Abstract: Polypropylene (PP) film was treated by cold plasma and followed by a vapor phase graft polymerization of acrylic acid (AAc). It was found that 15 minutes grafting was sufficient enough to decrease the water contact angle (WCA) of PP film from 97 to 32, which indicates a great improvement in its hydrophilicity. FTIR-ATR study confirmed the grafting of AAc on PP film. SEM observation clearly showed many bump-like substances in the size of around 1-2m. This modified hydrophilicity kept very well even after washing the grafted sample in boiling water for 10 minutes, which indicates that the ageing effect of merely plasma-treated PP film was overcome. By investigating the effect of reaction time and temperature on the degree of grafting, an optimum condition was found as grafting for 15min at 55C. Under the optimum condition, the degree of grafting and WCA of grafted sample reached 0.45% and 32, respectively. It was thought that this fast and effective method of graft polymerization in vapor phase could provide a strong experimental support to develop corresponding industrial applications in the field of surface modification.

Key words: cold plasma, vapor phase grafting, surface modification, hydrophilic, acrylic acid