Flexible moulding is a very popular go-to system across many industries when faced with a part reproduction application. It is more cost effective than 3D Printing for small runs and a great alternative to solid mould processes such a liquid injection moulding or resin transfer moulding.
The Rapid Prototyping Industry has adopted flexible moulding for a wide range of applications including automotive casting, aviation and consumer electronics. This process is also making an impact with large volume production tasks, architectural element production, and composite manufacturing and even with art reproduction and restoration projects.
Momentive Performance Materials, a global leader in silicones and advanced materials, is launching 3 new grades designed specifically for flexible moulding applications. These new products will join the already very popular RTV664, an addition cure silicone system with FDA (food grade) approval.
TSE3478T is a 2-part addition cure silicone; this oil bleed system is easy to degas, has a handy 10:1 mix ratio and works to standard cure conditions. The product cures to a 40 Shore A Translucent rubber with a tensile strength of 6.0MPa, 380% elongation and extremely low shrinkage.
TSE3480T is a 2-part addition cure silicone; a non-oil bleed system which offers improved mould life. As with TSE3478T, this system has a handy 10:1 mix ratio and works to standard cure conditions. The product cures to a 37 Shore A Translucent rubber with a tensile strength of 6.0MPa, 380% elongation and extremely low shrinkage.
RTV664 is a 2-part addition cure silicone; it is a non-oil bleed system with a high cured shore hardness and FDA approval. This product has a shorter work life and demould time at room temperature than the new materials, however this cannot be speeded up with the addition of heat. RTV664 cures to a 62 Shore A light blue rubber with very good tensile strength (6.4 MPa), 245% elongation and very low linear shrinkage.
RTV788-20 is a 2-part condensation cure silicone; this non-oil bleed system is best suited for soft mould making. Again it has a handy 10:1 mix ratio and works to standard cure conditions, however unlike the TSE3478T & TSE3480T the RTV7888-20 work life and demould time cannot be quickened with heat. The product cures to a soft 20 Shore A light pink rubber with a tensile strength of 3.4MPa, 350% elongation and low shrinkage.
During testing, the above Momentive Performance Materials flexible mould making silicones excelled in performance compared to other silicone offerings. Providing a greater number of releases and showing better mould life.
Momentive flexible moulding silicone offer excellent transfer of pattern detail, a moderate to long mould life and have no casting temperature restrictions. Not all of these are benefits which can be attributed to other flexible mould materials such as latex, polysulfide, and PVC – these systems would not tolerate exotherms higher than 65°C and have very short mould life.
Although the relative material cost of silicone for flexible mould making is high compared to latex and PVC, silicone balances out the economic cost with its performance attributes required for fine detail castings and productivity.