An absolute method for the determination of crystallinity in polymers

Corradini, Paolo; Martuscelli, E.; Martynov, M.A.

doi:10.1002/macp.1967.021080124

“…Excellent consistency was of course obtained between density, "X-ray" and "infra-red determinations of crystallinity, but since each was ultimately based on the same measure, internal consistency was to be expected. Recently, Corradini, Martuscelli and Martynov (48) and Martuscelli and Martynov (49) have suggested a method which involves preparation of an intimate mixture of the polymer in question with a simple crystalline organic substance, e.g., pentaerythritol, C,H,,O,. Then the intensity ratio of a diffraction peak attributable to the polymer and a peak attributable to the standard substance was said to be where the subscripts p and s refer to the polymer and standard substance respectively; I , and I, are the integral intensities of the peaks corrected for multiplicity, Lorentz, and polarization factors; F, V,, p and W are the structure factor, the unit cell volume, the density and weight fraction of the substance in the mixture and x,, is the weight fraction crystallinity of the polymer.…”

Section: Extrapolations Of Property Correlations To the Unit Cell Or mentioning

confidence: 99%

Meaning and measurement of crystallinity in polymers: A Review

Kavesh¹,

Schultz

²

1969

Polymer Engineering & Sci

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A useful concept in polymer science is the degree of crystallinity-the fraction of the polymer that exists in a relatively ordered state. Methods of determination of the degree of crystallinity using density, infrared, thermal, N.M.R. and X-ray measurements are examined in light of modern notions of the structure of semi-crystalline polymers. POLYMER STRUCTURE AND CONCEPT OF DEGREE OF CRYSTALLINITYInvestigators early recognized that polymers were intermediate in order between ideally crystalline solids and liquid-like amorphous materials. X-ray diffraction patterns of polymers showed broad but distinct crystal-like Bragg reflections superimposed on a background of diffuse liquid-like scattering. In order to explain such observations the micellar theory of polymer crystallization was devised. The long polymer chains were visualized as being randomly tangled in the solid state. In areas where a few chains came together in approximately parallel orientation, a crystallite or micelle was believed formed (Fig. 1 ) .According to this view then, polymeric material consisted of numerous small crystallites randomly distributed through the solid and linked by the intervening amorphous areas. Investigations of the width of the Bragg reflections, Bunn and Alcock ( 1 ) for example, showed polyethylene "crystallites" to be only 100-300 A in size, in good accord with the concepts of the model. It was, therefore, entirely reaThis article was originally published in the September issue (p. 331) without the five illustrations referenced in the text. It i sreprinted here in its entirety to provide readers with the complete paper for reference purposes. The publisher regrets any inconvenience or embarrassment this error has caused the authors, editor or readers.

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“…The meaning of crystallinity measurements in polymers is discussed by Stratton (162) and Bodor (29) considers factors causing line broadening in the diffraction patterns of high polymers. An absolute method for crystallinity determination in certain polymers was described by Corradini, et al (48) and a wide-angle method for degree of crystallinity measurements of linear polyethylene was developed by Gopalan and Mandelkern (75). A low-angle method which permits the investigation of molecular dimensions in bulk polymers was worked out by Krigbaum and Godwin (105).…”

mentioning

confidence: 99%

X-ray diffraction

Merritt¹,

Streib²

1968

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Meaning and measurement of crystallinity in polymers: A Review

Kavesh¹,

Schultz

²

1969

Polymer Engineering & Sci

View full text Add to dashboard Cite

A useful concept in polymer science is the degree of crystallinity-the fraction of the polymer that exists in a relatively ordered state. Methods of determination of the degree of crystallinity using density, infrared, thermal, N.M.R. and X-ray measurements are examined in light of modern notions of the structure of semi-crystalline polymers. POLYMER STRUCTURE AND CONCEPT OFDEGREE OF CRYSTALLINITY Investigators early recognized that polymers were intermediate in order between ideally crystalline solids and liquid-like amorphous materials. X-ray diffraction patterns of polymers showed broad but distinct crystal-like Bragg reflections superimposed on a background of diffuse liquid-like scattering. In order to explain such observations the micellar theory of polymer crystallization was devised. The long polymer chains were visualized as being randomly tangled in the solid state. In areas where a few chains came together in approximately parallel orientation, a crystallite or micelle was believed formed ( F i g . 1 ).According to this view then, polymeric material consisted of numerous small crystallites randomly distributed through the solid and linked by the intervening amorphous areas. Investigations of the width of the Bragg reflections, Bunn and Alcock (1) for example, showed polyethylene "crystallites" to be only 100-300 A in size, in good accord with the concepts of the model. It was, therefore, entirely reasonable to inquire in this context about the degree of crystallinity of the polymer; to question what fraction of the solid was composed of crystallites.In more recent times, of course, the power of the electron microscope has shown the polymeric solid to consist largely of folded chain lamellae. Linear polyethylene and polyoxymethylene, for example, are literally filled with these regularly stacked crystal structures. The breadth of the diffraction lines must now be interpreted as a result of either a mosaic structure or disorder within the lamellae. Furthermore, much evidence has suggested that the surface of the lamellae are composed of regular folds of minimum length so that effectively an interlamellar zone does not exist ( F i g . 2). On this basis then there is no amorphous phase, the degree of crystallinity is approximately 100% and observations which might be attributed to an amorphous phase are explained on the basis of disorder within the lamellae ( 2 ) . However, not a11 evidence is in accord with such a viewpoint. Some of the evidence to the contrary has previously been reviewed by Mandelkern ( 3 ) .In 1963, in a notable contribution, Ruland (4) presented a clear and rigorous criterion for distinguishing between X-ray patterns caused by one phase disordered systems and two phase crystalline and amorphous systems. Ruland began his analysis with the premise that the material in question is a one phase disordered paracrystal and on this basis, he developed expressions for both the sharpness and intensity of diffraction. First, the breadth of a diffraction peak was attributed solely to disorder so...

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An absolute method for the determination of crystallinity in polymers

Abstract: G. NATTA, and P. CORRADINI, Nuovo Cimento, suppl. 15, 10 (1960) 40.

Cited by 9 publications

References 8 publications

Meaning and measurement of crystallinity in polymers: A Review

Meaning and measurement of crystallinity in polymers: A Review

X-ray diffraction

Meaning and measurement of crystallinity in polymers: A Review

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