Transverse heterogeneity in PET fibers

Tomlin, D. W.; Roland, C. M.; Slutsker, L.I.

doi:10.1002/polb.1993.090311008

Cited by 5 publications

(1 citation statement)

References 46 publications

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“…Equation (4) assumes the stress on the amorphous material equals the total stress, which is only true for low levels of crystallinity. 59 When φc ≈ 0, the form birefringence is negligible, and the degree of crystallinity is simply related to the measured birefringence 60 φc = ∆n − Cσ fc∆c (5) It is usually assumed, but not always correct, 61 that strain-induced crystallization yields nearly perfectly oriented crystallites (fc = 1). Since for natural rubber at room temperature, high orientation is necessary to induce crystallization (strains > 200%), the assumption that fc = 1 is acceptable.…”

Section: Birefringencementioning

confidence: 99%

Strain-Crystallization of Guayule and Hevea Rubbers

Choi¹,

Roland

1997

Rubber Chemistry and Technology

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A comparison was made of the room temperature strain-crystallization of naturally-occurring cis-1,4-polyisoprenes having varying non-rubber content. A variety of measurements were employed to assess crystallization, including stress relaxation, optical birefringence, and the infrared absorption spectrum. All methods yielded the same result: The strain required to induce crystallization is less for polyisoprenes having larger concentrations of impurities. The ability to crystallize at lower orientation presumably underlies the superior failure properties of guayule rubber and the poorer grades of natural rubber (NR) in comparison to deproteinized NR.

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Section: Birefringencementioning

confidence: 99%

Strain-Crystallization of Guayule and Hevea Rubbers

Choi¹,

Roland

1997

Rubber Chemistry and Technology

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Proton NMR determination of crystallinity in poly(ethylene terephthalate)

Roland

Walton

Miller

1994

Magnetic Reson in Chemistry

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The results of proton NMR Tin measurements on poly(ethylene terephthalate) (PET) films and fibers processed under various conditions are presented. Consistent with previous results, two domains are found in isotropic, amorphous PET. The NMR results provide an accurate measure of crystallinity in PET films and fibers, without requiring any assumptions about the semi-crystaUine morphology of the polymer. The NMR technique is particularly advantageous for PET fibers where orientation effects interfere with the more traditional density determination of crystallinity. KEY WORDS NMR 1H NMR Crystallinity Poly(ethylene terephthalate)Received

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Deformation in lamellar and crystalline structures: in situ simultaneous small‐angle X‐ray scattering and wide‐angle X‐ray diffraction measurements on polyethylene terephthalate fibers

Murthy

Grubb

2003

J Polym Sci B Polym Phys

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Changes in the lamellar and crystalline structures were followed as a function of applied stress to understand the influence of the interactions between the crystalline and amorphous domains on the fiber properties. We observed a reversible transformation from a structure giving a four‐point small‐angle pattern to a structure giving a two‐point pattern; these structures corresponded to the lamellae with oblique and normal lamellar surfaces, respectively. The characteristics of these two structures such as the stack diameter, stack height, and tilt angle were different and were determined by the processing conditions and did not change when the fiber was elastically deformed. The structure giving a two‐point pattern was probably the load‐carrying lamellar entity in these fibers. The diameter of the lamellar stacks, tilt angle of the lamellae, and the strain in the lamellar spacing appeared to have the most influence on properties such as tenacity and dimensional stability. The long‐spacing strain, which is about the same as the fiber strain, determined the modulus at low elongation as well as ultimate elongation. These indicate that the lamellar stacks have at least as much influence as the interfibrillar chains on fiber properties. Structural features that determine the performance in semicrystalline polymers were investigated by analyzing four generations of polyethylene terephthalate fibers. Some of the fiber properties correlate with changes in the crystalline domains such as the crystalline orientation, size, and unit cell dimensions. Fibers in which the crystalline strain was large because of their strong linkages to the amorphous chains, and better load transfer, had the highest modulus and lowest ultimate elongation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1538–1553, 2003

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Transverse heterogeneity in PET fibers

Cited by 5 publications

References 46 publications

Strain-Crystallization of Guayule and Hevea Rubbers

Strain-Crystallization of Guayule and Hevea Rubbers

Proton NMR determination of crystallinity in poly(ethylene terephthalate)

Deformation in lamellar and crystalline structures: in situ simultaneous small‐angle X‐ray scattering and wide‐angle X‐ray diffraction measurements on polyethylene terephthalate fibers

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