Mapping structural gradients in isotactic polypropylene using scanning wide-angle X-ray scattering

Granlund, Håvard; Fløystad, Jostein Bø; Esmaeili, Morteza; Bakken, Eirik Torbjørn; Bech, Martin; Vullum, Per Erik; Andreassen, Erik; Breiby, Dag W.

doi:10.1016/j.polymer.2013.01.055

Cited by 8 publications

(16 citation statements)

References 28 publications

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“…S3), the most prominent being 002 t , 004 t , 006 t ,

\bar{2}

04 t , 110 α , and 040 α , where the subscript t denotes talc. The peaks are in full agreement with previous studies …”

Section: Resultssupporting

confidence: 93%

“…Melt flow rates are 1.3 and 0.8 g/min, respectively (ISO standard 1133, 230 °C/2.16 kg). As we have reported previously, the flake‐shaped talc particles have a significant aspect ratio, with average diameter and thickness of about 10 and 2 μm, respectively.…”

Section: Methodssupporting

confidence: 74%

“…In a previous study we used raster‐scanning WAXS to map the orientation of talc particles and PP lamellae within a cross‐sectional cut from an injection‐molded specimen, showing how the PP b ‐axis and talc c ‐axis align normal to the solidification front from the mold walls toward the core, as expected under shear flow. Orientation maps of cross sections perpendicular to the flow revealed a shift of the orientation distribution center from the geometrical specimen center.…”

Section: Introductionmentioning

confidence: 98%

“…As the resulting so‐called shish–kebab structure is flow‐induced, its presence naturally depends on the part geometry and the molding conditions, and it is often observed in regions with comparably high shear rate during molding, in layers near the mold surfaces. The injection molding process thus yields samples with anisotropic morphologies, and with heterogeneity from the surface to the core, and along the flow path, resulting from the thermomechanical history inside the mold cavity.…”

Section: Introductionmentioning

confidence: 99%

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Measuring and simulating morphology gradients in injection‐molded talc‐reinforced isotactic polypropylene

Granlund

Andreassen

Skjønsfjell

et al. 2014

J Polym Sci B Polym Phys

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Injection molded polymer parts are known to exhibit structural gradients of crystallinity, crystallite phases and crystallite orientations. The structural variations depend on the geometry, the material properties, and the processing conditions, and affect the mechanical properties of the molded part. We explore the use of raster‐scanning small‐ and wide‐angle X‐ray scattering (SAXS, WAXS) for mapping the microstructure in dogbone specimens of an isotactic polypropylene (PP) homopolymer and a talc‐reinforced isotactic PP compound. The specimens were injection molded with different mold temperatures and injection speeds, and the mapping approach revealed systematic structural heterogeneities and asymmetries. Accompanying numerical simulations of the injection molding process yielded predictions of the flow pattern, including the shear rate distribution and the resulting orientation of the flake‐shaped talc particles. We found a clear correspondence between the experimentally observed data and the simulations, in particular regarding the asymmetry of the orientation distributions relative to the center of the dogbone cross section, caused by asymmetric flow through the entrance of the mold. Furthermore, the shear rate distribution correlated with the occurrence of α‐ and β‐phases. Subtle differences in the crystallized structures along the long axis of the dogbones suggest an explanation to the observation that the specimens studied always tended to break at the same position in tensile tests. The results clearly demonstrate the potential of mapping experiments which combine lateral resolution on macroscopic length scales with the molecular‐scale resolution from scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1157–1167

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“…S3), the most prominent being 002 t , 004 t , 006 t ,

\bar{2}

04 t , 110 α , and 040 α , where the subscript t denotes talc. The peaks are in full agreement with previous studies …”

Section: Resultssupporting

confidence: 93%

Section: Methodssupporting

confidence: 74%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Measuring and simulating morphology gradients in injection‐molded talc‐reinforced isotactic polypropylene

