Adhesive properties of soy proteins modified by sodium dodecyl sulfate and sodium dodecylbenzene sulfonate

A study was conducted on adhesive and water-resistance properties of soy protein isolates modified by sodium dodecyl sulfate (SDS) (0.5, 1, and 3%) and sodium dodecylbenzene sulfonate (SDBS) (0.5, 1, and 3%) and applied on walnut, cherry, and pine plywoods. Soy proteins modified by 0.5 and 1% SDS showed greater shear strengths than did unmodified protein. One percent SDS modification had the highest shear strength within each wood type tested. Soy proteins modified with 0.5 and 1% SDBS also showed greater shear strengths than did the unmodified protein. The 1% SDBS-modified soy protein had the highest shear strength in all wood samples tested. Compared to the unmodified protein, the modified proteins also exhibited higher shear strengths after incubation with two cycles of alternating relative humidity and zero delamination rate and higher remaining shear strengths after three cycles of water soaking and drying. These results indicate that soy proteins modified with SDS and SDBS have enhanced water resistance as well as adhesive strength. Possible mechanisms for the effects of SDS and SDBS also are discussed.