Grafting of 2-Hydroxyethyl Methacrylate onto Isotactic Poly(propylene) Using Supercritical CO2 as a Solvent and Swelling Agent

Abstract

Grafting of 2-hydroxyethyl methacrylate (2-HEMA) onto isotactic polypropylene (iPP) was carried out by free-radical polymerization using supercritical carbon dioxide (SC CO2) as a solvent and swelling agent. The iPP film was first impregnated with the monomer 2-HEMA and initiator benzoyl peroxide (BPO) with SC CO2 at 308.15 K. After releasing CO2 , the 2-HEMA molecules in the film were grafted onto the iPP at a higher reaction temperature. By this method, the grafting level and the morphology can be controlled by soaking time, pressure, concentrations of 2-HEMA and BPO, reaction temperature, and reaction time. The products were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Contact angle measurements of 2-HEMA grafted iPP film using water as the test liquid showed a significant improvement of the surface polarity. The polymer films, having a markedly bumpy texture, were obtained under suitable conditions.