HSE & LSE Substrates Identification
Identifying Substrates and Pairing the Right Adhesive
When searching for the appropriate adhesive system to create the best bond to your substrate, most important to consider is surface condition. Features such as roughness, smoothness, how porous, coated, uncoated, cleanliness, flexibility and size of the part. However, one of the most critical issues to determine is surface energy of the substrate. You must identify the surface energy as either HSE or LSE. Most substrates are classified as either High Surface Energy (HSE) or Low Surface Energy (LSE) and are categorized by their dyne levels.
To understand the concept of surface energy, simply, if you have a substrate with a slippery, heavily coated surface, adhesives have a difficult time flowing into that substrate, therefore not creating a solid bond. These substrates are considered Low Surface Energy or LSE.
If you have a non-coated, clean, or coarse surface the adhesive can flow into that substrate, therefore creating a solid bond. These substrates are considered to be High Surface Energy or HSE.
The surface attraction between diverse materials is referred to as adhesive bond. The bond of the adhesion to the substrate is determined by the surface energy of the material. The higher the surface energy, the stronger the bond and lower the surface energy, the weaker the bond. If the substrate is classified as an HSE or a High Surface Energy surface, you can use solvent based acrylic adhesive systems for bonding. If the substrate is classified as LSE or a Low Surface Energy surface you can use modified solvent acrylic, rubber and/or silicone adhesive systems.
EXAMPLES OF SUBSTRATE TYPES
HSE substrates allow an adhesive to “wet out”, which elevates the bond. Some HSE substrates include; PET, ABS, Polycarbonate, Rigid PVC, Uncoated Papers, Acrylic, Nylon, Epoxy Paint, Polyurethane, Copper, Aluminum, Zinc, Tin, Lead, Stainless Steel, and Glass.
LSE substrates fight the adhesive and will not allow an adhesive to “wet out”, which decreases the bond. Some LSE substrates include; PVA, Polystyrene, Acetal, EVA, Tedlar, Silicone, Wood, Cement, Nylon, Polyester Fabric, Polyethylene, Polypropylene, PVF, PTFE, Powder Paint, Acetal, Coated Papers, Carpet and Flooring underlayment.
Similar to water, adhesive on a high surface energy surface flows and “wets out” the surface. Adhesives that do not wet a surface will not fill surface irregularities, making bonding a challenge. “Wetting out” is required to form a strong bond.