Structure and properties evaluation of epoxy resin modified with polyurethane based on polymeric MDI and different polyols
The present work investigates the properties and structure of epoxy resin (EP) modified with polyurethane (PUR). This latter was prepared using polymeric diphenylmethane diisocyanate and polyethylene glycol (PEG 400) or polyoxypropylene diol with different molecular weights (POPD 1002 and POPD 2002). It was confirmed that 5% of either PUR improved significantly the mechanical properties of EP. Impact strength and critical stress intensity factor values of modified epoxy compositions were increased by 200 and 100%, respectively, relative to pristine samples. Fourier-transform infrared spectra confirmed the occurrence of chemical reactions between reactive groups of EP and PUR. The fracture surface of EP modified with PUR based on PEG exhibited less plastic yielding, while river-like lines with more pronounced plastic deformations were shown by EP modified with 5% PUR with longest chains.