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. 
For more part design and specific processing information, consult the appropriate literature available from your TPE supplier.
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