Some experimental results for the end-linked polydimethylsiloxane network system

Small-strain equilibrium modulus data of polydimethylsiloxane (PDMS) networks are reviewed. 58 different articles in the literature with values of the modulus of end-linked PDMS networks were found [1-58] including more than 250 values of the small-strain equilibrium modulus as function of variables in the crosslinking system. The dominating variable is shown to be the molecular weight of PDMS as expected, whereas the functionality of the crosslinker methylhydrosiloxane/ dimethylsiloxane copolymer is shown to be less important in good agreement with the phantom model. The data collected was fitted to the phenomenological model of Langley and Graessley including an entanglement contribution. The fitted entanglement plateau (0.16 MPa) is in good agreement with literature values and with the theoretical prediction of the tube model. Experimental data for the Mooney-Rivlin constants was found and it was shown that C2 is constant with increasing functionality. Furthermore it was found that trapped entanglements can be split into two categories, viz. locked entanglements contributing to the C1 term and traditionally trapped entanglements contributing to C2.