Some remarks on the mechanical relaxations in aliphatic, partially aromatic and wholly aromatic polyamides

Frosini, Vittorio; Butta, E.

doi:10.1002/pol.1971.110090403

Cited by 46 publications

(20 citation statements)

References 8 publications

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“…The lowest temperature process (5) takes place at -120~ (local mode relaxation of the -CH2-groups); the y-transition takes place between -76~ and -46~ and the third (13) relaxation process occurs between 50 and 73~ depending on the applied frequency. Comparison with the DMA results on other polyamides [6] indicates that the y-relaxation probably corresponds to onset of motion of the amide-groups, while the 13-relaxation corresponds to onset of rotation of the phenylene-groups.…”

Section: Glass Transition Specific Heat Capacity and Secondary Trmentioning

confidence: 86%

Thermal analysis of poly(2-methylpentamethylene terephthalamide)

Menczel

Jaffé

Saw

et al. 1996

Journal of Thermal Analysis

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Poly(2-methylpentamethylene terephthalamide) (Nylon M5T) is a new high temperature aromatic polyamide developed by Hoechst Celanese. In this paper thermal properties of Nylon M5T chips, as well as as-spun and drawn fibers were studied by DSC, DMA, hot stage microscopy and WAXS. Tg of the fully amorphous Nylon M5T is 143~ when measured by DSC; T~ increases with crystallinity to 151~ The temperature dependence of the solid and melt specific heat capacities has also been determined. The heat capacity increase at the glass transition of the amorphous polymer is 103.9 J ~ mol -l. Tg by DMA for the as-spun fiber is 155~ for a drawn fiber is 180~ Three secondary transitions were observed by DMA in addition to the glass transition. These correspond to a local mode relaxation of the methylene groups at -120~ onset of rotation of the amide-groups at -65~ and the onset of the rotation of the phenylenegroups (at 630C). The erystallinity of Nylon M5T strongly depends on the rate of cooling from the melt. The isothermal crystallization data are melt temperature dependent: two-dimensional crystallization takes place when the samples are crystallized from higher melt temperatures, and this phase changes into a spherulitic structure during cooling to room temperature. Spherulitic crystallization occurs when lower melt temperatures are used. This polymer has three crystal forms as indicated by DSC, DMA and WAXS data. The crystal to crystal transitions are clearly visible when amorphous samples are heated in the DSC, or the DMA curves of as-spun fibers are recorded. It is experimentally shown that a considerable melting of the lower temperature crystal forms takes place during the crystal to crystal transitions. The equilibrium melting point as measured by the Hoffman-Weeks method, has been determined to be 339~

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Section: Glass Transition Specific Heat Capacity and Secondary Trmentioning

confidence: 86%

Thermal analysis of poly(2-methylpentamethylene terephthalamide)

Menczel

Jaffé

Saw

et al. 1996

Journal of Thermal Analysis

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“…Frosini et al 6 investigated the dynamic mechanical properties of a number of aliphatic, partially aromatic, and wholly aromatic polyamides. In the case of PPTA, however, they did not observe the a-dispersion, although they found the /3-and @*-dispersions at 10 and 14OoC, respectively.…”

Section: Discussionmentioning

confidence: 99%

Dynamic mechanical properties of poly(p-phenyleneterephthalamide) fiber

Kunugi

Watanabe

Hashimoto

1979

J. Appl. Polym. Sci.

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SynopsisThe dynamic mechanical properties of poly@-phenyleneterephthalamide) fiber were investigated.Measurements of the dynamic mechanical properties were carried out on samples of low crystallinity and low orientation over a temperature range from -100 to +50O0C at a frequency of 110 Hz, at a heating rate of SoC/rnin. Five relaxation processes were revealed a t -30,60,170, 27OoC, and in the vicinity of 46OoC, respectively. The prominent dispersion peaks located at -30,60, and 46OOCwere termed the 7 , p, and a relaxations, respectively. The two weak peaks at 170 and 27OoC, observed in annealed samples, seem to correspond to the p-relaxations reported previously by Frosini et al. and Takayanagi et al. The effect of annealing on the behavior of these dispersion peaks was examined, and possible molecular interpretation of these relaxation processes are made.

