Structure And Properties Of Semi-interpenetrating Polymer Network Of Epoxy/Cyanate/Phenolphthalein Poly (Ether Ketone)

The semi-interpenetrating polymer network (semi-IPN) had been prepared by epoxy resin blending with Phenolphthalein poly (ether ketone) (PEK-C) using cyanate resin as curing agent. The curing kinetics, the effect of PEK-C content on product's structure, the mechanical properties, thermo properties, and micromorphologies of the product and the toughen mechanism has been studied.The curing process, the effect of PEK-C content on reaction activity had been studied and curing kinetic functions for each resin system had been confirmed by non-isothermo analyze using differential scanning calorimetric (DSC). The results showed that the curing process was: 150℃/4h+200℃/2h+230℃/4h and all the resin systems got their highest reaction extent; PEK-C could catalyze the self-polymerization of CE and reduce the reaction activity of epoxide with triazine. The resins' gelation time at 150℃and 200℃reduced form 4320s and 690s to 1920s and 208s respectively with PEK-C content increased from 0wt% to 15wt%. The reaction activity energy of the resins increased from 77kJ/mol to 85kJ/mol with increasing PEK-C content. The apparent reaction exponents of all the reins kept at 0.9, which indicated that the curing mechanism was not changed with adding PEK-C. The theoretic reaction rate was higher than the realisticl reaction rate before the highest reaction rate but the same after that.The structure and the conversion of reaction groups of the resins at gelation and after curing were studied by Fourier transform infrared (FTIR). The crosslinking density of the cured products was also studied by Dynamic Mechanical Analyze (DMA).The results showed that The main structure in the resins at gelation was triazine and dimer formed by CE. The cyanate conversion reduced from 0.58 to 0.45 and triazine's existence ratio was almost 0.7 at gelation with PEK-C content increased from 0wt% to 15wt%; After curing, the main structure in the resins was triazine and polyether component. The triazine's existence ratio in the resins increased from 0.23 to 0.55 with increasing PEK-C content from 0wt% to 15wt%. The epoxide had reacted mainly complete for all the resins, more of which had transformed into polyether structure. The product's crosslinking density had a little decreased with increasing PEK-C content. The molecular weight between crosslink points and PEK-C content had a linear relationship which was Mc=10.2T+324.5. The product's broken toughness, flexural modulus and flexural strength were tested by three point bending method using universal testing machine. The results showed that the product's broken toughness (K_IC and G_IC increased from 0.99 MPa·m^1/2 and 280 KJ·m² to 1.23 MPa·m^1/2 and 443 KJ·m² respectively with PEK-C content increased from 0wt% to 15wt%. The broken toughness got their highest value when PEK-C's content was 15wt%, which increased 20% and 58% respectively. With increasing PEK-C content, the product's flexural strength increased from 117Mpa tol23Mpa and then reduced to 113MPa, while the flexural modulus maintened at 2.90Gpa.The product's heat distortion temperature (HDT) was tested by HDT tester; the glass transition temperature (Tg) and morphology were tested by dynamic mechanical analyze (DMA); the product's thermal stability was tested by thermo gravity analyze (TGA). The results showed that with increasing PEK-C content, product's HDT increased from 203℃to 207℃and then reduced to 204℃; Tg increased from 232℃to 234℃and then reduce to 231℃. The cured resin was a semi-IPN structure with a single phase. The IDT and Et of the product decreased from 360℃and 174KJ/mol to 353℃and 154KJ/mol while the T_max maitained at 400℃. The thermal stability of the product decreased a little with increasing PEK-C content.The morphology of the broken surface was determined by scanning electron microscopy (SEM) and the toughen mechanism was studied. The result showed that broken surface became more and more rough with increasing PEK-C's content, which was the feature of toughness rupture. The elevation of toughness was due to the submit distortion of the matix induced by thermo particles when PEK-C content was less than 15wt%. The elevation of toughness was due to the submit distortion of the matix induced by thermo particles and the plastic distortion of the matrix induced by the plasticization of the linkages and the groups which didn't form network in the matrix when PEK-C content was 15wt%. At this time the latter factor was the main effect on toughness elevation.