Surface grafting polymerization of cast polypropylene (CPP)／acrylic acid(AA) system was studied with two-step method

which is a novel technique advantageous over traditional surface grafting polymerization initiated by UV．It consists of two steps. Firstly

dormant groups (semi-benzopinacol) were introduced on the CPP film under UV irradiation in the presence of benzophenone (BP) solution；and then

AA was grafted on the substrate surface by thermoactivating polymerization．The principle is as following

after BP is excited with UV irradiation

it extracts the H atoms from CPP surface and is reduced into semipinacol free radicals

meanwhile macromolecular free radicals are produced on CPP film surface．Because of spatial hindrance originated from its aromatic group

it is difficult for semipinacol free radicals to perform coupling termination and so does the surface radical．If no monomer was available

these two kinds radicals will combine．When CPP film with dormant groups is heated in a monomer solution

the C—C bonds of surface semipinacol groups break into the surface free radicals and semipinacol free radicals．The surface radicals induced monomer to propagate

result in grafting chains；whileas the reactivity of semipinacole free radical is too low to initiate grafting polymerization．Consequently

this method has two advantages：high grafting efficiency and suited to more monomers which can not be used directly in traditional photografting polymerization．The results show that acetic anhydride is an ideal solvent for CPP／AA surface grafting system；grafting yield increases with the growth of photosensitizer and monomer concentration；and polymerization temperature has positive effect on grafting yield．The contact angle of grafted CPP film against water decreases with the increase of grafting yield．In addition

the grafted CPP-g-AA film was identified by FTIR spectra．