Influence of processing on ethylene‐propylene block copolymers: Structure and mechanical behavior

Maspoch, M. Ll.; Gámez‐Pérez, José; Giménez, Enrique; Santana, Oliverio J.; Gordillo, Antonio

doi:10.1002/app.20834

Cited by 17 publications

(23 citation statements)

References 17 publications

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“…The orientation indexes are related with the arrangement of the a-crystallites parallel to the flow direction [10,11] and the value for a fully oriented sample is 1. In the case of nonoriented samples, obtained from compression molding, we found in a previous work [8] that A 110 ¼ 0.57 and A 130 ¼ 0.35, finding a good agreement with other authors [12].…”

Section: Waxs Characterizationsupporting

confidence: 90%

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Evaluation of the fracture behavior of multilayered polypropylene sheets obtained by coextrusion

Gámez‐Pérez¹,

Santana²,

Gordillo³

et al. 2007

Polymer Engineering & Sci

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The mechanical and fracture behavior of multilayered sheets (up to three layers) is presented. The sheets were processed by plane coextrusion-calendering using two polypropylene-based materials, isotactic polypropylene homopolymer (H0), and an ethylene-propylene block copolymer (C1) with 5.5% ethylene content in weight. Combining these materials five different sheets were produced, (H0, C1, H0-C1, H0-C1-H0, and C1-H0-C1), with an overall thickness of 0.5 mm. The processing variables (temperature, extrusion rate, calendering speed, etc.) were set constant among the different structures to facilitate the evaluation of the results. The structure of the sheets was characterized with wide angle X-ray scattering (WAXS). The mechanical behavior was determined from dumbbell tensile specimens in the melt flow (MD) and transverse to the melt flow (TD) directions. The fracture parameters were determined by the essential work of fracture (EWF) technique in mode I in both MD and TD directions. The results show variations on the induced orientation of the sheets, with remarkable differences on the fracture properties. The poor fracture resistance of the homopolymer (H0) film in TD is improved through coextrusion with C1, obtaining the best results for toughness in the case of the three-layered sheets. POLYM. ENG.

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Section: Waxs Characterizationsupporting

confidence: 90%

“…Both materials were commercial grades, kindly supplied by Basell, with similar MFI values (5.5 and 5.3 g/10 min for H0 and C1, respectively, at 2308C and 2.16 kg), so they could be easily coextruded. More information on these materials can be found in previous studies [6][7][8][9].…”

Section: Materials and Sheet Preparationmentioning

confidence: 99%

Evaluation of the fracture behavior of multilayered polypropylene sheets obtained by coextrusion

Gámez‐Pérez¹,

Santana²,

Gordillo³

et al. 2007

Polymer Engineering & Sci

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“…Because there is no theoretical value for a fusion enthalpy ( H f ) of a 100% crystalline copolymer, several authors 12,13 have proposed an approximation using a linear law of mixture using the following expression:…”

Section: Differential Scanning Calorimetrymentioning

confidence: 99%

Influence of the Injection‐Molding Parameters on the Cellular Structure and Thermo‐Mechanical Properties of Ethylene‐Propylene Block Copolymer Foams

Gómez¹,

Arencón²,

Sánchez‐Soto³

et al. 2012

Adv Polym Technol

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Microcellular injection-molding technology is capable of producing lightweight polymeric products. The foam morphology is determined by the injection-molding parameters, and it has been observed that depending on the parameter variations, the cell structure may exhibit substantial morphological differences through the entire section along the melt flow direction of the injected INJECTED ETHYLENE-PROPYLENE BLOCK COPOLYMER FOAMSpart. The effects of varying injection-molding parameters on foam morphology and thermal mechanical properties of a multiphase ethylene-propylene block copolymer (EPBC) were tested on 5-mm plaque specimens using a constant temperature profile. It has been found that injection speed does not have a significant effect on the thermal-mechanical properties of the foam, whereas shot volume and mold temperature do have a significant influence. Low shot volume produces uniform density cellular structures and larger cores, whereas lower mold temperatures help maintain small cell sizes. Furthermore, the effect of the copolymer's crystalline phase on foam morphology has been observed. This study identifies the achievable foam morphologies and the thermal-mechanical performance of cellular molded EPBC parts. C 2012 Wiley Periodicals, Inc. Adv Polym Techn 00: 1-13, 2012; View this article online at wileyonlinelibrary.com.

