| Summary: | 碩士 === 逢甲大學 === 化學工程學系 === 87 === Water-borne pressure-sensitive adhesives (PSAs) were prepared via the emulsion polymerization process at 65℃, with a constant mechanical agitation rate of 180 rpm. The recipes contain monomers (60g of 2-ethylhexyl acrylate (2-EHA), 30g of butyl acrylate (BA) and 1g of acrylic acid (AA), surfactants (either a nonionic surfactant (i.e., polyoxyethylene nonylphenyl ether, PA) or a mixture of PA and anionic surfactant (i.e., sodium dodecyl sulfate, SDS)), water (120g) and initiators (Na2S2O5 and (NH4)2S2O8, 0.18g each).
The copolymerized acrylic acid provides a functional group of COOH, which plays as the anionic surface-active moiety, and hydrogen-bound with the ethylene oxide linkage of the nonionic surfactant, exhibiting an enhanced steric stabilization.
Using a mixture of PA and SDS, the volume-average particle diameter (Dv) of latex was reduced greatly. However, the latex became unstable in the presence of excess amount of SDS or propionic acid, not attached to the particles.
Having high molecular weights implied by the high values of intrinsic viscosity (I.V.), the PSAs showed adhesion failure for all samples when detached. The system using a mixture of PA and SDS has a low Dv value and high I.V. value, and, therefore, the PSA of which exhibit both higher peel and shear strengths. The PSA produced from the mixed-surfactant system has a higher tack, due to the higher moisture content (i.e., lower oven drying speed) allowing the higher diffusion rate of molecules onto the substrate.
The fact that the moisture contents of the coated PSAs decrease with the oven temperatures leads to the increase in both the peel and shear strengths, as well as the tack. The trend reaches the maxima, and then decreases. In addition, the surfactants of more hydrophilile has the higher peel and shear strengths, and the tack.
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