Hot Melts

Ethylene Vinyl Acetate (EVA)

The foundational chemistry of the packaging and woodworking industries. EVA performance is governed by the ratio of vinyl acetate (VA) to ethylene content. Higher VA content increases chain polarity and flexibility, improving adhesion to polar substrates and reducing set temperature. Higher ethylene content produces a more crystalline structure with faster set times and higher cohesive strength, at the cost of adhesion range.

EVA remains the cost-performance standard for high-volume general industrial bonding where temperature resistance above 80-90°C is not required.

Higher VA means more flexible, broader adhesion. Higher ethylene means faster set, stronger crystalline cohesion. The ratio is the primary formulation lever.

Lowest raw material cost in the HMA range. Suitable for high-volume applications where temperature resistance requirements do not exceed approximately 80°C service.

Compatible with slot die, bead dispensing, and spray application. Available in stick, pellet, and block formats across a wide viscosity range.

Metallocene Polyolefins (mPO)

Metallocene catalysis produces polyolefins with a uniquely narrow molecular weight distribution (MWD), a degree of polymer architecture control unavailable with conventional Ziegler-Natta catalysts. This narrow MWD creates a very sharp phase transition: mPO goes from a low-viscosity melt to a high-strength crystalline solid almost instantaneously upon cooling, giving sub-second green strength in high-speed automated lines.

The narrow MWD also yields superior thermal stability with significantly reduced charring and char deposits in applicator systems, a major operational advantage in continuous-run production. mPO adhesives have largely displaced EVA in demanding high-speed packaging and product assembly applications.

Amorphous Poly-Alpha-Olefins (APAO)

APAOs are synthesized using traditional Ziegler-Natta multi-site catalysts, which produce polymers with a broad molecular weight distribution and an amorphous (non-crystalline) microstructure. This amorphous nature is the defining performance characteristic: where mPO crystallizes sharply upon cooling, APAO cools gradually through a wide softening range.

This extended softening range translates directly into extended open time, a critical requirement for applications where the adhesive must remain tacky after dispensing, spanning the distance from nozzle to substrate in spray applications, or wetting out large, irregular surfaces before bonding occurs.

APAOs also provide excellent adhesion to low-surface-energy (LSE) plastics and exceptional low-temperature flexibility, properties that make them the preferred chemistry for hygiene product manufacturing, mattress assembly, and automotive acoustic insulation where broad-area spray dispensing is the process method.

Physical Phase Change

Strength development is purely thermodynamic. As heat dissipates into the substrates and surrounding air, polymer chains re-entangle and the adhesive solidifies. The bond achieves its full design strength immediately after cooling to ambient temperature.

If reheated above the softening point, the adhesive reliquefies and the bond loses strength. This reversibility provides excellent reworkability but also defines the maximum service temperature of the assembly.

Two-Stage Cure Kinetics

Physical Stage: The prepolymer cools and solidifies, rapidly developing green strength. Assemblies can be handled, machined, or packaged immediately without clamping, improving manufacturing throughput.

Chemical Stage: Residual isocyanate (NCO) groups react with ambient moisture over 24–72 hours, forming stable urea linkages and a permanently crosslinked network. Once cured, PUR behaves as an elastomeric thermoset and can no longer be remelted.

Automotive & Transportation

Automotive cabins experience severe and sustained thermal cycling, from sub-zero overnight temperatures to elevated in-cabin heat on summer days. Conventional thermoplastic hot melts such as EVA and mPO gradually soften under prolonged heat and static shear loading, making them susceptible to creep. Moisture-cured PUR adhesives form an irreversible thermoset elastomer that maintains structural integrity throughout these demanding operating conditions.

PUR has therefore become the preferred chemistry for automotive headliner bonding, interior trim attachment, seating foam assembly, acoustic insulation lamination, and other applications requiring long-term heat resistance, vibration damping, and durable structural performance.

Electronics – Low-Pressure Molding & PCB Encapsulation

Low-Pressure Molding (LPM uses polyamide (PA) hot melts for PCB encapsulation, sensor potting, and watertight connector overmolding. PA exhibits exceptionally low melt viscosity, enabling injection into aluminum mold cavities at ultra-low pressures (1.5–40 bar). The adhesive crystallizes within seconds, simultaneously functioning as both the protective encapsulant and the external housing while providing a watertight (IP67), flame-retardant (UL94 V-0) enclosure without high-pressure tooling.

For micro-bonding and sealing of consumer electronics, including OLED displays, flexible circuits, and camera modules, PUR is the preferred chemistry. Its relatively low application temperature (100–110°C) minimizes thermal distortion of thin plastic housings and protects heat-sensitive components. After curing, the elastomeric network absorbs vibration and impact while still permitting localized thermal rework, improving manufacturing yield and component recovery.

Structural Woodworking & Edge Banding

In environments exposed to moisture, elevated temperatures, and repeated cleaning cycles, such as kitchen cabinetry, bathroom vanities, and exterior furniture, the adhesive bond must resist steam, water ingress, and long-term environmental aging. Moisture-cured PUR adhesives form a permanently crosslinked thermoset network that penetrates and mechanically interlocks with the porous cellular structure of wood and engineered particleboard, delivering exceptional water resistance and virtually invisible edge-banding bond lines.

For interior furniture and other applications where moisture exposure is minimal, highly filled EVA hot melts containing calcium carbonate (CaCO₃) offer a cost-effective alternative. These formulations provide reliable adhesion, improved gap-filling capability, and efficient processing on porous wood-based substrates while maintaining excellent production throughput.

Need Help Selecting the Right Hot Melt System?

Chemistry selection in hot melt adhesives depends on your substrate combination, required open time, service temperature, and production process. Our technical team provides product selection support, trial quantity sourcing, and application guidance across EVA, mPO, APAO, SBC, polyamide, and PUR systems.

Hot Melt Chemistry – Quick Reference