PlatSil® 73-15 vs RTV-4115 Silicone Comparison

PlatSil® 73-15 and RTV-4115 are both Shore A15 platinum-cure silicones with a 1:1 mixing system for flexible molds and casting applications. PlatSil® 73-15 has a published mixed viscosity of 2,500 cP and a 20-minute pour time, while RTV-4115 is listed at 4,000±200 mPa·s for Part A and a 30–40-minute working time. Both have published demold or cure times of approximately 4–5 hours, while their mechanical data show a different balance between stretchability and tensile and tear strength. This comparison focuses on these published differences to help users evaluate the most relevant processing and mold-performance characteristics.

PlatSil® 73-15 and RTV-4115 are both Shore A15 platinum-cure silicones, placing them in a soft and flexible mold range. An A15 profile can provide useful flexibility for complex shapes and undercuts, while its lower stiffness can also allow unsupported molds to deform under external pressure. Mold thickness and rigid support should therefore be considered for pressure casting and large molds.

Viscosity is one of the notable published differences. Polytek reports 2,500 cP for mixed PlatSil® 73-15, while MinghuiLink reports approximately 4,000±200 mPa·s for Part A of RTV-4115. Because these values are reported for different material states and measurement points, they should not be treated as a strict like-for-like viscosity ranking. The published data nevertheless show different processing characteristics that should be considered when selecting a mixing, pouring and air-removal method.

The working windows are more clearly separated. Polytek specifies a 20-minute pour time for PlatSil® 73-15, while MinghuiLink lists a 30–40-minute working time for RTV-4115. RTV-4115 therefore provides the longer published working window, while PlatSil® 73-15 requires the mold, master and pouring setup to be prepared before mixing.

The published demold and cure times are broadly similar. Polytek lists approximately 4–5 hours for demolding PlatSil® 73-15, while MinghuiLink specifies approximately 4–5 hours for RTV-4115. The similar stated turnaround makes working time a more noticeable processing difference. Demolding time should also not be assumed to mean that the silicone has reached all of its final cured properties, particularly when the mold will be subjected to substantial stretching or mechanical loading.

The mechanical profiles show a more substantial difference. PlatSil® 73-15 reports 640% elongation, compared with 450% for RTV-4115. RTV-4115 reports 5.0 MPa tensile strength and 26 N/mm tear strength, compared with 265 psi tensile strength and 55 pli Die B tear strength for PlatSil® 73-15. The reported tear values use different test methods and should not be directly ranked. The published data do, however, show higher reported elongation for PlatSil® 73-15 and higher reported tensile and tear strength for RTV-4115.