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“…Recent studies found that adding ethylene monomer to the propylene chain can improve transparency, relative softness and low-temperature impact strength. [32][33][34] Also, it has been found that the presence of ethylene monomer along the polypropylene chain disturbs the chain regularity and, consequently, decreases polymer crystallization ability; [34][35][36] e.g., its presence decreases crystallinity and linear growth rate and, moreover, induces the formation of the orthorhombic γ-phase. 36,37 However, the effects above have mostly been studied for quiescent crystallization, or under a rheometric flow 35 unable to impose high shear stresses similar to those typically encountered in industrial processing conditions.…”

Section: Introductionmentioning

confidence: 99%

High-Stress Shear-Induced Crystallization in Isotactic Polypropylene and Propylene/Ethylene Random Copolymers

Fernandez-Ballester

Cavallo

et al. 2013

Macromolecules

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IntroductionSemicrystalline polymers are usually processed from their molten state and subjected to intense shear and/or elongation flows. Such flow fields not only accelerate crystallization kinetics, which shortens the processing time, but can also change the morphology from isotropic spherulites to highly oriented shish-kebab structures 1-3 and, as a consequence, determine the ultimate product properties. Therefore, understanding the interplay between strong flow fields and the resulting structures is of importance for designing processing procedures to tailor these end product properties.Considerable work [4][5][6][7] has been devoted to this topic in the past half century. Many researchers have focused on the relation between shear flow and polymer crystallization, because shear fields are easily created with rotational 3 or sliding 8,9 plate-plate devices, on rotational rheometers, 10,11 and in pressure driven slit flows. 12,13 These test geometries are typically combined with time-resolved characterization techniques like mechanical spectrometry, 10, 11, 14 light scattering, 15,16 birefringence, 13, 17 X-ray scattering 7,18,19 and Fourier transform infrared (FTIR) spectroscopy, 9, 20, 21 etc. Significant progress has been made in understanding shear-induced crystallization, 4-7 while some of the fundamental issues remain unsolved. In particular, knowledge of basic mechanism of crystallization under high shear rates and stress-close to realistic processing conditions-is still limited. The need for such information is becoming urgent in order to improve the latest simulation models, since the results of numerical predictions of, for example, injection molding, 22 have to be validated and further refined from experimental evidence.Imposing a strong shear flow at chosen high shear rates or stresses under well-defined conditions requires a specially designed flow device. Both the pressure-driven slit flow apparatus constructed by Janeschitz-Kriegl et al. 12 and improved by Kornfield et al.,13 and the piston-driven slit rheometer developed by Mackley et al. 23 and modified by Peters and coworkers, 24,25 can operate in the high stress region (of the order of 0.1 MPa) and are easily combined with time-resolved birefringence 24,26 and/or X-ray scattering [27][28][29][30] AbstractCrystallization of an isotactic polypropylene (iPP) homopolymer and two propylene/ethylene random copolymers (RACO), induced by high-stress shear, was studied using in situ synchrotron wide-angle X-ray diffraction (WAXD) at 137 °C. The "depth sectioning" method (Fernandez-Ballester, Journal of Rheology 53:5 (2009), pp. 1229−1254) was applied in order to isolate the contributions of different layers in the stress gradient direction and to relate specific structural evolution to the corresponding local stress. This approach gives quantitative results in terms of the specific length of fibrillar nuclei as a function of the applied stress. As expected, crystallization becomes faster with increasing stress-from the inner to the outer layer-for...

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Influence of processing on ethylene‐propylene block copolymers: Structure and mechanical behavior

Cited by 17 publications

References 17 publications

Evaluation of the fracture behavior of multilayered polypropylene sheets obtained by coextrusion

Evaluation of the fracture behavior of multilayered polypropylene sheets obtained by coextrusion

Influence of the Injection‐Molding Parameters on the Cellular Structure and Thermo‐Mechanical Properties of Ethylene‐Propylene Block Copolymer Foams

High-Stress Shear-Induced Crystallization in Isotactic Polypropylene and Propylene/Ethylene Random Copolymers

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