MECHANICAL PROPERTIES OF ADHESIVES BASED ON SILICON-CONTAINING EPOXY RESIN

To enhance the properties of adhesives, hydroxyl-terminated polydimethylsiloxane (PDMS) was grafted to epoxy resin (analogue of ED-20) by cross-linking via 3-aminopropyltriethoxysilane. Based on resulting silicon-containing epoxy oligomers three series of polymers (SEP, SEA, SEI) with different content of siloxane were obtained. They differed in the type of hardener: oligoaminoamide PO-300 (SEP), modified cycloaliphatic polyamine Ancamine 2752 (SEA) and isomethyltetrahydrophtalic anhydride (i-MTHPA) (SEI), respectively. The aim of the work was to investigate the depen dence of mechanical and adhesive characteristics of modified epoxy polymers on both the applied hardener and the concentration of silicone. The small amounts of PDMS (from 0.1 to 5.0 parts by weight) were chosen because their effect on the properties of epoxies has not been sufficiently studied. Therefore, the addition of even 0.1 pbw of silicon-containing component was found to have a significant effect on the mechanical and adhesive behaviour of the samples. Depending on the content and type of hardener, some properties were both improved and impaired relatively to unmodified epoxy polymers. The impact of PDMS turned out to be the most favorable for mechanical properties of SEP-2.5 causing the increase in tensile strength by 98 % and in elongation at break by 69 %, whereas it was most destructive for SEA-0.1 with decline of tensile strength by 30 % and for SEA-0.25 with decrease in deformation by 50 %. However, the amine hardener provided the highest absolute values of mechanical performance, especially for neat samples. In return, adhesive strength was mostly the highest for series of epoxies hardened by i-MTHPA. The introduction of PDMS can alter it more; thus, shear strength of steel plates was augmented by 144 % for SEI-0.1. The largest increase was characteristic to tear strength of alumina substrates for SEA-0.25 (by 184 %), while the largest decrease — to tear and shear strength of steel substrates for SEP-2.5 (by 47 % and 59 % respectively).