Poly(1,4-phenyleneterephthalamides). Polymerization and Novel Liquid-Crystalline Solutions

Bair, T. I.; Morgan, Paul W.; Killian, F. L.

doi:10.1021/ma60060a042

Cited by 234 publications

(96 citation statements)

References 3 publications

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“…Rather than attempting to solve the integral equation (4), Onsager attacked the minimization of the free energy directly using the following trial orientation distribution: a 4?r sinh a cosh(a cos d ). (6) The functions <j(a) and p(a) can be expressed in terms of simple known functions. For small values of a one can write the power series 2…”

Section: Onsager Theory For the Phase Separation In A Solution Ofmentioning

confidence: 99%

“…This fractionation effect with the higher molecular weight fraction being in the anisotropic phase has also been observed for polydisperse solutions of polybenzamides 5 and polyphenyleneterephtalamides. 6 In the present work we extend the Onsager treatment for monodisperse systems to solutions of rodlike particles with the same diameter but two different lengths. It is found that the Onsager predictions about polydisperse solutions (i.e., the fractionation effect and the more perfect orientational ordering of the longer particles) are indeed borne out by the quantitative elaboration of the theory.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

On the isotropic-liquid crystal phase separation in a solution of rodlike particles of different lengths

Lekkerkerker

Coulon

Haegen

et al. 1984

The Journal of Chemical Physics

268

230

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The Onsager theory for the isotropic-anisotropic phase separation in a solution of rodlike particles is extended to the case of mixtures of such particles with different lengths. The concentration, composition, order parameters, and orientation dependent thermodynamic quantities of the coexisting phases are calculated for the case of a mixture of rods of two different lengths for different length ratios. It is found that there is a significantly higher mole fraction of the longer rods in the anisotropic phase than in the isotropic phase. The order parameter of the longer rods is higher than in the one component case, whereas the order parameter of the shorter rods first increases and then decreases as the mole fraction of the longer rods is increased. All these features are accentuated as the length ratio of the two kinds of rods increases.

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Section: Onsager Theory For the Phase Separation In A Solution Ofmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

On the isotropic-liquid crystal phase separation in a solution of rodlike particles of different lengths

Lekkerkerker

Coulon

Haegen

et al. 1984

The Journal of Chemical Physics

268

230

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show abstract

“…p-Aramid fiber is the prime example of a high performance synthetic fibers spun from rigid (or semi-rigid) polymer chains. Great success has been achieved by developing through these routes high performance p-aramid fibers like Kevlar® and Twaron® with typical fiber diameters of around 14 mm [16][17][18]. However, until recently few efforts were devoted to the development of electrospun p-aramid nanofibers.…”

Section: Introductionmentioning

confidence: 99%

High-performance electrospun co-polyimide nanofibers

Pantano

Pugno

Bastiaansen

et al. 2015

Polymer

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Abstract. Co-polyimide nanofiber based on BPDA (3, 30, 4, 40-Biphenyltetracarboxylic dianhydride)/PDA (p-Phenylene-diamine)/ODA (4, 40-Oxydianiline) (BPO) were produced by electrospinning followed by imidization from precursor polyamic acid (PAA) nanofiber. The aligned co-polyimide nanofiber mats possessed a modulus, strength and strain-at-break of respective 10 GPa, 1.04 GPa, and 13.5%. In comparison with previously reported co-polyimide nanofibers BPDA/BPA/ODA (BBO) with similar chemical structures, these BPO co-polyimide nanofibers can be as stiff and strong while at the same time exhibiting moderate ductility. On the other hand, the current BPO co-polyimide nanofibers exhibited a greater toughness than previously reported homo-polyimide (BPDA/PDA) nanofibers due to their relatively high strain-at-break, leading to similar levels of toughness as Kevlar fibers. A novel and efficient way to evaluate mechanical properties of aligned nanofiber bundles (~30 nanofibers in a bundle) by virtue of a micro-tensile tester was also reported. Young's modulus of 38 ± 2 GPa and tensile strength of 1550 ± 70 MPa were found for nanofiber bundles and were significantly higher than those of aligned mats, and are among the highest reported for electrospun fibers. Further evaluation of this bundle data using Daniel's theory based on Weibull statistics resulted in a predicted tensile strength of single copolyimide nanofibers of about 1.9 GPa.

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“…The spinning holes fulfill an important function. Under shear, the crystal domains become elongated and orientated in the direction of the deformation [12][13][14]. Once in the air gap, elongational stretching takes place.…”

Section: Spinning Fibresmentioning

confidence: 99%

High performance fibres and the mechanical attributes of cut resistant structures made therewith

Rebouillat¹,

Steffenino²

2006

WIT Transactions on the Built Environment, Vol 85

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High performance materials are rarely used as 100% compound, therefore most of the time when reference is made to these categories of materials it is as a matter of fact a reference to a system comprising a well-combined ingredients exhibiting together high performances in use. Fibres, micro-fibres and now nanofibres are definitely part of the high performance reinforcing ingredients, which in a system largely contributes to the performance in use of the designed system.High performance fibres, and more specifically aramids for their outstanding heat and mechanical properties, although most often used as reinforcing compound, are also used more uniquely and directly in situations where mechanical and thermal protections are required. It is therefore useful as a preliminary grounding to review these types of materials in terms of their properties. Then their attributes and potential contribution alone or in a system become more specific and can be extrapolated more easily. The mechanical performance and more specifically the cut resistance of articles made of high performance materials are generally measured against several norm specifications. Those are not designed to predict the "real" in use performance of the considered protective articles. This gap is even larger when the cut resistance of the compounding fibre increases. Although relationships exist between the various cut performance levels obtained with the ASTM, ISO and EN norms (respectively American, International and European standards), there is a need for a more fundamental understanding and interpretation of the data. The ASTM and ISO approaches remain the most suitable methods for that purpose. Various parameters, such as the high performance material and fibre composition, the effect of kinetic such as the cutting speed and the speed profile, the force distributions, the artefacts generated by various surface coatings are presented and discussed aiming at improving the interpretations of the data generated through the norm procedures. Therewith, significant progress in the understanding of the cut fundamentals and the norm harmonization are made available to the users of high performance fibres, such as KEVLAR®.

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Poly(1,4-phenyleneterephthalamides). Polymerization and Novel Liquid-Crystalline Solutions

Cited by 234 publications

References 3 publications

On the isotropic-liquid crystal phase separation in a solution of rodlike particles of different lengths

On the isotropic-liquid crystal phase separation in a solution of rodlike particles of different lengths

High-performance electrospun co-polyimide nanofibers

High performance fibres and the mechanical attributes of cut resistant structures made therewith

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