Compare low-density polyethylene (LDPE) with high-density polyethylene (HDPE): which property correctly describes LDPE relative to HDPE?

Introduction / Context:Polyethylene exists in several forms, notably LDPE and HDPE, which differ in branching, crystallinity, density, and mechanical/thermal properties. Understanding these differences guides material selection for films, containers, pipes, and packaging.

Given Data / Assumptions:

• LDPE has more chain branching and lower crystallinity than HDPE.
• HDPE is denser, stiffer, and has higher softening point.
• Both are chemically inert polyolefins under normal conditions.

Concept / Approach:Increased branching in LDPE reduces chain packing efficiency, lowering crystallinity and density. This leads to reduced stiffness and hardness but improved flexibility and clarity. HDPE, with minimal branching, packs more efficiently, producing a stiffer, harder, and higher-temperature-tolerant material.

Step-by-Step Solution:Relate structure (branching) → properties (crystallinity, density).LDPE: lower density and crystallinity → more flexible.HDPE: higher density and crystallinity → harder, stiffer.

Verification / Alternative check:Datasheets show LDPE tensile modulus lower than HDPE, confirming greater flexibility. Vicat softening and melting points are lower for LDPE as well.

Why Other Options Are Wrong:Harder/Tougher: these describe HDPE more than LDPE for most grades.Chemically more inert: both exhibit excellent chemical resistance; not a distinguishing advantage for LDPE.

Common Pitfalls:Equating “toughness” with “flexibility”; HDPE may have higher impact toughness while still being less flexible than LDPE.

Final Answer:More flexible