Online measurements of crystallinity using Raman spectroscopy during blown film extrusion of a linear low‐density polyethylene

Cherukupalli, Srinivas S.; Ogale, Amod A.

doi:10.1002/pen.20144

Cited by 33 publications

(31 citation statements)

References 21 publications

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“…Raman spectra were quantified for crystallinity values following a protocol that was established in earlier studies. [20,21] Real-time temperature measurements were also performed using an IRCON IR pyrometer (Modline 340, Niles, IL).…”

Section: Process Measurements and Instrumentationmentioning

confidence: 99%

“…Recently, we have reported on the use of real-time Raman spectroscopy to estimate crystallinity development during blown film extrusion of polyolefins. [20,21] Our study established Raman spectroscopy as a robust and nondestructive technique to monitor crystallinity evolution in industrial settings, as it offers remote sampling capabilities when coupled via fiber optics. The integration of real-time experimental results with modeling efforts was reported in a recent study.…”

Section: Introductionmentioning

confidence: 99%

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Molecular orientation evolution during low‐density polyethylene blown film extrusion using real‐time Raman spectroscopy

Gururajan¹,

Ogale²

2008

J Raman Spectroscopy

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Real-time polarized Raman spectroscopy was used in this study to measure the molecular orientation evolution during blown film extrusion of low-density polyethylene (LDPE). Spectra were obtained at different locations along the blown film line, starting from the molten state near the die and extending up to the solidified state near the nip rolls. The trans C-C symmetrical stretching vibration of polyethylene (PE) at 1132 cm −1 was analyzed for films possessing uniaxial symmetry. For the given peak, the principal axis of the Raman tensor is coincident with the c-axis of the orthorhombic crystal, and was used to solve a set of intensity ratio equations to obtain second ( P 2 (cos θ) ) and fourth ( P 4 (cos θ ) ) moments of the orientation distribution function. The orientation parameters (P 2 , P 4 ) were found to increase along the axial distance in the film line even past the frost-line height (FLH). The P 2 values also showed an increasing trend with crystalline evolution during extrusion, consistent with past observations that molecular orientation takes place even after the blown film diameter is locked into place. It was also found that the integral ratio (I 1132 /I 1064 ) obtained from a single, ZZ-back-scattered mode can provide a reasonable estimate of molecular orientation. These results indicate the potential of real-time Raman spectroscopy as a rapid microstructure monitoring tool for better process control during blown film extrusion.

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Section: Process Measurements and Instrumentationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular orientation evolution during low‐density polyethylene blown film extrusion using real‐time Raman spectroscopy

Gururajan¹,

Ogale²

2008

J Raman Spectroscopy

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“…The calculated degree of crystallinity of the 1.5, 2.0 and 2.4 mm GMBs obtained from the first melt curve using method-4 were insignificantly different but were slightly less than the calculated degree of crystallinity of 1.0 mm GMB (Figure 14), although the specimens from 1.0, 1.5, 2.0 and 2.4 mm have the same physical characteristic (Table 2, Figure 4). This trend may be: (a) showing the counteracting effects of an increase in crystallisation rates of the thinner GMBs due to the higher stress induced by the higher take-up ratio being opposed by the decrease in crystallisation rates for thinner GMBs because of their higher cooling rates and lesser time for crystallisation and annealing (Cherukupalli and Ogale 2004); or (b) an anomaly resulting from the different movement of the specimens in the DSC (as explained earlier). If explanation (a) is true, then it appears that the effect of the takeup-ratios of 1.5, 2.0 and 2.4 mm GMB was cancelled by the effect of their cooling rates; however, the effect of the higher take-up ratio for the 1.0 mm GMB on crystallisation was slightly higher than the effect of the cooling rates that 1.0 mm GMB experienced during the manufacturing process.…”

