Lyotropic Main Chain Liquid Crystal Polymers

Northolt, M. G.; Sikkema, D. J.

doi:10.1007/978-94-011-1870-5_6

Cited by 14 publications

(4 citation statements)

References 177 publications

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“…In the case of flexible chain polymers, such as polyethylene in the case of Dyneema and Spectra, solid-state drawing is used to obtain the necessary level of chain extension needed to exploit the intrinsic properties of the polymer chain − . In the case of rigid rod polymers, chain extension is already build in by the chemist and alignment in the extended chain configuration is achieved during fiber spinning, coagulation and heat setting ,,, . A key factor in the preparation of high strength polymer fibers based on rigid rod polymers is the formation of lyotropic solutions.…”

Section: Introductionmentioning

confidence: 99%

“…At higher concentrations, rigid rod molecules will aggregate to form liquid crystalline ordered domains, with the number of ordered domains increasing with solution concentration. PPTA in sulphuric acid forms lyotropic solutions provided that (i) the polymer molecular weight is above a certain limit, (ii) the strength of the sulphuric acid is close to 100%, (iii) the polymer concentration is above a certain limit but below a further, higher limit, and (iv) the temperature is within a specific range ,,, . Using a dry-jet (air-gap) wet spinning process these anisotropic solutions can be spun into high-tenacity, high-modulus fibers .…”

Section: Introductionmentioning

confidence: 99%

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All-Aramid Composites by Partial Fiber Dissolution

Zhang

Mousavi

Soykeabkaew

et al. 2010

ACS Appl. Mater. Interfaces

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The area of self-reinforced polymer composites is one of the fastest growing areas in engineering polymers, but until now these materials have been mainly developed on the basis of thermoplastic fibers of moderate performance. In this work, we report on a new type of self-reinforced composites based on high-performance aramid fibers to produce an "all-aramid" composite by applying a surface-dissolution method to fuse poly(p-phenylene terephthalamide) (PPTA) fibers together. After immersion in concentrated (95%) sulphuric acid (H(2)SO(4)) for a selected period of time, partially dissolved fiber surfaces were converted into a PPTA interphase or matrix phase. Following extraction of H(2)SO(4) and drying, a consolidated all-aramid composite was formed. The structure, mechanical- and thermal properties of these single-polymer composites were investigated. Optimum processing conditions resulted in unidirectional composites of high reinforcement content (approximately 75 vol %) and good interfacial bonding. The all-aramid composites featured a Young's modulus of approximately 65 GPa at room temperature, and a tensile strength of 1.4 GPa, which are comparable with or exceed the corresponding values of conventional aramid/epoxy composites. However, since fiber, matrix and interphase in all-aramid composites are based on the same high-temperature resistant PPTA polymer, a high modulus of approximately 50 GPa was maintained up to 250 degrees C, demonstrating the potential of these materials for high-temperature applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

All-Aramid Composites by Partial Fiber Dissolution

Zhang

Mousavi

Soykeabkaew

et al. 2010

ACS Appl. Mater. Interfaces

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“…Poly( p -phenylene terephthalamide) (PPTA, brand names: Kevlar, Twaron) is one of the best studied cases of a high strength and high modulus polymer fiber. − It is therefore a well-suited model system to test advances in analytical techniques for investigating the microstructure of such fibers. Transmission electron microscopy/diffraction (TEM/TED) techniques are restricted to probing thin fiber sections and an extrapolation to a whole fiber is complicated by the sectioning process. − Scanning probe techniques, like atomic force microscopy (AFM), are surface sensitive and do not provide a complete information. − With the advent of third-generation synchrotron radiation (SR) sources, complementary scanning micro-X-ray diffraction (μ-XRD) experiments on single polymeric fibers have become possible. − Thus, μ-XRD experiments with a 3 μm diameter beam have demonstrated a gradient in orientation distribution in an about 12 μm diameter Kevlar 29 fiber which disappears upon tensile deformation .…”

Section: Introductionmentioning

confidence: 99%

Rotational Disorder in Poly(p-phenylene terephthalamide) Fibers by X-ray Diffraction with a 100 nm Beam

2003

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Single fibers of poly(p-phenylene terephthalamide) (PPTA; brand names Kevlar x , where x = 29, 49, 149) have been scanned with an about 100 nm synchrotron radiation X-ray beam normal to the fiber axis. Models of rotational disorder of the crystalline domains are discussed based on Monte Carlo simulations of the spatial variation of the 110/200 reflection intensities. For Kevlar149 the principal disorder appears to be a rotational domain-disorder across the fiber. The data suggest also the presence of a core and possibly a skin layer, which are both more disordered. Kevlar29,49 appear to have the same type of layering but with different volume fractions. There is also some evidence for a volume fraction without rotational correlation, which might be related to a morphology formed at the onset of coagulation.

