Ziegler–Natta polyethylene: the low-pressure Ziegler process most characteristically produces which type of polyethylene?

Introduction / Context:Polyethylene manufacturing follows distinct routes. LDPE is typically made via free-radical polymerization at very high pressures, producing highly branched chains. Ziegler–Natta catalysis, developed for low-pressure operation, yields linear chains with higher crystallinity, characteristic of HDPE.

Given Data / Assumptions:

• Ziegler–Natta = transition-metal catalyst system (e.g., TiCl4 with organoaluminium cocatalyst).
• Operates at relatively low pressures and temperatures compared to LDPE processes.
• Target property: higher density through low branching and high crystallinity.

Concept / Approach:The catalyst surface controls chain growth stereochemistry and suppresses long-chain branching, yielding linear polyethylene. This increases crystallinity and density, hence HDPE. Statements that the process uses no catalyst or very high pressure are incorrect; those describe neither Ziegler–Natta practice nor LDPE's classic high-pressure radical route.

Step-by-Step Solution:Associate Ziegler–Natta with low-pressure catalysis.Recognize linear PE product → higher density.Select HDPE as the correct outcome.

Verification / Alternative check:Process encyclopedias classify HDPE under Ziegler–Natta/catalytic routes, whereas LDPE is produced in tubular/autoclave reactors at 1000–3000 bar.

Why Other Options Are Wrong:No catalyst: false—Ziegler–Natta requires catalysts.LDPE/high pressure: those describe the radical route, not Ziegler–Natta.

Common Pitfalls:Assuming all polyethylene is made the same way; conflating product density with processing pressure.

Final Answer:High-density polyethylene (HDPE)