DOC KB-MAT-002REV 2026-09-21CLASS: PUBLIC
PP vs ABS vs Rotomolded PE vs Aluminum: Case Materials Compared
Direct answer
Polypropylene (PP) injection molding is the default for lightweight, watertight consumer and light-industrial cases; ABS gives a stiffer, better-finished shell at higher weight and cost; rotomolded polyethylene wins on extreme impact durability and low-temperature toughness at the cost of weight; aluminum suits EMI shielding and high-heat duty but dents and costs more.
§01Comparison at a glance
| Property | PP (injection) | ABS (injection) | PE (rotomolded) | Aluminum |
|---|---|---|---|---|
| Density | ≈0.90 g/cm³ (floats) | ≈1.05 g/cm³ | ≈0.94 g/cm³, thick walls | 2.7 g/cm³ |
| Impact behavior | good, ductile | stiffer, can crack | excellent, absorbs hits | dents, rarely fails |
| Low-temp limit (typical) | −20 to −40 °C (compound-dependent) | ≈−20 °C | −40 °C and below | no embrittlement |
| Continuous heat (typical) | 60–90 °C | 70–85 °C | 70–90 °C | >150 °C |
| Water sealing | excellent with gasket | excellent with gasket | excellent | good, seams matter |
| UV life (unstabilized) | moderate | poor–moderate | good with additives | excellent |
| Tooling cost | high (mold) | high (mold) | low–moderate (cast mold) | sheet tooling |
| Unit cost at volume | low | medium | medium–high | high |
§02How to choose
- Choose PP for the best weight-to-cost ratio, chemical resistance and buoyancy — the standard for tool cases, equipment cases and most OEM programs at production volume.
- Choose ABS when appearance matters: higher gloss, better paintability and stiffness for panel-mounted interiors. It is heavier and less forgiving at low temperature.
- Choose rotomolded PE for brutal duty — military, outdoor, overland — where a thick, stress-free shell and −40 °C toughness outweigh the weight penalty.
- Choose aluminum for EMI/RFI shielding, high ambient heat, or fire-adjacent duty, accepting dents and higher cost.
§03The hybrid pattern
Many leading brands use PP shells with PE or TPE end caps and handles: injection molding delivers the precise gasket groove and latch bosses, while softer overmolds absorb shock at the corners. When comparing quotations, ask which resin grades and wall thicknesses are specified — "polypropylene case" can span a wide quality range.