Tack and shear strength of hybrid adhesive systems made of phenol-formaldehyde, dextrin and fish glue, and acrylic pressure-sensitive adhesive

Abstract

AbstractThe development of adhesives that have good initial adhesion (tack) that provides improved mat integrity during shape-forming of wood composites has been the subject of recent research. Hybrid adhesives were made based on thermosetting phenol-formaldehyde (PF), to which three tacky adhesives were added: high tack fish glue (FG), dextrin glue (DX) and a commercial acrylic, pressure-sensitive adhesive (PSA). Tacky adhesives were blended with PF at weight levels of 25%, 50% and 75%. The time-dependent tack development of the resulting hybrid adhesives was evaluated by means of a texture analyzer. The bond strength of adhesives was measured after curing by shear block test. PF/DX blends exhibited the highest tack during longer open times, while blends of PF and FG had low tack during shorter times. PF/PSA blends lost their bond strength completely after being heated at the curing temperature of PF. PF/FG blends did not show a significant decrease in bond strength compared to pure PF. The addition of DX had no effect on shear strength at ratios <75%.