Hot-Melt Adhesives Chemicals

EVA-based hot melts are the most widely used for packaging and carton forming — economical and easy to process. APAO hot melts offer better heat resistance and flexibility for hygiene products (diapers, sanitary napkins). Polyamide (PA) hot melts bond metals and provide excellent chemical resistance for automotive and industrial use. Reactive PUR hot melts develop exceptional final strength through moisture-triggered crosslinking — ideal for woodworking and footwear.

Open time is the period after hot-melt application during which parts can be joined and still achieve good bonding. Set time is the time needed after joining to reach handling strength. Short open time/fast set is needed for high-speed automated assembly lines. Longer open time is needed for manual assembly. APAO and rubber-based systems can be formulated for longer open times than EVA.

Fischer-Tropsch (FT) waxes, paraffin wax, and microcrystalline wax control melt viscosity at application temperature, crystallization rate (which affects set speed), and surface tack. FT waxes are preferred for high-performance formulations due to their narrow melting range and low color. Oxidized polyethylene waxes improve adhesion to polar substrates.

Reactive polyurethane (PUR) hot-melts apply at 100–130°C — lower than non-reactive HMA — forming an initial physical bond on cooling. Final cure occurs over 24–72 h via moisture cure with atmospheric water, building a crosslinked network with very high heat and creep resistance. PUR hot-melts are widely used in panel lamination, automotive interiors, and high-performance footwear assembly.

Standard packaging hot-melts apply at 150–180°C with viscosity 800–2000 mPa·s. Low-temperature hot-melts (formulated with metallocene-PE) apply at 110–130°C, reducing energy consumption and substrate damage. Bookbinding hot-melts apply at 180–200°C with extended open time. Hygiene-product hot-melts (APAO-based) apply with spray patterns at 140–160°C onto nonwoven substrates.

Hot-melt adhesives are exposed to elevated temperatures during processing and application — antioxidants are essential to prevent thermo-oxidative degradation that would cause color change, viscosity drift, and odor. Hindered phenolic antioxidants (Irganox 1010, 1076) at 0.1–0.5% provide primary protection. Phosphite secondary antioxidants (Irgafos 168) extend protection and prevent color formation during processing.