Chennai-based Chemplast Sanmar's ₹3,850-crore initial public offering (IPO) will open on August 10 at a price band of ₹530-541 per share of face value of ₹5 each. The offer comprises fresh issue of shares worth ₹1,300 crore and an offer for sale worth ₹2,550 crore by promoters. The speciality chemicals manufacturer's public issue will close on August 12.