Question: What is HCR?
Answer: This heat cure rubber or high consistency rubber is an old technology. Its physical form appears to be a solid block of rubber as pre-cure material. As a result of thixotropic untreated silica and a very high viscosity polymer, HCR is a very high consistency material. Since untreated silica is very thixotropic, it requires high shear to break the hydrogen bond. This leads to a reduction in viscosity and flows into molds. High pressure presses are typically used to mold HCR. The properties of HCR in comparison with other silicone materials are illustrated in the table below.
Type of Silicone Rubber Tensile Strength Tear Strength Elongation
Units: Mpa Units: kN/m Range
HCR – High Consistency Rubber 4 to 13 9 to 55 90 to 1120%
FSR – Fluorosilicone Rubber 9 to 12 18 to 46 160 to 700%
LSR – Liquid Silicone Rubber 4 to 12 11 to 52 220 to 900%
RTV – Room Temperature Vulcanize 6 9 370%