Preparation And Properties Of Carbon Nanotube Modified Phase Change Microcapsule/epoxy Resin Composites

Microencapsulated phase-change materials(MPCMs)have been widely applied in matrix materials as thermal energy-storage or smart functional composites.Besides,it had been mainly used in building applications.However,miniaturization of electronic components as well as development in multifunctional performances has led to being innegligible,high calorific value.If microencapsulated phase-change materials(MPCMs)that absorbs or releases a large quantity of latent heat were involved in electronic devices,both energy savings and constant temperature maintainment of these devices can be achieved.At present,only a few studies have attempted to incorporate MPCMs into epoxy to prepare temperature-controlling functional composites;especially,less concern is focused on their cure process.Follow this,my research work is taken into two parts:(1)The physically doped CNTs-modified MPCMs/EP composites were successfully prepared through a casting method.The results from scanning electron microscope(SEM),differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA)revealed that microcapsules are tightly integrated with the epoxy matrix with achieving uniform dispersion,which ensures that the otropic heat transfer of the composites.In addition,the CNTs-modified MPCMs endow epoxy composites with smart temperature-controlling function.For the composite system incorporated with microcapsules doped with CNTs in the core,the heat storage capacity is enhanced with the increase of the filled amount.The results from the heat resistance test indicate that all samples showed good thermal stability.In order to research their curing process,non-isothermal DSC was used to study its curing behavior.The results showed that the initial curing temperature,peak temperature and terminal curing temperature increase with the increase of the heating rate.The addition of the CNTs-modified MPCMs reduces the activation energy of the composites.However,the reaction order does not change evidently.Furthermore,the rheological properties of the composites were investigated by Anton Paar rotational rheometer.The results showed that the viscosity of composites has a certain dependence on temperature,and the gel time is shortened with the increase of curing temperature.The shear viscosities of all the samples decrease at low shear rates,however,when the shear rate is larger than 20 s-1,the composite system behaves Newtonian's behaviour.(2)Epoxy composites incorporated with various type of MPCMs modified using layer-by-layer assembly technique were also successfully prepared.SEM photos showed that the MPCMs with 1 or 3 poly(4-styrenesulfonic acid)sodium(PSS)/CNTs bilayers are tightly embedded and uniformly dispersed in epoxy matrix.The TGA results indicated that the addition of CNTs-assembled MPCMs does not change the degradation process of epoxy.The temperature at the maximum degradation rate of composites appears at 375 ?.The non-isothermal curing kinetics of the composites was investigated using DSC.The kinetics parameters of composites system were analyzed by Kissinger,Flynn-Wall-Ozawa,and Crane methods,respectively.The results showed that the activation energy of composite filled with MPCMs with three(PSS/CNTs)bilayers is lower than that filled with MPCMs with one(PSS/CNTs)bilayer.However,the mechanism of curing reaction is not changed.Moreover,Anton Paar rotational rheometer was ultilized to explore the effect of CNTs-assembled MPCMs on the rheological behavior of composites.The suitable temperature range for their manufacturing process is between 40 ? and 80 ?.The change of shear viscosity vs.shear rate of the samples follow the law of Newtonian fluids as the shear rate is beyond 20 s-1,with the viscosity ranging between 1.18 Pa·s and 1.40 Pa·s.