Physical properties of polyethylene: the approximate density of high-density polyethylene (HDPE) is closest to which value (in g/cc at room temperature)?

Introduction:
HDPE is a semicrystalline thermoplastic whose density exceeds that of LDPE due to higher crystallinity and linear chain structure. Recognizing the typical density range is useful in material identification and quality checks.

Given Data / Assumptions:

• Room-temperature density values are considered.
• Typical HDPE density range is about 0.94–0.97 g/cc depending on grade.

Concept / Approach:
Higher crystallinity increases mass per unit volume. HDPE’s linear chains pack efficiently, producing densities around 0.95 g/cc, whereas LDPE is lower (~0.91–0.93 g/cc). Values near or above 1.0 g/cc are uncommon for polyolefins absent heavy fillers.

Step-by-Step Solution:
Recall HDPE density window: approximately 0.94–0.97 g/cc.Select the closest nominal value: 0.95 g/cc.Eliminate unrealistic options for neat HDPE (1.05, 1.18 are too high; 0.85 is too low).

Verification / Alternative check:
Material datasheets for general-purpose HDPE grades list densities around 0.955 g/cc (per ASTM D1505 methods), confirming the choice.

Why Other Options Are Wrong:

• 1.18 and 1.05 g/cc: characteristic of filled polymers or other plastics (e.g., PET ~1.38), not neat HDPE.
• 0.99 g/cc: above typical HDPE unless heavily filled.
• 0.85 g/cc: too low for polyethylenes.

Common Pitfalls:
Confusing HDPE with PP (≈0.90–0.91 g/cc) or with filled/foamed grades that alter apparent density.

Final Answer:
0.95 g/cc