Investigation of craze development using small-angle X-ray scattering of synchrotron radiation

Pomper, T.; Lode, U.; Karl, Andreas; Krosigk, G. von; Minko, Sergiy; Luzinov, Igor; Senkovsky, V.; Voronov, A.; Wilke, W.

doi:10.1080/00222349908248145

Cited by 15 publications

(8 citation statements)

References 14 publications

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“…Cross-shaped SAXS scattering originating from the fibrillar crazes (Figure A) can be observed when the stress was applied. The SAXS model for fibrillar craze has demonstrated that the streak scattering parallel to the loading direction (meridional direction) is ascribed to the total reflection at fibrillar crazes/intact PLLA interfaces, while the two equatorial lobes perpendicular to the loading direction (equatorial direction) are caused by the alternating fibrils/microvoids structure (Figure A) in the fibrillar crazes. , As the situation here is that the equatorial scattering of stressed sample is a superposition of the equatorial lobes scattering caused by the alternating fibrils/microvoids structure (Figure A) and the streak scattering originated from the FCS (Figure a3), it is difficult to estimate the parameters of fibrillar crazes with SAXS craze model. , However, as shown in Figure A, the alternating fibrils/microvoids can be treated as two-dimensional lattice with quasi-long-range order. Both the mean diameter of fibrils ( d ) and interfibrillar distance ( D ) can be derived from the one-dimensional correlation function proposed by Strobl. , The electron density correlation function K ( z ) is derived from the inverse Fourier transformation of the experimentally intensity distribution I ( s ) as follows: where z is perpendicular to the loading direction and I ( s 12 ) is obtained by integrating along the equator.…”

Section: Results and Discussionmentioning

confidence: 89%

“…The resultant values are summarized in Table , the diameter of the fibrils ( d ) in fibrillar craze first reaches its maximum at 7.5 nm when the sample was stressed to yield point and then drops slightly during the following stretching, while the interfibrillar distance ( D ) remains stable at about 21.1 nm during the whole stretching. Moreover, as shown in Figure , fibrillar crazes generate cross-shaped SAXS scattering (Δ I craze ) concentrating on equatorial (Δ I craze∥ ) and meridional (Δ I craze⊥ ) sections. , Hence, the propagation of fibrillar crazes can be assessed by tracking the variation of the meridional ratio, Δ I craze⊥ /Δ I craze . Additionally, the scattering originated from fibrillar crazes (Δ I craze ) is much stronger than that from the FCS (Δ I cryst , only concentrating on the equational section) because of the much higher electron difference between the fibrils and microvoids in fibrillar crazes (Figure A) compared to that in PLLA between crystalline and amorphous region.…”

Section: Results and Discussionmentioning

confidence: 99%

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In Situ Formation of Microfibrillar Crystalline Superstructure: Achieving High-Performance Polylactide

Jiang

Wang

et al. 2017

ACS Appl. Mater. Interfaces

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As a biobased and biodegradable polyester, polylactide (PLA) is widely applied in disposable products, biomedical devices, and textiles. Nevertheless, due to its inherent brittleness and inferior strength, simultaneously reinforcing and toughening of PLA without sacrificing its biodegradability is highly desirable. In this work, a robust assembly consisting of compact and well-ordered microfibrillar crystalline superstructure (FCS) surrounded by slightly oriented amorphism, is achieved by a combined external force field. Unlike the classic crystalline superstructures such as shish-kebabs, cylindrites, and lamellae, the newfound FCS with diameter of about 100 nm and length of several tens of micrometers is aggregated with well-aligned crystalline nanofibers. FCS can serve as discontinuous fiber to self-reinforce the amorphous PLA; more importantly, FCS can also act as rivets to pin the propagating fibrillar crazes leading to the formation of dense fibrillar crazes during stretching, which dissipates much energy and translates the failure of PLA from brittle to ductile. Consequently, PLA with FCS exhibits exceptionally simultaneous enhancement in ductility, strength, and stiffness, outperforming normal PLA with increments of 728, 55, and 70% in elongation at break, strength, and modulus, respectively. Therefore, FSC exhibits competitive advantages in achieving high-performance PLA even for other semicrystalline polymers. More significantly, this newfound crystalline superstructure (FCS) provides a new structural model to establish the correlation between structure and performance.

