Self-synthesized epoxy terminated polydimethylsiloxane with various molecular weights toughening epoxy resin

Polydimethylsiloxane terminated by epoxy group (EPPDMS) with various molecular weight (Mn) were synthesized by 1,3-bis[3-(2,3-epoxypropoxy)-propyl]1,1,3,3-tetramethyldisiloxane (DOTMDS) and dimethylcyclosiloxane (Dn). The epoxy value measured by potentiometric titration, were 0.161, 0.092, 0.065, 0.044 mol/100 g, and the Mn (calculated from epoxy value) 1,242, 2,174, 3,077, 4,545 g/mol, respectively (corresponding to EP-PDMS1, 2, 3, 4). With the increasing ratio of Dn/DOTMDS, we can see the increase of Mn and the decrease of epoxy group content according to FTIR result. Then these EP-PDMS were used to improve the toughness of the epoxy resin (diglycidyl ether of bisphenol A, DGEBA). Mechanical tests showed that, the impact strength of the epoxy resin was improved by EP-PDMS. The toughening effect was decreased when EP-PDMS with relative higher Mn was used. This was ascribed to that the EPPDMS with high Mn was easier to agglomerate, and the active group was easier to be embedded which in turn resulted in lower toughening efficiency. This was also confirmed by scanning electron microscopy results. J. VINYL ADDIT. TECHNOL., 00: 000-000, 2016. VC 2016 Society of Plastics Engineers results. J. VINYL ADDIT. TECHNOL., 24: 268-274, 2018. (c) 2016 Society of Plastics Engineers