Living hinges.
Polypropylene.
Million-cycle flex.
Living hinge reference. Thin polypropylene section flexes repeatedly. Millions of cycles without failure. Specific design rules.
Key principles.
PP standard
PP standard living hinge material. Best fatigue resistance.
0.3-0.5 mm
Critical thickness for proper flex.
1-2 mm
Effective hinge length 1-2 mm.
Smooth flow
Smooth material flow into hinge zone critical.
Activates
First flex aligns molecules. Always perform after molding.
1M+ cycles
Properly designed PP hinges 10M+ cycles tested.
FAQ
Why polypropylene?
PP unique fatigue resistance. Other plastics fail much earlier in flex.
Cycle life expected?
>10M cycles for properly designed PP hinge. Tested standard.
Activation step?
First flex orients molecules. Required after molding for full performance.
Mold design?
Gating away from hinge. Smooth material flow. Avoid sharp transitions.
Common applications?
Snap-shut packaging, ammunition cases, medical device cases, fishing tackle.
Other materials?
Some PE grades. Minimal compared to PP. PP almost always preferred.
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