Chlorinated poly(vinyl chloride) (CPVC) is similar in many ways to its thermoplastic parent poly(vinyl chloride) (PVC), Chlorination imparts superior high temperature properties, which make CPVC preferable for many and varied applications.Our primary purpose in studying CPVC with x-ray photoelectron spectroscopy (XPS) was to see whether we could gain insight into how chlorine substitutes into the PVC molecule. We also hoped we would obtain insights into the chlorination reaction itself, and how variations would affect the final product.