different rate for same hsn code

hello sir

we are in tarpaulin manufacturing business
my query is we have got two rate for same hsn code as if i am selling laminated rolls it comes under 28% and if i same laminatrd rolls are converted in tarpaulines it comes under 18% and also the fabric used as raw material on which i laminate comes under 28% and other raw material such as granuels comes under 18%, so how to manage all the different rates