Polyimide(PI)synthesized from aromatic diamine and dianhydrides via two-step poly-condensation method was highly soluble in TGDDM(MY-720)and DGEBA(E-51)at desirable temperature.TGDDM-PI(M-PI)and DGEBA-PI(E-PI)composit...Polyimide(PI)synthesized from aromatic diamine and dianhydrides via two-step poly-condensation method was highly soluble in TGDDM(MY-720)and DGEBA(E-51)at desirable temperature.TGDDM-PI(M-PI)and DGEBA-PI(E-PI)composites within 0.5%-3%PI loading could be prepared without organic solvent.On the cryogenically fractured surfaces of M-PI and E-PI composites,no obvious heterogeneous phase was observed by SEM.The mechanical properties were promoted significantly by PI,especially for impact strength.Adding 2%PI-2W into MY-720 and E-51 composites,the impact strength increased to 21 and 51 kJ/m2,the tensile strength increased by 62%and 19%,and the flexural strength by 18%and 13%,respectively,with slight increases in tensile modulus.These results were related to the promotion in plasticity of composites and changes in fragile→ductile fracture mode.Moreover,Tg and thermal stability of M-PI and E-PI were increased effectively.展开更多
The curing behavior of diglycidyl ether of bisphenol-A(DGEBA) with aromatic diamide-diimide-diamines having aryl ether,sulfone and methylene linkages was studied by differential scanning calorimetry(DSC).Nine diamide-...The curing behavior of diglycidyl ether of bisphenol-A(DGEBA) with aromatic diamide-diimide-diamines having aryl ether,sulfone and methylene linkages was studied by differential scanning calorimetry(DSC).Nine diamide-diimide-diamines of varying structure were synthesized by reacting 1 mole of dianhydride with 2 moles of L-cysteine(S) in a mixture of acetic acid and pyridine(3:2 V/V) followed by activation with thionyl chloride(SOCl_2) and then condensation with excess of diamines.Structural characterization...展开更多
Here, dielectric spectroscopy is used in the fre- quency range from 10-2 Hz up to 107 Hz and we found dynamics of the primary α-and intermolecular Johari–Goldstein β-processes are strongly correlated in diglycidyl-...Here, dielectric spectroscopy is used in the fre- quency range from 10-2 Hz up to 107 Hz and we found dynamics of the primary α-and intermolecular Johari–Goldstein β-processes are strongly correlated in diglycidyl-ether of bis-phenol-A and poly phenyl glycidyl-ether (PPGE) over a wide temperature from 193 to 345 K and pressure P range from 0.1 to 600 MPa. In contrast with the widespread opinion of statistical independence of these processes the α-β mutual dependence is quantitatively confirmed in [1] analysing the temperature and pressure behavior of the α-and (JG) β-processes the investigation of the ratio of dielectric strength of two processes close to Tg evidence that the importance of secondary dy namics in relaxing external electric stresses increase in glass formers at high pressures with respect to that of the structural relaxation. We suggest that the thermal agitation, acting above Tg is at the basis of the observed result.展开更多
The curing behavior of diglycidyl ether of bisphenol-A （DGEBA） with different phosphorus containing diamidediimide-tetraamines （DADITAs） was studied by DSC. Eight DADITAs of varying structures were synthesized by ...The curing behavior of diglycidyl ether of bisphenol-A （DGEBA） with different phosphorus containing diamidediimide-tetraamines （DADITAs） was studied by DSC. Eight DADITAs of varying structures were synthesized by reacting 1 mole of pyromellitic anhydride （PMDA）/3,3＇-benzophenone tetracarboxylic dianhydride （BTDA）/1,4,5,8-naphthalene tetraearboxylic dianhydride （NTDA）/4,4＇-oxydiphthalic anhydride （ODPA） with 2 mole of L-tryptophan （T） in a mixture of acetic acid and pyridine （3：2 V/V） followed by activaton with thionyl chloride and then condensation with excess of phosphorus containing triamines tris（3-aminophenyl） phosphine （TAP） and tris（3-aminophenyl） phosphine oxide （TAPO）. DADITAs obtained by reacting PMDA/BTDA/NTDA/ODPA with L-tryptophan followed by condensation with TAP/TAPO were designated as PTAP, PTAPO, BTAP, BTAPO, NTAP, NTAPO, OTAP and OTAPO respectively. The structural characterization of synthesized DADITAs was done by FTIR, ~H-NMR, I3C-NMR, 31p-NMR spectroscopic techniques and elemental analysis. Thermal stability of the isothermally cured epoxy was investigated using dynamic thermogravimetry analysis. The glass transition temperature （Tg） was highest in DGEBA cured using PTAP. All epoxy thermosets exhibited excellent flame retardancy, moderate changes in Tg and thermal stability. Due to presence of phosphorus in curing agents, all epoxy resin systems met the UL-94 V-0 classification and the limiting oxygen index （LOI） reached up to 38.5, probably because of the nitrogen-phosphorus synergistic effect.展开更多
Diglycidyl ether of bisphenol-A (DGEBA), having number average molecular weight (Mn) 375, was modified by incorporating the hydroxyl terminated polybutadiene (HTPB) based prepolymer using isophorone diisocyanate as a ...Diglycidyl ether of bisphenol-A (DGEBA), having number average molecular weight (Mn) 375, was modified by incorporating the hydroxyl terminated polybutadiene (HTPB) based prepolymer using isophorone diisocyanate as a coupling agent. To increase the compatibility between the epoxy resin and HTPB part, polar groups were introduced in the later to achieve physical and chemical interactions between the two phases. The finally modified DGEBA system was cured with amine based hardener. FTIR and 1H-NMR were used to monitor the whole modification procedure. The rubber particles size and distribution was monitored as a function of HTPB contents in the resin system using scanning electron microscopy (SEM). The mechanical, thermal and thermo-mechanical properties have shown that the tensile strength, toughness, ductility and impact strength of the modified cured system have been successfully increased at some optimum HTPB contents without affecting the inherent thermal and thermo-mechanical stability associated with DGEBA resin system. Some of the mechanical properties like flexural modulus, tensile modulus and compressive strength decreased with increasing rubber contents.展开更多
基金This work was financially supported by the National Key Research and Development Program of China(No.2016YFC0204300)the National Natural Science Foundation of China(Nos.21777043,21976056).
