Dispersed phase morphology of impact PP copolymers. Effects of blend composition as determined by TREF

Zacur, R.; Goizueta, Graciela; Capiati, Numa J.

doi:10.1002/pen.11324

Cited by 28 publications

(23 citation statements)

References 26 publications

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“…Such bimodal molecular weight distributions indicate compositional heterogeneity due to the co‐elution of non‐identical products. This is often observed for the mid‐elution temperature fractions of ICPPs fractionated by TREF14, 26, 27 where semi‐crystalline EPCs and PP homopolymer co‐elute due to the isotacticity distribution found in PP 14, 28. PP homopolymer will not elute entirely at high temperatures, since PP fractions of lower isotacticity will become soluble within the same lower temperature range of the semi‐crystalline EPC phase of corresponding crystallisability.…”

Section: Resultsmentioning

confidence: 97%

Fractionation and Analysis of an Impact Poly(propylene) Copolymer by TREF and SEC‐FTIR

Goede

Mallon

Pasch

2010

Macro Materials & Eng

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TREF fractionation was combined with SEC‐FTIR analysis to measure the compositional heterogeneity within a commercial impact PP copolymer. The chemical composition of all fractions was determined as function of their molecular weight distribution. This approach proved to be highly successful at identifying different constituents within fractions exhibiting bimodal molecular weight distributions. Furthermore, the determination of ethylene and propylene crystallinity distribution across the molecular weight distribution confirmed the morphological nature of each of the components of the bimodal distribution. It is demonstrated that the combination of TREF and SEC‐FTIR provides a simple alternative to more time‐consuming conventional ways of characterising impact PP copolymers of complex heterogeneity.magnified image

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Section: Resultsmentioning

confidence: 97%

Fractionation and Analysis of an Impact Poly(propylene) Copolymer by TREF and SEC‐FTIR

Goede

Mallon

Pasch

2010

Macro Materials & Eng

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“…As a result, the heterogeneous solid-state structure may be complex. 9,15 In the AFM phase image of the 35/65 hmsPP/znPE melt blend in Figure 1(b), the hmsPP phase is dispersed as 1-2-m domains in the znPE matrix. The light vertical streaks in the znPE matrix are artifacts of microtoming.…”

Section: Bulk Morphologymentioning

confidence: 96%

“…6 The phase separation of amorphous EPR fractions in impact polypropylene resins is extensively documented. 9,15 In blends of these resins with polyethylene, it is energetically advantageous for amorphous EPR to distribute as an interfacial layer between domains of the crystallizable polypropylene and polyethylene constituents. However, in blown films, surface segregation is an attractive alternative.…”

Section: Films With Znpementioning

confidence: 99%

“…However, in blown films, surface segregation is an attractive alternative. The high ethylene content of amorphous EPR fractions, roughly 50% on a molar basis, 9 creates the additional possibility that lower molecular weight, higher branch content znPE chains are miscible with amorphous EPR.…”

Section: Films With Znpementioning

confidence: 99%

“…Typically, EPR made in a secondary step following propylene polymerization is chemically heterogeneous, containing high ethylene amorphous fractions in addition to low ethylene crystallizable fractions. 9 This study was undertaken to examine the effect of blend constituents, especially amorphous EPR fractions, on the surface characteristics of blown films. Atomic force microscopy (AFM) was used to probe the surface of films blown from ethylene copolymers and their blends with hmsPP.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of an amorphous surface layer on blown polyolefin film

Chang

Chum

Hiltner

et al. 2002

J of Applied Polymer Sci

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This study concerned an amorphous surface layer on blown polyethylene film with a composition different from that of the bulk. The surface layer was characterized by gentle probing with an atomic force microscope. The demonstration of an amorphous layer uniformly covering the surface of a blown Ziegler-Natta-catalyzed polyethylene (znPE) film reproduced previous reports. Removing the surface layer by solvent washing confirmed the hypothesis that the layer consisted of lower molecular weight, higher branch content fractions. A blown film of znPE blended with up to 30 wt % impact-modified high-melt-strength polypropylene (hmsPP) also exhibited an amorphous surface layer. In thin films, it was advantageous for the mobile, amorphous fractions of ethylene-propylene rubber (EPR) to locate at the surface rather than at the phase interface. The amorphous EPR tended to segregate into pools on the film surface, and this pointed to a substantial difference between the amorphous surface layers on the znPE and hmsPP/znPE blend films. Surface enrichment best described the compositional gradient that resulted from the concentration of lower molecular weight, higher branch content chains at the surface of the znPE film. Surface segregation was more appropriate for the emergence of EPR fractions as a separate phase on the surface of the hmsPP blend film. Films blown from a blend of a Ziegler-Natta-catalyzed polyethylene and a metallocene-catalyzed polyethylene (zn/mPE) and its blend with hmsPP reproduced the primary features of surface enrichment and surface segregation. Some differences between the znPE and zn/mPE films were attributed to the metallocene constituent of zn/mPE.

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Phase interactions and structure evolution of heterophasic ethylene–propylene copolymers as a function of system composition

Doshev

Lohse

Henning

et al. 2006

J of Applied Polymer Sci

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Heterophasic copolymers comprised of polypropylene (PP) matrix and ethylene-propylene copolymer (EPC) dispersed phase were investigated with respect to the dispersed phase composition, i.e., ethylene/propylene ratio. The rheological properties, morphology, as well as thermal and mechanical relaxation behavior were studied to describe the structure evolution and phase interactions between the components of the PP copolymers. Decrease of the ethylene content of the EPC leads to a higher matrix-dispersed phase compatibility, as evaluated by the shift of the glass transition temperatures of EPC and PP towards each other. At ethylene content of EPC of 17 wt %, the glass transition temperatures of the both phases merged into a joint relaxation. The effect of the EPC composition on the internal structure of the dispersed domains and on the morphology development of the heterophasic copolymers was demonstrated. Decreasing ethylene content was found to induce a refinement of the dispersed phase with several orders of magnitude down to 0.18 m for propylene-rich EPC. Optical microscopy observations showed that the dispersed propylene-rich phase is preferably rejected at the interlamellar regions of the spherulites and/or at the interspherulitic regions, while the ethylene-rich domains are engulfed within the PP spherulites. Both of these processes impose an additional energetic barrier and influence the spherulite growth rate of the heterophasic materials.

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Dispersed phase morphology of impact PP copolymers. Effects of blend composition as determined by TREF

Cited by 28 publications

References 26 publications

Fractionation and Analysis of an Impact Poly(propylene) Copolymer by TREF and SEC‐FTIR

Fractionation and Analysis of an Impact Poly(propylene) Copolymer by TREF and SEC‐FTIR

Characterization of an amorphous surface layer on blown polyolefin film

Phase interactions and structure evolution of heterophasic ethylene–propylene copolymers as a function of system composition

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