Spherulites of poly

Figure 4.12 Spherulites of poly( 1-propylene oxide) observed through crossed Polaroid filters by optical microscopy. See text for significance of Maltese cross and banding in these images. [From J. H. MaGill, Treatise on Materials Science and Technology, Vol. lOA, J. M. Schultz (Ed.), Academic, New York, 1977, with permission.]...

Lovinger A (1980) Crystalline transformations in spherulites of poly(vinylidene fluoride). Polymer 2/ 1317... 

Fig. 5.17 Early stages in the growth of spherulites (a) the sheaf-life stage in the growth of a polyethylene spherulite and (b) the beginnings of radial growth in a spherulite of poly(4-methylpentane). ((a) Reprinted by permission of Kluwer Academic Publishers (b) Cambridge University Press 1981.)...

J.K. Hobbs, T.J. McMaster, M.J. Miles and P.J. Barham, Direct observations of the growth of spherulites of poly(hydroxybutyrate-co-valerate) using atomic force microscopy. Polymer 39, 2437-2446 (1998). 

Fig. 7. (a) Banded spherulites of poly(trimethylene glutarate) viewed between crossed polars in a polarizing microscope. From Ref 118.. (b) lamellar texture in a banded spherulite of butyl-branched linear low density polyethylene crystallized at 124°C. From Ref. 119. 

Fig. 19. Banded spherulite of poly(trimethylene terephthalate) crystallized from the melt at 150°C (139).

Fig. 20. In panel A diffraction patterns on different positions inside a spherulite of poly(3-hydroxybutyrate) are shown. The diffraction patterns are mapped onto the position inside the spherulite. The spherulite was mapped with a lO- im beam on a microfocus beamline at the ESRF. The data presented here shows approximately 150 ixrc of the spherulite. Panel B shows one of the diffraction patterns. It could be indexed to an orthorombic unit cell with dimensions a = 0.576, b = 1.32, and c = 0.596 nm. The degree of disorder increases toward the center of the spherulite. Courtesy of A. Mahendrasingam.

Fig. 4.34 Examples of spherulites (a) Spherulites in polyethylene (Armistead et al. (Reprinted by permission from Armistead et al. Copyright 2003, American Chemical Society), (b) Ringed spherulites of poly(hydroxybutyrate), (Hobbs et al. (2000)) Reprinted by permission of John Wiley and Sons, Inc.

Figure 10.5 Spherulites of poly(vinylidene fluoride) grown at 162.5°C as imaged in the polarising optical microscope. In (a) the light is plane-polarised whereas in (b) it is circularly polarised.

Figure 10.17 Etched surface showing lamellar detail in a banded spherulite of poly(vinylidene fluoride). Moving outwards along the radius (arrowed) the lamellar orientation changes from being seen close to flat on [B] to being edge on [A]. In region [A] the very dark radial features are a consequence of material being stripped from the specimen surface during replication.

Mahendrasingam A, Martin C, FuUer W, Blundell D, MacKerron D, Rule R, Oldman R, Liggat J, Riekel C, Engstrom P. Microfocus X-ray diffraction of spherulites of poly-3-hydroxybutyrate. J Synchrotron Radiat 1995 2 308-312. 

Figure 10 J (a) A typical spherulite of poly(e-caprolactone) (PCL) homopolymers in a PCL/poly( vinyl chloride) hlend, and (h) a schematic illustration showing the inside of spherulites.

Figure 2.9 A series of wide-angle X-ray diffraction photographs from crystals located along the vertical line within a spherulite of poly(hydroxy butarate) shown in the left inset. The enlarged diffractograms are from three areas separated by 60 m as shown in the optical micrograph. Courtesy of C. Riekel, ESRF.

Figure 5.5 (a) A negative spherulite of poly(ethylene oxide) and (b) a spheruiite of poly(ethylene adipate). (See color insert.)... 

Figure 39 A banded spherulite of poly(vinylidene fluoride) crystallized at 163 °C, viewed along a direction close to the radial crystallographic b direction. Lamellae can be seen to be inherently planar rather than S-shaped as in polyethylene...

Horikiri S, Kodera K. Spherulites of poly(2,6-dimethyl-l,4-phenylene)oxide. Polym. J. 1973 4 213-214... 

Figure 34 AFM phase images of the growth fronts of spherulites of poly (hydroxybutyrate-co-valerate) developing at different temperatures. Scale bar is lOOnm. Reproduced with permission from Matyjaszewski, K. Gnanou, Y. Leibler, L. (Eds) Macromolecular Engineering, v. 3, 1515-1574 (2007). Copyright Wiley-VCH Vetlag GmbH Co. KGaA.

Figure 6 Spherulites of isotactic poly-l-butene (a, during growth) and of polyethylene (b, after completion) by optical microscopy (OM) under crossed polars. Reproduced from Ref. [3] with permission of John Wiley Sons, Inc.

Figure 11 Left Spherulites of a Ziegler-Natta isotactic poly(propylene) with Mw = 271,500 g/mol and mmmm — 0.95, isothermally crystallized at 148°C. Right Banded spherulites of a linear polyethylene with Mw = 53,600 g/mol slowly cooled from the melt.

Tant, M. R. and Culberson, W. T., Effect of molecular weight on spherulite growth rate of poly(ethylene terephthalate) via real-time small angle light scattering, Polym. Eng. Sci., 33, 1152-1156 (1993). 

The topographical AFM images of poly(ethylene vinyl acetate) films with various thicknesses ranging from 20 to 460 nm are shown in Fig. 33 [80]. The bulk-like spherulites are seen in the 460-nm film. In thick films, the surface morphology of the film is very similar to the bulk. As the thickness decreases to 152 nm, more small spherulites are observed. This is possibly due to the... 

Significant variation of the ultimate mechanical properties of poly(hexamethylene sehacate), HMS, is possible by con-trol of thermal history without significant variation of percent crystallinity. Both banded and unbanded spherulite morphology samples obtained by crystallization at 52°C and 60°C respectively fracture in a brittle fashion at a strain of r O.Ol in./in. An ice-water-quenched specimen does not fracture after a strain of 1.40 in./in. The difference in deformation behavior is interpreted as variation of the population of tie molecules or tie fibrils and variation of crystalline morphological dimensions. The deformation process transforms the appearance of the quenched sample from a creamy white opaque color to a translucent material. Additional experiments are suggested which should define the morphological characteristics that result in variation of the mechanical properties from ductile to brittle behavior. 

In conclusion, the deformation behavior of poly(hexamethylene sebacate), HMS, can be altered from ductile to brittle by variation of crystallization conditions without significant variation of percent crystallinity. Banded and nonbanded spherulitic morphology samples crystallized at 52°C and 60°C fail at a strain of 0.01 in./in. whereas ice-water-quenched HMS does not fail at a strain of 1.40 in./in. The change in deformation behavior is attributed primarily to an increased population of tie molecules and/or tie fibrils with decreasing crystallization temperature which is related to variation of lamellar and spherulitic dimensions. This ductile-brittle transformation is not caused by volume or enthalpy relaxation as reported for glassy amorphous polymers. Nor is a series of molecular weights, temperatures, strain rates, etc. required to observe this transition. Also, the quenched HMS is transformed from the normal creamy white opaque appearance of HMS to a translucent appearance after deformation. 

Figure 3 Polarizing optical micrographs of poly(ethylene terephthalate) (PET) crystallized at 240°C in the absence (A) and in the presence (B) of a shearing. As a consequence of the shearing, nucleation becomes increasingly profuse, and the shape of the spherulites becomes elliptical. (From ref. 11)...

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