Tech Tips

Overmolding: Chemical and Mechanical Bonding

Posted On April 14, 2017 By Tony Holtz

Overmolding is not a new manufacturing technology, but there is still some confusion about how to design for the two-part process. One of the largest areas to consider? Bonding. A number of materials can be used to overmold components together, but without a chemical bond or mechanical interlock, some overmolded parts won’t stand the test of time.

mechanical bonding illustration
Three types of mechanical bonding techniques.
Chemical Bonding

This bonding process involves two chemically compatible materials that are molded together to form a strong bond with each other. It’s important to note that not all materials play well with one another. The compatibility chart below indicate whether a chemical or mechanical bond is recommended for key thermoplastic and thermoset materials.

Mechanical Interlocking

What happens when your materials are not compatible, the desired bonding strength cannot be achieved, or you want to ensure your materials don’t peel apart from repeated use? This is where designing a mechanical interlock, which physically holds the overmolded material to the substrate, makes sense. There are many ways to design these into parts (see example), so discuss the options with your manufacturer.

Chemical Bonding Compatibility
                                                                                                                 Substrate Material
Overmold Material ABS Lustran ABS/PC Cycolo C2950-111 PC Lexan
940-701
PBT Valox
357-1001
PP Profax 6323 Nylon 66
Zytel 103 HSL NC010
TPU - Texin
983-000000
C C C C M M
TPV - Santoprene
101-87
M M M M C M
TPE - Santoprene
101-64
M M M M C M
LSR - Elastosil
3003/30 A/B
- - M M - M
TPC - Hytrel 3078 C C C C M M
TPE-Versaflex OM
1060X-1
C C C M M M
TPE-Versaflex OM
6240-1/td>
M M M M M C
TPE-Versaflex OM
6258-1
M M M M M C
TPE-Versaflex OM
1040X-1
C C C M M M

 

M = mechanical bond recommended

C = chemical bond

If you have further questions regarding rapid overmolding at Proto Labs, contact one of our applications engineers at 877-479-3680 or customerservice@protolabs.com.

Tagged: overmolding, chemical bonding, thermoplastics
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