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Crystallization in miscible and immiscible polymer blends

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dc.title Crystallization in miscible and immiscible polymer blends en
dc.contributor.author Svoboda, Petr
dc.relation.ispartof Polypropylene: Synthesis, Applications and Environmental Concerns
dc.identifier.isbn 9781624171420
dc.date.issued 2013
dc.citation.spage 37
dc.citation.epage 70
dc.type bookPart
dc.language.iso en
dc.publisher Nova Science Publishers, Inc.
dc.description.abstract Crystalline morphology influences greatly mechanical properties. Firstly the influence of crystallization temperature on elastic behavior of miscible polypropylene (PP)/hydrogenated polybutadiene (hBR) blends is discussed in terms of residual strain values after pre-defined stretching. The structure was directly observed in nano-scale by transmission electron microscopy (TEM) and quantitatively evaluated by differential scanning calorimetry (DSC). PP/hBR blends serve as a model for explanation of the elastic behaviour of polyolefinic TPE containing PP. There is a big difference in structure and properties for neat PP and PP/hBR blend. Regardless on crystallization temperature, PP shows always yielding point, i.e. plastic deformation after stretching even to small deformation. In neat PP, the crosshatch lamellar crystals were always formed. The situation for PP/hBR blend was completely different. The elastic properties are highly affected by crystallization temperature. The optimum in temperature of cooling medium was found to be around room temperature. In this case the formation of long crosshatch lamellae was prevented and the small fragmented crystal lamellae were formed. The fragmented crystallites play a role of tie points for amorphous chains to render good elastomeric behaviour. There is no yielding point in stress-strain curves for those blends. When the blend crystallizes at high temperature, big crosshatch lamellae were formed and the blend showed very poor elastic properties. Secondly, isothermal crystallization of immiscible PP/ ethylene-octene copolymer (EOC) blends was studied by DSC and optical microscopy at various temperatures (123-140°C). By DSC it was found that small amounts of EOC (10-30%) increase the bulk crystallization kinetics; in some cases even 80% increase was observed. Larger amounts of EOC (50-80%) have caused a decrease in crystallization kinetics. Optical microscopy has revealed that crystallization kinetics of a single spherulite is decreased by the presence of EOC, and at the same time there are more spherulites in the blend. EOC acts as a nucleation agent increasing the bulk crystallization rate and at the same time it acts as an obstacle to the growing front of a spherulite when the PP lamellae have to go around the EOC obstacle. At low PP content (20%) PP forms very small isolated particles with size smaller than 1 micrometer. At 40% of PP a structure resembling a co-continuous one was found. When the PP is a majority phase (20-40% of EOC) rather large EOC particles were found. © 2013 Nova Science Publishers, Inc. All rights reserved. en
utb.faculty University Institute
dc.identifier.uri http://hdl.handle.net/10563/1008036
utb.identifier.rivid RIV/70883521:28610/13:43871029!RIV14-MSM-28610___
utb.identifier.obdid 43871382
utb.identifier.scopus 2-s2.0-84892095437
utb.source c-scopus
dc.date.accessioned 2018-07-27T08:47:41Z
dc.date.available 2018-07-27T08:47:41Z
utb.ou Centre of Polymer Systems
utb.identifier.utb-sysno 000072543
utb.identifier.nkp 006357932
utb.contributor.internalauthor Svoboda, Petr
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