Adhesives & Sealants

It gives the adhesive quick grab and peel strength. Base polymers such as EVA, SIS and SBS are strong but not very sticky on their own; a compatible tackifier resin lets the blend flow onto a surface in a fraction of a second and resist peeling. C5 aliphatic, C9 aromatic and blended hydrocarbon resins and rosin esters are the main families. Compatibility with the base polymer decides the choice, so trial blends before switching.

They change how moisture cures the sealant. In a standard one-part polyurethane, water reacts with isocyanate and releases carbon dioxide, which can form bubbles in thick beads and high-build coats. Oxazolidines and aldimines react with moisture first and release an amine, plus a hydroxyl group from oxazolidines, that then reacts with the isocyanate without producing gas. Mono-oxazolidines are also used as moisture scavengers to dry polyols, fillers and pigments.

A structural adhesive forms a load-bearing joint, often above 10 MPa in lap shear, using epoxy, polyurethane, acrylic or phenolic chemistry that cures after the parts are joined. A contact adhesive is a solvent- or water-based elastomer, often polychloroprene or nitrile rubber, coated on both surfaces, left until touch-dry, then pressed together for instant grab. Contact adhesives suit laminates, foam, leather and rubber; structural adhesives can replace rivets, screws and welds.

Because water, polymer dispersions, cellulose thickeners and starch feed bacteria and fungi. Without an in-can preservative, a drum of PVA or acrylic adhesive can lose viscosity, smell, build gas or grow mould before it is used. Isothiazolinones such as CMIT/MIT and BIT are common in-can choices, dosed as the supplier's TDS directs and within local regulatory limits. Clean tanks, pipes and filling lines matter as much as the preservative itself.