Section: Crystallinity Test Resultsmentioning

confidence: 91%

“…Keller and Machin (1967) modified the row-nucleated structure model with respect to the level of stress into two models: (a) Keller/ Machin I: under low stress the lamellae grow radially outward in the form of twisted ribbons and (b) Keller/Machin II: under high stress the lamellae grow laterally outward without twisting and the chain axis ( Figure 3) is preferentially oriented in the machine direction. According to the findings of Sukhadia (1994), Simpson and Harrison (1994), Ghaneh-Fard (1999), Lu et al (2001), Godshall et al (2003), Cherukupalli and Ogale (2004), Zhang et al (2004) and Fatahi et al (2005), the mechanical and physical response of polyethylene films manufactured using the blown film method are a strong function of its morphological structure. For example, Lu et al (2001) studied HDPE blown films and found that the morphological structure of HDPE films was comprised of two superimposed row-nucleated structures.…”

Section: Introductionmentioning

confidence: 96%

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Effects of blown film process on initial properties of HPDE geomembranes of different thicknesses

Ewais¹,

Rowe²

2014

Geosynthetics International

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The differences in the properties of five high density polyethylene geomembranes (GMBs) of different thicknesses made by the same manufacturer from same GMB resin are investigated. The 1.0, 1.5, 2.0 and 2.4 mm thick GMBs investigated were manufactured during the same production run by changing the pulling speed of the GMB out of the extrusion die, such that, the pulling speed decreased with increasing thickness. There were no differences in the initial HP-OIT or Std-OIT values of the different GMBs. However, there were differences in the key mechanical and physical properties of the GMBs that cannot be simply explained by the increase in the amount of material due to increasing GMB thickness. These differences are explained by differences in the morphological structure of the GMBs arising from the different thermal and stress histories experienced during the manufacturing process. The effects of the differences in the morphological structure are discussed in terms of: the decrease in the relative differences between the stress-elongation curves in the machine and cross-machine directions as thickness increases; changes in the enthalpies of melting and crystallisation by differential scanning calorimetry with changing thickness; and the different stress crack resistance (SCR) for the GMBs. For example, thinner GMBs had a greater difference between the SCR in the machine and cross-machine direction. Increasing the GMB thickness from 1.5 to 2.4 mm resulted in increasing the SCR from , 800 to , 1100 h in the cross-machine direction and decreasing its SCR from , 4100 to , 2000 h in the machine direction. Thus, GMBs of different thickness manufactured from the same resin can be expected to have differences in their physical and mechanical properties that are dependent on the additional material but also the difference in the tension and cooling rate experienced during the manufacturing process.

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Raman Spectroscopy in Process AnalysisUpdate based on the original article by M. Anne Leugers and Elmer D. Lipp,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

Lipp

Leugers

Chen

et al. 2012

Encyclopedia of Analytical Chemistry

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Process analysis involves the on‐line measurement of chemical or physical properties of a process, generally a manufacturing process, which provides timely data so that the process can be monitored and conditions adjusted if necessary. As a tool for process analysis, Raman spectroscopy has some desirable attributes. Foremost among these are the options for sampling. The use of visible and near‐infrared (NIR) light for the Raman measurement allows the use of commonly available fiber optics for both delivery of light to a sampling point, and then collection of the scattered light and return to a spectrometer. The probes can be insertable into a process or fully noncontact. The noncontact probes operate through windows on the process and provide one of the few means of collecting analytical information without disturbing the process. Raman spectra often provide a high level of chemical and structural information, and the seconds to minutes time frame of the measurement is well suited to process control. In this article, we discuss modern Raman instrumentation and provide a number of application examples, both conventional manufacturing processes and unconventional applications, where the principles and goals of process analysis still apply.

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Online measurements of crystallinity using Raman spectroscopy during blown film extrusion of a linear low‐density polyethylene

Cited by 33 publications

References 21 publications

Molecular orientation evolution during low‐density polyethylene blown film extrusion using real‐time Raman spectroscopy

Molecular orientation evolution during low‐density polyethylene blown film extrusion using real‐time Raman spectroscopy

Effects of blown film process on initial properties of HPDE geomembranes of different thicknesses

Raman Spectroscopy in Process AnalysisUpdate based on the original article by M. Anne Leugers and Elmer D. Lipp,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

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