Preparation Of Polydopamine Nanoparticles/Polyurethane Composites And Study On Their Gamma-Radiation Resistance

Polyurethane?PU?is a widely used polymer material.Due to its excellent radiation resistance,PU can be well applied in irradiation environment.But continuous use in irradiated environment will make it aging rapidly.In order to improve the service life of PU under irradiation environment,polydopamine nanoparticles?PDAPs?were first used as free radical scavengers to improve the irradiation resistance of polyurethane.But the stabilization of PDAPs under gamma irradiation has not been reported.Therefore,polydopamine nanoparticles?PDAPs?with an average particle size of about 180 nm were irradiated with⁶⁰Co source at doses of 200 kGy and 400 kGy respectively.The morphology,thermal stability and radical signal of?-irradiated PADPs were characterized by SEM,TEM,TGA and EPR spectrum.The results suggested that 200 kGy irradiation dose has little effect on the morphology and thermal stability of PDAPs.As?-irradiation dose increased up to 400 kGy,morphology of PDAPs were obviously deformed,thermal stability and EPR intensity was significantly decreased.These results indicated that PDAPs degraded significantly under 400kGy?-irradiation.Furthermore,a degradation mechanism of PDAPs under?-irradiation was explored.PU/PDAPs nanocomposites with different PDAPs contents were simply prepared by solution casting method.Morphological studies of PU/PDAPs composites shows that When the content of PDAPs is 1 wt.%and 2.5 wt.%,it can be well dispersed in PU/PDAPs composites,a slight agglomeration occurs when the content is 5 wt.%.The thermal decomposition results showed that PU/PDAPs nanocomposites exhibited better thermal stability than pure PU.The toughness and strength of PU/PDAPs composites were significantly improved due to the hydrogen bonds between PDAPs and polyurethane molecular chains.The tensile strength increased from 5.49 MPa?PU0?to 7.61 MPa?PU5?,with an increase of about 38.6%Then PU/PDAPs nanocomposites were irradiated at 100 and 200 kGy with a ⁶⁰Co source.Due to the powerful free radical scavenging ability of PDAPs,the radiation resistance of PU has been improved obviously.Morphological studies showed that the PU/PDAPs nanocomposites with only 1%PDAPs contents have a significant improvement in the cross section morphologies after irradiation.Compared with pure PU,the thermal stability of PU/PDAPs nanocomposites with different PDAP content hardly changed after irradiation.In addition,the fracture strength of PU/PDAPs composites increased from 1.48 MPa?0 wt.%?to5.48 MPa?5 wt.%?,the decrease ratio of breaking strength decreased from 73%?0 wt.%?to23%?5 wt.%?at 200 kGy.According to these results,the addition of PDAPs remarkably improved the radiation resistance of polyurethane,and the mechanism was discussed in detail in this paper.