Granlund

Andreassen

Skjønsfjell

et al. 2014

J Polym Sci B Polym Phys

Self Cite

View full text Add to dashboard Cite

show abstract

“…Healy et al utilized SAXS and WAXD to examine the residual chain orientation in microinjection‐molded linear polyethylene, and unraveled that it is the oriented crystal growth instead of residual chain orientation that contributes to the majority of the orientation. Granlund et al mapped the two‐dimensional (2D) chain orientation distribution in the cross‐section parallel and perpendicular to the flow direction in injection‐molded talc‐reinforced isotactic polypropylene using the raster scanning SAXS and WAXD, and indicated the structural heterogeneities and asymmetries as a result of lateral temperature gradient across the mold. Ulcer et al applied matrixing microbeam XRD and transmission optical photomicrographs to analyze the structure at the weld region of poly(arylene ether ketone), and revealed that the sample exhibits a multilayer structure at the weld line region.…”

Section: Introductionmentioning

confidence: 99%

Predicting the location of weld line in microinjection‐molded polyethylene via molecular orientation distribution

Liao

Zhao

Yang

et al. 2019

J Polym Sci B Polym Phys

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The microstructure and molecular orientation distribution over both the length and the thickness of microinjection‐molded linear low‐density polyethylene with a weld line were characterized as a function of processing parameters using small‐angle X‐ray scattering and wide‐angle X‐ray diffraction techniques. The weld line was introduced via recombination of two separated melt streams with an angle of 180° to each other in injection molding. The lamellar structure was found to be related to the mold temperature strongly but the injection velocity and the melt temperature slightly. Furthermore, the distributions of molecular orientation at different molding conditions and different positions in the cross section of molded samples were derived from Hermans equation. The degree of orientation of polymeric chains and the thickness of oriented layers decrease considerably with an increase of both mold temperature and melt temperature, which could be explained by the stress relaxation of sheared chains and the reduced melt viscosity, respectively. The level of molecular orientation was found to be lowest in the weld line when varying injection velocity, mold temperature, and melt temperature, thus providing an effective means to identify the position of weld line induced by flow obstacles during injection‐molding process. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1705–1715

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Simultaneously improving stiffness, toughness, and heat deflection resistance of polylactide using the strategy of orientation crystallization amplified by interfacial interactions

Sang

Chen

et al. 2018

Polymer Crystallization

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A core‐shell toughening agent was incorporated Polylactide (PLA) to prepare the high‐PLA‐content (≥85 wt%) blends with high impact strength due to good interfacial adhesion. Interestingly, the synergistic effect of strong interfacial adhesion and intense shear flow on crystallization of PLA is proved whereas retarded crystallization occurs in the presence of impact modifier solely in this work. Moreover, by introducing intense shear flow in injection molding, thickness of oriented crystal layer and crystallinity of the PLA parts improve compared with conventional injection molding. Accordingly, oriented crystal and well dispersed second phase particles induced by intense shear flow result in promising balance of thermomechanical peoperties, i.e., modulus, strength, impact toughness and heat resistance can be achieved to 1890 MPa, 64.5 MPa, 29.6 kJ/m2, 145.5°C by adding 15 wt% of impact modifier, respectively, compared with those (1875 MPa, 64.5 MPa, 1.7 kJ/m2, 59.0°C) of conventional injection molded PLA parts.

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Mapping structural gradients in isotactic polypropylene using scanning wide-angle X-ray scattering

Cited by 8 publications

References 28 publications

Measuring and simulating morphology gradients in injection‐molded talc‐reinforced isotactic polypropylene

Measuring and simulating morphology gradients in injection‐molded talc‐reinforced isotactic polypropylene

Predicting the location of weld line in microinjection‐molded polyethylene via molecular orientation distribution

Simultaneously improving stiffness, toughness, and heat deflection resistance of polylactide using the strategy of orientation crystallization amplified by interfacial interactions

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