What is Biaxially Oriented Polypropylene ? commonly known as BOPP,

The Reserve Bank of India (RBI) is taking a major step toward introducing polymer (plastic) currency in India. Its subsidiary, BRBNMPL, has launched a global tender to source specialized polymer sheets for a trial run.

Key Points:

• The Trial: The RBI is seeking 68,000 reams of polymer substrate to print two denominations (likely ₹10 and ₹20).

Why use Polymer instead of Paper?

The transition to polymer is primarily driven by three factors: Security, Durability, and Lifecycle Cost.

Biaxially Oriented Polypropylene, commonly known as BOPP, is a specialized, high-performance plastic film. It is the core material used to create modern polymer banknotes.

• Polypropylene (PP): This is the base plastic—a durable, versatile, and lightweight thermoplastic polymer derived from petroleum.

• Biaxially Oriented: This refers to the manufacturing process. The film is stretched in two directions (biaxially):

  • Machine direction (lengthwise)

  • Transverse direction (crosswise)

Why the “Stretching” Matters?

Standard polypropylene is strong, but when it is “biaxially oriented,” it undergoes a transformation that makes it ideal for high-precision uses like currency:

• Strength & Durability: Stretching aligns the polymer molecules, giving the film significantly higher tensile strength. It becomes much harder to tear, puncture, or fray compared to normal plastic.

• Dimensional Stability: It does not stretch or shrink easily when exposed to changes in temperature or humidity. This is critical for banknotes, which must remain a consistent size to be accepted by vending machines and ATMs.

• Clarity: The stretching process makes the film naturally crystal clear. This allows manufacturers to leave transparent “windows” in the banknote, which are a key anti-counterfeiting feature.

Why it is the “Gold Standard” for Banknotes?

Beyond just being plastic, BOPP is chosen because it solves the major weaknesses of traditional cotton-paper notes:

• Non-Porous Surface: Unlike paper, which acts like a sponge (absorbing dirt, sweat, oils, and moisture), BOPP is non-porous. This keeps the notes cleaner and prevents them from getting “soggy” or smelling bad after extensive circulation.

• Chemical Resistance: It is highly resistant to oils, chemicals, and water. You could theoretically wash a polymer note in a washing machine, and it would emerge intact.

• Surface Treatment: During manufacturing, the surface of BOPP can be treated (e.g., using corona or plasma discharge) to make inks and security coatings adhere permanently, preventing the design from wearing off.

• Recyclability: While paper notes are usually shredded and buried in landfills, BOPP notes can be granulated and melted down to be repurposed into other plastic goods, such as furniture, plant pots, or construction materials.