NMR study of polyethylene crystallization kinetics under high pressure

Brown, D.R.; Jonáš, J.

doi:10.1002/pol.1984.180220409

Cited by 12 publications

(4 citation statements)

References 32 publications

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“…Combining eqs. (4), (5), and (6), we have -T (7) x x lo2 K' Plots of lnrO.l against T;/TAT are shown in Figure 8. It can be seen that the data from the solutions can be approximate by a single straight line.…”

Section: Kinetic Parameters and Composition Of The Solutionmentioning

confidence: 98%

See 1 more Smart Citation

NMR Approach to the kinetics of polymer crystallization. II. Polydimethylsiloxane solutions

Feio¹,

Buntinx

Cohen‐Addad

1989

J Polym Sci B Polym Phys

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The dilution effect on the crystallization kinetics of PDMS/toluene solutions, ranging from a polymer volume fraction of ϕ = 1.00 (pure PDMS) to ϕ = 0.32, was studied using 1H high‐power NMR. Spin‐spin magnetic response was analyzed into relaxation components, arising from the different phases of the semicrystalline sample, through a spin‐echo technique. The intensity and shape of the amorphous component provide relevant information concerning (1) the global crystallization process and (2) the state of hindrance of the amorphous chains induced by the growing crystalline domains. It was shown that, in solutions, the main effect on the crystallization kinetics of changing concentration is to depress the equilibrium melting temperature of the system. However, a radically distinct crystallization rate between the pure and the more concentrated system must be explained in terms of the activation energy for interphase chain transport. Thermodynamic parameters of PDMS crystallites were also deduced from a model. Comparison between the isothermal development of the overall crystallinity and the variation of a characteristic relaxation time of the amorphous PDMS proton response gives an insight into the relative predominance of nucleation or growth rates in the crystallization mechanisms.

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Section: Kinetic Parameters and Composition Of The Solutionmentioning

confidence: 98%

“…Since every experimental determination of ro.l for the solutions falls on the same straight line in Figure 8, the term B / n in eq. (7) can easily be evaluated from a linear regression. Thus, we find B / n = -86.8.…”

Section: Lamellar Thermodynamic Parametersmentioning

confidence: 99%

NMR Approach to the kinetics of polymer crystallization. II. Polydimethylsiloxane solutions

Feio¹,

Buntinx

Cohen‐Addad

1989

J Polym Sci B Polym Phys

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“…Under pressure, overall kinetics was strong-minded in category i). by in-situ nuclear magnetic resonance (NMR) measurements by Brown & Jonas [45], in category ii). by dilatometric measurements [6,[46][47][48][49], in category iii).…”

Section: Introductionmentioning

confidence: 99%

An Original Model Experiment Designed for High-Pressure Crystallization with a Polymer Processing Concern

Boyer

Haudin

2013

KEM

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A comprehensive understanding of the inherent link between in-situ growth kinetics of a polymer spherulite and high-pressure constraints under controlled temperature is concerned. As a matter of fact, while the link with temperature is well illustrated, little comprehensive study has been conducted to quantify the effect of pressure. This is yet required to model ‘extreme’ polymer processing conditions.Mainly, the experimental set-ups developed to reproduce the pressure effect can be classified into four families: “simple” cells, dilatometric set-ups, differential thermal analysis and diamond anvil plus in-situ measurement. In this context, an original model experiment, named CRISTAPRESS, has been constructed. The cell design exploits the optical properties of semi-crystalline spherulites. Time-resolved light depolarizing microscopic observations are conducted concomitantly with a fine PVT control, for high pressure up to 200 MPa and temperature up to 300 °C. The physical analysis of isothermal and isobaric holding of a model polymer shows the influence of temperature and pressure on the key kinetic parameters of crystallization, i.e., the growth rate and the number of activated nuclei, as well as on the subsequent morphologies. Simple modeling dealing with the Avrami equation and the Hoffman & Lauritzen theory is established.

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“…12 Methods of nuclear magnetic resonance (NMR) have been used successfully to characterize the crystalline structure within many polymeric materials. [13][14][15][16][17][18][19][20][21][22][23] In fact, relatively cost-effective low-resolution NMR scanners are used routinely to determine crystallinity in semi-crystalline commodity polymers. 24 The nucleus of choice is typically the 1 H, whose sensitivity along with modern pulsed NMR instrumentation allows the measurement of % crystallinity in seconds or less.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Crystallinity, Chain Mobility, and Crystallite Size during Polymer Crystallization

2004

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A 1H NMR method is described for examining crystallinity, chain mobility, and crystallite size in real time during polymer crystallization. The method is demonstrated by following the crystallization of natural rubber at −10 °C. At selected stages during the crystallization, a Bloch decay was recorded along with Goldman−Shen decays for a series of mixing times using a filter duration to destroy the rigid-phase magnetization. The fast-relaxing components of the Bloch and Goldman−Shen decays correspond to the rigid/crystalline fraction of the sample and were fitted to Gaussian functions. The slow-relaxing components were obtained experimentally using the Goldman−Shen sequence measured with a short mixing time (1 ms). By combining the fitted Gaussian portions with the experimentally determined slow-relaxing components, the Bloch and Goldman−Shen decays could be analyzed across the entire crystallization process. The Bloch decays provided information on the amount and nature of the rigid fraction, while the Goldman−Shen spin-diffusion data provided information on domain size. The formation of noncrystalline rigid domains was observed for the initial stages of the crystallization process. Data clearly indicate lateral growth of crystallites with relatively uniform thickness during the primary crystallization process. Later stages of crystallization are characterized by increasing heterogeneity in crystalline density and perfection.

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NMR study of polyethylene crystallization kinetics under high pressure

Cited by 12 publications

References 32 publications

NMR Approach to the kinetics of polymer crystallization. II. Polydimethylsiloxane solutions

NMR Approach to the kinetics of polymer crystallization. II. Polydimethylsiloxane solutions

An Original Model Experiment Designed for High-Pressure Crystallization with a Polymer Processing Concern

Evolution of Crystallinity, Chain Mobility, and Crystallite Size during Polymer Crystallization

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