Mechanical properties of modified epoxy: effect of chain length

Purpose - To evaluate the mechanical properties of cured epoxy modified with amine terminated poly (ethylene glycol) benzoate (ATPEGB) along with the comparison of results with change in chain length of ATPEGB. Design/methodology/approach - ATPEGB prepared from poly (ethylene glycol) (PEG) of different molecular weights (200, 400 and 600) were used as modifiers for epoxy resin here. For effective toughening, different compositions were made by adding various concentration of each ATPEGB to epoxy. The impact, adhesive, tensile and flexural strengths of modified and unmodified epoxy were characterised and compared for each ATPEGB. Findings - Modification of epoxy resin using each ATPEGB showed significant enhancement of mechanical strengths over unmodified epoxy. The modification caused a chemical linking between ATPEGB and resin which led not only to a phase separation but also to ensuring their intrinsically strong chemical bonds across the ATPEGB phase/resin matrix interface and this was the main cause to the improved mechanical strengths. The optimum results were obtained at 12.5 phr (parts per hundred parts of epoxy resin) concentration of each modifier. Research limitations/implications - The modifiers, ATPEGB, used in the present context were synthesised from PEG of molecular weight 200, 400 and 600. Besides, it could be synthesised from PEG of molecular weight 4,000 and 20,000, etc. and modification of epoxy resin could also be studied effectively by using these. Originality/value - The method for enhanced toughness of cured epoxy was novel and could find numerous applications as surface coating and adhesive onto an intricate structure.