Question

Buna N is a copolymer of

• A. Butadiene & Acrylonitrile
• B. Butadiene & Styrene
• C. Butadiene & Isoprene
• D. Butadiene & Ethylene

Hint:

Buna N is widely used for making oil-resistant rubber products like seals and hoses.

Answer 1

The Correct Option is A

Step 1: Understanding Buna polymers.
Buna rubbers are synthetic rubbers prepared by copolymerization of butadiene with other monomers. The name “Buna” comes from butadiene and sodium (Na), used as a catalyst.
Step 2: Composition of Buna N.
Buna N, also known as nitrile rubber, is produced by copolymerizing butadiene with acrylonitrile. This composition gives the rubber oil and chemical resistance.
Step 3: Analysis of options.
(A) Butadiene & Acrylonitrile: Correct — This combination forms Buna N.
(B) Butadiene & Styrene: Forms Buna S (SBR rubber).
(C) Butadiene & Isoprene: Not Buna N.
(D) Butadiene & Ethylene: Not used for Buna rubbers.
Step 4: Conclusion.
Buna N is a copolymer of butadiene and acrylonitrile, hence option (A) is correct.

Answer 2

The name "Buna" itself is a useful clue here, it comes from "Butadiene" plus "Na" (sodium, once used as a polymerization catalyst), and the letter that follows tells you the second monomer copolymerized with butadiene. Checking each option against that naming convention resolves the question.

1. Butadiene & Acrylonitrile: This combination is known as Buna N (nitrile rubber), where the "N" stands for the nitrile group contributed by acrylonitrile. This nitrile content gives the rubber excellent resistance to oils and fuels, which is why nitrile rubber is used for fuel hoses and oil seals.
2. Butadiene & Styrene: This combination is Buna S (styrene-butadiene rubber, SBR), where the "S" stands for styrene, a completely different copolymer used mainly in tyres, not the one named in the question.
3. Butadiene & Isoprene: This is not one of the standard named "Buna" rubbers, isoprene-based rubber is typically discussed separately as polyisoprene or synthetic natural rubber.
4. Butadiene & Ethylene: This pairing is not used to produce any of the classic Buna rubbers, ethylene-based elastomers (like EPDM) are a separate category involving propylene and a diene monomer, not this combination.

Since the "N" in Buna N specifically denotes acrylonitrile as the comonomer, only the butadiene-acrylonitrile combination correctly matches the name.

Therefore, the correct answer is Butadiene & Acrylonitrile.