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Section: Results and Discussionmentioning

confidence: 89%

Section: Results and Discussionmentioning

confidence: 99%

In Situ Formation of Microfibrillar Crystalline Superstructure: Achieving High-Performance Polylactide

Jiang

Wang

et al. 2017

ACS Appl. Mater. Interfaces

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“…However, the sample with only 12 wt% SEBS content (NC_A_12) develops a diamond‐shaped central scattering during the test. Such a scattering feature can be attributed to void formation . Thus, the finding could be explained if the low SEBS content of NC_A_12 has facilitated void formation in this sample already at strains below its yield point.…”

Section: Resultsmentioning

confidence: 77%

SAXS investigation of structure–property relationship of polypropylene/montmorillonite composites during load cycling

Zeinolebadi

Stribeck

Vuluga

et al. 2013

Polymers for Advanced Techs

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Polypropylene (PP) can hardly be reinforced by the layered silicate montmorillonite (MMT), but the material fatigue appears somewhat reduced. The probable reason is amplified competitive nucleation of the PP by MMT component. Utilizing small‐angle X‐ray scattering (SAXS) from synchrotron, we investigate the nanostructure evolution of the PP in straining experiments from neat PP and compatibilized composite materials. The compatibilizer is a styrene–ethylene/butylene–styrene copolymer (SEBS). Oriented injection‐molded test bars are studied. The discrete SAXS probes variations of sizes and distances among those crystalline domains that are not placed at random. Crystallite dimensions and distances are documented for modeling purposes. The nanoscopic strain is computed from the distance variation and compared with the macroscopic strain. Differences between macroscopic and nanoscopic strain are observed. They require postulating regions with statistical placement of crystallites (poorly arranged region, PAR) in addition to the SAXS‐probed well‐arranged semi‐crystalline entities (WAE). The extensibility of WAEs must be different from that of the PARs. In neat PP, the observed WAEs are well developed and stronger than the PARs. In the composites, the WAEs are made from thin and less extended crystalline domains. They are weaker than the PARs that appear reinforced. Thus, enclosing each MMT layer a PAR is formed, and the WAEs generated farther away remain imperfect. Consequently, in the composites, the narrow crystalline domains from the WAEs do not break into even smaller pieces, and the fatigue of the composites is lower than that of the neat PP. Copyright © 2013 John Wiley & Sons, Ltd.

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“…From the SEM images in Figure 1, we notice that the stretching-induced connecting bridge crystal is arranged neatly, and the distance of neighborhood bridge crystals is similar; thus, a pair of symmetrical scattering signals from the adjacent fibrils crystals formed pore's walls will appear along the meridional direction. 34 We integrate the SAXS streak signal along the radial direction; the Iq 2 −q curves are given in Figure 6. Before integration, the instrument background was subtracted considering sample absorption.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Stretching-Induced Uniform Micropores Formation: An in Situ SAXS/WAXS Study

Lei

Tian

et al. 2018

Macromolecules

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Although the microporous membrane prepared based on the melt stretching mechanism has been commercialized for more than 20 years, the formation process from the initial lamellae structure to final fiber connecting bridges and pores is still unclear. In this work, to clarify the transformation mechanism, in situ SAXS and WAXS were carried out during hot stretching at 130 °C to 100%. The scattering patterns from the annealed film, cold stretched film to 20% (stretched at room temperature), and heating to 130 °C were also collected. The preparation technology was similar to that during the commercial fabrication. It was found that during cold stretching to 20% many long and narrow crazes are formed between separated lamellae clusters, and a part of destroyed crystals appeared. After heating to 130 °C, oriented structure and needlelike voids appeared, which was related to the shrinkage of oriented amorphous chains along the transverse direction, due to the tension stress effect. Also some oriented crystal structure was formed. During hot stretching to 20%, the lamellae which are close to the craze wall are rotated as the fibril crystal as the axle and the connecting bridges were formed among the separated lamellae cluster. Further stretching to 100%, these connecting bridges transformed to fiber bridges, contributed by strain-induced crystallization. During the whole hot stretching, the amorphous chains oriented along the machine direction and also crystallized into fiber bridges. This is the first time to clearly describe the lamellae to fiber bridges transformation during the preparation of microporous membrane.

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Investigation of craze development using small-angle X-ray scattering of synchrotron radiation

Cited by 15 publications

References 14 publications

In Situ Formation of Microfibrillar Crystalline Superstructure: Achieving High-Performance Polylactide

In Situ Formation of Microfibrillar Crystalline Superstructure: Achieving High-Performance Polylactide

SAXS investigation of structure–property relationship of polypropylene/montmorillonite composites during load cycling

Stretching-Induced Uniform Micropores Formation: An in Situ SAXS/WAXS Study

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