文摘Polyimide(PI)synthesized from aromatic diamine and dianhydrides via two-step poly-condensation method was highly soluble in TGDDM(MY-720)and DGEBA(E-51)at desirable temperature.TGDDM-PI(M-PI)and DGEBA-PI(E-PI)composites within 0.5%-3%PI loading could be prepared without organic solvent.On the cryogenically fractured surfaces of M-PI and E-PI composites,no obvious heterogeneous phase was observed by SEM.The mechanical properties were promoted significantly by PI,especially for impact strength.Adding 2%PI-2W into MY-720 and E-51 composites,the impact strength increased to 21 and 51 kJ/m2,the tensile strength increased by 62%and 19%,and the flexural strength by 18%and 13%,respectively,with slight increases in tensile modulus.These results were related to the promotion in plasticity of composites and changes in fragile→ductile fracture mode.Moreover,Tg and thermal stability of M-PI and E-PI were increased effectively.
文摘The curing behavior of diglycidyl ether of bisphenol-A(DGEBA) with aromatic diamide-diimide-diamines having aryl ether,sulfone and methylene linkages was studied by differential scanning calorimetry(DSC).Nine diamide-diimide-diamines of varying structure were synthesized by reacting 1 mole of dianhydride with 2 moles of L-cysteine(S) in a mixture of acetic acid and pyridine(3:2 V/V) followed by activation with thionyl chloride(SOCl_2) and then condensation with excess of diamines.Structural characterization...
文摘Here, dielectric spectroscopy is used in the fre- quency range from 10-2 Hz up to 107 Hz and we found dynamics of the primary α-and intermolecular Johari–Goldstein β-processes are strongly correlated in diglycidyl-ether of bis-phenol-A and poly phenyl glycidyl-ether (PPGE) over a wide temperature from 193 to 345 K and pressure P range from 0.1 to 600 MPa. In contrast with the widespread opinion of statistical independence of these processes the α-β mutual dependence is quantitatively confirmed in [1] analysing the temperature and pressure behavior of the α-and (JG) β-processes the investigation of the ratio of dielectric strength of two processes close to Tg evidence that the importance of secondary dy namics in relaxing external electric stresses increase in glass formers at high pressures with respect to that of the structural relaxation. We suggest that the thermal agitation, acting above Tg is at the basis of the observed result.
文摘The curing behavior of diglycidyl ether of bisphenol-A （DGEBA） with different phosphorus containing diamidediimide-tetraamines （DADITAs） was studied by DSC. Eight DADITAs of varying structures were synthesized by reacting 1 mole of pyromellitic anhydride （PMDA）/3,3＇-benzophenone tetracarboxylic dianhydride （BTDA）/1,4,5,8-naphthalene tetraearboxylic dianhydride （NTDA）/4,4＇-oxydiphthalic anhydride （ODPA） with 2 mole of L-tryptophan （T） in a mixture of acetic acid and pyridine （3：2 V/V） followed by activaton with thionyl chloride and then condensation with excess of phosphorus containing triamines tris（3-aminophenyl） phosphine （TAP） and tris（3-aminophenyl） phosphine oxide （TAPO）. DADITAs obtained by reacting PMDA/BTDA/NTDA/ODPA with L-tryptophan followed by condensation with TAP/TAPO were designated as PTAP, PTAPO, BTAP, BTAPO, NTAP, NTAPO, OTAP and OTAPO respectively. The structural characterization of synthesized DADITAs was done by FTIR, ~H-NMR, I3C-NMR, 31p-NMR spectroscopic techniques and elemental analysis. Thermal stability of the isothermally cured epoxy was investigated using dynamic thermogravimetry analysis. The glass transition temperature （Tg） was highest in DGEBA cured using PTAP. All epoxy thermosets exhibited excellent flame retardancy, moderate changes in Tg and thermal stability. Due to presence of phosphorus in curing agents, all epoxy resin systems met the UL-94 V-0 classification and the limiting oxygen index （LOI） reached up to 38.5, probably because of the nitrogen-phosphorus synergistic effect.
文摘Diglycidyl ether of bisphenol-A (DGEBA), having number average molecular weight (Mn) 375, was modified by incorporating the hydroxyl terminated polybutadiene (HTPB) based prepolymer using isophorone diisocyanate as a coupling agent. To increase the compatibility between the epoxy resin and HTPB part, polar groups were introduced in the later to achieve physical and chemical interactions between the two phases. The finally modified DGEBA system was cured with amine based hardener. FTIR and 1H-NMR were used to monitor the whole modification procedure. The rubber particles size and distribution was monitored as a function of HTPB contents in the resin system using scanning electron microscopy (SEM). The mechanical, thermal and thermo-mechanical properties have shown that the tensile strength, toughness, ductility and impact strength of the modified cured system have been successfully increased at some optimum HTPB contents without affecting the inherent thermal and thermo-mechanical stability associated with DGEBA resin system. Some of the mechanical properties like flexural modulus, tensile modulus and compressive strength decreased with increasing rubber contents.
