Bonding between silicones and thermoplastics using 3D printed mechanical interlocking

• Published in: Materials & design 2020-01, Vol.186, p.108254, Article 108254
• Main Authors: Rossing, Lars, Scharff, Rob B.N., Chömpff, Bryan, Wang, Charlie C.L., Doubrovski, Eugeni L.
• Format: Article
• Language: English
• Subjects: 3D printing; Bonding; Casting; Fused Deposition Modeling; Mechanical interlocking; Silicones
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2019.108254

Silicones have desirable properties such as skin-safety, high temperature-resistance, and flexibility. Many applications require the presence of a hard body connected to the silicone. Traditionally, it has been difficult to create strong bonding between silicones and hard materials. In this study, a technique is presented to control the bonding strength between silicones and thermoplastics through mechanical interlocking. This is realized through a hybrid fabrication method where silicone is cast onto a 3D-printed mold and interlocking structure. The influence of the structure's design parameters on the bonding strength is explored through theoretical modeling and physical testing, while the manufacturability of the 3D-printed structure is ensured. A CAD tool is developed to automatically apply the interlocking structure to product surfaces. The user interface visualizes the theoretical strength of the cells as the designer adjusts the cell parameters, allowing the designer to iteratively optimize the structure to the product's load case. The bonding strength of the presented mechanical interlocking structure is more than 5.5 times higher than can be achieved with a commercially available primer. The presented technique enables custom digital design and manufacturing of durable free-form parts. This is demonstrated through application of the technique in over-molded products, airtight seals, and soft pneumatic actuators. [Display omitted] •New 3D printed structures create a strong bonding between silicone and plastic.•Hybrid fabrication is used to cast silicone onto a 3D-printed mold and structure.•A verified model relates the bonding strength to the structure's parameters.•A CAD tool generates the developed interlocking structure onto product interfaces.•The bonding structure is applied in soft robots, sealings, and overmolded parts.