An investigation was carried out on estimation of hydrophilicity, wettability and water-absorptivity, and surface analysis by X-ray photoelectron spectroscopy of the low-and high-density polyethylene (LDPE and HDPE) plates photografted with methacrylic acid (MAA) and acrylic acid (AA) at different monomer concentrations or temperatures. Wettability of the MAA-grafted LDPE and HDPE plates increased with grafted amounts, and became constant when the substrate surfaces were fully covered with the grafted polymer chains. On the other hand, for the AA-grafted LDPE and HDPE plates, wettability had the maximum value, and then gradually decreased against the grafted amount probably due to aggregation of grafted PAA chains, although the surfaces were covered with grafted PAA chains at lower grafted amounts compared with grafted PMAA chains. Waterabsorptivity sharply increased at lower grafted amounts due to formation of shorter grafted polymer chains for photografting at lower monomer concentrations or due to restriction of the location of grafting to the outer surface region for photografting at lower temperatures. Therefore, for photograftings of AA or onto the HDPE plates, the substrate surfaces were covered with grafted polymer chains and the grafted layers formed possessed higher water-absorptivity at lower grafted amounts.

In this study, hydrophilic monomers were photografted onto the PP plates at different monomer concentrations and temperatures, and grafted PP plates were bonded with enzymatically modified chitosan solutions. Their adhesive strength properties were discussed in relation to the grafting conditions and hydrophilic properties such as wettability and water-absorptivity. In addition, the location of failure was investigated by X-ray photoelectron spectroscopy analysis of failed surfaces. Wettability of the grafted PP plates except for the PP grafted with acrylic acid (PP-g-PAA) plates remained constant above the grafted amounts at which the PP surfaces were fully covered with grafted polymer chains. On the other hand, wettability of the PP-g-PAA plates passed through the maximum value and then gradually decreased with the grafted amount probably because of the aggregation of grafted PAA chains. Waterabsorptivity of the grafted layers formed at lower monomer concentrations or temperatures sharply increased at lower grafted amounts. The adhesive strength increased with an increase in the grafted amount and substrate breaking was observed for PP-g-PAA plates because enzymatically modified chitosan solutions were successfully penetrated in the grafted layers and quinone derivatives reacted with carboxy groups of grafted PAA chains. Failure occurred in the layers composed of grafted PAA chains and components containing in enzymatically modified chitosan solutions and the location was shifted to the inside of grafted layer, as the grafted amount increased.