Two different hyperbranched polymers (HBPs) were synthesized as tougheners for an aeronautical graded epoxy matrix. The first, labelled HBPG (HBP Glassy) is a glassy polyester characterized by a glass transition temperature (Tg) higher then room temperature (~90°C): this system was synthesized by means of bulk poly-condensation reaction starting from 4,4-bis(p-hydroxyphenyl) pentanoic acid as polymer precursor. The second HBP typology, identified as HBPR (HBP Rubbery) is a polyamide ester with a Tg lower then room temperature (~20°C), thus in rubbery state at testing temperature. The HBPR filler was obtained by bulk poly-condensation of succinic anhydride and diethylamine. In both cases, DSC was employed to measure polymer-based filler glass transition temperature. HBP/epoxy systems were prepared at two filler concentrations, i.e. 0.1 and 5wt%, and later tested by using different experimental techniques in order to assess effects of the filler nature on rheological, mechanical and fracture performances. Final rheological results have demonstrated that HBPG induces an higher increase of the viscosity compared to that associated to HBPR (at same weight contents). Nevertheless the glassy HBP provides the best results in term of thermo-mechanical and fracture performances, with a lower loss of glass transition temperature and an higher increase of KIC and GIC values.
Fracture toughness and mechanical characterization of epoxy nanocomposites based on different hyperbranched polymers typologies
Zotti A;Zuppolini S;Zarrelli M;Borriello A
2020
Abstract
Two different hyperbranched polymers (HBPs) were synthesized as tougheners for an aeronautical graded epoxy matrix. The first, labelled HBPG (HBP Glassy) is a glassy polyester characterized by a glass transition temperature (Tg) higher then room temperature (~90°C): this system was synthesized by means of bulk poly-condensation reaction starting from 4,4-bis(p-hydroxyphenyl) pentanoic acid as polymer precursor. The second HBP typology, identified as HBPR (HBP Rubbery) is a polyamide ester with a Tg lower then room temperature (~20°C), thus in rubbery state at testing temperature. The HBPR filler was obtained by bulk poly-condensation of succinic anhydride and diethylamine. In both cases, DSC was employed to measure polymer-based filler glass transition temperature. HBP/epoxy systems were prepared at two filler concentrations, i.e. 0.1 and 5wt%, and later tested by using different experimental techniques in order to assess effects of the filler nature on rheological, mechanical and fracture performances. Final rheological results have demonstrated that HBPG induces an higher increase of the viscosity compared to that associated to HBPR (at same weight contents). Nevertheless the glassy HBP provides the best results in term of thermo-mechanical and fracture performances, with a lower loss of glass transition temperature and an higher increase of KIC and GIC values.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
