Polypropylene
Lightweight, chemical-resistant thermoplastic with good fatigue resistance and living hinge capability. Polypropylene is widely used in packaging, automotive, and medical applications.
About Polypropylene
Polypropylene (PP) is a semi-crystalline thermoplastic known for its excellent chemical resistance, low density (lightest of all common plastics at 0.91 g/cm³), and unique living hinge capability. A properly designed PP hinge can flex millions of times without failure.
FabRapid machines and injection molds polypropylene for chemical tanks, battery cases, medical packaging, and consumer products with living hinges. PP is more challenging to machine than ABS or nylon due to its softness and tendency to "gum up" on cutting tools, but experienced operators achieve good results with sharp tools and appropriate cutting parameters.
PP offers the best chemical resistance of any commodity plastic, resisting most acids, bases, and organic solvents. It is also FDA-compliant for food contact in multiple grades.
Material Properties
Compatible Manufacturing Processes
Polypropylene can be processed using these manufacturing methods.
Available Surface Finishes
Surface treatments compatible with Polypropylene.
Common Applications
Design Guidelines for Polypropylene
Design living hinges with 0.25-0.5 mm thickness at the flex point for optimal cycle life
PP is soft and waxy — use sharp tools with high positive rake to prevent material dragging
For injection molding, PP has high shrinkage (1.5-2.0%) — compensate in mold design
Minimum wall thickness: 1.5 mm for CNC machining due to PP's flexibility
Polypropylene FAQ
Standard adhesives do not bond well to PP due to its low surface energy. Surface treatment (plasma, flame, or corona treatment) is required before bonding. Specialized PP adhesives and hot-melt adhesives are also available. Welding (ultrasonic, hot-plate) is generally more reliable.
Yes. Medical-grade PP is widely used for syringes, specimen containers, IV components, and sterilization trays. It can be sterilized by autoclaving (121°C), gamma radiation, or ethylene oxide. It is FDA 21 CFR compliant and available in USP Class VI grades.
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