Question

Kevlar is a nylon obtained by condensation polymerization of 1, 4- diaminobenzene and 1, 4-benenedicarboxylic acid. Its fibres are five times stronger than steel & hence are used for making bullet-proof vests. There are two compounds of boron which are also used for making bullet-proof vests. 

Now answer the following questions. 

(i) Name the two compounds of boron which are used for making bullet-proof vests and how are they prepared ? 

(ii) What are the other advantages of using boron based compounds over Kevlar for making bullet-proof vests ? 

Answer 1

(i) The compounds of boron which are used for making bullet-proof vests are : boron nitride (BN) and boron carbide (B₄C). These are prepared from boron oxide as follows : 

B₂O₃ + 2NH₃ → 2BN + 3 H₂O (T = 1173 K) 

2B₂O₃ + 7C → B₄C + 6CO (T = 1873 K) 

(ii) Boron has high ability to absorb neutrons and hence boron carbide or boron nitride based bullet-proof vests can also act as protective shield against radioactive radiations.