Polypropylene versus polyethylene (polythene): why is polypropylene generally preferred in many applications? Select the most accurate reason based on mechanical properties.

Introduction / Context:
In polymer selection for consumer goods, packaging, automotive trims, and houseware, polypropylene (PP) and polyethylene (PE, often called polythene) are common choices. This question asks why PP is often preferred, focusing on mechanical property advantages relevant to real-world use.

Given Data / Assumptions:

• Comparison at room temperature between commodity grades (e.g., PP homopolymer and LDPE/HDPE).
• Interest is in hardness and tensile strength for stiffness and load-bearing capacity.
• Flammability of both materials is comparable without special additives.

Concept / Approach:
Polypropylene typically exhibits higher hardness and tensile strength than many polyethylene grades, especially LDPE. This translates to better rigidity (higher flexural modulus) and improved creep resistance at ambient temperatures, which are desirable for living hinges, caps, appliance parts, and reusable containers.

Step-by-Step Solution:
Identify property targets: hardness and strength drive stiffness and durability.Compare typical data: PP has higher modulus and tensile strength than LDPE and is comparable to or stiffer than many HDPE grades.Evaluate flammability: both are combustible; “non-inflammable” is incorrect without flame retardants.Hence the best answer combines (b) and (c).

Verification / Alternative check:
Datasheets show PP tensile strength commonly higher than LDPE, with hardness and softening point (Vicat) also higher, supporting improved rigidity and heat resistance.

Why Other Options Are Wrong:
Non-inflammable: incorrect without FR additives; both PP and PE burn.Only hardness or only strength misses the broader advantage.“Better solvent for plasticisers” is irrelevant and not a benefit.

Common Pitfalls:
Assuming one material is inherently flameproof; overlooking grade-to-grade variations (copolymers, fillers, and orientation can change properties).

Final Answer:
Both (b) and (c)