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“…[17][18][19] The γ-absorption observed around 150 K is attributed to the motion of methylene parts of nylon-6 chains. 15,[17][18][19][20] The peak temperature of α a -absorption increased in the order of the nylon-6 homopolymer, the (SUSGF/Ny6) and the (SMSGF/Ny6). It is clear that the thermal molecular motion of nylon-6 segments in the amorphous regions was more restricted at the interface region between SMSGF and matrix nylon-6 of the (SMSGF/Ny6) in comparison with that of the (SUSGF/Ny6).…”

Section: Sem Observation Of (Gf/ny6)s Morphologymentioning

confidence: 99%

“…The absorption observed at 330 K corresponds to the α a -absorption being characteristics of micro-Brownian motion in amorphous phases of nylon-6. [15][16][17] The absorption observed at 220 K is the β-absorption being attributed to segments containing amide groups not involved in the formation of hydrogen bonds. [17][18][19] The γ-absorption observed around 150 K is attributed to the motion of methylene parts of nylon-6 chains.…”

Section: Sem Observation Of (Gf/ny6)s Morphologymentioning

confidence: 99%

“…[15][16][17] The absorption observed at 220 K is the β-absorption being attributed to segments containing amide groups not involved in the formation of hydrogen bonds. [17][18][19] The γ-absorption observed around 150 K is attributed to the motion of methylene parts of nylon-6 chains. 15,[17][18][19][20] The peak temperature of α a -absorption increased in the order of the nylon-6 homopolymer, the (SUSGF/Ny6) and the (SMSGF/Ny6).…”

Section: Sem Observation Of (Gf/ny6)s Morphologymentioning

confidence: 99%

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Effect of Interfacial Interaction between Glass-Fiber and Matrix Nylon-6 on Nonlinear Dynamic Viscoelasticity and Fatigue Behavior for Glass-Fiber Reinforced Nylon-6

Komatsu

Takahara

Kajiyama

2002

Polym J

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ABSTRACT:Effect of (glass-fiber/matrix nylon-6) interfacial interactions on fatigue behaviors of glass-fiber reinforced nylon-6 (GF/Ny6) under a strain controlled condition was investigated on the basis of in situ nonlinear dynamic viscoelasticity. Ny6s mixed with surface-modified and -unmodified short glass-fibers (SMSGF and SUSGF) were used as specimens. An extent of nonlinearity of dynamic viscoelasticity was expressed by nonlinear viscoelastic parameter, NVP, which was calculated from coefficients of the Fourier expanded series of the response signal during a fatigue cycle. The nonlinear dynamic viscoelasticity for both (GF/Ny6)s became remarkable with the progress of fatigue damage. The magnitude of NVP for the (SUSGF/Ny6) was always greater than that for the (SMSGF/Ny6) at a given fatigue time. Since the interface between SUSGF and Ny6 was peeled off during the fatigue test due to the weak interaction, the fatigue damage easily occurred for the (SUSGF/Ny6). Such leads to the non-uniform propagation of the imposed strain through the (SUSGF/Ny6), resulting in an increase of NVP. In the case of the (SMSGF/Ny6), the fatigue damage slowly progressed due to the strong interfacial interaction. Consequently, the nonlinearity of the dynamic viscoelasticity for the (SMSGF/Ny6) was depressed in comparison with the (SUSGF/Ny6).KEY WORDS Fatigue Behavior / Short Glass-Fiber Reinforced Nylon-6 / Interfacial Interaction / Nonlinear Viscoelastic Parameter / Polymer composites are a class of materials that polymer matrix is reinforced by fillers such as glassfibers or carbon-fibers with a small amount. Recently, polymer composites have been widely used for structural components of transports and constructions as substitutes of metal materials due to their comparatively high specific strength and modulus. When polymer composites are applied to the above-mentioned purpose, it is important to understand the fatigue mechanisms, and to predict the fatigue lifetime. This is because the fatigue fracture of them could cause fatal accidents.Fatigue mechanisms of fiber-reinforced polymers have been discussed on the basis of scanning electron microscopy (SEM) observations of fractured surfaces. 1, 2 In general, a fatigue damage of polymer composites starts from debonding at fiber ends. Then, the debonding progresses along the (fiber / polymer) interface, and eventually, polymer composites are fractured. In the case of weak interfacial interaction, debonding easily progresses even at the initial stage of fatigue cycles. On the contrary, interfacial debonding is hard to occur for composites with strong interfacial interaction and thus an imposed load effectively transfers from matrix polymer to fibers, resulting in an improvement of fatigue strength. 1,[3][4][5][6][7] Although SEM is an useful apparatus, fatigue tests must be interrupted to observe sample surfaces. Therefore, it seems difficult by SEM observation to follow how fatigue damages such as interfacial debonding progress in a specimen. In order to clarify the fatigue fracture...

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Some remarks on the mechanical relaxations in aliphatic, partially aromatic and wholly aromatic polyamides

Cited by 46 publications

References 8 publications

Thermal analysis of poly(2-methylpentamethylene terephthalamide)

Thermal analysis of poly(2-methylpentamethylene terephthalamide)

Dynamic mechanical properties of poly(p-phenyleneterephthalamide) fiber

Effect of Interfacial Interaction between Glass-Fiber and Matrix Nylon-6 on Nonlinear Dynamic Viscoelasticity and Fatigue Behavior for Glass-Fiber Reinforced Nylon-6

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