Some studies of deformation processes in fully-spherulitic polypropylene

Way, Jerome; Atkinson, J. R.

doi:10.1007/bf00550338

Cited by 56 publications

(16 citation statements)

References 14 publications

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“…17 Rodrigues-Navarro also showed this effect. 18 Thus, both aragonite growth by CPA and by ion attachment are faster along the c-axis.Spherulites are found in a wide variety of materials systems, including geologic minerals, 19,20 metal alloys, 21 nonmetallic elements, 5,22 salts, 23,24 organic molecules, 13,25 proteins, 26 and a vast number of synthetic 2,3,27,28 and natural 4 polymers.Many biominerals have also been described as spherulitic based on their morphologies, including coral skeletons, 10,11,29,30 avian eggshells, 31−33 fish otoliths, 12,34,35 crustacean statoliths, 36 sponges, 37 and kidney stones. 38,39 The only evidence of spherulites in biominerals obtained from crystal orientation analysis, however, is in bioinduced, kidney stones, which are calcium oxalate monohydrate pathological biominerals.…”

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confidence: 99%

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Sun¹,

Marcus

Frazier³

et al. 2017

ACS Nano

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Coral skeletons were long assumed to have a spherulitic structure, that is, a radial distribution of acicular aragonite (CaCO 3 ) crystals with their c-axes radiating from series of points, termed centers of calcification (CoCs). This assumption was based on morphology alone, not on crystallography. Here we measure the orientation of crystals and nanocrystals and confirm that corals grow their skeletons in bundles of aragonite crystals, with their caxes and long axes oriented radially and at an angle from the CoCs, thus precisely as expected for feather-like or "plumose" spherulites. Furthermore, we find that in both synthetic and coral aragonite spherulites at the nanoscale adjacent crystals have similar but not identical orientations, thus demonstrating by direct observation that even at nanoscale the mechanism of spherulite formation is non-crystallographic branching (NCB), as predicted by theory. Finally, synthetic aragonite spherulites and coral skeletons have similar angle spreads, and angular distances of adjacent crystals, further confirming that coral skeletons are spherulites. This is important because aragonite grows anisotropically, 10 times faster along the c-axis than along the a-axis direction, and spherulites fill space with crystals growing almost exclusively along the c-axis, thus they can fill space faster than any other aragonite growth geometry, and create isotropic materials from anisotropic crystals. Greater space filling rate and isotropic mechanical behavior are key to the skeleton's supporting function and therefore to its evolutionary success. In this sense, spherulitic growth is Nature's 3D printing. KEYWORDS: Ion attachment, crystallization by particle attachment, CPA, biomineralization, PEEM, PIC-mapping, mesocrystal S pherulites are polycrystalline structures in which acicular crystals radiate from a common center and grow approximately synchronously so the final shape of a spherulite resembles a sphere. 1−7 Figure 1 shows two types of spherulites: "spherical spherulite", in which the crystal fibers start from a point, or "plumose spherulite", in which crystal fibers radiate at an angle from the line. 7 Spherulites start forming as an aggregate of parallel acicular crystals termed "fibers", then form a "sheaf of wheat" structure, and with the growth of more fibers eventually become complete spheres. 8 In an ideal spherulite, fibers radiate from the center and contain all possible orientations within the sphere. Since the fast-growing axis in aragonite (CaCO 3 ) is the c-axis, 9 in spherulites each fiber elongation direction coincides with the crystalline c-axis. 10,11 In real spherulites, biogenic 12 and synthetic, 7 the crystal orientations are not perfectly radial nor continuously varying with angle, they deviate slightly from radial and exhibit small but abrupt changes in orientation, termed "branching". In Figure 1 branching angles are smaller than 30°in direction and in crystal lattice orientation. This is distinct from crystallographic branching, which occurs in sno...

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mentioning

confidence: 99%

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Sun¹,

Marcus

Frazier³

et al. 2017

ACS Nano

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“…10a and c) when compared to the respective plates. However, at zone II PLM analysis along the TD-ND plane reveals the presence of elongated spherulites [37] in the weld seam (Fig. 10b) which is the result from the sheared melt flow.…”

Section: Resultsmentioning

confidence: 94%

Measuring the orientation of chains in polypropylene welds by infrared microscopy: A tool to understand the impact of thermo-mechanical treatment and processing

Damodaran

Schuster

Rode

et al. 2015

Polymer

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“…Thin black rings within iPP spherulites were first noted by Way and Atkinson in specimens maintained at 157°C for 13 h and successively cooled to room temperature before the solidification was complete 9, 10. To my knowledge, no other investigations on the origin of dark rings existing in undeformed iPP grown in a temperature field have been carried out, despite the importance of structural discontinuities in determining final properties of materials.…”

Section: Resultsmentioning

confidence: 95%

Influence of temperature changes on crystallization of an ethylene–propylene random copolymer

Raimo¹

2004

J of Applied Polymer Sci

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Unconventional procedures were used to crystallize an ethylene/propylene copolymer (E/P), with the aim of investigating the effect of temperature changes on crystallization kinetics and spherulitic morphology. The solidification process of specimens crystallizing under isothermal conditions was cyclically stopped for a while, by increasing the temperature, and afterward reestablished by cooling at the original temperature. The resulting morphology characterized by rings within spherulites was compared to that obtained by continuous isothermal crystallization. The different temperature dependencies of the thermal expansion coefficients of liquid and solid phases account for the presence of rings within spherulites grown in a temperature field.

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Some studies of deformation processes in fully-spherulitic polypropylene

Cited by 56 publications

References 14 publications

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Measuring the orientation of chains in polypropylene welds by infrared microscopy: A tool to understand the impact of thermo-mechanical treatment and processing

Influence of temperature changes on crystallization of an ethylene–propylene random copolymer

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