Thermal Expansion and Differential Scanning Calorimetry Phenomena in the γ-Relaxation Region (=150°K) of Nylon 6,6, Nylon 11, and Ethylene-co-(Vinyl acetate)

Wilson, Phillip S.; Lee, Shirley; Boyer, Raymond F.

doi:10.1021/ma60036a024

Cited by 9 publications

(3 citation statements)

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“…From this relation and the evolution of the specific volume, it is possible to estimate the coefficient of thermal expansion of the matrix during phases A and C. They are represented in Figure 4(a) and compared with several values from the literature. 24–27 The same analysis protocol was applied to specific volume evolutions obtained by Zoller and Walsh, 28 leading to values also plotted in Figure 4(a). The evolution of α Vol with temperature is not trivial.…”

Section: Experimental Characterizationmentioning

confidence: 99%

“…(a) Compared with several values from the literature. 24–28 (b) Compared with the proposed evolutions.…”

Section: Experimental Characterizationmentioning

confidence: 99%

“…23 These studies are however limited to a temperature range in the semi-crystalline state of the matrix, from 0 to 200 C. The measurement of the Poisson's ratio evolution with temperature has rarely been mentioned in previous studies, and this property is often calculated thanks to the aforementioned moduli. The coefficient of thermal expansion of PA66 has already been studied thanks to a mercury column dilatometer, 24 a linear dilatometer 25,26 or thermomechanical analysis (TMA). 27 The first method permits to follow the volume evolution of the sample from melting to room temperature.…”

Section: Introductionmentioning

confidence: 99%

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Thermomechanical characterization of a low viscosity PA66 thermoplastic matrix and associated continuous glass fibre composite under processing conditions

Péron

Jacquemin

Casari

et al. 2019

Journal of Composite Materials

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Characterizing the thermomechanical properties of thermoplastic resins and associated composites is of outmost importance to understand the development of process-induced stresses. To that extent, the characterization of a low viscosity PA66 matrix is proposed thanks to a homemade volumetric dilatometer named PvT-XT and a dynamic mechanical analyser on a wide temperature range. The PvT-XT results, reported for the first time, permit to identify the evolution of the coefficients of thermal expansion, of crystallization shrinkage and of the bulk modulus with temperature. Dynamic mechanical analyser experiments lead to the estimation of the Young’s modulus. The shear modulus as well as the Poisson’s ratio are then estimated thanks to analytical relations for isotropic and homogeneous materials. These properties are used to feed a new analytical model estimating the coefficients of thermal expansion of quasi-unidirectional composites. All the results are compared with the values from the literature or from complementary experiments, showing a good agreement which permits to validate the developed methodology.

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Section: Experimental Characterizationmentioning

confidence: 99%

“…(a) Compared with several values from the literature. 24–28 (b) Compared with the proposed evolutions.…”

Section: Experimental Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermomechanical characterization of a low viscosity PA66 thermoplastic matrix and associated continuous glass fibre composite under processing conditions

Péron

Jacquemin

Casari

et al. 2019

Journal of Composite Materials

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Glassy transitions in semicrystalline polymers

Boyer

1975

J. polym. sci., C Polym. symp.

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154

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Considerable confusion exists in the literature concerning the glass temperature, Tg, of many highly crystalline polymers, in particular, linear polyethylene (PE), poly(vinyl fluoride) (PVF), poly(vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), poly(oxymethylene) (POM), and poly(ethylene oxide) (PEO). We attempt to resolve some of this confusion first, by defining the nature of the problem; second, by developing criteria for defining the locations along a relative temperature scale (T/Tg or T/TM) of the key relaxations and transitions, Tg, T < Tg, TM, and Tαc for C‐C and CO backbone polymers free from long alkyl side groups; third, by developing a set of typical mechanical relaxation spectra for amorphous, semicrystalline, and single crystal materials of known Tg; fourth, by defining the concept of a double glass transition with values Tg(L) and Tg(U) and the optimum conditions for observing same. Finally, we apply these concepts and criteria to resolving the value of Tg for PVF and PVDF. Criteria employed include ratios of relaxation temperatures such as (T < Tg)/Tg, Tαc/TM, and Tg/TM, typical activation enthalpies for various relaxation processes, thermal expansion and heat capacity data. Two theoretical subjects are explored: the effect of crystallinity on increasing Tg and the effect of crystallinity on the relative strengths of the Tg and T < Tg processes. We also employ a “comparative anatomy” technique of comparing temperatures and related activation enthalpies of the several relaxations and transitions for a series of closely related polymers such as PE, PVF, PVDF, PTFE, Polytrifluorochloroethylene, and poly(vinyl chloride). We suggest that a new scientific discipline of interpreting the relaxation spectra of crystalline polymers may be emerging through integration of a large body of literature, the refinement of old criteria, and the development of new criteria. Even so, we are not yet able to offer a satisfactory interpretation of the relaxation spectra for POM and PEO.

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