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Secondary Operations: Overmolding
The use of overmolded soft-touch materials is commonly employed to add both functional and decorative elements to articles produced from rigid thermoplastic elastomers (TPE). Eastman Tritan™ copolyester demonstrates excellent adhesion with commercially available TPE grades. Before selecting the TPE grade for use, work with either the TPE supplier or Eastman to choose a grade which is formulated for use with a copolyester substrate—and designing your part for successful results.
Part design considerations:
- Optimize part thickness and TPE thickness for adhesion and dimensional stability. TPE thickness in excess of the Eastman Tritan™ copolyester part thickness could result in warpage when you remove it from the mold. The typical rule of thumb recommends a substrate thickness twice that of the TPE.
- Mechanical interlocks can be incorporated to improve TPE adhesion and promote part durability. Mechanical interlocks become particularly important with thin TPE layers or very demanding fitness-for-use requirements.
- For designs incorporating soft-touch features on multiple surfaces, flow-through designs should be used to improve adhesion and durability.
- To minimize the potential for peeling or delamination, the edge of the TPE should be flush with or below the level of the non-overmolded section of the rigid substrate.
Be sure to consider the specific end-use environment of the overmolded article when selecting the appropriate TPE grade to confirm that it means your specific fitness-for-use criteria.
| TMI TIP: Stop by booth 2480 at the National Restaurant Association (NRA) show May 21-24, 2016. Tritan experts will be on hand to answer all your questions about Tritan. Then take your swings at the Eastman Batting Cage. |
For more information about using Tritan in secondary operations, as well as tips for decorating, painting, overmolding, and printing techniques, download a copy of our Secondary operations guide.
