The stratum corneum (SC) stripping behavior of pressure sensitive adhesives (PSAs) with different storage elastic modulus was evaluated at neat-skin-surface temperatures. PSAs with different storage elastic modulus were prepared by varying the amount of additive cross-linking agent,and the SC stripping performance of the adhesive was measured in terms of the stained ratio of the stripped skin surface area to the total surface area and the amount of stripped skin, which was determined by protein testing of the tape surface. We found that PSAs with lower storage elastic modulus stripped the SC to a greater extent. It becomes obvious that a low storage elastic modulus PSA can better follow skin surface asperities. When cross sections of the skin and adhesive tape were examined under magnification,it was observed that the shapes of the skin and the stripped tape were distorted. By contrast,higher storage elastic modulus PSAs did not distort the skin shape.

View full abstract

In order to improve the adhesion properties of wood containing a great deal of oily compounds,which are believed to prevent wood from forming bonded structures,several adhesion tests were conducted.The adhesives used in the experiments were prepared by blending polyvinyl alcohol (PVA)samples with different degrees of saponification with four kinds of polymeric 4,4'-diphenylmethane diisocyanate(pMDI). The influence of the number of hydrophobic groups in the PVA molecule on the adhesion properties was examined,and the following conclusions were obtained.As the number of hydrophobic groups in the side chain of the PVA molecule increases,pMDI and essential oil of hinoki cypress(Chamaecyparis obtusa)disperse more finely in the aqueous PVA solution.However,after the hydrophobic content reached a certain level,the dispersing tendency of the two components did not improve further.The dynamic mechanical properties of the cured samples were measured and the apparent crosslink density was estimated from the storage modulus(E')at the rubbery plateau region of the curve. It was clear that the more finely the components were dispersed in the cured material,the greater the apparent crosslink density.The adhesion properties of birch coated with essential oil of Hinoki cypress were examined using the ordinary state test and water-resistance test,and the adhesion was good when the pMDI components were dispersed finely in the adhesive phase.The hydrophobic components in the side chain of the PVA molecule have a significant positive effect on the adhesive performance of wood containing a large amount of oily compounds.

View full abstract

Effects of compounding a bis-phenol A type phenoxy resin containing carboxyl groups(COOH-Px)on properties and morphologies of cured bis-phenol A type epoxy resin(Ep)/COOITPx blends as adhesives for FPCs were studied with comparing to those of cured Ep/bis-phenol A type phenoxy resin(Px)blends. It was found that cured Ep/Px blends form structures with micro phase-separated morphologies whereas cured Ep/COOH-Px blends form miscible morphologies. Cured Ep/COOH-Px blends show more improved flow properties with maintaining good reliability of insulation than that of cured Ep/Px blends. However,it was found that the peel strength of cured Ep/COOH-Px blends is lower than that of cured Ep/Px blends and then that was known as the problems of cured Ep/COOH -Px blends.

View full abstract