Shrinkage silicone rubber

Dai, L. Zhang, Z. Zhao, Y. Xie, Z., Polymeric Curing Agent Reinforced Silicone Rubber Composites with Low Viscosity and Low Volume Shrinkage. 

In passing from a liquid to a solid, shrinkage occurs. This can be large (a 20% solution of a polymer must reduce to one-fifth of its volume on setting) or small (less than 0.5% for some silicone rubbers). 

FIGURE 2.16 The effect of minimum film-formation temperature (MFFT) of a dispersion on its drying behaviour. Primal (Rohm Haas) dispersions were allowed to dry at room temperature, =21 °C, in a silicone rubber mould. An MFFT above room temperature results in incomplete coalescence of particles and poor film formation. The cracks and distortion that occur in the films result from the movement of water and shrinkage during drying, (a) AC-34 MFFT, 12 °C. (b) AC-73 MFFT, 37 °C. (c) B-85 MFFT, 90 °C. 

Method of setting How activated (UV, heat, mixing), proportions of components, setting time, shrinkage Ditto Silicone rubbers are available as 1 or 2 parts, set in 5 minutes to 48 hours and shrink 3% to 0.5%, depending on grade... 

---