Density

property

The mass per unit volume of a plastic material, typically expressed in g/cm³ or kg/m³, used to identify resin types, calculate material costs, and predict processing behavior.

In Simple Terms

Density tells you how much a plastic weighs for a given volume. It's like comparing how heavy a cup of water is versus a cup of oil - different plastics have different densities, which helps identify the material type and calculate shipping costs.

Why It Matters

Density is crucial for resin traders to verify material identity, calculate accurate pricing by weight versus volume, optimize shipping costs, and ensure customers receive the correct polymer grade for their specific applications.

Technical Details

Density measurement follows ASTM D792 or ISO 1183 standards, typically using displacement methods. Values range from 0.85-0.97 g/cm³ for polyolefins to 1.4-2.2 g/cm³ for engineering plastics. Crystallinity, fillers, and molecular structure significantly affect density measurements and material performance.

Real-World Examples

HDPE vs LDPE identification

HDPE density ranges 0.94-0.97 g/cm³ while LDPE is 0.91-0.93 g/cm³, allowing quick material verification during resin receiving

Filled compound verification

A PP compound with 20% talc filler shows density of 1.15 g/cm³ versus unfilled PP at 0.90 g/cm³, confirming filler loading

Shipping cost optimization

Low-density polyethylene film grade at 0.92 g/cm³ requires more volume per ton than PVC at 1.38 g/cm³, affecting freight rates