Abstract:Adhesion of a Ziegler-Natta catalyzed ethylene copolymer (ZNPE) to polypropylene (PP) was studied by measuring the delamination toughness G of coextruded microlayers by using the T-peel test. Low values of G compared to a homogeneous copolymer with approximately the same short chain branch (SCB) content were attributed to an amorphous interfacial layer of low molecular weight, highly branched ZNPE fractions. Blending ZNPE with a homogeneous metallocene catalyzed copolymer (mPE) increased G. In this regard, mPE… Show more
“…Polyolefin based materials and especially those based on polypropylene, due to their large versatility and competitiveness in costs, are a hot topic either in engineering or in the commodity polymer fields [5] in very different and strategic applications dealing with health, energy, or transport. Drug release and biocompatibility [6,7], adhesion [8,9], gas barrier properties [10,11], flame resistance [12][13][14], membrane 2 Journal of Polymers processes [15], fuel cells, lightest but strongest materials [16], optical properties and thermal stability [17], and commingled plastic waste recycling [18] are just a few examples where necessary are the new nanostructured materials based on polypropylene [19,20].…”
The main aim of the present work is to correlate the morphological changes observed in the modified PP/PA6 fifty/fifty blends molded at confined flow conditions with both their mechanical and thermal properties and the kind and the amount of the interfacial modifiers used. Both transmitted light optical microscopy in the positive phase contrast mode, PC TOM, and field emission scanning electronic microscopy, FE SEM, were the used techniques for, respectively, general morphology overview and fractures surface analysis. The interfacial modifiers, a succinic anhydride, aPP-SA, and a succinyl-fluorescein, aPP-SF/SA, grafted atactic polypropylenes obtained and well characterized in authors’ laboratories came from the chemical modification of an atactic polypropylene industrial by-product. The amounts of any of both the interfacial modifiers came coded by the Box-Wilson experiment design methodology applied to the overall PP/PA6 binary system, watching that the interfacial agent was not a third component on a ternary blend but a true interfacial modifier in a binary one. All the studies were carried out over suitable specimens according to each test procedure with no further material manipulations to preserve at any moment the morphology of the blends as they emerge from the compression molding step at confined flow conditions.
“…Polyolefin based materials and especially those based on polypropylene, due to their large versatility and competitiveness in costs, are a hot topic either in engineering or in the commodity polymer fields [5] in very different and strategic applications dealing with health, energy, or transport. Drug release and biocompatibility [6,7], adhesion [8,9], gas barrier properties [10,11], flame resistance [12][13][14], membrane 2 Journal of Polymers processes [15], fuel cells, lightest but strongest materials [16], optical properties and thermal stability [17], and commingled plastic waste recycling [18] are just a few examples where necessary are the new nanostructured materials based on polypropylene [19,20].…”
The main aim of the present work is to correlate the morphological changes observed in the modified PP/PA6 fifty/fifty blends molded at confined flow conditions with both their mechanical and thermal properties and the kind and the amount of the interfacial modifiers used. Both transmitted light optical microscopy in the positive phase contrast mode, PC TOM, and field emission scanning electronic microscopy, FE SEM, were the used techniques for, respectively, general morphology overview and fractures surface analysis. The interfacial modifiers, a succinic anhydride, aPP-SA, and a succinyl-fluorescein, aPP-SF/SA, grafted atactic polypropylenes obtained and well characterized in authors’ laboratories came from the chemical modification of an atactic polypropylene industrial by-product. The amounts of any of both the interfacial modifiers came coded by the Box-Wilson experiment design methodology applied to the overall PP/PA6 binary system, watching that the interfacial agent was not a third component on a ternary blend but a true interfacial modifier in a binary one. All the studies were carried out over suitable specimens according to each test procedure with no further material manipulations to preserve at any moment the morphology of the blends as they emerge from the compression molding step at confined flow conditions.
“…Numerous studies illustrate the application of microlayers in elucidating the cooperative microdeformation and crack propagation mechanisms that underlie toughness enhancement of polymer blends 14,15 and in quantifying the role of interfacial adhesion in blend performance. [16][17][18][19][20][21] The high specific interface area of microlayers has been exploited to study interfacial phenomena related to miscible polymers. [22][23][24] The stringent flow conditions of microlayer coextrusion provide a rare opportunity to combine miscible polymers on a small scale with little or no mixing.…”
Section: Introductionmentioning
confidence: 99%
“…Typically, the number of layers is in the hundreds, and the layer thickness is on the micron scale, which is comparable to the domain size of conventional polymer blends. Numerous studies illustrate the application of microlayers in elucidating the cooperative microdeformation and crack propagation mechanisms that underlie toughness enhancement of polymer blends , and in quantifying the role of interfacial adhesion in blend performance. − 2 Schematic of layer-multiplying coextrusion used for forced assembly of polymer nanolayers. The figure illustrates how two die elements multiply the number of layers from 2 to 8.…”
When two immiscible polymers are brought into intimate contact, highly localized mixing of polymer chains creates an "interphase" region. We have fabricated materials that are entirely interphase by forced assembly of two immiscible polymers. Assemblies of thousands of alternating layers of two polymers, with individual layer thickness on the nanometer size scale of the interphase, were created by layer multiplying coextrusion. The properties of the interphase materials were probed with conventional tools of polymer analysis. In this study, the effect of interaction strength was examined with assemblies that combined an amorphous polyester with a series of styrene-acrylonitrile copolymers that varied in acrylonitrile content from 0 to 30 wt %. Continuous, uniform layers were directly observed using atomic force microscopy. Interphase thickness was extracted from the layer thickness dependence of oxygen permeability. The interphase thickness showed the predicted dependency on the parameter and correlated with interphase strength as measured with the T-peel test. Unexpectedly, volumetric properties of the interphase deviated from additive predictions. Correspondence between the decrease in specific volume from macroscopic density and the decrease in free volume hole size from positron annihilation lifetime spectroscopy suggested that densification of the interphase occurred primarily by a decrease in free volume hole size rather than by a decrease in the number of free volume holes. The volume change did not directly correlate with the parameter. At present, the origin of the volume change is not clear.
“…In resent years, ethylene–octane copolymer (POE) has attracted increasingly interests in the modification of iPP, because of its good toughening effect compared with other elastomers 17. iPP and POE could be phase miscible or immiscible depending on the composition and the content of octane branching 18. The copolymer is immiscible with iPP in the molten state if the α‐olefin content is less than 50 mol % and miscible with amorphous phase of iPP if it is more than 50 mol % 19.…”
In this article, the phase morphology and mechanical properties of polypropylene (PP)/ethylene-octane copolymer (POE) blends with fixed ratio (60/40) obtained via different processing conditions, including barrel temperature, injection speed, and mold temperature, have been investigated. SEM was carried out for detailed characterization of phase morphology from the skin to the core, layer by layer. It was interesting that for all the processing conditions no dispersed POE elastomer was observed in the skin layer but elongated POE particles with large size were observed in the subskin layer. From the transition zone to the core layer, an increased phase separation was observed, which could lead to a formation of cocontinuous morphology, depending on the processing condition used. Higher barrel temperature, lower mold temperature, and higher injection speed could result in a smaller size of POE phase. The tensile strength and impact strength were found not sensitive to barrel temperature and mold temperature but to the low injection speed, both tensile strength and impact strength had a higher value for specimen obtained via low injection speed. The formation of the skin-core morphology and the effect of processing conditions on the phase morphology were discussed based on crystallization kinetics of PP matrix, rheology, and shear induced phase mixing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
