The spherulitic structures and morphologies of poly-(3-hydroxybutyrate) (PHB) crystallized from a so- lution and a thin melt film were investigated in this study. The formation mechanisms of banded spherulites under d...The spherulitic structures and morphologies of poly-(3-hydroxybutyrate) (PHB) crystallized from a so- lution and a thin melt film were investigated in this study. The formation mechanisms of banded spherulites under different crystallization conditions are proposed. It was found that the formation of banded spherulites was caused by the rhythmic crystal growth of the spherulites and lamellar twisting growth for the polymer crystallization from a thin melt film and a solution, respectively.展开更多
The ring-banded spherulite is a special morphology of polymer crystals and has attracted considerable attention over recent decades. In this study, a new phase field model with polymer characteristics is established t...The ring-banded spherulite is a special morphology of polymer crystals and has attracted considerable attention over recent decades. In this study, a new phase field model with polymer characteristics is established to investigate the emergence and formation mechanism of the ring-banded spherulites of crystalline polymers. The model consists of a nonconserved phase field representing the phase transition and a temperature field describing the diffusion of the released latent heat. The corresponding model parameters can be obtained from experimentally accessible material parameters.Two-dimensional calculations are carried out for the ring-banded spherulitic growth of polyethylene film under a series of crystallization temperatures. The results of these calculations demonstrate that the formation of ring-banded spherulites can be triggered by the self-generated thermal field. Moreover, some temperature-dependent characteristics of the ring-banded spherulites observed in experiments are reproduced by simulations, which may help to study the effects of crystallization temperature on the ring-banded structures.展开更多
Phase behavior in blends of liquid crystalline poly(aryl ether ketone) (C-PAEK) and poly(aryl(ether) ketone) containing 4-methyl phenyl groups(T-PAEK) was investigated by differential scanning calorimetry(DSC),polariz...Phase behavior in blends of liquid crystalline poly(aryl ether ketone) (C-PAEK) and poly(aryl(ether) ketone) containing 4-methyl phenyl groups(T-PAEK) was investigated by differential scanning calorimetry(DSC),polarized light microscopy(PLM) and atomic force microscopy(AFM) techniques.In both(C-PAEK-rich) and T-PAEK-rich blends,the two components are molecular miscible in the melting state.For the 80/20 C-PAEK/T-PAEK blend,the bright core and rings are mainly composed of C-PAEK phase and dark rings consist of T-PAEK phase in the ring-banded spherulites.The development of the ring-banded spherulites in the C-PAEK/T-PAEK blends is a rhythmic growth process,and thus it is consistent with the structural discontinuity model proposed by Padden and Keith based on polyethylene spherulites.展开更多
基金Key Science Foundation of Education Ministry of China (Grant No. 207051) Key Lab Foundation of Anhui (Grant No. 2005383)
文摘The spherulitic structures and morphologies of poly-(3-hydroxybutyrate) (PHB) crystallized from a so- lution and a thin melt film were investigated in this study. The formation mechanisms of banded spherulites under different crystallization conditions are proposed. It was found that the formation of banded spherulites was caused by the rhythmic crystal growth of the spherulites and lamellar twisting growth for the polymer crystallization from a thin melt film and a solution, respectively.
基金Project supported by the National Key Basic Research Program of China(Grant No.2012CB025903)the National Natural Science Foundation of China(Grant No.11402210)+1 种基金the Northwestern Polytechnical University Foundation for Fundamental Research(Grant No.JCY20130141)the Ministry of Education Fund for Doctoral Students Newcomer Awards of China
文摘The ring-banded spherulite is a special morphology of polymer crystals and has attracted considerable attention over recent decades. In this study, a new phase field model with polymer characteristics is established to investigate the emergence and formation mechanism of the ring-banded spherulites of crystalline polymers. The model consists of a nonconserved phase field representing the phase transition and a temperature field describing the diffusion of the released latent heat. The corresponding model parameters can be obtained from experimentally accessible material parameters.Two-dimensional calculations are carried out for the ring-banded spherulitic growth of polyethylene film under a series of crystallization temperatures. The results of these calculations demonstrate that the formation of ring-banded spherulites can be triggered by the self-generated thermal field. Moreover, some temperature-dependent characteristics of the ring-banded spherulites observed in experiments are reproduced by simulations, which may help to study the effects of crystallization temperature on the ring-banded structures.
文摘Phase behavior in blends of liquid crystalline poly(aryl ether ketone) (C-PAEK) and poly(aryl(ether) ketone) containing 4-methyl phenyl groups(T-PAEK) was investigated by differential scanning calorimetry(DSC),polarized light microscopy(PLM) and atomic force microscopy(AFM) techniques.In both(C-PAEK-rich) and T-PAEK-rich blends,the two components are molecular miscible in the melting state.For the 80/20 C-PAEK/T-PAEK blend,the bright core and rings are mainly composed of C-PAEK phase and dark rings consist of T-PAEK phase in the ring-banded spherulites.The development of the ring-banded spherulites in the C-PAEK/T-PAEK blends is a rhythmic growth process,and thus it is consistent with the structural discontinuity model proposed by Padden and Keith based on polyethylene spherulites.
