Free radical meltgrafting of the multimonomer system of maleic anhydride (MAH)/styrene (St) onto high density polyethylene (HDPE) prepared by a singlescrew extruder was studied.It was found that the addition of St monomer could significantly improve the MAH grafting level of the grafted HDPE.With increasing the St concentration

the graft degree of MAH first increased and then decreased a little.The maximum MAH grafting degree and the minimum melt flow rate were obtained when the molar ratio of MAH to St was approximately 1∶1.The higher the graft degree

the smaller MFR value was

suggesting that the grafted PE chains induced intermolecular entanglements.The mechanical properties of the grafted polymer with the addition of small portions of St monomer were better than those of the neat HDPE in this case.The mechanism of the multimonomer melt grafting HDPE system was also discussed.It was proposed that MAH and St interacted and copolymerized with each other in the melt grafting system.The grafting of StMAH copolymer (SMA) onto HDPE greatly increased the grafting degree of the grafted HDPE.When the amount of St is larger than MAH

St would be first grafted onto the PE backbone

inhibiting the grafting of SMA.Besides

the crosslinking of PE was well depressed due to the increase of graft degree in the multimonomer melt grafting systems.And no obvious gel was obseved in the reflux process.