Start with the principle
TR90 is a familiar transparent-polyamide grade name, not a synonym for every nylon. Supplier properties refer to particular resin grades and test conditions. Processing, section shape and joints also affect a finished frame.
Three different properties
Elasticity concerns recovery after unloading. Stiffness concerns resistance to deformation; toughness concerns energy absorbed before fracture. A temple that bends easily has not thereby proved that it will survive unlimited bending.
Sport needs a complete protector
Frame flexibility alone says nothing about lens retention or the coverage and security needed for a particular sport. Describe your activity and check the intended protection of the complete eyewear.
A worked example
Teaching example: a narrow, springy frame can still squeeze the temples because it is held spread apart during wear. Replacing it with the same size in a “softer” material may not solve the fit problem.
CHECK YOUR UNDERSTANDINGDoes a successful twist demonstration certify sports protection?
No. Protection depends on the complete product and the hazard.
Sources & verification
Page updated: