Yasuo Hata

Comparative examination of acrylic acid and 4-vinylpyridine monomers in liquid-phase photografting on polyethylene film

Abstract The effect of monomer concentration on the location of acrylic acid (AA)- and 4-vinylpyridine (4VP)-grafted chains introduced into low-density polyethylene film (thickness = 30 μm) by liquid-phase photografting ( λ > 300 nm) was investigated together with the grafting behaviours at 60°. Benzophenone was used as a photoinitiator by coating it on the film surface. The grafting rate of AA increased with increasing the AA concentration (1.7, 3.4 and 6.8 wt%). The AA-grafted chains of the sample prepared in the system of 6.8 wt% AA concentration, where the formation of grafted polymer overcomes that of homopolymer, tended to penetrate into the film inside compared to those of the sample prepared in the system of 3.4 wt% concentration, in which the formation of homopolymer proceeds preferentially. With 4VP monomer, on the other hand, the grafting rate decreased while promoting the formation of homopolymer as the monomer concentration increases. The 4VP-grafted chains distributed in the film inside irrespective of the monomer concentration (1.9, 3.8 and 7.6 wt%). The resultant AA- and 4VP-grafted films were subjected to measurement of pH-responsive characters in order to understand relationship between the location of grafted chains and the function.

Stability of polymeric peracid derived from acrylic-acid-grafted polyethylene and hydrogen peroxide

Abstract The stability of polymeric peroxides with peracid structure, which were prepared by reacting acrylic-acid(AA)-grafted polyethylene film (thickness = 30 μm) with hydrogen peroxide in the presence of methanesulfonic acid, has been investigated in terms of the location of the AA-grafted chains and the introduction of a temperature-sensitive component into the grafted chains. AA-grafted films with different location of the grafted chains were prepared by vapor- and liquid-phase photografting. The peroxides on the grafted film with a homogeneous distribution of the grafted chains exhibited a higher stability at 20 and 40°C than on that with grafted chains localized on the film surface. Liquid-phase photografting of an AA/N-isopropylacrylamide (NIPAAm) monomer mixture was carried out to introduce a temperature-sensitive component in the AA-grafted chains. The peroxides on the resultant AA/NIPAAm(1/1)-grafted film showed a higher stability at 40°C than on the AA-grafted film since the AA/NIPAAm-grafted chains shrank at the temperature to stabilize the peroxides. Thus, the introduction of the temperature-sensitive component, NIPAAm, into the AA-grafted chains was useful for improving the stability of peroxides on the grafted film.

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

Abstract 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.

Factors Affecting Vapor-Phase Photografting of Methacrylic Acid on Low-Density Polyethylene Film

Abstract Factors affecting photografting (λ > 300 nm) of methacrylic acid on a low-density polyethylene film (thickness = 70 μm) were investigated in a vapor-phase system. Xanthone was coated on the film. Factors examined were pressure of the system (1, 20, and 50 mmHg), polymerization temperature (40, 50, and 60°C), and use of monomer mixed with water. It was found that the grafting rate decreases in the following order: 1 mmHg > 20 mmHg > 50 mmHg at 60°C, and 60°C > 50°C > 40°C under 1 mmHg pressure. The rate was sharply reduced by using monomer mixed with water (monomer/water = 1/1). The contact angle of water on the grafted films largely depended on the grafting conditions, decreasing in the same order as that of the grafting rate described above. Thus, higher wettability was recorded for grafted films prepared under grafting conditions where the grafting rate is slow. The resultant grafted chains are supposed to localize mainly on the film surface.