Lamellar thickening behaviour of nylon-6,6 crystal by annealing

Mitomo, Hiroshi; Nakazato, Keiichi; Kuriyama, Isamu

doi:10.1016/0032-3861(78)90095-2

Cited by 23 publications

(6 citation statements)

References 9 publications

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“…As the orientation of the chain axes with respect to the lamellar surface normals n~ does not stay constant, we are not able to confirm a stepwise increase by one or one-half monomer unit length steps throughout the annealing sequence. Our observation greatly differs from the result reported by Mitomo et al,27,28 who have shown that the lamellar thickness of nylon 6,6 increases stepwise by one-half monomer unit with increasing temperature or annealing time on annealing in the swollen state.…”

Section: Crystal Thicknesscontrasting

confidence: 99%

Thermal annealing of doubly oriented nylon 11 in contact with formic acid

Dosière

Point

1983

J. Polym. Sci. Polym. Phys. Ed.

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SynopsisThe most striking feature of the mechanism of thermal annealing of doubly oriented samples of low-density polyethylene (LDPE) and probably of high-density polyethylene (HDPE) is a progressive tilt of lamellar crystals around their crystallographic b axis. Such a rotation does not occur on thermal annealing in doubly oriented nylons. However, this rotation mechanism occurs during the thermal annealing of doubly oriented samples of nylon 11 in contact with a solvent below its dissolution temperature. As for oriented samples of polyethylene (PE), a correlation between the changes of macroscopic dimensions and long spacing obtained from the small-angle x-ray pattern is difficult to establish. In doubly oriented samples of nylon 11, the basal faces of the lamellar crystals are parallel to the a axis of the unit cell. Nevertheless, simple Miller indices cannot be assigned to the basal planes of the lamellae. On thermal annealing in formic acid, the basal planes of the lamellar crystals are, in some cases, parallel to (001) planes. Annealing in formic acid at room temperature induces a phase transition: the chain c axis remains oriented along the rolling direction and the (001) planes become parallel to the limiting planes of the lamellar crystals. Bulk doubly oriented samples of nylon 11 annealed in formic acid just below the "dissolution temperature" have the same texture of orientation as filter mats of single crystals grown from dilute solution; moreover, as these bulk specimens remain doubly oriented, they can be used for further physicochemical investigations. The usual interpretation of the small-angle x-ray pattern is also discussed on the basis of the results reported in this paper. adopted the following approach. Samples of low-density polyethylene (LDPE) are prepared so as to possess as simple a texture as possible; thereby some individual structural processes can first be identified, then studied in detail. Thus Hay and Keller4 prepare double-textured samples by drawing followed by rolling of melt-pressed sheets of LDPE. The macroscopic rolled sheet is defined by directions OX, OY, and 02. In these samples, the molecular axes are parallel to the rolling direction OY and the (100) planes are parallel to the rolling plane YOZ. The chains are folded in the lamellar crystals: the lamellar structure gives rise to discrete x-ray reflections at low angles. In the simple crystal-type texture

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Section: Crystal Thicknesscontrasting

confidence: 99%

Thermal annealing of doubly oriented nylon 11 in contact with formic acid

Dosière

Point

1983

J. Polym. Sci. Polym. Phys. Ed.

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“…The stability of the nylon crystals, as assessed by the temperature shift of the Brill transition, is highly dependent on the “crystal perfection” (deliberately loosely defined in the present context) . Excursions at high temperatures result in lamellar thickening, doubling, or even quadrupling of the initial, “standard” ≈6 nm lamellar thickness frequently reported for the alpha phase. , Considerable shifts not only of this Brill transition but also of the domain of stability of the pleated/rippled sheets are therefore likely.…”

Section: Discussionmentioning

confidence: 87%

Original Crystal Structures of Even–Even Polyamides Made of Pleated and Rippled Sheets

Lotz

2021

Macromolecules

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Original crystal structures of even−even polyamides are introduced. They are based on twisted conformations at the amide-aliphatic part links and are reminiscent of the pleated and rippled protein sheet structures introduced by Pauling and Corey in the early 1950s. Pleated sheets are chiral, and rippled sheets are made of two conformational isomers. They have specific X-ray diffraction "profiles". Publications on even−even polyamides describe such profiles, indicating that both pleated and rippled sheet variants exist. The pleated sheet structure is the stable crystal form of the whole family of nylons 2,2n. The rippled sheet applies for a high-temperature "alpha phase variant" of nylons with long aliphatic parts and more generally appears to be (one of?) the so-called "high-temperature α phase(s)" of even−even nylons. Pleated and rippled sheet crystal structures appear to be the entropically favored, high-temperature crystal form(s) of nylons. This new family of crystal structures and their possible variants with different sequences of twisted amide-aliphatic part junctions open a possible way for the (re)analysis of rare and unusual crystal morphologies produced at high Tc after partial melting/self-seeding.

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“…7a), the glass transition temperatures were appeared at 238 and 248 1C. The behavior of multi-melting peaks in Nylon66 has been observed and discussed before for both pristine Nylon66 [37,38] and Nylon66 composites [39][40][41][42][43]. Bell et al reported that Nylon66 exhibited two melting peaks, which might appear singly or together depending on the annealing and drawing treatment [44].…”

Section: Resultsmentioning

confidence: 80%