| Thermoplastic polyurethane(TPU)is a type of elastomer with both rubber and plastic properties.It is widely used in medical,packaging and interior applications due to its good biocompatibility,excellent processability and wear resistance.However,TPU's low mechanical strength,poor heat resistance,susceptibility to self-degradation,yellowing and brittleness under ultraviolet light limit the practical applications.Due to their unique mechanical properties and nano characteristics,nanomaterials are often used as functional materials to improve the defects of TPUs.It is particularly important to design a nanomaterial that is simple in process,unique in structure and versatile in function.In this thesis,two organic amines with different structures:alkylamine tetraethylenepentamine(TEPA)and aromatic amine 4,4-diaminodiphenylmethane(DDM),were used as amine modifiers to modify graphene oxide(GO)to produce TEPAmodified GO(TEPA-GO)and DDM-modified GO(DDM-GO)respectively.In situ growth of silica(SiO2)on its surface by low-temperature precipitation to obtain SiO2coated modified GO nanocomposites TEPA-GO@SiO2 and DDM-GO@SiO2.TEPAGO@SiO2/TPU nanocomposites and DDM-GO@SiO2/TPU nanocomposites were produced by solution blending of fillers dispersed in TPU.The effects of different filler additions on the mechanical properties,thermal stability,rheological properties and UV shielding properties of TPU were studied.The comparative analysis of the modification effects of two modifiers also was carried out.The specific conclusions are as follows:1?TEPA-GO was prepared by hydrothermal method at 180? for 10h in different proportions.Thermal stability analysis shows that the best modification was achieved when TEPA:GO=10:1.Compared to GO,the initial degradation temperature(T10)and charred residues were increased by 183%and 63%respectively.With the introduction of SiO2 nanoparticles,the thermal stability of TEPA-GO is further improved,and the residual carbon rate of TEPA-GO@SiO2 is increased by 8%at 600?.When the filling amount of TEPA-GO@SiO2 was 0.5wt%,the tensile strength and elongation at break of TPU composites increased by 51%and 19%respectively,and the hardness increased by 17%;the thermal stability of TPU composites slightly improved with the addition of TEPA-GO@SiO2;the rheological results showed that the introduction of TEPAGO@SiO2 impeded the flow of TPU chain segments and improved their resistance to deformation;the UV shielding performance of TPU composites was improved by 9%when TEPA-GO@SiO2 was added at 2 wt%.2?Different ratios of DDM-GO were prepared at 95? and 10h.The study showed that the thermal stability was best when DDM:GO=3:1.Compared with GO,the T10 and residual carbon rate of DDM-GO were increased by 261%and 67%respectively;with the introduction of nano-SiO2,the residual carbon rate of DDM-GO was increased by 7%;mechanical property analysis showed that the tensile strength of TPU composites was increased by 66%and the hardness was increased by 16%at 0.5 wt%of DDM-GO@SiO2 filling,while the elongation at break continued to increase with the increase of filling The elongation at break continued to decrease with increasing filling.Thermal stability results showed that the introduction of DDM-GO@SiO2 slightly increased the maximum degradation rate temperature(Tmax)and carbon residue rate of TPU.The rheological performance analysis showed that DDM-GO@SiO2 made the TPU molecular chains less mobile.The UV shielding performance showed that the shielding efficiency increased gradually with the increase of DDM-GO@SiO2 filling amount,which could be improved by 21%compared to pure TPU when the filling amount was 2wt%.3?In order to further analyse the difference in the modification effect of TEPA and DDM on GO and the difference in the enhancement effect between TEPA-GO@SiO2 and DDM-GO@SiO2 used in TPU,their mechanical properties,thermal stability,rheological properties and UV shielding properties were compared.The results showed that the morphology of DDM-GO was significantly different from TEPA-Go and its thermal stability was significantly better than TEPA-GO.Mechanical and thermal stability results showed that the interaction between TEPA-GO@SiO2 and TPU were mainly due to the interaction between the "soft segment" and the TPU composite,which made the toughness of the TPU composite was improved.On the other hand,DDM-GO@SiO2 has a predominantly "hard segment" effect on the TPU,making the TPU more rigid and less tough.The rheological properties showed that the addition of both fillers to the TPU increased the G',G" and complex viscosities and improved the rheological behaviour.The UV shielding properties showed that DDM-GO@SiO2 has a better shielding effect than TEPA-GO@SiO2.Figure 61 Table 11 Reference 85... |
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