, adhesives and joints can respond differently to heat. Applying one component’s rating to everything else skips these differences. Follow the care instructions for the assembled product.
Keep heat and impact separate
Heat resistance does not prove resistance to a fall or a ball strike. Avoid hot-water or hairdryer experiments and ask how the actual frame should be cleaned and adjusted.
A worked example
Teaching example: a PEI front is fitted with coated plastic lenses. Even if the resin tolerates a particular laboratory condition, no evidence about those lens coatings follows from that fact. This example supplies no safe temperature for home testing.
CHECK YOUR UNDERSTANDINGCan the resin data sheet set the cleaning temperature for the whole pair?
No. The finished product includes other materials and connections.
Sources & verification
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