Influence of the introduction of small hydrophilic groups on the kinetic hydrate inhibition effect of poly(N-vinylcaprolactam)

Traditional amide-based hydrate inhibitors, vital for preventing blockages, face limitations due to increasingly stringent environmental regulations. This study focuses on modifying poly(N-vinylcaprolactam) (PVCap) to improve its inhibition and biodegradation properties, by introducing –OH, –NH2, or –COOH groups into the molecular structure. The results revealed that the –OH group significantly improved both hydrate inhibition and biodegradability, while the –COOH and - NH2 groups had moderate and counter-effects, respectively. Compared to end hydroxyl modification, multiple –OH groups in the vinylcaprolactam/vinylalcohol copolymer weaken the inhibition effect, despite enhancing biodegradability. Optimal hydrophilicity was found to enhance PVCap's KHI performance, emphasizing the delicate balance needed to optimize stability and effectiveness. PXRD, Raman spectroscopy and interfacial tension tests were used to elucidate the impact of the modified PVCaps on hydrate structure and gas–liquid interfacial properties. The results further highlighted the significance of appropriate amphiphilicity in augmenting the KHI effect of the modified PVCaps.