Structural development of poly(ethylene terephthalate) during uniaxial stretching above the glass‐transition temperature: Study of the statistical influence of the stretching variables

2012

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This work investigates the solid state uniaxial stretching of neat polyethylene therephthalate, PET, and its montmorillonite, MMT, nanocomposites (0.3 wt % of MMT particles with different initial agglomerate sizes) showing intercalated and tactoid morphologies, followed by in situ WAXS and SAXS experiments under an X-ray synchrotron source. The distinct nanocomposite morphologies were assessed by WAXS and transmission electron microscopy. The in situ WAXS experiments during stretching evaluated the evolution of phase's mass fractions and the average level of molecular orientation upon uniaxial deformation, and the in situ SAXS experiments assessed the evolution of craze-like structures and void sizes. Multiscale structure evolution models are proposed and compared for neat PET and its nanocomposites. Main global mechanisms are identical although with distinct evolutions of phase mass fractions. Also craze-like/voids structures evolve with distinct sizes. Intercalated MMT morphology induces an earlier formation of periodical mesophase, a retarded widening of craze-like structures and the smallest void sizes.V C 2012 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 128: 2884-2895, 2013

Section: Simultaneous Deformation and In Situ Synchrotron Characterizmentioning

confidence: 99%

In situ WAXS/SAXS structural evolution study during uniaxial stretching of poly(ethylene therephthalate) nanocomposites in solid state: Poly(ethylene therephthalate)/montmorillonite nanocomposites

2012

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“…A peak‐fitting program was used to deconvolute the peaks of the distinct phases that were fitted by a Gaussian function. The morphology of the studied samples was assumed to consist of two phases: (i) amorphous—isotropic phase and (ii) mesophase—anisotropic phase, with degree of packing and order between the crystalline and the amorphous phase. The amount of amorphous phase was assumed to be proportional to the area of the peak taken from the meridional profile.…”

Section: Methodsmentioning

confidence: 99%

In situ WAXS/SAXS structural evolution study during uniaxial stretching of poly(ethylene terephthalate) nanocomposites in the solid state: Poly(ethylene terephthalate)/titanium dioxide and poly(ethylene terephthalate)/silica nanocomposites

2013

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This work reports an in situ WAXS and SAXS investigation, under X-ray synchrotron source radiation, on the structural evolution during solid-state uniaxial deformation of poly(ethylene terephthalate) (PET) nanocomposites with 0.3 wt % of 3D nanoparticles [nanotitanium dioxide (TiO 2 ) and nanosilica (SiO 2 )]. Good dispersion and average agglomerate sizes of nanoparticles of about 80 nm for both nanocomposites were revealed by transmission electron microscopic characterization. The influence of the nanofillers on the deformation-induced phase's formation and their evolution along the stretching process were compared with respect to the neat PET. WAXS results indicated that the structural evolution of all samples passes through three main stages, with evolution of amorphous phase into mesophase, a rapid increase of molecular orientation, and the formation of a periodical mesophase (PM). The incorporation of the nanofillers promoted a higher fraction, and an earlier formation, of PM during stretching when compared with pure PET. Furthermore, the presence of TiO 2 nanoparticles in the PET matrix resulted in the earliest formation and the highest amount of PM and the retardation of crack growth and bigger voids when compared with PET/SiO 2 nanocomposite. A multiscale structural evolution mechanism is proposed to interpret these results. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 000: 000-000, 2013

“…The samples used in this work were prepared following the procedure described in a previous work 43. In summary, PET pellets were compression molded and quenched to obtain amorphous plaques.…”

Section: Methodsmentioning

confidence: 99%

Solid‐state structural evolution of poly(ethylene terephthalate) during step uniaxial stretching from different initial morphologies: An in situ wide angle x‐ray scattering study

2011

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This work reports an in situ wide-angle Xray scattering (WAXS) study of the structural evolution of PET with distinct initial morphologies during step uniaxial stretching in the solid state. Two types of samples were analyzed under synchrotron X-ray radiation, namely quasi-amorphous (QA) and semicrystalline (SC) (with 2D and 3D order). Results show that initially different QA morphologies evolve following the same stages: (i) stage I (before neck), at almost constant orientation level the amorphous phase evolves into mesophase; (ii) stage II (neck formation), there is a rapid increase of polymer orientation and the appearance of a periodical mesophase from the highly oriented mesophase; (iii) stage III (necking propagation), there is a leveling off of the average polymer orientation together with partial conversion of the periodical mesophase and mesophase into highly oriented amorphous. The behaviors of the two SC morphologies are completely distinct. A 2D order crystalline morphology evolves with stretching likewise the QA through three stages: (i) at early stages of deformation the polymer orientation remains unchanged while the amorphous phase amount increases slightly, stage I; (ii) in stage II, a fast increase of polymer orientation is accompanied by large formation of mesophase; and (iii) in stage III there is the level off of polymer orientation as the chains approach their finite extensibility and the 3D crystalline order is achieved. Evolution of SC sample with 3D crystalline order mainly features constant orientation increase together with mesophase increment. Structure deformation models are suggested.