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Resin · Polypropylene (PP) · Commodity

Polypropylene — the chemical-resistant commodity resin.

The cheapest engineering thermoplastic. Excellent chemical resistance — PP survives exposure to most acids, bases, and organic solvents that degrade ABS or PC. Integral living-hinge capability (fatigue life in the millions of cycles). The default choice for containers, automotive trim, and any part seeing chemical or moisture exposure.

QUICK SPECS
Tensile strength30–35 MPa
Elongation at break100–600% (grade-dependent)
Flexural modulus1,200–1,600 MPa
Heat deflection temp100 °C at 0.45 MPa
Chemical resistanceExcellent (most acids, bases, solvents)
Moisture absorption<0.1% (essentially zero)
Density0.90 g/cm³ (lightest common plastic)
Shrinkage1.5–2.0% (high, requires large tolerance)
STATUSIN OPERATION
§ 01 / WHEN

When to choose PP over other commodity plastics

The decision tree for commodity resins:

  • Chemical exposure? → PP
  • Living hinge? → PP (only resin with true million-cycle hinges)
  • Clarity needed? → PC or acrylic (not PP — it's translucent at best)
  • Cosmetic A-surface? → ABS or PC/ABS (PP has a matte, low-lustre finish)
  • Cost-critical only? → PP (cheapest by weight)
  • Food contact? → PP (FDA-approved grades standard)
§ 02 / COMMON

Common grades

GradeBest forNotes
HomopolymerRigid containers, capsStiffest PP, most brittle
Copolymer (random)Clear containers, thin-wall moldingBetter clarity, moderate stiffness
Impact copolymerAutomotive bumpers, cratesHigher impact, slightly lower stiffness
Glass-filled (PP-GF)Structural automotive partsGF20 or GF30 stiffness; brittle at cold
Talc-filledAppliance housings, low-cost structuralCheaper alternative to GF; heavy-feel
Medical gradeSyringes, IV parts, traysUSP Class VI, autoclavable
READY WHEN YOU ARE

PP moldings — the high-volume commodity choice.

Upload STEP. PP molds fast, costs little, and handles chemistry that defeats other resins.

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