EKO-TECH TAPES
Surface Energy Classification
Surface energy (typically expressed in dyn/cm or mN/m) describes how readily an adhesive wets a substrate. For practical selection, materials fall into three classes:
- High surface energy – good wet-out; bonding is generally straightforward.
- Medium surface energy – moderate wet-out; adhesive selection is important.
- Low surface energy – poor wet-out; often requires surface activation or LSE adhesives.
High Surface Energy
On high surface energy materials, surface molecules attract each other strongly and readily attract liquid molecules. The result is easy wet-out and generally straightforward bonding. Typical values are in the hundreds to thousands of dyn/cm (mN/m). Common examples include metals (steel, aluminum, copper), glass, and ceramics.
What it means in practice
Medium Surface Energy
This is the “middle zone” between easy and difficult wet-out. Typical values are around 36–300 dyn/cm (mN/m), with many engineering substrates clustering near 36–60 dyn/cm. Common examples: ABS, PC, rigid PVC, PET, PMMA, laminates, plus natural materials like wood, stone, concrete (high variability).
In practice
Low Surface Energy
On low-surface-energy (LSE) substrates, surface molecules are “content,” showing little attraction to liquids—wet-out is poor and contact angles are high (often >90°). LSE is typically < 36 dyn/cm (mN/m), commonly ~18–34 dyn/cm. Examples include polyolefins (PP, PE/HDPE/LDPE), many TPE/POE, silicone rubbers, and fluoropolymers (PTFE, FEP, ETFE)—among the hardest to bond.
In practice
Surface energy of various materials
Plastics
Plastics and Surface Energy
Plastics span a wide range of surface energies, which dictates wet-out and bondability. Polyolefins and fluoropolymers (< ~36 dyn/cm, LSE) are difficult to bond and often need activation (corona/plasma/flame), primers, or LSE-optimized adhesives. Engineering plastics such as ABS, PC, PET, PA, PMMA (typically ~36–60 dyn/cm) offer moderate wetting—cleaning and light scuffing can help. The chart below summarizes typical ranges to guide adhesive selection.
Low-Surface-Energy (LSE) Plastics
LSE plastics typically have lower density and softening/melting ranges, and their non-polar surfaces resist wet-out—liquids and adhesives tend to bead. Bonding is challenging and often requires surface activation (corona/plasma/flame), primers, or LSE-optimized adhesives and tapes (e.g., LSE acrylic foams). The toolbox is smaller than for HSE substrates, but proven options exist, including dedicated 3M or tesa solutions.
Engineering Plastics
Engineering plastics are widely used: lightweight, strong, formable, and cost-effective. They exhibit higher surface energy than LSE plastics (typically ~36–60 dyn/cm), which improves wet-out and makes bonding easier with tapes and liquid adhesives. Examples include ABS, PC, PET, PA, PMMA, rigid PVC; thorough cleaning and occasional light scuffing usually suffice.
Traditional Materials
A broad class with surface energies typically higher than most plastics and lower than metals (often around 100–400 dyn/cm). It includes glass, ceramics, concrete and natural materials such as wood, leather, textiles. They generally wet out and bond readily with tapes or liquid adhesives, but account for specifics: porosity and moisture (wood/concrete) call for dust removal, drying, and often a primer/sealer, while glass/ceramics usually need thorough degreasing.
Metals
Metals are robust and perform across wide temperature and environmental ranges. Their very high surface energy enables easy wet-out, so they’re generally easy to bond. Suitable options include acrylic PSAs/tapes, acrylic foam tapes, epoxies, cyanoacrylates, and structural acrylics. Always clean/degrease and remove oxides/coatings—oils and corrosion inhibitors reduce adhesion.
