Poly(hexamethylene terephthalate)—II. The crystal structure of forms I and II, from electron and x-ray diffraction, and packing analyses

Brisse, F.; Palmer, A.; Moss, Barbara; Dorset, Douglas L.; Roughead, W. A.; Miller, Dennis K.

doi:10.1016/0014-3057(84)90115-0

Cited by 35 publications

(20 citation statements)

References 19 publications

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“…(2) can be expressed as (4) For a relaxation with zero activation entropy (ΔS=0), corresponding to the lower limit of the activation energy of viscoelastic relaxations, eq. (4) with ΔS=0 can be simplified as (5) Starkweather has suggested that this lower limit of activation energy corresponds to the relaxation process characterized by local and non-cooperative motions. [39][40][41] In such a noncooperative relaxation process, the molecular motions are of short range without considerable interaction between the relaxing molecule and the neighboring ones (simple relaxations).…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7] Poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) (Figure 1(B)) has also attracted considerable attention from academia and industry because of its high potential to be used for fiber, film, and engineering plastic. [8][9][10][11][12][13][14][15] Copolymerization is very often used for tailoring the macroscopic properties of polymers through variation of the copolymer composition.…”

Section: Introductionmentioning

confidence: 99%

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Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate)

Jeong

Lee

2006

Macromol. Res.

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The dynamic mechanical thermal properties of poly(hexamethylene terephthalate) (PHT), poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) and their P(HT-co-CT) random copolymers in the amorphous state were examined as a function of temperature and frequency. All the samples exhibited two main relaxation processes in the plot of tan δ versus temperature: the primary α-relaxation associated with the glass transition and the secondary β-relaxation attributed to the local segmental motions of mostly cyclohexylene rings for PCT and to cooperative motions of methylene, carboxyl, and phenylene groups for PHT. Both α-and β-relaxation temperatures increased with increasing CT content. The activation energy of the α-relaxation increased with increasing CT content, whereas that of the β-relaxation decreased. The sub-glassy secondary β-relaxation processes of PCT and PHT were investigated in terms of the cooperativity of main-chain segmental motions.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate)

Jeong

Lee

2006

Macromol. Res.

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“…Among these peaks, the diffractions at 17.9 and 23.68 are attributed to the typical b crystal (triclinic unit cell) while, on the other hand, the other four diffraction peaks indicate the a crystal (monoclinic unit cell). [17][18][19] Apparently, the PHT samples melt-crystallized at low to moderate temperatures (90-135 8C) yield mixed fractions of both a and b crystals, depending on the temperature and/ or time. Figure 3(B) shows a completely different diffractogram for the PHT sample subjected to crystallization at high temperatures (i.e.…”

Section: Crystal Forms and Spherulitic Morphology In Crystallized Phtmentioning

confidence: 99%

“…Three crystal cell types, described in terms of a, b, and g in PHT, have been identified, and preliminary studies in the literature have shown that PHT may possess various combinations of these three different crystal unit cells depending on thermal and/or solution treatments. [17][18][19] The a form in PHT is characterized by a monoclinic chain packing, and is favored for crystallization under stress. The b and g forms are both characterized by the same triclinic chain packing.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Polymorphism and Dual Crystalline Morphologies in Poly(hexamethylene terephthalate)

Woo

Chiang

et al. 2004

Macromol. Rapid Commun.

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Summary: The polymorphisms in poly(hexamethylene terephthalate) (PHT), along with their associated melting and spherulite morphologies, were examined by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and polarized‐light microscopy (PLM). The morphology and crystal cells were dependent on the temperature of crystallization. When melt‐crystallized at low temperatures (90–135 °C), PHT showed at least five melting peaks and two re‐crystallization peaks upon DSC scanning, and the samples displayed various fractions of both α and β crystals. However, only a single melting peak was obtained in PHT melt‐crystallized at 140 °C or above, which displayed a single type of β crystal. In addition, two different forms of spherulites were identified in melt‐crystallized PHT, with one being a typical Maltese‐cross spherulite containing the α crystal, and the other being a dendrite‐type packed mainly with the β crystal. This study provides timely evidence for a critical interpretation of the relationship between multiple melting and polymorphisms (unit cells and spherulites) in polymers, including semi‐crystalline polyesters.

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“…It is well known that PHT may adopt three crystal forms designated as α , β, and γ depending on crystallization conditions. The α ‐form is monoclinic whereas both β and γ forms are triclinic but differ to each other in the b dimension.…”

Section: Resultsmentioning

confidence: 99%

Biodegradable Copolyesters of Poly(hexamethylene terephthalate) Containing Bicyclic 2,4:3,5‐Di‐O‐methylene‐d‐Glucarate Units

Japu

Ilarduya

Alla

et al. 2014

Macro Chemistry & Physics

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A set of copolyesters (PHTxGluxy) with compositions ranging between 90/10 and 50/50 in addition to the parent homopolyesters poly(hexamethylene terephthalate) (PHT) and PHGlux, are prepared by the melt polycondensation of 1,6‐hexanediol (HD) with mixtures of dimethyl terephthalate (DMT) and dimethyl 2,4:3,5‐di‐O‐methylene‐d‐glucarate (Glux). The copolyesters have trueM¯normalw in the 35 000–45 000 g mol−1 range, their microstructure is random, and they start to decompose at a temperature well above 300 °C. Crystallinity of PHT is repressed by copolymerization so that copolyesters containing more than 20% of sugar‐based units are essentially amorphous. On the contrary, PHTxGluxy displays a Tg that increases monotonically with composition from 16 °C in PHT up to 73 °C in PHGlux. Compared with PHT, the copolyesters show an accentuated susceptibility to hydrolysis and are sensitive to the action of lipases upon incubation under physiological conditions. The degradability of PHTxGluxy increases with the content in Glux units.

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Poly(hexamethylene terephthalate)—II. The crystal structure of forms I and II, from electron and x-ray diffraction, and packing analyses

Cited by 35 publications

References 19 publications

Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate)

Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate)

Analysis of Polymorphism and Dual Crystalline Morphologies in Poly(hexamethylene terephthalate)

Biodegradable Copolyesters of Poly(hexamethylene terephthalate) Containing Bicyclic 2,4:3,5‐Di‐O‐methylene‐d‐Glucarate Units

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