Unique Shoe-Lacing System Features PC Overmolded with Soft-Touch TPE
Rotary dial of patented Freelock wire closure system allows wearer to dial in comfort.
Customized TPE compounds, particularly the ‘soft-touch feel’ variety, are proliferating in a myriad of various applications from tool handles and consumer electronics to automotive, appliances and shoes. A comfortable feel is a key attribute of such materials and in the case of shoes, this is particularly desirable in every aspect. (I’m saying this the week after the terrific experience of NPE2018, including all the walking it entailed.)
A unique shoe-lacing system developed by Korea’s Shin Kyung Inc., features such a TPE. The Freelock wire closure system is said to eliminate the challenges of conventional shoe laces, which are time-consuming to adjust to the ideal level of tightness—critical for both comfort and safety—particularly for demanding activities such as running. The patented Freelock’s innovative mechanism for tightening, securing and loosening laces accomplishes this by means of multiple wires contracted or released as needed by a simple twist of a rotary dial.
The two-component dial is comprised of a PC base overmolded with Thermoplast K from Kraiburg TPE (U.S. office in Buford, Ga.). Shin Kyung selected this TPE compound for its combination of excellent processing characteristics, tensile strength, and aesthetics. The material also met key specifications such as easy colorability in line with brand footwear shades; high flowability for short cycle times; and uncompromising long-term adhesion to the PC in order to withstand the frequent tuning and tension applied to the rotary dial across the shoe’s lifetime. Moreover, this Kraiburg TPE compound reportedly offers excellent surface quality along with that pleasant soft-touch feel while retaining its firm grip.
In-mold assembly, decorating, labeling, finishing: In-mold “what-have-you” has been a trend in injection molding for years.
Hard/soft overmolding has become a fundamental technique for injection molders in recent years, and a growing number of molders are extending that technology thermoset/thermoplastic combinations.
Next month’s mammoth triennial plastics show in Düsseldorf, Germany, challenges injection molding machine builders to demonstrate technological leadership in addressing the needs of the marketplace.