Polypropylene
Pronunciation: pol-ee-proh-puh-leen
A rigid thermoplastic polymer commonly used for structural orthotic shells due to its strength, light weight, and formability under heat.
Full Definition
Polypropylene is the standard rigid shell material in lower-limb orthotics, most notably ankle–foot orthoses (AFOs) and knee–ankle–foot orthoses (KAFOs). It is vacuum-formed or hand-formed over a plaster or CAD/CAM-milled positive model at elevated temperatures. Thickness (typically 3–6 mm for lower-limb devices) determines rigidity and must be specified precisely in prescriptions and laboratory documentation. Editors should note that 'polypropylene' is written as one unhyphenated word; the abbreviation 'PP' is acceptable in technical specifications but should be expanded on first use in clinical reports. It is distinct from polyethylene and copolymer materials, which have different flexibility and fatigue characteristics.
Usage
Usage note: Specify thickness in millimetres and colour/grade whenever editing fabrication documentation. Do not abbreviate to 'poly' in formal clinical records.
In Context
- "The AFO shell was vacuum-formed from 4 mm natural polypropylene over a rectified plaster cast." — Orthotic fabrication record
- "Polypropylene thickness should be documented in millimetres in all laboratory work orders." — Orthotic service quality standards document