Study on surface appearance of polyolefin plates modified by photografting: Effect of polymerization conditions

Thermal and photo- grafting of vinyl monomers on polypropylene plates of 1 mm thickness were carried out in water using benzoyl peroxide and benzophenone respectively as initiators. The resulting grafted samples were subjected to electron microscopy in a morphological observation of their surfaces. The grafted samples prepared by thermal grafting revealed a flat surface irrespective of the type of monomer used. The appearance of the surface of the samples prepared by photografting may be classified roughly into two types, flat or grainy. The flat surfaces were provided by the hydrophobic monomers methyl methacrylate and styrene. The grainy type was obtained using the hydrophilic monomers acrylic acid, methacrylic acid and N-vinylpyrrolidone.

Photografting of the hydrophilic monomers was characterized by the high susceptibility of the grafted chains to photodecomposition. It was supposed that the formation of a grainy surface is closely related to an abnormal polymerization in which grafted chains are more susceptible to photodecomposition.