Crystallization, melting, and morphology of low molecular weight polyethylene fractions

Stack, G. M.; Mandelkern, L.; Voigt‐Martin, I. G.

doi:10.1021/ma00133a011

Cited by 78 publications

(47 citation statements)

References 17 publications

(24 reference statements)

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“…With high molecular weight polymers, the differences in molecular weights are much less significant relative to their total molecular weight and the trend of melting temperatures displays an asymptotic behavior towards higher molar masses. 4,[32][33][34][35][36] Hence, only the polymer fragments of lower molecular weights can be distinguished sufficiently well by their melting temperatures. The observed series of increasing melting points corresponds well with a series of PET oligomers of increasing molecular weights and supports the hypothesis that the oligomer molecular mass is strongly affected by the amount of scission agent used.…”

Section: Degradation Of Pet With Adipic Acidmentioning

confidence: 99%

Designing oligomeric ethylene terephtalate building blocks by chemical recycling of polyethylene terephtalate

Geyer

Röhner

Lorenz

et al. 2013

J of Applied Polymer Sci

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The intelligent recycling of plastics waste is a major concern. Because of the widespread use of polyethylene terephtalate, considerable amounts of PET waste are generated that are ideally re‐introduced into the material cycle by generating second generation products without loss of materials performance. Chemical recycling methods are often expensive and entail environmentally hazardous by‐products. Established mechanical methods generally provide materials of reduced quality, leading to products of lower quality. These drawbacks can be avoided by the development of new recycling methods that provide materials of high quality in every step of the production cycle. In the present work, oligomeric ethylene terephthalate with defined degrees of polymerization and defined molecular weight is produced by melt‐mixing PET with different quantities of adipic acid as an alternative pathway of recycling PET with respect to conventional methods, offering ecofriendly and economical aspects. Additionally, block‐copolyesters of defined block length are designed from the oligomeric products. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39786.

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Section: Degradation Of Pet With Adipic Acidmentioning

confidence: 99%

Designing oligomeric ethylene terephtalate building blocks by chemical recycling of polyethylene terephtalate

Geyer

Röhner

Lorenz

et al. 2013

J of Applied Polymer Sci

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show abstract

“…Taking the quantity AHu12ae as the constant a, eq 11 can be expanded in series to obtain + ... (12) T m = T , + ---c a ( A n 2 ca(AT13 Ip, e According to eq 12 the magnitude of the deviation from linearity will depend on the values of c and a, the equilibrium melting temperature, and the undercooling (AT) at which the crystallization is conducted.…”

Section: (7)mentioning

confidence: 99%

A Re-examination of the Relation between the Melting Temperature and the Crystallization Temperature: Linear Polyethylene

Alamo¹,

Viers²,

Mandelkern³

1995

Macromolecules

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102

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Analysis of the dependence of the melting temperature on the crystallization temperature has been frequently used to estimate the equilibrium melting temperature of a polymer. In the present paper the underlying basis for this extrapolative method is examined in detail. Two distantly different types of nucleation are considered. One is the Gibbs two-dimensional nucleus; the other, certain kinds of three-dimensional nuclei. Thickening, subsequent to nucleation, is also taken into account. Appropriate experiments with linear polyethylenes that have most probable molecular weight distributions, as well as with a molecular weight fraction, were carried out over a wide range in crystallization temperatures. Three distinct regions are observed. The high-temperature region is curved and precludes an extrapolation of the data to the equilibrium melting temperature. Reasons for this behavior are presented. Evidence for its being a general phenomenon is also given. A melting temperature of 141 "C was directly observed for linear polyethylene.

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“…Studies of the morphology and crystallization kinetics of n ‐alkanes and low molecular weight PEs with increasing chain length have determined the lowest molecular length at which folded‐chain crystallites are formed 20–22. When crystallization is conducted from the melt, the minimum chain length to form folded crystals is 1500 g/mol, and it is ∼1200 g/mol for crystallization from dilute solution.…”

Section: Resultsmentioning

confidence: 99%

Phase behavior of low molecular weight polyethylenes from homogeneous and heterogeneous solutions

Chatterjee

Alamo

2002

J Polym Sci B Polym Phys

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The pseudophase diagrams of solutions of low molecular weight polyethylene (PE) (number‐average molecular weight < 1500 g/mol) in octamethyl cyclotetrasiloxane (OCTS) and isododecane (IS) were determined by direct observation of cloud points and optical microscopy. In addition, melting temperatures were also determined by differential scanning calorimetry. In the range of single liquid–solid transitions, the data conformed to the classical melting temperature composition relation as a result of the formation of extended crystallites. The melting data were used to determine the interaction parameter of the PE in OCTS (1.4 ± 0.1) and IS (0.22 ± 0.05). The structural and thermal properties of the gels formed by a competing liquid–liquid and liquid–solid phase separation, under nonequilibrium conditions, contrast with the properties of the crystals formed from a single liquid–solid transition. Coarsening within the liquid phases was evidenced by optical microscopy, and insights about the mechanism of the kinetics of the coarsening process are given. The temporal changes of the melting temperature of crystallites formed from the heterogeneous phase (OCTS) reveal dynamics within a nonequilibrium state. In contrast, the crystallites formed from a homogeneous solution (IS) showed negligible melting‐temperature changes with time. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 878–889, 2002

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Crystallization, melting, and morphology of low molecular weight polyethylene fractions

Cited by 78 publications

References 17 publications

Designing oligomeric ethylene terephtalate building blocks by chemical recycling of polyethylene terephtalate

Designing oligomeric ethylene terephtalate building blocks by chemical recycling of polyethylene terephtalate

A Re-examination of the Relation between the Melting Temperature and the Crystallization Temperature: Linear Polyethylene

Phase behavior of low molecular weight polyethylenes from homogeneous and heterogeneous solutions

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