Reactive SBC-based hot melt system homes in on headlight lens sealingReactive SBC-based hot melt system homes in on headlight lens sealing

Japan’s Moresco Corp. (Kobe) has debuted a reactive styrenic block copolymer hotmelt sealant that can also be foamed. The target application for this heat-resistant adhesive is as a sealant for headlamp lens, where it would replace butyl rubber.

The hotmelt sealant is described as being very tacky and soft, with good flow properties, meaning it can tackle applications with complex shapes. When applied, moisture in the air is sufficient to catalyze cross-linking, meaning no heat need be applied. Cross-linking also gives the SBC-based sealant its heat resistance of up to 180°C compared with just 120°C for a non-reactive type.

In addition, Moresco has over the years also been proactively developing polyolefin-based hot metal adhesives for use in automobile interiors. Reactive hot melt adhesives contain no solvents and boast improved heat resistance. Because they are solvent-free, major automobile manufacturers have adopted this series of adhesives for its human and environment-friendly features.

Some people like the unique smell of brand-new cars, but what they are really smelling is the solvents used for adhesives, many of which contain hazardous chemical substances. Such substances can cause dizziness, headaches, and breathing problems. Hot melt adhesives, however, do not cause such symptoms because they contain no solvents.

The solvent-free Moresco-Melt RO series is used for adhesion of door trim It is a reactive hot melt adhesive that cures through the moisture content in the air or the material to be adhered. It exhibits high adhesive properties and heat resistance for polypropylene (PP) parts.

Moresco has also developed the heat-resistant Morescomelt RAC-90 for bonding of PP to steel as well as acrylonitrile-butadiene-styrene (ABS) resin. This balanced adhesion towards both ABS and steel allows the use of both PP and ABS in a single component assembly. Adhesive force towards ABS is reportedly 1o-times that of conventional adhesives. RAC-90 also features extended open time of up to 45 seconds, resulting in improved workability.

Also in the Moresco line-up are the heat-resistant RAC-30 and RAC-60 grades, whose main use is in headliners. RAC-30, with a softening point of 159 deg C and heat resistance of around 100 deg C, has a short open time but boasts excellent heat resistance.

A final new product is TN-877, featuring excellent PP adhesion and retention, as well as a long open time upwards of 45 seconds. The material is particularly suited to adhesion of heel pads and deck boards in automobiles. Heat resistance is close to 80°C.