| 1. ↓ / 2. → | ABS | ASA | CA | PA 6 | PA 6.6 | PBT | PC | PC/ABS | PE-HD | PETP | PMMA | POM | PP | PS | SAN | TPE-A | TPE-E | TPE-O | TPE-S | TPE-U | TPE-V |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ABS | + | + | + | + | + | + | + | + | o | + | + | − | − | o | + | − | o | − | − | + | − |
| ASA | + | + | + | · | + | + | + | + | − | + | + | − | − | − | + | · | + | · | · | + | · |
| CA | + | + | + | · | · | + | · | · | − | · | · | − | − | o | + | · | · | · | · | + | · |
| PA 6 | + | · | · | + | + | + | o | + | o | · | · | − | o | − | o | o | − | − | − | + | − |
| PA 6.6 | + | + | · | + | + | + | o | + | o | · | · | − | o | − | o | o | − | · | − | + | − |
| PBT | + | + | + | + | + | + | + | + | o | + | o | o | o | − | + | − | o | · | o | o | − |
| PC | + | + | · | · | o | + | + | + | − | + | o | o | − | − | + | − | + | − | o | + | − |
| PC/ABS | + | + | · | + | + | + | + | + | − | + | · | o | − | − | + | − | o | − | o | + | − |
| PE-HD | o | − | − | o | o | o | o | − | + | + | o | − | o | o | o | − | − | o | o | − | · |
| PETP | + | + | · | · | · | + | + | + | − | + | · | o | · | · | + | − | − | · | − | + | − |
| PMMA | + | + | · | · | · | o | o | · | − | · | + | · | o | − | + | · | · | · | o | o | · |
| POM | o | o | − | − | − | o | o | o | − | o | · | + | o | o | o | − | − | · | − | + | · |
| PP | o | − | − | o | o | o | − | − | o | · | − | o | + | o | o | − | − | · | + | − | + |
| PS | − | − | − | − | − | o | − | − | − | · | − | · | − | + | o | − | − | − | − | − | − |
| PVC (flexible) | + | + | + | · | · | + | + | + | o | · | + | · | o | o | · | · | · | · | · | + | · |
| SAN | + | + | + | · | · | + | + | + | o | + | + | · | − | o | + | − | − | · | − | + | − |
In two-component injection molding, adhesion forms not with an adhesive but by diffusion: the hot melt injected on top partially softens the surface of the premolded part, and the chains of the two polymers intermingle at the interface. For this intermingling to happen, the two materials must be chemically related. The strongest bond is seen in pairs of the same material, followed by neighbors in the same polymer family.
As compatibility decreases, the bond first weakens and then disappears completely. At the interface between an apolar material (PE, PP) and a polar material (PA, PC, PBT) the chains do not intermingle; even if the part looks joined when it is ejected, it separates under load or during thermal cycling.
If a chemical bond is not possible, the solution lies in the mold design: the two components are mechanically interlocked. Through-holes, dovetail sections, undercut channels and fully enclosing geometries join the parts even without adhesion. In this case the interface should not be considered leak-tight; for parts in contact with liquids, a separate seal geometry should be considered.
In addition to the table, three things determine the strength of adhesion: the surface temperature of the premolded part (if it has cooled, diffusion decreases), the waiting time between the two injections and the filler content of the material — glass fiber reduces the contact area at the interface.
1. Taking the "o" mark to mean medium. In the source legend, "o" shows that there is no adhesion; poor adhesion is the "−" mark. Because it is counterintuitive, this is the most common mistake.
2. Ignoring the direction. The table is directional: the row is the premolded component and the column is the overmolded component. The same pair can give a different result in reverse order — PETP onto PE-HD is "+", while PE-HD onto PETP appears as "−". Which material is molded first is a design decision.
3. Treating an empty cell as "does not bond". An empty cell shows that there is no data in the source. No decision should be made for those pairs without a sample test.
No. In the source table both the PE-HD → PP and PP → PE-HD cells are "o", meaning no adhesion. The idea that olefins bond to each other is a common misconception; adhesion is reliable only within the same type (PE/PE, PP/PP).
In the table POM gives "+" to only two materials: itself and TPE-U. All other pairs show no adhesion or poor adhesion. In 2K parts containing POM, mechanical interlocking should be designed instead of a chemical bond.
It depends on the hard component: TPE-U is compatible with ABS and PC, TPE-E additionally with PC, and TPE-V with PP. Pairs that seem intuitive, such as PA 6 → TPE-A and ABS → TPE-S, do not bond in the table.
"o" does not mean medium; it means NO ADHESION. Poor adhesion is shown with "−". This legend is the source's own notation, and because it is counterintuitive it is the most common reading mistake.
No. An empty cell shows that there is no data for that pair in the source. No adhesion and no data are different things; a pair in an empty cell requires a sample test.
No, it gives direction. Adhesion varies with the material grade, the additive and filler content, the surface temperature of the premolded part and the waiting time. The final decision is made on the basis of the raw material manufacturer's data sheet and a sample test.