Hello Mugilash, 

If you have interest in plastic engineering then you can surely opt for that. But speaking frankly the the placement are close to zero in india for plastic engineers as their demand is more in abroad. Even the research has been conducted which says that plastic engineering is the least payed job in the world. So if you are passionate then only you go for that otherwise choose some other course. 

I hope you will find my answer helpful. 

All the best.