A series of novel poly(amide-imide)(PAl)films with different amide contents were prepared from pyromellitic dianhydride and four amide-containing diamines.These PAl films exhibited excellent mechanical and thermal pro...A series of novel poly(amide-imide)(PAl)films with different amide contents were prepared from pyromellitic dianhydride and four amide-containing diamines.These PAl films exhibited excellent mechanical and thermal properties with tensile strength of 203.7-297.4 MPa and Tg above 407℃.The rigid backbone structures combined with strong intermolecular interactions provided PAl films with ultralow in-plane CTE values from-4.17 ppm/℃to-0.39 ppm/℃in the temperature range of 30-300℃.The correlation between thermal expansion behavior and aggregation structures of PAl film was investigated.The results suggested that hydrogen bonding interactions could be maintained even at high temperature,thus resulting in good dimension reversibility of films in multiple heating-cooling cycles.It is demonstrated that dimensional stabilities of PAl films are determined by the rigidity,orientation,and packing of molecular chains.Heat-resistant PAl films with ultralow CTE can be developed as flexible substrates by regulating backbones and aggregation structures for optoelectronic application.展开更多
Two micron SiC particles with angular and spherical shape and the sub-micron Al2O3 particles with spherical shape were introduced to reinforce 6061 aluminium by squeeze casting technology. Microstructures and effect o...Two micron SiC particles with angular and spherical shape and the sub-micron Al2O3 particles with spherical shape were introduced to reinforce 6061 aluminium by squeeze casting technology. Microstructures and effect of thermal-cooling cycle treatment （TCCT） on the thermal expansion behaviors of three composites were investigated. The results show that the composites are free of porosity and SiC/Al2O3 particles are distributed uniformly. Inflections at about 300℃ are observed in coefficient of thermal expansion （CTE） versus temperature curves of two SiCp/Al composites, and this characteristic is not affected by TCCT. The TCCT has significant effect on thermal expansion behavior of SiCp/Al composites and CTE of them after 3 cycles is lower than that of 1 or 5 cycles. However, no inflection is observed in Al2O3p/Al composite, while TCCT has effect on CTE of Al2O3p/Al composite. These results should be due to different relaxation behavior of internal stress in three composites.展开更多
Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 μm to 25 μm,and the effect of aggregation structure on thermal expansion behavior along different directions was studi...Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 μm to 25 μm,and the effect of aggregation structure on thermal expansion behavior along different directions was studied.Both in-plane and out-of-plane linear thermal expansion(CTEand CTE) were respectively characterized by thermal mechanical analysis and FT-near-IR interference method.Volumetric and anisotropic behavior of thermal expan sion were also investigated.With increasing film thickness,CTEgradually increased from 32.2 ppm/℃ to46.1 ppm/℃ while CTEdecreased from 149.7 ppm/℃ to 128.2 ppm/℃.Volumetric thermal expansion of polyimide films was less sensitive to the va ried thickness,but anisotropy of thermal expansion was reduced.Polyimide film of 5 μm thickness showed large birefringence,indicating more considerable in-plane chain orientation anisotropy.Besides,molecular chains were more densely packed along in-plane direction when film thickness increased,while became loosely stacked in the out-of-plane direction.In contrast to the enhanced lateral chain packing for thicker film s,higher vertical chain packing order was found in thinner films.The variation of aggregation structure during thermal expansion procedure was analyzed by temperature-dependent WAXD.It is proved that thermal expansion behavior of thinner films could be largely attributed to molecular chain packing,whereas that may be influenced by many factors for thicker films in addition to the effect of chain packing.The results revealed that thermal expansion of films with thickness variation is closely related to molecular chain orientation and packing,which is associated with both chemistry and morphological structure of polyimide.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(No.51803221).
文摘A series of novel poly(amide-imide)(PAl)films with different amide contents were prepared from pyromellitic dianhydride and four amide-containing diamines.These PAl films exhibited excellent mechanical and thermal properties with tensile strength of 203.7-297.4 MPa and Tg above 407℃.The rigid backbone structures combined with strong intermolecular interactions provided PAl films with ultralow in-plane CTE values from-4.17 ppm/℃to-0.39 ppm/℃in the temperature range of 30-300℃.The correlation between thermal expansion behavior and aggregation structures of PAl film was investigated.The results suggested that hydrogen bonding interactions could be maintained even at high temperature,thus resulting in good dimension reversibility of films in multiple heating-cooling cycles.It is demonstrated that dimensional stabilities of PAl films are determined by the rigidity,orientation,and packing of molecular chains.Heat-resistant PAl films with ultralow CTE can be developed as flexible substrates by regulating backbones and aggregation structures for optoelectronic application.
基金Project(20080430895) supported by China Postdoctoral Science FoundationProject(2008RFQXG045) supported by Special Fund of Technological Innovation of HarbinProject(HITQNJS.2009.021) supported by Development Program for Outstanding Young Teachers in Harbin Institute of Technology
文摘Two micron SiC particles with angular and spherical shape and the sub-micron Al2O3 particles with spherical shape were introduced to reinforce 6061 aluminium by squeeze casting technology. Microstructures and effect of thermal-cooling cycle treatment （TCCT） on the thermal expansion behaviors of three composites were investigated. The results show that the composites are free of porosity and SiC/Al2O3 particles are distributed uniformly. Inflections at about 300℃ are observed in coefficient of thermal expansion （CTE） versus temperature curves of two SiCp/Al composites, and this characteristic is not affected by TCCT. The TCCT has significant effect on thermal expansion behavior of SiCp/Al composites and CTE of them after 3 cycles is lower than that of 1 or 5 cycles. However, no inflection is observed in Al2O3p/Al composite, while TCCT has effect on CTE of Al2O3p/Al composite. These results should be due to different relaxation behavior of internal stress in three composites.
基金financially supported by the National Natural Science Foundation of China (No.51803221)。
文摘Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 μm to 25 μm,and the effect of aggregation structure on thermal expansion behavior along different directions was studied.Both in-plane and out-of-plane linear thermal expansion(CTEand CTE) were respectively characterized by thermal mechanical analysis and FT-near-IR interference method.Volumetric and anisotropic behavior of thermal expan sion were also investigated.With increasing film thickness,CTEgradually increased from 32.2 ppm/℃ to46.1 ppm/℃ while CTEdecreased from 149.7 ppm/℃ to 128.2 ppm/℃.Volumetric thermal expansion of polyimide films was less sensitive to the va ried thickness,but anisotropy of thermal expansion was reduced.Polyimide film of 5 μm thickness showed large birefringence,indicating more considerable in-plane chain orientation anisotropy.Besides,molecular chains were more densely packed along in-plane direction when film thickness increased,while became loosely stacked in the out-of-plane direction.In contrast to the enhanced lateral chain packing for thicker film s,higher vertical chain packing order was found in thinner films.The variation of aggregation structure during thermal expansion procedure was analyzed by temperature-dependent WAXD.It is proved that thermal expansion behavior of thinner films could be largely attributed to molecular chain packing,whereas that may be influenced by many factors for thicker films in addition to the effect of chain packing.The results revealed that thermal expansion of films with thickness variation is closely related to molecular chain orientation and packing,which is associated with both chemistry and morphological structure of polyimide.
