Question

Which of the following packaging material provides approximately five times more barrier to $CO_2$, $O_2$, and water vapour than PET?

• A. PVC
• B. PEN
• C. PS
• D. PVDC

Hint:

PEN is like the "Stronger Brother" of PET. It is better at everything (barrier, heat resistance, strength) but much more expensive, so it is often blended with PET to save costs.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify a polymer used in food packaging that has superior barrier properties compared to the commonly used Polyethylene Terephthalate (PET).

Step 2: Detailed Explanation:

• Polyethylene Terephthalate (PET): PET is the industry standard for beverage bottles because of its transparency, strength, and decent gas barrier. However, for products very sensitive to oxygen (like beer or small carbonated drinks), PET's barrier is sometimes insufficient.

• Polyethylene Naphthalate (PEN): PEN is a high-performance polyester. It is structurally similar to PET but uses a naphthalene ring instead of a benzene ring.

• Superiority of PEN: This structural change makes the polymer chain stiffer. As a result, PEN offers significantly better barrier properties. It provides approximately 5 times the oxygen barrier, 4-5 times the $CO_2$ barrier, and better moisture barrier compared to PET. It also has higher thermal stability.

• Other Options: PVC (A) and PS (C) generally have poorer barrier properties than PET for these gases. PVDC (D) is an excellent barrier material often used as a coating, but PEN is the specific structural polymer known for being the "high-performance version" of PET.

Step 3: Final Answer:
PEN (Polyethylene Naphthalate) is the material with approximately five times better barrier properties than PET.