Undesirable odor in some adhesives is caused by many factors including raw material properties, manufacturing process parameters, storage, application, and aging.
Nature of the Raw Materials
Only low molecular weight substances (below Mw 294) produce an odor. Very often the presence of monomer residues like styrene, vinyl-acetate, and acrylic esters are responsible. Oligomers in C5, C9, and terpene resins are also a potential source, as well as by-products in natural resins like the sulphur containing molecules in tall oil rosins. Synthetic stabilizers and thioethers may develop a very unpleasant odor.
While an odor free, neutral behavior adhesive is the common expectation, it is particularly important in the automotive, medical, and disposable hygiene industries. Careful selection of raw materials will help in odor prevention. The Eastman hydrogenated C5 and C9 hydrocarbon resins and hydrogenated rosin resins are recommended for low to no odor applications requirements.