Study on liquid-liquid phase separation of metallocene polyethylene blends
Li, YY; Liu, CY; Sun, X; He, JS
AbstractThe crystallization kinetics of polyethylene blends(metallocene based HDPE and commercial LDPE) were investigated for studying liquid-liquid phase separation in these blends. All the quenched blend samples were first melt at 180 degreesC for 5min. Isothermal crystallization was taken at appropriate temperature(a temperature low enough for the HDPE to crystallize but high enough that the LDPE would remain molten) using differential scanning calorimetry(DSC). In contrast,when the melt was held for 5min or 15min at 150 degreesC(in the region of liquid-liquid phase segregation),the kinetics of the isothermal crystallization of the annealed samples had a distinctly faster tendency than the samples without annealing and there were no difference when extending the annealing time. Based on Hoffman theory and further experimental data,the possibility of nucleation and co-crystallization at being kept at 150 degreesC for 5min or 15min was eliminated. So it is strongly indicative of the existence of liquid-liquid phase segregation in the melt of polyethlene blends. If the annealed samples did not undergo phase separation between two components, their crystallization kinetics should be the same as those observed for the unannealed samples. Now in the present case, phase separation occurs, then the crystallization kinetics becomes faster in order to approach that of the pure HDPE. This conclusion is based on a widely accepted assumption. It says that when both components are miscible and one of them is crystallizable,the crystallization rate of their blend is slower,compared to that of its pure components due to the rejection of the noncrystallizable component from the pristine fraction in the crystallization process. Annealing blends of HDPE and LDPE at 150 degreesC induced phase separation in the the melt. HDPE enriched in these blends brought about an accelerated kinetics for the annealed samples.
KeywordMetallocene Polyethylene Blends Liquid-liquid Phase Segregation
Indexed BySCI
WOS IDWOS:000165910900010
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Document Type期刊论文
Corresponding AuthorLi, YY
AffiliationChinese Acad Sci, Inst Chem, Ctr Mol Sci, State Key Lab Engn Plast, Beijing 100080, Peoples R China
Recommended Citation
GB/T 7714
Li, YY,Liu, CY,Sun, X,et al. Study on liquid-liquid phase separation of metallocene polyethylene blends[J]. ACTA POLYMERICA SINICA,2000(6):707-710.
APA Li, YY,Liu, CY,Sun, X,&He, JS.(2000).Study on liquid-liquid phase separation of metallocene polyethylene blends.ACTA POLYMERICA SINICA(6),707-710.
MLA Li, YY,et al."Study on liquid-liquid phase separation of metallocene polyethylene blends".ACTA POLYMERICA SINICA .6(2000):707-710.
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