Polyolefins, such as polypropylene and polyethylene, have always been tough to bond with adhesives. These plastics have such little surface energy that adhesives bead up on their surfaces like water on a freshly waxed car.
Materials with high surface energy allow liquids to spread out across their surfaces. Common plastics, such as ABS or polycarbonate, have a high have a high surface energy of 40 to 50 dynes per square centimeter. In contrast, polyolefins have a surface energy of just 20 to 30 dynes per square centimeter.