Infrared determination of orientation, orientation distribution, and crystallinity in polyethylene films

Tobin, Marvin C.; Carrano, M. J.

doi:10.1002/pol.1957.1202410512

Cited by 53 publications

(14 citation statements)

References 12 publications

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“…Our results favor the third alternative : the experimental linear relationship between sin2 x and AT, shown in Figure 4, has been found by the method of least squares to be best represented by the equation 294.5 sin2 xlO0 + AT = 223 (5) Equation ( 5 ) gives extrapolated values of AT = 223 a t xlm = 0 and of AT = -72 at XI,,,, = go', the fully relaxed condition. It also shows that the change-over point from positive to negative birefringence occurs a t xlw = 60.5'.…”

Section: Resultsmentioning

confidence: 48%

The orientation of the crystalline and amorphous regions in polyethylene film

Holmes¹,

Palmer²

1958

J. Polym. Sci.

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The orientation in the crystalline and amorphous regions of a series of polyethylene films prepared by the tubular films extrusion process has been studied by a combination of x‐ray diffraction and optical methods. All of these films show a relaxation orientation differing both from the fully relaxed type of orientation previously proposed by the authors, and from the more complicated type of orientation suggested by Keller. In all films there is cylindrical symmetry about the machine direction and the b‐axes of the crystallites are preferentially oriented in the plane perpendicular to this direction. The preferred directions of the a and c crystallite axes depend both on the extrusion conditions and on the nature of the polymer; at low blow‐up ratios and high haul of speeds the c axes tend to lie more nearly parallel to the machine direction, but as the blow‐up ratios is increased and the haul‐off speed decreased rotation of the crystallites about their b axes occurs, and eventually the a axes tend to lie more nearly parallel to the machine direction. Both the preferred crystallite orientation and its angular distribution have been measured for a large number of films made from various ethylene polymers, and a linear relation between a function of the orientation angle and the optical birefringence has been established. As the c axes tilt away from the machine direction towards the plane perpendicular to this direction the birefringence steadily decreases, and eventually becomes negative. An expression is given for the birefringence of such a cylindrically symmetrical array of crystallites tilted to various angles, and is used to predict the orientation at which the crystallite birefringence contribution will be zero and also the extreme values of the crystalline birefringence contribution in the fully drawn and fully relaxed conditions. By comparing the theoretical and experimental relations between crystallite orientation and birefringence, it has been deduced that in these films the amorphous material appears to provide a nearly constant small positive contribution to the birefringence irrespective of the birefringence contribution of the crystallite regions; this means that in the negatively birefringent films some of the molecules in the amorphous regions are crossed with respect to those in the crystalline regions. When allowance is made for this amorphous contribution, crystallinities calculated from the extrapolated observed and theoretical extreme values of the birefringence are in reasonable agreement with the x‐ray measured crystallinity of 45%. The mechanism resulting in the formation of this unusual orientation is considered in reference to the manufacturing process.

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Section: Resultsmentioning

confidence: 48%

The orientation of the crystalline and amorphous regions in polyethylene film

Holmes¹,

Palmer²

1958

J. Polym. Sci.

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“…Similar to propylene, FTIR spectroscopy also supplies information on the relative crystallinity of ethylene in EPCs. As the crystallinity in polyethylene increases, the 720 cm −1 band, originating from long continuous methylene sequences, splits and the intensity of the 730 cm −1 component increases 43, 44. The 730 cm −1 band has been identified as a true crystallinity band35 and, therefore, the ratio of the band intensities at 720 and 730 cm −1 is related to the relative crystallinity in polyethylene 44–46.…”

Section: Resultsmentioning

confidence: 99%

“…As the crystallinity in polyethylene increases, the 720 cm −1 band, originating from long continuous methylene sequences, splits and the intensity of the 730 cm −1 component increases 43, 44. The 730 cm −1 band has been identified as a true crystallinity band35 and, therefore, the ratio of the band intensities at 720 and 730 cm −1 is related to the relative crystallinity in polyethylene 44–46. In Figure 5 the 998 cm −1 /972 cm −1 and 730 cm −1 /720 cm −1 ratio's are constructed across the Gram‐Schmidt curves of all fractions in order to study the distribution of ethylene and propylene crystallinity across the molecular weight profiles.…”

Section: Resultsmentioning

confidence: 99%

Fractionation and Analysis of an Impact Poly(propylene) Copolymer by TREF and SEC‐FTIR

Goede

Mallon

Pasch

2010

Macro Materials & Eng

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TREF fractionation was combined with SEC‐FTIR analysis to measure the compositional heterogeneity within a commercial impact PP copolymer. The chemical composition of all fractions was determined as function of their molecular weight distribution. This approach proved to be highly successful at identifying different constituents within fractions exhibiting bimodal molecular weight distributions. Furthermore, the determination of ethylene and propylene crystallinity distribution across the molecular weight distribution confirmed the morphological nature of each of the components of the bimodal distribution. It is demonstrated that the combination of TREF and SEC‐FTIR provides a simple alternative to more time‐consuming conventional ways of characterising impact PP copolymers of complex heterogeneity.magnified image

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“…Unfortunately, this method can only be applied if the film density and thickness are known. 8 Zerbi et al9 recently suggested the use of spectral bands corresponding to the bending vibrations: 1474 and 730 cm-' (crystalline phase) and 1464 and 720 cm-' (amorphous phase). This procedure was selected for this work as the preparation technique in pellets provides intense absorptions in such spectral bands while the absorption at 1303 cm-' gives low intensity due to the high crystallinity of the HDPE.…”

Section: Ftir Spectrophotometrymentioning

confidence: 99%

FTIR and DSC study of HDPE structural changes and mechanical properties variation when exposed to weathering aging during Canadian winter

Pags

Carrasco

Saurina

et al. 1996

J. Appl. Polym. Sci.

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SYNOPSISThe aging of high-density polyethylene (HDPE) when exposed to drastic climatic conditions (Canadian winter, characterized by low temperature and abrupt temperature variations between the night and the day) was studied. The importance of degradation was determined by evaluating the microstructural changes in HDPE (i.e., oxidations, ramifications, and polymeric chain breaking) by means of FTIR spectrophotometry. The crystallinity variation in HDPE by FTIR and DSC was also studied. Both techniques led to coherent results: there was a loss of crystallinity due to weathering degradation. This crystallinity reduction produced a drastic decrease in impact energy. However, the other properties evaluated were not significantly affected.

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Infrared determination of orientation, orientation distribution, and crystallinity in polyethylene films

Cited by 53 publications

References 12 publications

The orientation of the crystalline and amorphous regions in polyethylene film

The orientation of the crystalline and amorphous regions in polyethylene film

Fractionation and Analysis of an Impact Poly(propylene) Copolymer by TREF and SEC‐FTIR

FTIR and DSC study of HDPE structural changes and mechanical properties variation when exposed to weathering aging during Canadian winter

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