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“…After washing with water by countercurrent, the fi bres are neutralized, washed again to remove traces of sulfuric acid and salts, and dried. The system of parallel fi bres then undergoes heat treatment as a function of the assortment being processed: insignifi cant thermal drawing at 400-420°C to increase the [2,4,5,7,12,13,[26][27][28][29][30][31][32][33]. An important feature of the technology is the simplicity of recycling the solvent -sulfuric acid -and treating the washing wastewaters.…”

Section: Part I Superstrong High-modulus Fibres/thread Made From P-pmentioning

confidence: 99%

High-strength, high-modulus fibres based on linear polymers: principles of production, structure, properties, use

Perepelkin

2010

Fibre Chem

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The evolution of modern technology, transportation, sports, and tourism is greatly determined by the use of new materials, especially materials capable of withstanding limiting mechanical loads. Materials with high specifi c mechanical characteristics that allow creating highly reliable articles and structures of minimum weight are promising [1][2][3][4][5][6][7][8]. The highstrength and high-modulus fi bres used for this purpose belong to the low-and medium-tonnage group. They are manufactured from different kinds of aromatic and some aliphatic polymers. The highly oriented structure, which makes it possible to attain extremal mechanical properties in highly loaded textile items and high-strength composites, is a distinctive feature of these fi bres.The basic kinds of high-strength, high-modulus fi bres used on large scales are fi bres made from aromatic p-polyamides. They were created in the 1970s at almost the same time in the USA and Russia [3][4][5][6][7]. As a result of conducting extensive research on synthesis of new fi bre-forming polymers, creating the corresponding technologies, and investigating the structure and properties of these types of fi bres, development was basically of several kinds: -high-strength and high-modulus para-aramid fi bres based on poly-p-phenylene terephthalamide (PPTA -Twaron, Netherlands, and Kevlar, USA) with a dynamic deformation modulus of 90 to 160 GPa and a mechanical deformation modulus of 70 to 120 GPa; -high-modulus para-aramid fi bres made from heterocyclic p-polyamides and the close copolyamides (SVM, Rusar, and Armos, Russia) with a dynamic deformation modulus of 120 to 160 GPa and a mechanical deformation modulus of 95 to 120 GPa. SVM fi bres (historically, the fi rst kind of high-modulus heterocyclic aromatic fi bres) have been based on polyamidobenzimidazole synthesized from heterocyclic p-diamine and terephthalochloride. The copolymeric heterocyclic para-aromatic fi bres Armos and Rusar are based on the same components, with incorporation of p-phenylenediamine as the third comonomer.Other kinds of high-strength and high-modulus fi bres have also been created: -fi bres made from a copolymer close in composition to poly-p-phenylene terephthalamide with a 5-15% aromatic comonomer content (Terlon, Russia). These fi bres differ little in composition and properties from PPTA fi bres;-high-strength fi bres based on para/meta-polyaramid synthesized from p-phenylenediamine, para/metadiaminodiphenyl oxide, and terephthalic acid with a dynamic deformation modulus of 90 to 110 GPa, mechanical deformation modulus of 60 to 80 GPa for high-strength textile articles and reinforcement of elastomeric composites, primarily rubbertextile items (Technora, Japan). 2

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Lyotropic Main Chain Liquid Crystal Polymers

Cited by 14 publications

References 177 publications

All-Aramid Composites by Partial Fiber Dissolution

All-Aramid Composites by Partial Fiber Dissolution

Rotational Disorder in Poly(p-phenylene terephthalamide) Fibers by X-ray Diffraction with a 100 nm Beam

High-strength, high-modulus fibres based on linear polymers: principles of production, structure, properties, use

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