The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR) . The analysis on kinetics demonstrates that TBC8-eb can not only accelerate the crystallization rate but also transform most of the original spherulite crystals of PLLA into sheaf-like crystals. Furthermore,the free energy of folding(σe) of PLLA and PLLA with TBC8-eb is 0.15 and 0.06 J·m-2,respectively,which suggests that the addition of TBC8-eb favors the regular folding of molecule chains in the crystallization of PLLA,improv-ing its crystallization rate. The FTIR results show that TBC8-eb can accelerate the conformational ordering of PLLA in the isothermal crystallization. The conformational ordering of PLLA nucleated with TBC8-eb begins with the interchain interaction of CH3,and then a short helix emerges where a couple of CH3 groups interact.
Oleylamine(G18) and octanol(G8) were grafted onto the surfaces of the multi-walled carbon nanotubes(CNTs).The grafted CNTs were dispersed into palmitic acid(PA) and paraffin wax(PW) to prepare phase change composites.The heat storage/retrieval experiments showed that the composites kept stable after repeating melting and solidification for 80 times.The structure of the G18-CNT/PA and G8-CNT/PA was homogenous compared with the pristine CNT(P-CNT)/PA.The latent heat capacity(Ls) of solid liquid phase change of G18-CNT/PW was higher than that of PW while those of the G8-CNT/PW and P-CNT/PW were lower than that of PW.Compared with PA,all PA based composites with both P-CNTs and grafted CNTs decreased Ls evidently.The Ls values of G18-CNT composites in both matrices were higher than that of the counterparts of G8-CNT.The thermal conductivities of all the PA based composites in the study were higher than that of PA,as well as those of all the PW based composites.However,the thermal conductivities of the G18-CNT composites in both matrixes were lower than those of the G8-CNT composites in both matrixes at all measured temperatures.
