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TIME-TEMPERATURE-MISCIBILITY AND MORPHOLOGY OF POLYOLEFIN BLENDS

Chinese Journal of Polymer Science 2000年第3期18卷 263-270页

作者： RobertA.Shanks gandaraamarasinghe CRC for Polymers Applied Chemistry RMIT University GPO Box 2476V Melbourne AustraliaCRC for Polymers Applied Chemistry RMIT University GPO Box 2476V Melbourne Australia

Miscibility and crystallization have been studied for polypropylene-polyethylene and polyethylene-polyethyleneblends. In the case of the polypropylene blends the composition of interest is 20% polypropylene. At this composition thepolypropylene has been found to be soluble in linear low density polyethylene but insoluble in high, low and very lowdensity polyethylenes. The miscibility has been concluded from the crystallization kinetics and polarised optical microscopywith a hot stage. Polyethylene-polyethylene blends have been formed from polymers with similar average branching contentbut where they have different melting temperatures. Important consequences are to introduce long branches into apolyethylene that only has short branches, and to modify the morphology of a polyethylenes so that haze, gloss and strainhardening are improved. Polyethylene blends must be developed after careful consideration of the branch content anddistribution within each of the constituents. It is not sufficient to simply blend polyethylenes, with the desired range ofproperties, without regard to the miscibility of the blend composition.

关键词： Polypropylene Polyethylene Blend Miscibility Thermal analysis Morphology Crystallization Melting

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ANALYSIS OF BRANCHING DISTRIBUTION IN POLYETHYLENES BY DIFFERENTIAL SCANNING CALORIMETRY

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Chinese Journal of Polymer Science 2003年第2期21卷 231-239页

作者： RobertShanks FeiChan gandaraamarasinghe RobertShanks PresentedattheInternationalSymposiumonPolymerPhysics 2002QingdaoChinaReceivedAugust312002 AppliedChemistry RMITUniversityGPOBox2476VMelbourne3001Australia

Short chain branching has been characterized using thermal fractionation, a stepwise isothermal crystallizationtechnique, followed by a melting analysis scan using differential scanning calorimetry. Short chain branching distributionwas also characterized by a continuous slow cooling crystallization, followed by a melting analysis scan. Four differentpolyethylenes were studied: Ziegler-Natta gas phase, Ziegler-Natta solution, metallocene, constrained-geometry single sitecatalyzed polyethylenes. The branching distribution was calculated from a calibration of branch content with meltingtemperature. The lamellar thickness was calculated based on the thermodynamic melting temperature of each polyethyleneand the surface free energy of the crystal face. The branching distribution and lamellar thickness distribution were used tocalculate weight average branch content, mean lamellar thickness, and a branch dispersity index. The results for the branchcontent were in good agreement with the known comonomer content of the polyethylenes. A limitation was that high branchcontent polyethylenes did not reach their potential crystallization at ambient temperatures. Cooling to sub-ambient wasnecessary to equilibrate the crystallization, but melting temperature versus branch content was not applicable after cooling tobelow ambient because the calibration data were not performed in this way.

关键词： Polyethylene Short chain branching Lamellar thickness Branch distribution Thermal fractionation DSC

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